THE 6.2 LITER DIESEL ENGINE

THE 6.2 LITER DIESEL ENGINE
THE 6 .2 LITER
DIESEL ENGINE
Product
Service
Training
16015.05-1C
6 .2 Liter Diesel Engine
Foreword
T h is b o o k le t is s u p p lie d by GM P rod uct S ervice T ra in in g to GM dealer service personnel upon th e ir
c o m p le tio n o f th e s u b je c t c o u rs e c o n d u c te d at GM T ra in in g C enters.
W h ile th is b o o k le t w ill serve as an e x c e lle n t review o f the e xte n sive program presented in the tra in in g
ce n te r se ssion , it is not in te n d e d to s u b s titu te fo r the va rio u s service m an u a ls n o rm a lly used on the job.
The range o f s p e c ific a tio n s and v a ria tio n in pro ce d u re s betw een c a rlin e s and m odels requires th a t the
d iv is io n se rvice p u b lic a tio n s be referred to, as necessary, when p e rfo rm in g these o p e ra tio n s.
A ll in fo rm a tio n c o n ta in e d in th is b o o k le t is based on the la te s t d a ta a va ila b le at the tim e of p u b lic a tio n
approval. The rig h t is reserved to m ake p ro d u c t or p u b lic a tio n changes, at any tim e , w ith o u t n o tice. This
b o o kle t, or any p o rtio n th e re o f, m ay n ot be reproduce d w ith o u t w ritte n co n s e n t o f GM P roduct Service
T ra in in g , G eneral M o to rs C o rp o ra tio n .
P o rtio n s o f th is b ook w ere p ro d uce d u sin g in fo rm a tio n provided by D e tro it D iesel A llis o n D ivision,
S tanadyn e D iesel S yste m s and R obert B osch C o rp o ra tio n .
— NOTE —
Many of the words and terms in this section are explained in the
“glossary” section at the back of this book. If the meaning of a new or confusing
word or term isn’t clear, always take the time to look it up.
Table of Contents
Page
Page
1. General Info rm a tion and M a in te n a n c e ................1-1
V a lv e s .....................................................................2-19
General D e s c rip tio n .................................................1-1
Valve Stem Oil S e a l/O r Valve S p rin g ................2-19
Engine Id e n tific a tio n ...............................................1-2
Piston C onstruction (Figure 2-17) .................... 2-20
LH6 (C) Engine S p e c ific a tio n s ............................... 1-4
Piston S e le c tio n ................................................... 2-21
General Engine D e s c rip tio n ............................... 1-4
Piston In s p e c tio n ................................................. 2-22
T echnical Engine S p e c ific a tio n s ...................... 1-4
Piston Related C ylinder Case O p e ra tio n s .. . .2-23
LL4 (J) Engine S p e cific a tio n s ............................... 1-6
Rod and P is to n ..................................................... 2-24
General Engine D e s c rip tio n ............................... 1-6
C r a n k s h a ft............................................................ 2-24
Technical Engine S p e c ific a tio n s ...................... 1-6
C rankshaft Rear Main S e a l ............................... 2-25
Torque S p e c ific a tio n s ........................................ 1-9
Upper Rear Main Seal R e p a ir............................. 2-26
Reference In fo rm a tio n ........................................ 1-11
Lower Rear Main Oil Seal R e p la c e m e n t......... 2-27
6.2 Liter Diesel Service In fo rm a tio n ...................... 1-16
Main Bearings ................................................... . 2-28
O peration In Snow (Diesel E n g in e s ) ............... 1-16
C onnecting Rod B e a r in g s ................................. 2-30
S tarting the Diesel E n g in e ................................. 1-16
Rod A ssem bly ..................................................... 2-30
Em ergency “ Jum p S ta rtin g ” .............................1-18
Torsional Damper 6 .2 L ........................................2-31
Diesel M a in te n a n c e .............................................1-18
C a m s h a ft.............................................................. 2-31
Engine Oil A d d itiv e s .............................................1-19
C am shaft Bearings ............................................ 2-32
Diesel Engine Oil Usage ....................................1-19
F ly w h e e l................................................................ 2-33
Used Lube Oil A nalysis W arning V a lu e s .........1-20
Front C o v e r...................... ..................................... 2-34
2. Engine System s and C o n s tr u c tio n ...................... 2-1
Exhaust M a n ifo ld s ...............................................2-34
Engine Design Features ........................................ 2-1
Lubrication S y s te m ............................................ 2-35
6.2L Valve Train ................................................... 2-3
Engine and Transm ission Oil C ooler
Diagnosis, A ll M o d e ls ................................... 2-37
1985 and Later Rocker Arm A s s e m b ly ............. 2-4
Oil F iller T u b e ....................................................... 2-38
Roller H ydraulic L i f t e r s ......................................2-5
Vacuum P u m p ..................................................... 2-40
Roller L ifte r W ear — Diesel E n g in e s ............... 2-10
C ooling S y s te m ................................................... 2-45
Valve L ifte r D ia g n o s is ........................................ 2-10
C ooling System D iagnosis ............................... 2-46
C ylinder H e a d ........................................................2-12
Fan C lutch D iagnosis ........................................ 2-48
Pre-Com bustion C h a m b e rs ............................... 2-13
W ater P u m p ..........................................................2-50
C ylinder C a s e ........................................................2-2
Broken G low Plug T ip .......................................... 2-13
R a d ia to r ................................................................ 2-51
Servicing C ylinder Head and G a s k e t............... 2-13
C ooling System S c h e m a tic ............................... 2-55
V-8 Diesel Head G asket Leakage .................... 2-13
1985 C ooling S y s te m .......................................... 2-55
V-8 Diesel Head G asket In sta lla tio n
C h e c k lis t............................................................ 2-14
Low C oolant Lamp In o p e ra tiv e ........................ 2-57
Leaking C ylinder Head G a s k e t........................ 2-15
Low C oolant Lam p “ O n” A ll the T im e ............. 2-58*
Base Engine T ro u b le s h o o tin g ...........................2-60
Valve Stem C le a ra n c e ........................................ 2-18
3. Charge A ir S y s te m ................................................... 3-1
Valve Spring T e n s io n .......................................... 2-18
A ir Flow To C om bustion C h a m b e r ...................... 3-1
Inspection (Timing C h a in ) ................................. 2-18
4. Fuel System . . : ............................................ .......... 4-1
Valve G uide B o r e s ...............................................2-19
4A. Low Pressure Fuel Delivery S y s te m ............. 4-1
Valve S e a ts ............................................................ 2-19
Fuel System C o m p o n e n ts ............................... 4-1
Page
Fuel Return S y s te m .......................................... 4-1
Fuel R ecom m endations .............................4-2
Page
S tatic T im in g ..................................................... 4-94
Fuel Tank C o m p o n e n ts ............................... 4-3
Checking Probe H older A lignm ent For
Tim ing A c c u r a c y ........................ ................. 4-95
1982-1983 W ater Drain Syphon Valve
(Figure 4 - 5 ) ................................................. 4-7
C hecking Or A d ju stin g Pump T im ing
(S ta tic ).............................................................. 4-96
Diesel Fuel C o n ta m in a tio n ............................. 4-8
Pump Tim ing Mark Location and W hite
Smoke At I d le .................................................4-97
Diesel Fuel System C leaning Procedure .4-9
M echanical Fuel P u m p s ................................. 4-12
6.2L Diesel C alifornia Engine Tim ing “ C-K”
W ith YF5 C alifornia Em issions Light
Duty 6.2L D ie s e l.......................................... 4-100
How the M echanical Fuel Pump W orks .. 4-12
T im ing Meters ................................................. 4-100
Fuel Pump S e rv ic e ............................................ 4-13
Injection N o z z le s ............................................ 4-101
M echanical Fuel Pump T e s t s .................... 4-13
Nozzle T e s tin g .................................................4-104
A voiding A ir In ta k e ........................................4-14
D iagnosing A ir In Fuel L in e s ...................... 4-15
O scilloscope Pattern, Fuel Injection
P u m p .............................................................. 4-106
1982-83 Prim ary Fuel F i l t e r ........................ 4-16
C a v ita tio n ..........................................................4-106
Line H e a te r..................................................... 4-17
Fast (Cold) Idle Speed S y s te m ...................... 4-107
Fuel Lines and L ift P u m p ............................. 4-11
Secondary Fuel F ilte rs ................................. 4-18
5. Em ission S y s te m s ................................................... 5-1
Fuel F ilt e r ........................................................4-21
5A. General Em ission S y s te m s .............................5-1
Fuel F l o w ........................................................4-23
Crankcase V entilation S y s te m ..................5-2
W ater In Fuel .................................................4-24
Crankcase Depression Regulator, CDR . .5-2
Model 80 Fuel F ilte r Seal L e a k a g e ........... 4-27
Exhaust Gas R ecirculation, EGR ............. 5-4
Fuel F ilte r/W a te r S eparator ...................... 4-28
EPR/EGR S o le n o id s ....................................5-7
M o d ific a tio n s To M odel 80 Fuel Sentry For
DDA (G & P) A p p lic a tio n s ........................ 4-30
High Pressure Fuel Delivery S y s te m ......... 4-32
4B. High Pressure Fuel Delivery S y s te m ............. 4-33
Federal EPR/EGR System O peration . . . .5-8
EGR/EPR Problem D ia g n o s is .................... 5-11
LL4 Model — Vacuum R egulator Value
(V R V )............................................................5-12
Fuel Injection P u m p .......................................... 4-33
T hrottle Position S w itch A d justm ent Tool 5-13
Injection Pump D e s c rip tio n .............................4-34
T ransm ission Vacuum R egulator Valve
A djustm ent ( L L 4 ) ......................................5-16
Injection Pump O p e ra tio n ............................... 4-35
Injection Pump R o to r........... ............................ 4-53
In jection Pump R e p a irs ....................................4-56
1982, 1983 and Early 1984 Drive Shafts
W ith a R etaining C lip (R in g )........................ 4-70
Pressure Testing O f Fuel Injection Pump
On the B e n c h .................................................4-89
High A ltitu d e A d justm e nt, 1982 “ C-K” Trucks
W ith 6.2L Diesel Engine and LH6
(Light Duty E m is s io n s )................................. 4-92
High A ltitu d e A d justm e nt, 1983 and Later
“ C-K-P-G” Trucks W ith 6.2L Diesel
Engine and LL4 (Heavy Duty) or LH6
(Light Duty) E m is s io n s ................................. 4-93
5B. C a lifornia (NB2) Diesel E lectronic
C ontrol System (D E C S )............................... 5-18
1984-1985 DDAD 6.2L D EC S.................... 5-18
E lectronic Vacuum M odulated EGR
LH6 6.2L C a lifornia D ie s e l..................5-19
1985 D iagnostic M o d e s ...........................5-24
DDC Tool Check 6 .2 L L H 6 ...................... 5-26
1984 Diesel D iagnostic C ircu it Check .. 5-29
1985 DECS w ith On-Vehicle Self
D ia g n o s tic s .......................................... 5-29
1985 D iagnostic C ircuit C h e c k ............. 5-32
E lectronic C ontrol M odule (E C M ).........5-34
Page
Page
1984 C a lifo rn ia 6.2L Diesel ECM Usage 5-35
The D-Truck (CUCV) System is
Com posed o f ...............................................6-24
1985 C a lifornia 6.2L Diesel ECM Usage 5-35
1984 ECM C heck 6 .2 L (L H 6 ).................... 5-38
Engine Speed Sensor (R P M )..................5-44
Exhaust Gas R ecirculation Control
(EGR)....................................................... 5-48
EPR V a lv e ................................................... 5-50
System Operation, D -T ru c k ...........................6-26
G low Plug System T roubleshooting Procedure,
D -T ru c k ...................................................................6-26
1985 6.2L (LH6/LL4) G low Plug
Control System, CKG P-Truck........................ 6-34
Desired EGR Pressure C alculation . . . .5-51
1983 Diesel G-Truck Engine Run-On, 6.2L
Diesel w ith Base Engine W arning Lights . .6-37
EPR Solenoid Electrical Check
(1984 & 1985).......................................... 5-56
6.2L Diesel Drive Belts, 1982-1984 C/K/P/G
Truck W ith 6.2L Diesel E n g in e ...................... 6-38
EPR Vacuum Check (1984 & 1985).........5-58
Strain Gage MAP S e n s o r........................ 5-63
7. D ia g n o s is ...................................................................7-1
MAP S e n s o r ...............................................5-64
G eneral/M ech anical D iagnosis ........... ............... 7-1
T hrottle P osition Sensor, T P S ................5-70
General D iagnosis C h a r ts ................................. 7-1
1984 & 1985 TPS C h e c k ...........................5-70
General D iagnosis C ondition s ........................ 7-15
T h ro ttle P osition Sensor, TPS
A d ju s tm e n t............................................ 5-76
Smoke D iagnosis P rin c ip le s ............................. 7-15
Torque Converter C lutch C ontrol .........5-78
W hite Sm oke D iagnosis C h a rt...........................7-18
Cold Advance C ircuit, C A C .................... 5-84
Rough Idle D ia g n o s is ...........................■£?......... 7-19
6. E lectrical S y s te m ..................................................... 6-1
S tarting S y s te m ....................................................... 6-1
Black Smoke D iagnosis C h a rt...........................7-17
G low Plug R esistance P ro c e d u re .................... 7-23
Starter M o t o r ....................................................... 6-1
Rough Idle/P erform an ce D iagnosis
C o n d itio n s ....................................................... 7-24
B a tte rie s ................................................................ 6-4
M.P.G. D iagnosis P rin c ip le s ............................... 7-24
Block H e a te r..........................................................6-4
Fuel System D ia g n o s is ......................................7-26
G low P lu g s ............................................................ 6-4
D iagnosis of Fuel System C o n d itio n s ............. 7-27
G low Plug Design C onsiderations ..................6-6
Brakes D iagnosis — Diesel V e h ic le s ............. 7-29
Electro-M echanical Thermal C o n tr o lle r .........6-8
Diesel Engine Oil Leak D ia g n o s is .................... 7-29
E lectronic M odule G low Plug C o n tro lle r.........6-9
System O peration, (Engine Cold-Pre-Glow) . .6-12
General G low Plug System D iagnosis ............... 6-14
RTV Sealer and G asket E lim in a to r ...................... 7-30
Explanation of A bbreviations ...........................7-33
Procedure 1. C hecking Cranking S p e e d ............. 7-33
Prelim inary C h e c k s ............................................ 6-14
Procedure 2. C hecking fo r Adequate
Supply of Fuel to Injection Pump .................... 7-34
G low Plug C o n troller and Advanced
Engine T im ing .................................................6-15
Procedure 3. M easuring Housing Pressure
and Transfer P re s s u re ........................................7-35
Prelim inary D iagnosis W ith A m m e te r............. 6-16
Procedure 4. C hecking for A ir L e a k s .................... 7-38
1982-1984 6.2L Diesel G low Plug
System D iagnosis .......................................... 6-17
A ir Leak D ia g n o s is ...............................................7-38
Procedure 5. Causes of Underrun or S talling . . . 7-39
Installation of G low Plug System Inhibit
S w itc h ................................................................ 6-23
Procedure 6. C hecking For S ticky or S tuck
Advance M e c h a n is m .......................................... 7-40
Tools fo r D ia g n o s is ............................................ 6-14
D-Truck (CUCV) M ilitary 6.2L (LL4) PTC
Glow Plug S y s te m ...............................................6-24
8. G lo s s a ry .....................................................................8-1
1. General Information
and Maintenance
General Description
The 6.2L Diesel Engine is a 90° V-8 configuration using conventional push rods. It is a four stroke cycle operation
and naturally aspirated; it does not use a turbocharger for air induction.
This is an engine designed, engineered, and tested for demanding light truck applications — w ith em phasis on fuel
efficiency and em issions control see Fig. 1-1.
VACUUM
PUMP
VALVE COVER
WATER CROSSOVER
HOUSING
WATER PUMP BACKING
PLATE
OIL FILLER
TUBE
WATER PUMP
TIMING CHAIN
& SPROCKETS
PUMP DRIVE
GEAR
DIP STICK
PUMP DRIVEN
GEAR
TORSIONAL
DAMPER
OIL PAN
Figure 1-1, 6.2L Major Components
1-1
1. General Information and Maintenance
Engine Identification
A. #1 C Y L IN D E R IN TA K E R U N N E R — A steel stam p placed on the engine part way through the assembly
process, is located on the block under the #1 inlet runner. The stamp identifies the broadcast code, which
essentially defines the engine configuration, plus the month and date of build. A typical marking would be a
broadcast code UHH0311, indicating the engine was built on March 11.
B. T H E TR A C EA B ILITY LABEL glued to the engine contains tw o bar codes. The #1 code would include the
number 10, indicating an “ engine” , plus the broadcast code, which could be 1 of 37 codes presently released (i.e.,
UHH). The #2 bar code w ould contain a com puter letter, plus com ponent identification, com ponent m anufacturing
location, Julian date and a serial number. As an example, the first piece of inform ation on the bar code would be a
letter “ T” , w hich is sim ply for program m ing in the computer. The next inform ation would be a number 10 to define
the com ponent as being an engine. The next bit of inform ation would be the letter “ R” to signify the product was
made at the Moraine Engine Plant and the Julian date follows, w hich for March the 11th, the 70th day of the year,
would be 070. After the date the serial number of the engine appears, which is started new for each broadcast code
at the beginning of the Model Year. For each of the 36 broadcast codes there w ill be a separate set of serial
numbers starting w ith #1 for the 1983 M.Y. and continuing until the last product of the current Model Year is
manufactured.
BROADCAST CODE
UHH
/
SUFFIX
03
1
MONTH
11
t
DAY
SUFFIX CODES
T — 1982
U — 1983
F — 1984
D - 1985
H — 1986
J — 1987
C. E N G IN E PLA N T IN -PR O C E S S BAR C O D E ID E N TIFIC A TIO N — Top of left-hand rocker cover consists of
numerical codes to identify type of engine and in-plant serial number for internal use only. Cannot be used to
reference engine in communication with the engine plant.
D. WATER PU M P — Cast identification on front of water inlet tube, depressed cast numbers. Cast date alpha and
3 numbers. Pattern number alpha and 1 number.
E. C Y L IN D E R H E A D — Drill points on end o f head to identify internal machining changes and type of head.
F. IN L E T M A N IF O L D — Cast identification on top of #4 inlet runner (right side— rear). Raised cast numbers. Cast
date and shift underneath.
G. C Y L IN D E R C A SE — Casting plant pattern identification. Raised cast in clock to show tim e of casting. Pattern
number in valley under inlet manifold.
H. C Y L IN D E R C A S E — Cast identification on top of left-hand flywheel housing surface. Raised cast numbers
w ith cast date underneath. Pattern number to right of cast number. (CFD) Central Foundry Defiance.
I. EXH A U ST M A N IF O L D — Cast identification on outside face. Raised cast numbers. Pattern number and date
cast clock casting plant ID.
J. IN JE C T IO N PU M P — Printed plate riveted to left side of pump body. Model number and serial number.
K. (TPS) 6 D IG IT ID E N T IF IE R Throttle
Position
Switch
1-2
1. General Information and Maintenance
Figure 1-2, Engine Identification.
1-3
1. General Information and Maintenance
L H 6
(C )
E n g in e
S p e c ific a tio n s
General Engine Description
• M O D E L ......................................................................................................................................................................................LH6
• REGULAR PRODUCTION OPTION (RPO) CODE < 8 5 0 0 LBS. G V W R ........................................................................... LH6
• VEHICLE IDENTIFICATION NUMBER (VIN) C O D E ................................................................................................................. C
• ENGINE TYPE.........................................................................................4-STROKE CYCLE 90° V-8 NORMALLY ASPIRATED
• COMBUSTION CHAMBER T Y P E ......................................TURBULENCE SWIRL PRE CHAMBER (RICARDO COMET V)
Firing Order.................................................................................................................................................................... 1-8-7-2-6-5-4-3
Cylinder B lo c k ........................................................................................................................Cast Iron with Combined Cylinders
Valve T im in g ................................................................................................................... Chain and Sprockets (Overhead Valves)
Bore and S tro k e .............................................................................................................................. (101mm (3.98") x 97mm (3.80")
D isplacem ent....................................................................................................................................... 6.2L (6217 cc) (379.4 cu. in.)
Horsepower L H 6 ........................................................................................................................130 Net H.P. (97 Kw) @ 3600 RPM
Torque LH6 .............................................................................................................................. 240 lb. ft. (325.4 N-m) @ 2000 RPM
Volume of Acyl. at B D C ........................................................................................................................815.4048 cc (49.756 cu. in.)
Volume of Acyl. at T D C ................................................................................................................................ 37.8148 (2.3075 cu. in.)
Compression Ratio L H 6 .......................................................................................................................................................21.5 to 1
Dimensions & weight (approx.)
Length — mm (in.).......................................................................................................................................................750 (29.5)
Width — mm (in.)......................................................................................................................................................... 692(27.2)
Height — mm (in.).......................................................................................................................................................696 (27.4)
Weight — kg (lb s .).......................................................................................................................................................318(701)
Technical Engine Specifications
Injector n o zzle .............................................................................................................................. .... BOSCH DNOSD 248
Bmep — kPa (lb/in.2) ..................................................................................................................... .... 579 (83.9)
Fuel consumption — kg/hr (lb/hr)............................................................................................... .... 30.6 (67.6)
Specific fuel cons. — g/kW-hr (lb/bhp h r).................................................................................. .... 283.5 (.466)
Fuel pump suction at pump inlet
Maximum — kPa (in. Hg)
Clean system ............................................................................................................................ 20 (6)
Dirty system .............................................................................................................................. 41(12)
Airflow — m3/min (ft3/min) .......................................................................................................... .... 9.9 (350)
Air intake restriction, max. — kPa (in. H20)
(Dry type air cleaner)
Full load — dirty ..................................................................................................................... .... 5.0 (20)
clean ..................................................................................................................... .... 2.5(10)
Exhaust temp. — °C ( ° F ) ............................................................................................................ .... 657 (1230)
Exhaust flow — m3/min (ft3/m in)................................................................................................. .... 30.9 (1090)
Exhaust back press., max. — kPa (in. Hg) Full lo a d ................................................................ .... 9 (2.5)
Coolant flow — litre/min (gal/m in)................................................................................................. 249 (66)
Max. top tank temp, allowed — °C ( ° F ) .................................................................................... .... 99 (210)
Heat rejection — kW (Btu/min)........................................................................................................ 123.1 (7000)
Coolant inlet restriction, max. — kPa (in. H g)........................................................................... .... 10 (3)
Lubricating oil press., normal — kPa (lb/in.2) ........................................................................... .... 275-345 (40-50)
Lubricating oil temp., in-pan — °C ( ° F ) .................................................................................... .... 82-127 (180-260)
Cooling index — Min air to boil
With 24 km/h (15 mph) maximum ram air — ° C (° F )................................................................ 40(104)
Deaeration — Air injection capacity (corrected — m3/min. (cfm ).......................................... .... 0.0085 (0.3)
Drawdown — Min requirement or 10% of total cooling system capacity —
whichever is larger — litre (q ts )................................................................................................. 3.8 (4.0)
1-4
1. General Information and Maintenance
Figure 1-3, Engine Performance Curve, 6.2L — Light Duty (LH6).
1. General Information and Maintenance
L L 4
(J )
E n g in e
S p e c ific a tio n s
General Engine Description
•
•
•
•
•
M O D EL........................................................................................................................................................................................ LL4
REGULAR PRODUCTION OPTION (RPO) CODE > 8500 LBS. G V W R ..............................................................................LL4
VEHICLE IDENTIFICATION NUMBER (VIN) C O D E ................................................................................................................. J
ENGINE TYPE .......................................................................................4-STROKE CYCLE 90° V-8 NORMALLY ASPIRATED
COMBUSTION CHAMBER T Y P E ...................................... TURBULENCE SWIRL PRE-CHAMBER (RICARDO COMET V)
Firing Order.....................................................................................................................................................................1-8-7-2-6-5-4-3
Cylinder B lo c k ........................................................................................................................ Cast Iron with Combined Cylinders
Valve T im ing....................................................................................................................Chain and Sprockets (Overhead Valves)
Bore and S tro ke...............................................................................................................................(101 mm (3.98") x 97mm (3.80")
D isplacem ent........................................................................................................................................6.2L (6217 cc) (379.4 cu. in.)
Horsepower 1982-84 LL4........................................................................................................ 135 Net H.P. (101 Kw) @ 3600 RPM
1983 LL4 Industrial........................................................................................... 145 Net H.P. (108 Kw) @ 3600 RPM
1985 L L 4 ............................................................................................................. 160 Net H.P. (119 Kw) @ 3600 RPM
Torque 1982-84 All LL4...........................................................................................................240 Lb. Ft. (325.4 N-m) @ 2000 RPM
1985 LL4 ........................................................................................................................ 275 Lb. Ft. (373 N m) @ 2000 RPM
Compression Ratio 1982 .....................................................................................................................................................20.3 to 1
1982-85
21.3 to 1
Dimensions & weight (approx.)
Length — mm (in.)....................................................................................................................................................... 750 (29.5)
Width — mm (in.)......................................................................................................................................................... 692(27.2)
Height — mm (in.)....................................................................................................................................................... 696 (27.4)
Weight — kg (lb s .)....................................................................................................................................................... 318(701)
Technical Engine Specifications
Injection pump (tim ing).................................................................................................................................STANADYNE DB2
Injector nozzle................................................................................................................................................ BOSCH DNOSD 248
Engine speed — r/min................................................................................................................................... 3600
Brake horsepower — kW (b h p )................................................................................................................... 108 (145)
Bmep — kPa (lb/in.2) ..................................................................................................................................... 579 (83.9)
Peak torque — N m (Ib-ft) @ r/min...............................................................................................................325.4 (240) @ 2000
Fuel consumption — kg/hr (lb /h r)...............................................................................................................30.6 (67.6)
Specific fuel cons. — g/kW-hr (lb/bhp-hr)....................................................................................................283.5 (.466)
Fuel pump suction at pump inlet
Maximum — kPa (in. Hg)
Clean system ....................................................................................................................................... 20 (6)
Dirty s y s te m ..........................................................................................................................................41 (12)
Airflow — m3/min (ft3/m in )............................................................................................................................ 9.9 (350)
Air intake restriction, max. — kPa (in. H20)
(Dry type air cleaner)
Full load — d irty ....................................................................................................................................... 5.0 (20)
— c le a n ..................................................................................................................................... 2.5(10)
Exhaust temp. — °C (°F ).............................................................................................................................. 657 (1230)
Exhaust flow — m3/min (ft3/m in )................................................................................................................. 30.9 (1090)
Exhaust back press., max. — kPa (in. Hg) Full load ................................................................................9 (2.5)
Coolant flow — litre/min (gal/min)...............................................................................................................249 (66)
Max. top tank temp, allowed — °C (°F )......................................................................................................99 (210)
Heat rejection — kW (Btu/m in)................................................................................................................... 123.1 (7000)
Coolant inlet restriction, max. — kPa (in. H g ) ...........................................................................................10 (3)
Lubricating oil press., normal — kPa (lb/in.2) ............................................................................................. 275-345 (40-50)
Lubricating oil temp., in-pan — ° C (° F )......................................................................................................82-127 (180-260)
Cooling index — Min air to boil
With 24 km/h (15 mph) maximum ram air — °C ( ° F ) ........................................................................... 40 (104)
Deaeration — Air injection capacity (corrected — m3/min. (cfm) ..........................................................0.0085 (0.3)
Drawdown — Min requirement or 10% of total cooling system capacity —
whichever is larger — litre (qts)...............................................................................................................3.8 (4.0)
1-6
1. General Information and Maintenance
Figure 1-4, Engine Performance Curve, 6.2L — Heavy Duty (LL4)
1-7
1. General Information and Maintenance
G E N E R A L DATA:
C R A N K S H A FT:
Type
90° V8 D iesel
D is p la c e m e n t
6.2 L ite r
RPO
LH6, LL4
Bore
101 mm
S troke
97 mm
C o m p re s s io n R atio
21.5:1
F irin g O rder
1-8-7-2-6-5-4-3
C Y L IN D E R B O R E :
Main
Journal
D iam eter
#1, 2, 3, 4
74.917-74.941
#5
74.912-74.936
Taper
.005 Max.
O ut O f Round
.005 Max.
M ain Bearing
C learance
#1, 2, 3, 4
.045-.083
#5
.055-.093
C ra n k s h a ft End Play
Crankpin
0.10-0.25
D iam eter
60.913-60.939
Taper
.005 Max.
D ia m e te r
100.987-101.065
O ut O f Round
.005 Max.
O ut o f Round
.02 Max.
Rod B earing C learance
.045-.100
T ap er-T hrust Side
.02 Max.
Rod Side C learance
.17-.63
P IS T O N :
(Bores
1-6)
C lea ra nce
★
B
.089-.115
★
Z
.112-.138
VALVE S YSTEM :
Bores 7 & 8 to be f it .013 L ooser
*B O H N PISTONS
*Z O LLN E R PISTONS
L ifte r
H y d ra u lic R oller
R ocker Arm R atio
1.5 to 1
Face A ngle (All)
45°
o
CD
Seat A n g le (All)
P IS T O N Rl NIG:
Seat R unout
Groove
Clearance
Compression
Gap
Oil
Top
.076-. 178
2nd
.039-.080
Top
.3-.55
2nd
.75-1.0
Groove Clearance
.040-.096
Gap
0.25-0.51
PISTO N PIN:
30.9961-31.0039
Clearance
.0101-.0153
Fit in Rod
.0081-.0309
C A M SH A FT:
Journal Diameter
Stem C learance
Valve
S pring
Ex
1.57-2.36
In
.026-.069
Ex
.026-.069
Pressure
C losed
356 @ 46.0
N @ mm
Open
1025 @ 35.3
In
7.133
Ex
7.133
#1, 2, 3, 4
55.025-54.975
#5
51.025-50.975
Journal Clearance
.026-.101
Cam shaft End Play
.051-.305
46
T IM IN G C H A IN D E F L E C T IO N :
New C hain
.500" Max.
Used C hain
.800" Max.
NOTICE: A ll d im e n s io n s are in m illim e tre s (mm)
u n le ss o th e rw is e s p e cifie d .
1-8
.89-1.53
In s ta lle d H e ig h t
Diameter
± Lift
.05
Seat W id th
.05
In
1. General Information and Maintenance
Torque Specifications
E N G IN E
Baffle to block and stud .............................
Bell or clutch housing.................................
Camshaft sprocket bolt (pump drive gear)
Camshaft thrust bearing.............................
Connecting rod n u ts ....................................
Cylinder head b o lts ......................................
Cylinder head temperature s w itc h ...........
Cylinder head water cover p la t e ................
Exhaust m a n ifo ld ........................................
Fast idle support to injection pump .........
Front cover to block ....................................
Fuel delivery (lift) pump to b lo c k ................
Fuel delivery (lift) pump plate to block. . . .
Fuel injection pump (driven) gear to pump
Fuel injection pump to front c o v e r ...........
Fuel line bracket to rocker cover studs . . .
Fuel lines to b ra ck ets.................................
Fuel lines to injection p u m p ......................
Fuel lines to n o zzle ......................................
Fuel lines to secondary filter and lift pump
Flywheel to cran ksh aft...............................
Glow p lu g s ...................................................
Glow plugs controller.................................
Glow plugs temperature switch ................
HPCA and fast idle temperature switch ..
Intake manifold to head .............................
Lifting brackets.............................................
Main brg. cap bolts inner.............................
Main brg. cap bolts outer ...........................
Nozzle to head .............................................
Oil fill tube n u ts.............................................
Oil pan bolts (except two rear)....................
Oil pan bolts two r e a r .................................
Oil pump to main brg. c a p ...........................
Pressure plate to flyw heel...........................
Rocker arm cover b o lts ...............................
Rocker arm sh aft..........................................
Sec. filter adapter to m anifold....................
Thermostat to crossover.............................
Torsional d a m p e r........................................
TPS and VRV to injection p u m p ................
Vacuum pump c la m p .................................
Valve lifter guide clam p ...............................
Water outlet crossover...............................
Water pump to front cover to b lo ck...........
Water pump plate to front c o v e r................
Water pump plate to water p u m p .............
Nm
FT. LBS.
25-37
34-50
25-35
34-48
55-66
75-90
13-20
18-27
44-52
60-70
(torque angle method)
10-12
7-9
25-37
34-50
18-26
25-35 *
18-27
13-20
25-37
34-50
20-30
27-40
4-7
6-10
13-20
18-27
25-37
34-50
13-20
18-27
3-4
2-3
20-32
15-24
20-32
15-24
17-19
24-26
60-70
80-95
08-12
11-16
13-20
18-27
10-12
7-9
7-9
10-12
25-37
34-50
33-44
45-60
104-118
141-160
93-107
126-145
44-60
60-80
13-20
18-27
6-14
4-10
13-20
18-27
60-74
80-100
25-35
34-48
13-25
18-35
37-44
50-60
25-37
34-50
25-37
34-50
140-162
190-220
5-7
4-5
25-37
34-50
13-25
18-35
25-37
34-50
25-37
34-50
13-20
18-27
18-27
13-20
1-9
1. General Information and Maintenance
SPECIAL TO O LS
J-6098-10
Cam shaft Brg Rem & Inst
J-33043-5
T.P.S. Gage Block
J-26999-10
Compression Gage Adapter
(.751-.773)
LL4 (700R4 Transmission)
J-29134
Piston Pin Retaining Ring
J-7049
Valve Guide Reamer Set
J-29664
M anifold Cover
J-5830
Valve Guide Reamer Set
J-29666
A irline Adapter
J-8037
Piston Ring Com pressor
J-29873
Nozzle Socket
J-22102
Front Cover Seal Installer
J-33042
S tatic Tim ing Gage
J-23523-D
Harmonic Balancer Remover
J-33153
Rear Main Seal Installer
J-8089
Wire Brush, Com bustion Chamber
J-33154
Rear Main Seal Packer
J-8101
Valve Guide Cleaner
J-26513
Valve Spring Compressor
J-8056
Spring Tester
J-6098.01
Cam shaft Brg Rem & Inst
J-8062
Valve Spring Compressor
Used W ith J-6098-10)
J-29834
Valve Lifter Remover
T.P.S. And Vacuum
J-6098-11, -12
Camshaft Brg Rem & Inst
J-33043-2
C646-.668)
Regulator Valve Gage Block
J-33043-4
T.P.S. Gage Block
(.602-.624)
J-33888
G-Van Engine Lifting Fixture
(No’s. 2, 3, 4, No. 5, No. 1)
J-34352
Diesel Fuel Hydrometer
J-29872
Pump Adjusting Tool
J-29843
Torx Bit Set
J-33300-100
Tach-N-Time
J-34029
DVOM
J-29075B
Diesel Nozzle
J-29125
DVOM
J-29079-125
Adapter Tester Set
J-34520
DVOM W ith Probes And Sockets
J-29079-95
6.2L Nozzle Adapter Kit
J33081
Advance Piston Hole Plug (Spring
Side) Seal Installer
J-34116
Cylinder Balance Rough Idle
Test Harness
J-9553-01
Drive Shaft Retaining Ring Remover
J-28552
Pressure Gage and Hose Assy. 0-15 PSI
J-29692-B
Injection Pump Holding Fixture
J-26999-12
Compression Gage
J-33198
Synkut Oil
J-34151
Housing Pressure Adapter
J-29601
Face Cam Setting Tool
J-34750
DECS — DDC Tool
J-29135
Cap Plug Set
J-29745-A
Injection Pump Drive Shaft Seal
Protector
1-10
1. General Information and Maintenance
Reference Information
6.2L DIESEL ENGINES
C Y L IN D E R BORE A N D PISTO N SKIRT SIZES
METAL STAMP
GRADE #
METRIC
(mm)
BOHN
ENGLISH
(in.)
ZOLLNER
METRIC
ENGLISH
(mm)
(in.)
* * CYLINDER BORE
METRIC
ENGLISH
(mm)
(in.)
A
100.885
100.898
3.9719
3.9724
100.862
100.875
3.9709
3.9719
100.987
101.000
3.97585
3.97635
B
100.898
100.911
3.9724
3.9729
100.875
100.888
3.9719
3.9720
101.000
101.013
3.97635
3.97685
C
100.911
100.924
3.9729
3.9734
100.888
100.901
3.9720
3.9725
101.013
101.026
3.97685
3.97735
D
100.924
100.937
3.9734
3.9739
100.901
100.914
3.9725
3.9730
101.026
101.039
3.97735
3.97785
E
100.937
100.950
3.9739
3.9744
100.914
100.927
3.9730
3.9735
101.039
101.052
3.97785
3.97835
G
100.950
100.963
3.9744
3.9749
100.927
100.940
3.9735
3.9740
101.052
101.065
3.97835
3.97885
“ Cylinder bores #7 and #8 are marked one size class smaller than actual size, i.e. a bore measuring “ B” class is
stamped “ A ” class.
O V ER SIZE D P IS TO N S (PLAN T USE ONLY)
SIZE
METRIC
BOHN
ENGLISH
ZOLLNER
METRIC
ENGLISH
“ CYLINDER BORE
METRIC
ENGLISH
X
101.029
101.041
3.9775
3.9780
101.009
101.022
3.9767
3.9772
101.130
101.143
3.98149
3.98200
Y
101.041
101.054
3.9780
3.9785
101.022
101.035
3.9772
3.9777
101.143
101.156
3.98200
3.98251
Z
101.054
101.067
3.9785
3.9790
101.035
101.048
3.9777
3.9782
101.156
101.169
3.98251
3.98303
— NOTE —
Service replacement pistons are fitted by measuring cylinder bores and honing as outlined
in the Service Manual for a piston fit.
1-11
1. General Information and Maintenance
Reference Information
6.2L DIESEL ENGINES
PISTON TO CYLINDER BORE CLEARANCE
(Except Bores #7 & #8)
CLEARANCE CYLINDER BORES
(#7 and #8 only)
METRIC
ENGLISH
Bohn
.085mm
.115mm
.0035"
.0045"
,102mm
,128mm
.0040"
.0050"
Zollner
.112mm
.138mm
.0044"
.0054"
.125mm
.151mm
.0049"
.0059"
CASE, CAMSHAFT, AND CAMSHAFT BEARINGS (mm)
#1
#2
#3
#4
#5
Camshaft Journal Dia.
55.025
54.975
55.025
54.975
55.025
54.975
55.025
54.975
47.025
46.975
Finished Cam Bearing I.D.
55.088
55.063
55.088
55.063
55.088
55.063
55.088
55.063
47.076
47.051
.113
.038
.113
.038
.113
.038
.113
.038
.101
.026
Cam Bore Dia. (Case)
59.17
59.12
58.92
58.87
58.67
58.62
58.42
58.37
50.42
50.37
Cam Bearing O.D.
59.30
59.25
59.05
59.00
58.80
58.75
58.55
58.50
50.55
50.50
.18
.08
.18
.08
.18
.08
.18
.08
.18
.08
Camshaft Brg. Clearance
Press Fit (Bearing to Case)
FUEL PUMP PUSH ROD
Pushrod O.D.
12.662/12.649
(.49857.4980")
Pushrod Guide
12.713/12.687
(.50057.4995")
Clearance .025mm-.064mm
(.001 "-.0025")
SU R FA C E F IN IS H E S
CRANKSHAFT
Oil Seal Diameter
Main Journals
Pin Journals
Thrust Face (front)
(rear)
SURFACE FINISH
MICROMETERS
.40
.32
.32
.50
.32
max.
max.
max.
max.
max.
1-12
Mating Face
SURFACE FINISH
MICROMETERS
1.60-2.80
CAMSHAFT
Lobes
Journals
.50 max.
.50 max.
CONNECTING ROD
CASE
Crank Bores
Cylinder Bores
Deck Face
HEAD
1.50-3.0
.40- .90
1.60-2.80
W rist Pin Bore
Crank Bore
Joint Face (rod & cap)
Side Face (both sides)
.20-.50
2.00 max.
1.25 max.
2.00 max.
1. General Information and Maintenance
Reference Information
6.2L DIESEL E N G IN E S
CAMSHAFT BEARINGS
BEARING #
DELCO MORAINE PART #
GOULD PART #
BEARING COLOR CODE
1
18007491
14028905
Plain (no color)
2
18007492
14028906
Pink
3
18007493
14028907
Yellow
4
18007494
14028908
Green
5
18007495
14028909
Orange
LIFTERS
LIFTER TO CLEARANCE
DIAMETER
Hydraulic Valve Lifter
23.41mm
23.39mm
.9217"
.9209"
Case Lifter Bore
23.47mm
23.45mm
.9240
.9232
.040mm
.080mm
.0015"
.0031"
MAIN BEARINGS
CRANKSHAFT
MAIN BRGS.
#1-#4
MAIN
BRG. #5
LOWER
BRGS.
COLOR CODES
FOR CASE,
CRANK & ALL
BEARINGS
.026 U.S.
74.917mm
74.925mm
74.912mm
74.920mm
.026 U.S.
Blue
2
.013 U.S.
, 4.925mm
74.933mm
74.920mm
74.928mm
.013 U.S.
Red
1
Std.
74.933mm
74.941mm
74.928mm
74.936mm
Std.
W hite
(plain for
Std. Bearings)
METAL
STAMP
CODE
UPPER
BEARINGS
79.850mm
79.842mm
3
79.842mm
79.834mm
79.834mm
79.826mm
CYLINDER CASE
MAIN BRG. #1-#5
BEARING CLEARANCES
MAIN BEARING CLEARANCES
(CALCULATED CLEARANCE)
* (ACTUAL CLEARANCE)
Bearings #1, 2, 3, & 4
.035mm
.073mm
.0014"
.0029"
.045mm
,083mm
.0018"
.0033"
Bearing #5
,040mm
.078mm
.0016"
.0031"
.055mm
,093mm
.0022"
.0037"
* Actual clearance is based upon estim ated bearing distortion for bearings #1,2,3, & 4 (.01 mm) and bearing #5 (.015mm).
1-13
1. General Information and Maintenance
Reference Information
6.2L DIESEL ENGINES
C R A N K S H A F T PIN JO U R N A LS A N D C O N . ROD B EA R IN G S
CRANKSHAFT PIN
JOURNAL DIA.
CONNECTING ROD
BEARINGS
ROD & CAP BEARINGS
COLOR CODES
CONNECTING ROD
BEARING I.D.
64.150mm
64.124mm
60.913mm
60.926mm
Green
Std. in Rod
.026 U.S. in Cap
.026 U.S.
(Green)
60.926mm
60.939mm
Yellow
Std. in Rod
Std. in Cap
Std.
(Yellow)
C O N N E C T IN G ROD TO C R A N K S H A F T JO U R N A L BEARING C LE A R A N C E
(Calculated Clearance)
,035mm
.090mm
* (Actual Clearance)
.0014"
.0035"
.045mm
.100mm
.0018"
.0039"
‘ Actual Clearance based upon estim ated bearing distortion of 0.01 mm.
PISTO N A N D ROD P IN S
PISTON PIN BORE SIZES
PISTON PIN O.D.
ROD PIN BUSHING BORE
COLOR CODE
METRIC
ENGLISH
METRIC
ENGLISH
METRIC
ENGLISH
31.0088
31.0114
1.2208
1.2209
30.9961
30.9987
1.2203
1.2204
31.012
31.027
1.2209
1.2215
Green
31.0114
31.0140
1.2209
1.2210
30.9987
31.0013
1.2204
1.2205
31.012
31.027
1.2209
1.2215
Orange
31.0140
31.0166
1.2210
1.2211
31.0013
31.0039
1.2205
1.2206
31.012
31.027
1.2209
1.2215
Blue
PIN C LE A R A N C E S
PIN TO PISTON BORE CLEARANCE
* PISTON PIN TO ROD PIN BUSHING CLEARANCE
METRIC
ENGLISH
METRIC
ENGLISH
.0101mm
.0153mm
.0004"
.0006"
.0081mm
.0309mm
.0003"
.0012"
Piston Pin PIN 14025530
Connecting Rod Assem bly P/N 14025523
— *NOTE —
No selective assembly for wrist pin to rod bushing.
1-14
1. General Information and Maintenance
Reference Information
6.2L DIESEL E N G IN E S
PRECHAMBER SELECT FIT TO CYLINDER HEAD
1982-84
PRECHAMBER
PLUG CLASS
DESIGNATION
1985
C-BORE DEPTH
IN HEAD (mm)
DEPTH OF PRECHAMBER
TOP FLANGE (mm)
RELATIONSHIP OF TOP PRECHAMBER
TO HEAD MATING FACE (mm)
4.989 (.1964")
5.014 (.1974")
5.039 (.1984")
5.014 (.1974")
-.0 0 0 (-.0 0 0 ")
+ .050 ( + .002")
M
W
4.963 (.1954")
4.9988 (.1964")
5.013 (.1974")
4.988 (.1964")
-.0 0 0 (-.0 0 0 ")
+ .050 (-.0 0 2 ")
N
X
4.937 (.1944")
4.962 (.1954")
4.987 (.1964")
4.962 (.1954")
-.0 0 0 (-.0 0 0 ")
+ .050 (-.0 0 2 ")
P
Y
C-BORE DIA. IN HEAD
FLANGE DIA. OF PRECHAMBER
PRESS FIT— PRECHAMBER
INTO PRECHAMBER BORE
39.675 (1.5620")
39.650 (1.5610")
39.701 (1.5630")
39.676 (1.5620")
0.051mm (.002")
0.001mm (.000")
VALVE STEM DIA. (mm)
VALVE GUIDE (mm)
CLEARANCE (mm)
, t
8.679
8.661
.3417"
.3410"
8.730
3.705
.3437"
.3427"
.026
.069
.0010"
.0027"
E h
9.454
9.436
.3722"
.3715"
9.505
9.480
.3742"
.3732"
.026
.069
.0010"
.0027"
Piston Protrusion Above B lo c k .......................................................... ..............................................................049" + .010"
Valve P ro tru s io n ................................................................................... ............... (max.) Exhaust — .035", Intake — .045"
Cylinder Head Thickness (Firedeck to rocker cover s e a t ) ............. ..........................................................3.858" + .005"
Cam Lobe L i f t ....................................................................................... ..............................................................280" ± .002"
1-15
1. General Information and Maintenance
6.2 Liter Diesel Service Information
Operation in Snow (Diesel Engines)
Driving in a heavy snow storm or in dry loose snow that may swirl around the front of the vehicle, w ill cause snow
to be drawn into the air intake system. Continuing to operate your vehicle under these conditions may cause the air
cleaner to plug causing excessive black smoke and loss of power. Should the air cleaner become plugged with
snow in extreme conditions the air cleaner element can be removed to allow the vehicle to be driven to a place
of safety.
Starting the Diesel Engine
The follow ing procedure is recommended for starting your diesel engine. Please note that a diesel engine starts
differently from a gasoline engine.
1. Apply the parking brake.
2. Autom atic Transm issions — Shift the transm ission to “ P” (Park) or “ N” (Neutral) (“ P” preferred). A starter safety
device is designed to keep the starter from operating if the shift lever is in any drive position. (If you need to
re-start the engine while the vehicle is moving, move the shift lever to “ N” ).
Manual Transm ission — Press the clutch pedal to the floor and shift the transm ission to Neutral. Hold the
clutch pedal to the floor w hile you are starting the engine. A starter safety device is designed to keep the starter
from operating if the clutch pedal is not pushed down all the way.
3. Turn the ignition key to “ RUN.” DO NOT TURN IT TO “ START.” W ith the ignition in “ Run,” the “ GLOW PLUGS”
light w ill com e on. This tells you that small heating elements, called “ glow plugs,” are warming part of the
engine for improved starting. When the engine is ready to start, the “ GLOW PLUGS” light w ill go out.
If the engine is warm, the “ GLOW PLUGS” light may not come on. This is normal.
During cranking, and/or after starting, the “ GLOW PLUGS” light may cycle on and off a few times. This is
normal; however, if the light cycles continuously, you should contact your authorized dealer as soon as practical.
4. W ith the “ GLOW PLUGS” light out, if the temperature is more than 0°C (32 °F), press down the accelerator pedal
halfway and hold; if the temperature is less than 0°C (32 °F), press the accelerator pedal to the floor and hold;
then crank the engine by turning the ignition key to “ Start.” Release the key when the engine starts.
Pumping the accelerator pedal before or during cranking w ill not aid in starting, and could keep the engine from
starting.
If the engine does not start after cranking 10 to 15 seconds, release the ignition key. W ait 10 to 15 seconds; then
repeat Step 4. If attem pting to start the engine after running out of fuel, refer to the “ N otice” under “ Fuel
Requirements” in this section.
Do NOT use starting “ aids” in the air intake system. Such “ aids” can cause immediate engine damage.
When the engine is cold, let it run for a few seconds before moving the vehicle. This w ill allow oil pressure to build
up. Increased operating noise and light smoke are normal when the engine is cold.
5. Apply the regular brakes and shift into the proper gear. Release the parking brake and drive off.
NOTICE: Do not leave your vehicle unattended with the engine running. If the engine should overheat, you would not be there to react to the
“TEMP” warning light or gage. This could result in costly damage to your vehicle and its contents.
W hile you are w aiting for the “ GLOW PLUGS” light to go out, fasten your seat belt and ask your passengers to do
the same.
C O LD W E A T H E R STA R TIN G (DIESEL E N G IN E S )
If you plan ahead for cold weather, starting and driving your vehicle should be no problem. The follow ing tips will
help assure good starting in cold weather.
Oil gets thicker as it gets colder, which slow s down the engine cranking speed. Your diesel engine runs through the
heat of com pression (and glow plugs when cold), rather than through the use of spark plugs as in a gasoline
engine. So, your engine must crank faster than a gasoline engine before it will start.
To be sure the engine can turn fast enough to start, use the proper viscosity engine oil when prevailing
temperatures drop below 0°C (32°F). (See the oil quality and oil viscosity recom m endations in this section.) Using
the proper viscosity oil w ill make starting easier down to -1 8 ° C (0°F). When prevailing temperatures drop below
- 1 8 °C (0°F), the engine block heater may be needed for starting.
1-16
1. General Information and Maintenance
If you park your vehicle in a garage, you should not need to use the block heater until the GARAGE temperature
drops below - 1 8 ° C (0°F), regardless of outside temperatures.
The engine block heater is designed to warm the block area, w hich w ill let the engine turn faster. To use the block
heater:
1. Open the hood.
2. Unwrap the electrical cord located in the engine com partment. (After using the block heater, be sure to properly
restow the cord, to help keep it away from moving engine parts.)
3. Plug the cord into any three-prong 110 volt outlet (normal household current).
NOTICE: If the cord is too short, use a heavy-duty, three-prong extension cord. Do not use an extension cord such as you would
use fo r a lam p because the cord may overheat.
• Use the block heater in accordance with the chart shown in Figure 1-5.
FIGURE 1-5, ENGINE BLOCK HEATER USAGE*
Viscosity
Grade Oil
32° to 0°F
(0° to - 18°C)
Below 0°F
(Below - 18°C)
30
2 HOURS
MINIMUM
8 HOURS
MINIMUM
15W-40
NOT REQUIRED
8 HOURS
MINIMUM
10W-30
NOT REQUIRED
8 HOURS
MINIMUM
*The tim es listed are m inim um times. It w ill not harm either the block heater or the vehicle to leave it
plugged in longer than the tim es stated.
In cold weather when the vehicle is to be parked for an extended period of tim e (overnight), the engine-block heater
may be used to reduce the engine warm-up time, and consequently, reduce the heater warm-up time.
At temperatures below - 7 ° C (20°F), Number 2-D diesel fuel may clog the fuel filter. This is normally caused by
paraffin in the fuel turning into wax as it gets colder. If the engine starts but stalls out after a short tim e and will
not re-start, the fuel filte r may be clogged. For best results in cold weather, use Number 1-D diesel fuel or a
“ winterized” Num ber 2-D fuel. (For more inform ation, see “ Diesel Fuel Requirements and Fuel System ” in Section 4
of this manual.
IF E N G IN E FA ILS TO START
1. Do NOT use starting “ aids,” such as ether or gasoline, in the air intake. Such “ aids” can cause im m ediate
engine damage.
2. Turn the ignition key to “ Run.” Check to be sure the “ GLOW PLUGS” light is out before turning the ignition key
to “ Start.”
3. If the “ GLOW PLUGS” light fails to go out, there may be a system m alfunction. If this happens, you can usually
still start the engine after w aiting a few seconds, but you should contact your authorized dealer as soon as
practical for a starting system check.
4. Be sure you have the proper viscosity oil and that you have changed it at the recommended intervals. Using oil
of improper viscosity may make starting more difficult.
5. If your batteries do not have enough charge to start the engine, see “ Emergency Starting” in this section on
page 1-18.
6. If the “ GLOW PLUGS” light is out and your batteries are sufficiently charged, but the engine w ill not start,
contact your authorized dealer.
1-17
1. General Information and Maintenance
7. If the engine starts, runs a short time, then stops, wax form ing in the fuel could be plugging the filter. (This can
happen if you use the im proper fuel at colder temperatures.) If this happens, contact your authorized dealer. (For
more inform ation, see “ Diesel Fuel Requirements and Fuel System” in Section 4 of this manual.)
Emergency “Jump Starting”
Vehicles equipped w ith diesel engines use tw o 12-volt batteries to provide the electrical energy needed for the glow
plugs and the starter. If the batteries become discharged, the diesel engine can be “ jum p started” using another
vehicle. The procedure for “ jum p starting” is the same as for a vehicle with a single battery. Jum per cables may be
connected to either battery. However, it is suggested that the connection be made to the battery on the right side
since it is closer to the starter and the resistance is less.
Diesel Maintenance
E N G IN E O IL A N D O IL FILTER
Oil and filte r change intervals depend upon truck usage. Figure 1-6 should assist in determ ining the proper oil and
filter change intervals.
Diesel fuel is really oil, thus it creates a lot of soot when it burns. A considerable am ount of this soot goes past the
rings into the crankcase. This dirties the lubricating oil. The only way to get rid of it is to change the oil and oil
filter at the recommended intervals.
A fter driving in a dust storm, change oil and filter as soon as you can.
The capacity when changing the oil and filte r is 7 quarts.
The oil filter used for both LH6 and LL4 is the AC model PF35.
Diesel engines have an oil cooler w hich is located in the radiator outlet tank with the transm ission cooler.
TYPE OF USE
CHANGE INTERVAL
• CHANGE ENGINE OIL AND FILTER EVERY 2,500
MILES (4,000 KILOMETERS) or 3 MONTHS,
WHICHEVER COMES FIRST.
• FREQUENT LONG RUNS AT HIGH SPEEDS AND
HIGH AMBIENT TEMPERATURES.
• OPERATING IN DUSTY AREAS.
• TOWING A TRAILER.
• IDLING FOR EXTENDED PERIODS AND/OR LOW
SPEED OPERATION SUCH AS FOUND IN POLICE,
TAXI OR DOOR-TO-DOOR DELIVERY SERVICE.
• OPERATING WHEN OUTSIDE TEMPERATURES
REMAIN BELOW FREEZING AND WHEN MOST
TRIPS ARE LESS THAN 4 MILES (6 KILOMETERS).
• OPERATING ON A DAILY BASIS, AS A GENERAL
RULE, FOR SEVERAL MILES AND WHEN NONE OF
THE ABOVE CONDITIONS APPLY.
• CHANGE ENGINE OIL AND FILTER EVERY 5,000
MILES (8,000 KILOMETERS) OR 12 MONTHS
WHICHEVER COMES FIRST.
Figure 1-6, Oil Change Interval.
— NOTE —
Always change oil and filter as soon as possible after driving in a dust storm. Also, always
use SF/CD or SF/CC quality oils of the proper viscosity.
1-18
1. General Information and Maintenance
OIL VISCOSITY
Engine oil viscosity (thickness) has a noticeable effect on fuel economy. Lower viscosity grade engine oils can
provide increased fuel economy; however, higher temperature weather conditions require higher viscosity grade
engine oils for satisfactory lubrication. The chart shown in Figure 1-4 lists the engine oil viscosities that w ill provide
the best balance of fuel economy, engine life and oil economy.
Engine Oil Additives
C A U TIO N —
DO N O T USE A N Y S U P P LE M E N TA L O IL A D D ITIVES. U SIN G O IL A D D ITIV E S
M A Y CAUSE E N G IN E D A M A G E.
DIESEL ENGINES USE THESE SAE VISCOSITY GRADES
I
I
I
I
SAE 30 PREFERRED
l
i
SAE 15W - 40
100
80
*F - 2 0
Am.
’C -3 0
20
T “
30
-* -r
40
TEMPERATURE RANGE YOU EXPECT BEFORE NEXT OIL CHANGE
Figure 1*7, Ambient Temperature Range For Engine Oil.
Diesel Engine Oil Usage
A.P.I. OIL CLASSIFICATIONS
A.P.I., the American Petroleum Institute, has devised a service classification system based on ten classes. Gasoline
engine oils are described in six and diesel engines are described in four. Generally, the higher the letters in a class,
the more an oil is required to do.
A.P.I. service classifications of engine oils refer to the performance characteristics of the oils and types of services
they can be used in.
1-19
1. General Information and Maintenance
R E C O M M E N D E D O IL
Use engine oils labeled w ith the A.P.I. (American Petroleum Institute) designations SF/CC and CD. The A.P.I.
designations are listed somewhere on the oil can, usually on the top or label.
Several different designations may appear on the can. Be sure the oil has BOTH the SF and the CC or CD
designations, regardless of the order in which they appear on the oil can.
SF/CD (best choice) and SF/CC (acceptable) oils combine excellent film strength w ith the best available additive
package to prevent wear and protect against piston ring sticking at higher mileages. DO NOT USE SAE 10W-40
OILS IN THE 6.2L DIESEL ENGINES.
Used Lube Oil Analysis Warning Values
F R E Q U E N C Y O F LUBE O IL S A M P L E S FO R A N A LYSIS
The interval at w hich used lube oil samples may be obtained for analysis can be scheduled for the same period as
when other preventative m aintenance is conducted. For example, in highway vehicle applications, a sam ple may be
obtained every 2,500 m iles when engines are brought in for fuel and coolant filter replacement.
USED LUB O IL A N A L Y S IS PR O G R A M
A used lube oil analysis program is useful for monitoring the condition of the crankcase oil in all engines.
Primarily, used lube oil analyses indicate the condition of the oil but not necessarily the condition of the engine.
Never tear down an engine based solely on the analysis results obtained from a single used oil sample. However,
the condition of the engine should be investigated using conventional mechanical and/or electronic diagnostic
instrum ents. Frequently, visual inspections are all that is required to detect problem areas related to engine wear. It
is also prudent to obtain another oil sample from the suspected distressed unit for analysis.
Abnorm al concentrations of some contam inants such as diesel fuel, coolant, road salt, or airborne dirt cannot be
tolerated for prolonged periods. Their presence w ill be reflected in accelerated engine wear, w hich can result in less
than optim um engine life. The oil should be changed im m ediately if any contam ination is present in concentrations
exceeding the warning lim its given.
Experience in specific engine applications operating specific model engines is a prerequisite for proper
interpretation of laboratory used lube oil sam ple analysis results. It is imperative to remember, in scrutinizing
laboratory used lube oil sam ple results, that it is the change in value or deviation from baseline data obtained from
the new oil (same brand or mixture of brands) that is significant. This is especially im portant to remember in
investigations such as wear metal analysis, total base number and viscosity determinations.
1-20
1. General Information and Maintenance
NOTES
1-21
2. Engine Systems
and Construction
Engine Design Features
The 6.2L Diesel engine features overhead valves & stainless steel swirl pre-chambers. It is an over square design;
that is the bore is larger than the stroke. This provides higher RPM for heavy duty usage. The 6.2L is built in 2
versions. The LH6 Lt-duty is for use in 6,000-8,500 GVW Lt. Duty trucks and has 46mm diam eter intake valves and
42mm diam eter exhaust valves. The LL4 Heavy duty version is for use in trucks in the 8500-10,000 GVW range and
has 50mm diam eter intake valves and 42mm diameter exhaust valves in 1982 and 1983. The 1984 and later LL4
versions w ill use 46mm diam eter intake valves and 38mm diameter exhaust valves. The 1985 Calif. LH6 uses 46mm
intake and 39mm exhaust valves. The firing order is 1-8-7-2-6-5-4-3 and #1 cylinder is left bank forward.
Cylinders #1, 3, 5, 7 are on the left bank and cylinders #2, 4, 6, 8 are on the right bank.
This engine is sim ilar to a V-8 gasoline engine in many ways but major differences occur in the cylinder heads,
com bustion chamber, fuel distribution system, air intake m anifold and the method of ignition. The cylinder case,
crankshaft, main bearings, rods, pistons and w rist pins are a heavy duty design, because of the high com pression
ratio required in the diesel engine to ignite fuel. Ignition of the fuel in a diesel engine occurs because of heat
developed in the com bustion cham ber during the compression stroke. Thus, no spark plugs or high voltage ignition
are necessary for a diesel engine.
Intake and exhaust valves in the cylinder heads operate the same as in a gasoline engine but are of special design
and material for diesel operation. The special alloy steel pre-chamber inserts in the cylinder head com bustion
chambers are serviced separately from the head. W ith the cylinder head removed, they can be pushed out after
removing the glow plugs and injection nozzles. Glow plugs and injector nozzles are threaded for assembly into the
head. The nozzles are spring loaded and calibrated to open at a specified p.s.i. of fuel pressure.
Because the intake m anifold is always open to atm ospheric pressure, there is no vacuum supply and a vacuum
pump is required to operate accessories such as air conditioning, door diaphragms and cruise control.
The engine is designed w ith a 101mm (3.98 inch) bore and a 97mm (3.8 inch) stroke, w hich produces 6217 CC (379.4
cubic inches). The com pression ratio is 21.5 to 1. The cylinder head incorporates a 17 bolt head design which
locates 5 bolts around each cylinder. This helps gasket durability, by increasing clam ping load.
The cylinder head includes a high swirl pre-combustion chamber w hich mixes fuel and air to provide an efficient
fuel burn and low em issions. A glow plug is used to assist in starting this system. A special cavity in the piston top
further assists in m ixing the com bustion products for com plete burning.
The main bearing caps all use 4 bolts to provide a rigid support for the crankshaft and minimize stress.
The rolled fille t nodular iron crankshaft utilizes a torsional damper, tuned to reduce vibrations.
This engine uses roller hydraulic valve lifters running on a forged steel camshaft.
The fuel system includes a water sensor, w hich signals high water levels and a need for service. Additional water
separation, and a drain valve is provided at the filter.
A block heater is standard equipm ent to aid starting in severe weather.
2-1
1. Engine Systems and Construction
Cylinder Case
The cylinder case is made of one piece cast iron
com prised of a special alloy containing carbon, silicon,
and chrom ium . This mixture provides good elasticity,
and therm al expansion. The 6.2L is designed to match
fit the cylinder bore w ith the piston. This is done by
dividing the total diam eter tolerance size range of
100.987-101.065 mm (3.975-3.979) into 6 size ranges.
Each of the bore sizes is identified by a code letter
A-B-C-D-E-G. This identification is metal stamped on
the cylinder case pan rail adjacent to the proper
cylinder, “ A ” size pistons for “ A ” size cylinder bores
etc., by using this select fit method, the clearance is
controlled to .089-.138mm (.0035 in.-.005 in.). See
Figure 2-2.
There are 5 main bearings numbering 1 through 5 from
the front of the engine. There is an arrow on the cap
w hich points toward the front of the engine.
Figure 2-1, Cylinder Case.
Each main bearing cap is retained w ith 4 bolts in order
to provide a more rigid support for the crankshaft and
minimize stress. The caps are made of nodular cast
iron, and are torque driven in place on the machine
line before boring, just the same as they are finally
torque driven at assembly.
The center or number 3 bearing is the thrust bearing.
The main bearings are select-fitted to each of the 5
main bearing bores. The proper size code is stamped
on the pan rail at the corresponding main bearing bulk
head. The total diam eter size range of the main
bearing bores #1 through 5 is 79.826 - 79.850mm. The
spread of .024mm (.0096") is divided into 3 sizes. It will
be stamped 1-2 or 3 on the pan rail. Each of the sizes
is matched to the corresponding size of split bearing
insert in the case half only. The split bearing insert for
the main cap is match fitted to the crankshaft main
journal.
Figure 2-3 shows the plant chart for main bearing
installation. This m atches the main bearing journal
diam eter w ith the case bore to come up with the
proper size inserts.
These numbers 1, 2 & 3 are prim arily for plant use in
selecting the inserts of the standard, ,013mm (.0005 in.)
U.S., and ,026mm (.001 in.) U.S.
These three bearings w ill be used in the field to obtain
proper clearance on a crankshaft.
Figure 2-2, Bottom of Case.
CRANKSHAFT MAIN
JOURNAL DIAMETER
FRONT, FRONT
INTERMEDIATE
CENTER & REAR
INTERMEDIATE
MAIN BEARINGS
74.917
74.925
CYLINDER & CASE
MAIN BEARING BORE DIAMETER
79.834 f 4 |
79.826 1 1 1
79,850 i * > \
79.842 l ° l
79.842 ( A l
79.834 l “ l
1- 026 U.S. IN CASE
1- 026 U.S. IN CAP
1.013 U.S. INCASE
1-.026 U.S. IN CAP
1-STD IN CASE
1- 026 U.S. IN CAP
1- 026 U S. IN CASE
1.013 U.S. IN CAP
1-013 U.S. INCASE
1- 013 U.S. IN CAP
1 STD IN CASE
1-.013 U.S. IN CAP
1-.026 U S IN CASE
1-STD IN CAP
1-.013 U.S. IN CASE
1-STD IN CAP
1-STD IN CASE
1-STD IN CAP
1-.026 U.S. IN CASE
1-.026 U.S. IN CAP
1-.013 U.S. IN CASE
1-.026 U.S. IN CAP
1-STD IN CASE
1-.026 U.S. IN CAP
1- 026 U.S. INCASE
1.013 U.S. IN CAP
1-.013 U.S. IN CASE
1-.013 U.S. IN CAP
1-STD IN CASE
1-.013 U.S. IN CAP
1.026 U.S. INCASE
1-STD IN CAP
1- 013 U.S. IN CASE
1-STD IN CAP
1-STD IN CASE
1-STD IN CAP
BLUE
74.925
74.933
ORANGE
-
74.933
74.941
NOTE -
All values in Figure 2-3 are metric and
the undersize specification refers to the
change in running clearance when a pair
of bearings are fitted e.g. .001" U.S. half
fitted with a std. half would give a total
change in running clearance of .0005".
WHITE
74.912
74920
REAR MAIN
BEARING
BLUE
74.920
74.928
ORANGE
74.928
74.936
WHITE
Figure 2-3, Bearing Chart.
2-2
2. Engine Systems and Construction
Service w ill continue to selectively fit bearing halves in the field by using plastigage, trying to obtain a clearance of
.045-.083mm (.0018-.0032 in.) on #’s 1 thru 4, and .055-.093mm (.002-.0036 in.) on #5. The standard, .013mm (.0005 in.)
U.S. and .026mm (.001 in.) U.S., bearings are for dealer service in selecting those clearances.
6.2L Valve Train
VALVE TR A IN
1982-1984 RO CKER A R M & S H A F T D ESIG N
W ith the high com pression ratio of the pre-chamber diesel, there is m inim al valve-to-piston clearance. Because it is
im portant to have a rigid valve train that insures a precise valve train motion through the speed range, a shaft
supported valve rocker arm design is used. Nodular iron rocker arms w ith a steel backed bushing are used. The
shafts are bolted to case stanchions on the cylinder head. The design has a steel backed bronze alloy bushing
in the rocker arm w hich is final bored after being press fit into the cast arm. This bushing uses a performed
circum ferential oil groove and 2 cross oil grooves for directing lubrication to the mating shaft surface. Oil is
supplied to the rocker arm via the hollow push rod and the arm in turn has drilled passages that provide a flow
path for oil to the bushing.
The 1982 engine used a hardened steel spacer and a metric washer at the rocker shaft attachment. The 1983-84
engine uses an unhardened spacer and a steel cleat. The steel cleat has a large gap 90° to the bolt. This prevents
any closure, and the cleat spreads the load.
Spacer part # — New 14057297
— Old 14028990
1983-84 Cleat — 14057296
1983-84 Rocker Arm Assem bly 14061505
2-3
2. Engine Systems and Construction
1985 and Later Rocker Arm Assembly
Figure 2 -5,1985 and Later Rocker Arm Assembly.
• THE 1985 AND LATER ROCKER ARM ASSEMBLY CONSISTS OF:
1. Steel stam ped rocker arms.
2. A large diam eter steel shaft bolted directly to the cylinder head pedestals.
3. Individual plastic locater buttons for each arm.
The rocker arm is open-topped perm itting splash lubrication of the bearing surface.
• TO REMOVE THE ROCKER ARMS IT IS NECESSARY TO DO THE FOLLOWING:
1. Remove rocker arm assem bly from the cylinder head.
2. Insert a screwdriver in the bore of the rocker shaft, breaking off the ends of the nylon rocker arm retainers.
3. Using a pair of pliers, pry up on the flat tops of the retainers, removing them.
4. Remove the rocker arms.
• TO INSTALL THE ROCKER ARMS IT IS NECESSARY TO DO THE FOLLOWING:
1. Install the rocker arm or arms on the rocker shaft, lubricating them w ith engine oil. One com m on rocker arm
(Part #23500073) is used in all locations.
2. Center each arm on the Va inch hole in the shaft. Install a new nylon rocker arm retainer (Part #23500076) in each
1/4 inch hole, using a drift of at least V2 inch diameter.
2-4
2. Engine Systems and Construction
(ffW---
A 5MM BEAD OF 1052734 OR
1052915 R.T.V. MUST BE
APPLIED AND SEALER MUST
BE WET TO TOUCH WHEN
BOLTS ARE TORQUED.
NOTE: PUSH ROD INSTALLED
WITH PAINTED OR MARKED
Figure 2-6, Valve Train.
Roller Hydraulic Lifters
Roller hydraulic lifters are used to reduce the am ount of friction between the valve lifter and the cam shaft lobe. See
Figure 2-6. A requirement w ith the use of a roller lifter is a positive guide device to insure the roller w ill track
consistently. First; the line of action of lifter m otion is offset from the cam shaft center line, to reduce the skewing
m otion of the lifter during the cam opening and closing. Second, a lifter guide plate is used, to restrain lifter motion
to less than tw o degrees about its axis. A guide plate clam p holds 2 of the guide plates in position. The clam p is a
self-contained bolt attached to a bracket. And there are 4 lifters and 2 guide plates to every guide plate clamp.
1982-1983 guide plates are stamped steel. 1984 and later guide plates are sintered iron.
-
NOTE -
It is important that the lifter guide plates and retaining brackets are properly installed to
prevent lifter rotation; so it is suggested that after installing the guide plates and retainers,
to rotate the crankshaft by hand 720° which will cycle the camshaft 360° or one full
revolution. Make sure while doing this, that the lifters move up and down in the guide
plate. If the engine will not turn over by hand, then one of the lifters is not free to
move up & down in the guide plate.
2-5
1
2. Engine Systems and Construction
OPERATION
Oil is supplied to the lifter through a hole in the side of
the lifter body w hich indexes w ith a groove and hole in
the lifter plunger. Oil is then metered past the oil
metering valve in the lifter, through the push-rods to
the rocker arms. (Figure 2-7)
When the lifter begins to roll up the cam lobe, the ball
check is held against its seat in the plunger by the ball
check spring w hich traps the oil in the base of the
lifter body below the plunger. The plunger and lifter
body then raise as a unit, opening the valve. The force
of the valve spring w hich is exerted on the plunger
through the rocker arm and push-rod causes a slight
amount of leakage between the plunger and lifter body.
This “ leak-down” allow s a slow escape of trapped oil
in the base of the lifter body. As the lifter rolls down
the other side of the cam lobe and reaches the base
circle or “ valve closed” position, the plunger spring
quickly moves the plunger back up to its original
position. This movement causes the ball check to open
against the ball spring and oil from w ithin the plunger
is drawn into the base of the lifter. This restores the
lifter to zero lash.
ENGINE
VALVE CLOSED
ENGINE
VALVE OPEN
PUSH ROD
PLUNGER
LIFTER BODY
HECK BALL
SPRING
PLUNGER
RETURN
SPRING *
ROLLER
CHECK BALL
(OPEN)
CHECK BALL
(CLOSED)
Figure 2-7, Roller Valve Lifter Operation.
VALVE LIFTER SERVICE REMOVAL
Valve lifters and push rods should be kept in order so
they can be re-installed in their original position. The
push rods must be installed w ith painted end up. This
is necessary as the premium ball is located on the
upper end only.
1. Remove rocker arm covers.
2. Remove rocker arms.
3. Remove guide clam ps and guide plates. It may be
necessary to use mechanical fingers to remove the
guide plates.
4. Remove lifters using Tool J-29834 and a magnet
through access holes in cylinder head.
• DISASSEMBLY (Figure 2-8)
1. Remove the retainer ring w ith a small screwdriver.
2. Remove push-rod seat and oil metering valve.
3. Remove plunger and plunger spring.
4. Remove check valve retainer from plunger, then
remove valve and spring.
CLEANING AND INSPECTION
A fter lifters are disassembled, all parts should be
cleaned in clean solvent. A small particle of foreign
material under the check valve will cause m alfunction­
ing of the lifter. Close inspection should be made for
nicks, burrs or scoring of parts. If either the roller body
or plunger is defective, replace w ith a new lifter
assembly.
2-6
2. Engine Systems and Construction
ROLLER LIFTER INSPECTION
1. Roller should rotate freely, but w ithout excessive play.
2. Check for m issing or broken needle bearings.
3. Roller should be free of pits or roughness. If present, check cam shaft for sim ilar condition. If pits or roughness
are evident replace the lifter and camshaft.
LIFTER ASSEMBLY
1. Assem ble ball check spring and retainer into plunger, (Figure 2-6). Make sure retainer flange is pressed tight
against bottom of recess in plunger.
2. Install plunger spring over check retainer.
3. Hold plunger w ith spring up and insert into lifter body. Hold plunger vertically to prevent cocking spring.
4. Assemble oil metering valve and push rod seat and seat retaining ring in groove.
Lifters must be assembled w hile submerged in kerosene or diesel fuel and leak-down tested before placing into
service.
INSTALLATIO N
Prime new lifters by w orking lifter plunger w hile submerged in new kerosene or diesel fuel. Lifter could be damaged
if dry when starting engine.
Coat the roller and bearings of lifter with 1052365 lubricant or equivalent.
1. Install the lifters into the original position in the cylinder block.
2. Install valve lifter guide plate.
3. Install guide plate clamp. Crankshaft m ust be m anually rotated 720° after assembly of lifter guide plate clam p to
insure free movement of lifters in guide plates.
• PUSHROD
The pushrods have a different degree of hardness at each end. A paint mark at the hard end identifies it.
The reason for the additional hardness on the rocker arm end, is because the lifter no longer rotates and
consequently neither does the pushrod increasing wear spots. The pushrods could be installed the wrong way, so
mark the top of the pushrods as soon as you remove them from the engine.
2-7
2. Engine Systems and Construction
RO CK ER A R M S H A F T IN S TA LLA TIO N , 6.2L DIESEL
Rocker arm shafts may break if installed improperly. Uneven torquing causes stress at bolt holes.
The proper method to install rocker shafts is as follows:
1. Set engine balancer tim ing mark at TDC mark on engine.
2. Rotate engine 3 1/2 " counter clockw ise (measured on balancer) or to first lower water pump bolt (See Figure 2-9).
This procedure w ill position the engine so that no valves are close to a piston head. This is 30° BTDC.
3. Before installing bolts through shaft be certain that ring around shaft is installed w ith “ s p lit” at bottom (See
Figure 2-10) on 1982 models. On 1983 and later the split is 90° to the right. On 1985 and later no split ring
is used.
4. Snug both bolts on each shaft.
5. Tighten bolts evenly to 55 N.m. (40 lb. ft.) torque.
2-8
2. Engine Systems and Construction
Figure 2-10, 1982-84 Rocker Shafts.
2-9
2. Engine Systems and Construction
Roller Lifter Wear — Diesel Engines
Roller lifter wear, sticking, or looseness can be caused by high carbon content in the engine oil, w hich is the
product of com bustion and can be caused by a m alfunctioning EGR and/or EPR system.
When you encounter this type of condition, be sure the EGR and EPR systems are functioning properly and that
there are no exhaust leaks in the air inlet system. If the above systems are found to be OK, the operator of the
vehicle involved should be questioned about driving conditions and driving habits. Extended idle periods and/or low
speed operation w ill necessitate more frequent oil changes. Refer to the appropriate Owner’s Manual for
recommended oil change intervals for severe service driving conditions.
Valve Lifter Diagnosis
1. M O M E N T A R IL Y N O IS Y W H E N CAR IS STARTED:
This condition is normal. Oil drains from the lifters w hich are holding the valves open when the engine is not
running. It w ill take a few seconds for the lifter to fill after the engine is started.
2. IN T E R M IT T E N T L Y N O IS Y O N IDLE ONLY, DISA PPEA R IN G W H E N E N G IN E SPEED IS IN CR EASED:
Interm ittent clicking may be an indication of a pitted check valve ball, or it may be caused by dirt.
Correction: Clean the lifter and inspect. If check valve ball is defective, replace lifter.
3. N O IS Y AT S L O W IDLE O R W IT H H O T OIL, Q U IET W IT H CO LD O IL OR AS E N G IN E SPEED IS
IN C R EA SED :
High leak down rate. Replace suspect lifter.
4. N O IS Y AT H IG H CAR S P EE D S A N D Q U IET AT LO W SPEEDS:
a. High oil level — Oil level above the “ Full” mark allows crankshaft counterweights to churn the oil into foam.
When foam is pumped into the lifters, they will become noisy since a solid colum n of oil is required for proper
operation.
Correction: Drain oil until proper level is obtained. See PERIODIC MAINTENANCE Section.
b. Low oil level — Oil level below the “ A dd” mark allows the pump to pump air at high speeds which results in
noisy lifters.
Correction: Fill until proper oil level is obtained. See PERIODIC MAINTENANCE Section.
c. Oil pan bent on bottom or pump screen cocked or loose; replace or repair as necessary.
5. N O IS Y AT IDLE B E C O M IN G LO UDER AS E N G IN E SPEED IS IN C R E A S E D TO 1500 RPM:
This noise is not connected w ith lifter m alfunction. It becomes most noticeable in the car at 10 to 15 mph “ L”
range, or 30 to 35 mph “ D” range and is best described as a hashy sound. At slow idle, it may be entirely gone
or appear as a light ticking noise in one or more valves. It is caused by one or more of the following:
a. Badly worn or scuffed valve tip and rocker arm pad.
b. Excessive valve stem to guide clearance.
c. Excessive valve seat runout.
d. Off square valve spring.
e. Excessive valve face runout.
f. Valve spring damper clicking on rotator.
2-10
2. Engine Systems and Construction
To check valve spring and valve guide clearance,
remove the valve covers:
a. Occasionally this noise can be elim inated by
rotating the valve spring and valve. Crank engine
until noisy valve is off its seat. Rotate spring. This
will also rotate valve. Repeat until valve becomes
quiet. If correct is obtained, check for an off square
valve spring. If spring is off square more than 1/16"
in free position, replace spring. (Figure 2-11).
b. Check for excessive valve stem to guide clearance.
If necessary, correct as required.
Figure 2-11, Checking Valve Spring.
6. VALVES NOISY REGARDLESS OF ENGINE SPEED:
This condition can be caused by foreign particles or excessive valve lash.
Check for valve lash by turning the engine so the piston in that cylinder is on top dead center of firing stroke. If
valve lash is present, the push-rod can be freely moved up and down a certain amount w ith rocker arm held
against valve. If OK, clean suspected valve lifters.
Valve lash indicates one of the following:
a. Worn push-rod.
b. Worn rocker arm and/or shaft.
c. Lifter plunger stuck in down position due to dirt or carbon.
d. Defective lifter.
Checking of the above four items:
1. Look at the upper end of push-rod. Excessive wear of the spherical surface indicates one of the following
conditions.
a. Improper hardness of the push-rod ball. The push-rod and rocker arm must be replaced.
b. Improper lubrication of the push-rod. The push-rod and rocker arm must be replaced. The oiling system to
the push-rod should be checked.
2. If the push-rod appears in good condition and has been properly lubricated, replace rocker arm and recheck
valve lash.
3. If valve lash exists and push-rod and rocker arm are okay, trouble is in the lifter. Lifter should be replaced.
2-11
2. Engine Systems and Construction
Cylinder Head
The cylinder head (Figure 2-12) is a very heavy design and made of cast gray iron. It is a 17 bolt design that has 5
bolts positioned around each cylinder, to provide a more effective seal, and improve gasket retention.
Figure 2-12, Cylinder Head.
-
NOTE -
The cylinder heads for the LH6, LL4 and different model years are different. This is
because of different; pre-chambers, nozzles, compression ratios, and valve sizes. Consult a
G.M. Parts Book or Fiche, to determine the proper cylinder head.
Cylinder heads for 6.2L engines should be checked to verify the correct part for the application before installation
on the block. The follow ing inform ation is provided for determining that the correct part number head has been
received.
YEAR
1982
1982
1983-84
1983
1984
PART#
14079354
14079335
14079336
14079337
14079304
MODELS
C.K-1,2,3
C,K,P-2,3
C,K,G-1,2,3
C,K,G,P
C,K,G,P
ENGINE
CODE
C
J
c
J
J
NOZZLE
THREAD
M24x2
M24x2
M24x1.5
M24x1.5
M24x1.5
INTAKE
VALVE
46mm
50mm
46mm
50mm
46mm
EXHAUST
VALVE
42mm
42mm
42mm
42mm
38mm
2-12
2. Engine Systems and Construction
Pre-Combustion Chambers
A design feature is the Ricardo Comet V pre­
com bustion chamber w hich has a spherical chamber
which mixes the air and fuel by air swirl (Figure 2-13).
This assists in promoting high turbulence. This is an
ante-or divided com bustion chamber, having the major
chamber in the cylinder head and only a small space
between the piston and the cylinder head. Close piston
clearance produces high turbulence in the ante
chamber and promotes rapid com bustion. The charge
is forced out of the throat area, agitating the entire
mixture and resulting in more com plete com bustion.
This design has a broad speed operating range. It also
provides low noise and effective em ission control. The
pre-chamber is installed in the cylinder head flush to
+ .050 mm (.002 in.).
Broken G low Plug Tip
A burned out glow plug tip may bulge then break off
and drop into the pre-chamber when the glow plug is
removed. When this occurs the nozzle should be
removed and the broken tip removed through the
nozzle hole. It may be necessary to remove the
cylinder head.
Servicing Cylinder Head and Gasket
For removal, see the Service Manual.
V-8 Diesel Head Gasket Leakage
There are various reasons why a cylinder head may not seal, that should be detected before a head gasket is
replaced. Some may not be readily apparent to the technician because the theory of sealing is not fully understood.
First get an understanding of what is going on in the engine and what the gasket must accomplish. The pressure
w ithin the diesel engine cylinder is much higher than a gasoline engine, 1000 vs 600 psi.
The sealing concept is to use most of the clam ping load, about 75%, to seal the compression. This is
accom plished by placing a round wire ring inside of a thin metal shield that surrounds the cylinder bore. When the
bolts are tightened we literally have line contact around the bore between the cylinder head and the block. Because
it is line contact the pressure exerted by the ring to the head and block is extremely high. The clam ping load is
used to com press the metal ring. The body of the gasket is a few thousands of an inch thinner than the ring after it
is crushed. Therefore none of the clam ping load is used to crush the body. The colored rings around the various
ho'es in the gasket are a cured RTV sealer. The sealer is about .005 inches in thickness, on each side. It is thick
enough so that it gets crushed between the head and block. The sealer keeps the com bustion gases from going
into the coolant and obviously keeps the coolant from leaking out through the gasket.
The gasket has another feature that needs explanation. The wire ring must cross over the pre-chamber which
should be flush w ith the head. If the pre-chamber is recessed the clam ping load in that area w ill not be as great. If
it is exposed, the clam ping load beside the pre-chamber will not be as great.
Now it should be better understood that the sealing surface is the wire ring in the gasket where it contacts the
block and head. Any damage to these surfaces will result in gasket leaks. Use of the motorized wire brush or
grinder could remove a few thousands of metal. The head may then clam p the body of the gasket rather than the
sealing ring.
W hile the cylinder heads are o ff the engine, they should be carefully inspected for a number of possible conditions,
one of which is warpage. If any cylinder head is warped more than .006" longitudinally, .003" transversely, it should
be replaced; resurfacing is not recommended.
2-13
2. Engine Systems and Construction
M inor surface cracks in the valve port area of the cylinder head, especially between the intake and exhaust valve
ports, are not a normal condition. These surface cracks may affect the function of the cylinder heads and they may
require replacement for this condition. The use of m agnaflux or dye check is recommended as cracks in the
cylinder head that affect performance are not always readily visible to the naked eye, therefore m agnafluxing is
necessary.
There is an indentation in the block and head surface where the sealing ring contacts both parts. W hile this
appears to be quite deep, actual measurements have shown that the groove is only one or tw o thousands deep and
does not affect sealing. There are gaskets available that are used with .030 inch oversize pistons. Use of these head
gaskets w ill move the sealing bead outboard of the existing groove. These gaskets w ill be used in the various kits.
Another condition is one that is evident by looking at the gasket once it is located on the dowel pins on the block.
The sealing bead is only slightly larger in diam eter than the bore. The bead may extend into the cham fer at the top
of the cylinder which results in an uneven crush of the wire and after a few miles w ill result in a leak.
To check for this lay the old gasket on the block. Look at each cylinder, the gasket should be concentric w ith the
bore. It may help to pull the metal ring out of the gasket so the block is more readily visible.
Make sure that the bolt holes in the cylinder block are drilled and tapped deep enough. The head should be placed
on the block w ithout a head gasket. Then run a .005 feeler gage around the edge of the head. There should be no
clearance, this indicates that dowel pins are not holding the head off the block. Then by hand, screw each of the
bolts in. The bolts should screw in far enough to contact the head. This will indicate that the holes are drilled
deep enough.
The bolt threads should be wire brushed to clean them and then coated w ith a sealant lubricant (1052080). This
should be on the threads and under the heads of the bolts. This is critical so that the friction on the bolt is reduced
during installation. Do not put the oil in the bolt hole, an excessive amount of oil could cause a hydraulic lock and
prevent the bolt from tightening up. Do not paint the head gasket with a sealant. Sealants w ill som etim es attack
the RTV sealer w hich results in a leak.
V-8 Diesel Head Gasket Installation Checklist
• Wire brush head bolts to clean threads.
• Apply P/N 1052080 sealant to bolt threads.
• Oil underneath head of bolts.
• Dowel pins hold head off block.
• Dowel pins o ff location.
• No dowel pins.
• Cylinder heads warped more than .006 inches longitudinally and .003" transversely.
• Pre-chamber + .002" inches from head (.004" maximum)
• No damage in sealing ring area.
• No stam ps in seal area around water passage.
• W ater passage seal surrounds all water passages.
• No chips in bolt holes.
• Bolt holes in cylinder block drilled and tapped deep enough.
• Follow torque sequence and installation torque procedure.
2-14
2. Engine Systems and Construction
U SIN G TO R Q U E W R E N C H W IT H A D APTER
When using a torque wrench w ith an adapter, the reading on the torque wrench will not reflect the actual torque of
the bolt due to the extra length of the com bined torque wrench and adapter. To obtain the correct torque readings
in these cases use the follow ing formula: M ultiply the length of the torque wrench by the number of pounds of the
desired torque. Then add the length of the torque wrench to the length of the adapter. Divide the first answer by the
second answer and the result w ill be the correct torque reading. (Figure 2-14)
EXAMPLE:
1. MULTIPLY LENGTH OF TORQUE WRENCH 20 BY
DESIRED TORQUE 200 FT. LBS. 20 x 200 = 4000.
2. ADD LENGTH OF TORQUE WRENCH 20 TO
LENGTH OF ADAPTER 6 20 + 6 = 26.
3. DIVIDE FIRST ANSWER (4000) BY SECOND ANSWER
(26). 4000 + 26 = APPROX. 154 FT. LBS.
EXTENSION
154 FT. LBS. WILL BE THE READING
ON THE TORQUE WRENCH WHEN THE
DESIRED TORQUE OF 200 FT. LBS. IS
ACHIEVED AT THE NUT.
TORQUE WRENCH IS MEASURED FROM CENTER
OF SOCKET END TO PIVOT POINT IN HANDLE
OR IF SOLID TO END OF HANDLE.
TORQUE WRENCH AND ADAPTER MUST
BE USED ONLY IN A STRAIGHT LINE.
Figure 2-14, Computing Actual Torque With Adapter.
Leaking Cylinder Head Gasket
Pre-chambers must not be recessed into the cylinder head or protrude out of the cylinder head by more than .004"
or a head gasket leak may result.
This measurement should be made at two or more points on the pre-chamber where the pre-chamber seats on the
head gasket heat shield and sealing ring. Using a straight edge and a thickness gage or dial indicator, measure the
difference between the flat of the pre-chamber and the flat surface of the cylinder head. A slight variance from one
side of the pre-chamber to the other provided both sides are w ithin the tolerance will result in a good seal.
2-15
2. Engine Systems and Construction
External engine coolant loss on the 6.2L Diesel has generally been from the rear lower corner on the left hand
cylinder head and the front lower corner on the right hand cylinder head. This coolant loss condition is the result of
inadequate sealing around the core cleanout hole in the cylinder head. (Figure 2-15)
A contour shaped brass plug, P/N 14079353, has been developed to seal this core hole. In 1983 mid-year, the core
cleanout hole w ill be m achined and a plug installed in production. 1985 and later units w ill have this hole
elim inated.
To reduce cylinder head gasket coolant leakage conditions, the following procedure should be adhered to whenever
a cylinder head is removed for service:
TORQUE AND ANGLE TURN CONTROL TORQUING PROCEDURE FOR CYLINDER BOLTS.
This new torquing procedure is to be used on all 6.2L Diesel engines. It is to correct external and internal leak
conditions.
1. After the removal of the cylinder head and gasket, all cylinder head bolts and bolts holes m ust be cleaned of all
sealer (e.g. wire brush).
2. Check head and block for warpage overall .006 in. (.15mm) or .003 in. (,075mm) w ithin 6 inches and .003"
transversely.
3. W ipe all surfaces clean.
4. Install new head gasket, either use: Victor (green) 14066260 (internal com bustion leaks) or, Fel-Pro (red) 14066246
(external coolant leaks). Install the gasket over the dowel pins. The pre-chamber shields m ust be up.
5. INSTALLATION OF BRASS PLUG IN CYLINDER HEAD COOLANT CORE HOLE. (See Figure 2-15).
a. Check if a plug has been previously installed. If a plug is present, visually check condition. If plug appears
questionable, remove and replace.
b. Check cored hole for excessive roughness or casting irregularities. Use a file to remove burrs and break sharp
edges. Clean w ith a wire brush and wash with solvent.
c. Coat the sides of brass plug and the hole with Loctite 620; or 271, (GM #1052624 kit).
2-16
2. Engine Systems and Construction
Using an Arbor Press or vice, slowly press brass plug
into the hole using a flat steel plate or the plastic
installation tool from kit #14077197 to squarely load the
plug. Press in until plug is flush with head surface. Do
not use a hammer as plug may be damaged. Allow
Loctite to set 30 minites.
-
NOTE -
If the plastic installation tool is
available, you may use a hammer
along with the plastic tool. Install the
plug until it is flush.
Sequence.
6. REPLACE ALL HEAD BOLTS WITH PART #14077193.
7. Due to clearance on C-K vehicles, the left rear cylinder head bolt must be installed into the head prior to
installation. (Refer to Step 9 for sealing of bolt).
8. Carefully guide the cylinder head into place.
9. Coat the thread and bottom of the bolt head of the cylinder head bolts with sealing com pound 1052080 or
equivalent, and install bolts finger tight.
10. In sequence, torque all bolts to 25 N.m. (20 ft. lb.). (Figure 2-16).
11. In sequence, re-torque all bolts to 65 N.m. (50 ft. lb.). (Figure 2-16).
12. In sequence, turn each bolt an additional 90 degrees (V\ turn). This is to assure a more uniform bolt tension.
(Figure 2-16).
-
NOTE -
All four steps (10,11, and 12) must be done in sequence each time.
-
NOTE -
There is a new head bolt released. Part #14077193. It has more threads. This was done
to improve bolt stretch for improved clamp load retension. The above procedure can be
done with either the old or the new bolt. But the new bolt (14077193) is preferred.
-
NOTE -
Part #14077197 is a brass plug kit. It contains the following:
2 ■14079353 brass plugs
1 • plastic driver installation tool
2-17
2. Engine Systems and Construction
Valve Stem Clearance
NOTICE: Excessive valve stem to bore clearance w ill cause excessive oil com bustion and may cause valve
breakage. Insufficient clearance w ill result in noisy and sticky functioning of the valve and disturb engine
smoothness.
1. Measure valve stem clearance as follows:
a. Clamp a dial indicator on one side of the cylinder head rocker arm cover gasket rail.
b. Locate the indicator so that movement of the valve stem from side to side (crosswise to the head) w ill cause a
direct movement of the indicator stem. The indicator stem must contact the side of the valve stem just above
the valve guide.
c. Drop the valve head about 1/16" (1.6mm) off the valve seat.
d. Move the stem of the valve from side to side using light pressure to obtain a clearance reading. If clearance
exceeds specifications, it w ill be necessary to ream valve guides for oversize valves as outlined.
Valve Spring Tension
1. Check valve spring tension w ith Tool J-8056 spring tester. Springs should be compressed to the specified height
and checked against the specifications chart. Springs should be replaced if not w ith 44 N (10 lbs.) of the
specified load (without dampers).
Inspection (Timing Chain)
The tim ing chain on the 6.2L engine w ill have slack or deflection. It can be measured whenever the front cover is
removed from the engine. This is done by using a dial indicator mounted to the front of the cylinder block w ith the
plunger contacting the tim ing chain between the tw o sprockets. The chain can be deflected outward a maximum
am ount with finger pressure on the internal side of the chain. The dial indicator can then be set at zero. The chain
can then be deflected inward using finger pressure on the external side of the chain. The total indicator travel can
be noted. On a used engine, the deflection cannot exceed .800". If it does, the sprockets and chain must be
examined for wear and replaced as necessary. The tim ing chain deflection w ith new parts cannot exceed .500".
2-18
2. Engine Systems and Construction
"'7
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- y
------------------------------------------------------------------------------------------------
f
Valve Guide Bores
^
Valves w ith oversize stem s are available (see specifications). To ream the valve guide bores for oversize valves use
Tool Set J-7049.
Valve Seats
Reconditioning the valve seats is very important, because the seating of the valves must be perfect for the engine
to deliver the power and performance built into it.
Another im portant factor is the cooling of the valve heads. Good contact between each valve and its seat in the
head is imperative to insure that the heat in the valve head w ill be properly carried away.
Several different types of equipm ent are available for reseating valves seats. The recommendations of the
manufacturer of the equipm ent being used should be carefully followed to attain proper results.
Regardless of what type of equipm ent is used, however, it is essential that valve guide bores be free from carbon or
dirt to ensure proper centering of pilot in the guide.
— NOTE —
Valve seats are induction hardened. Excessive stock removal
could cause damage to the seat.
Valves
Valves that are pitted can be refaced to the proper angle, insuring correct relation between the head and stem on a
valve refacing mechanism. Valve stems which show excessive wear, or valves that are warped excessively should
be replaced. When a valve head which is warped excessively is refaced, a knife edge will be ground on part or all of
the valve head due to the am ount of metal that must be removed to com pletely reface. Knife edges lead to
breakage, burning or pre-ignition due to heat localizing on this knife edge. If the edge of the valve head is less than
1/32" (.80mm) thick after grinding, replace the valve. Several different types of equipment are available for refacing
valves. The recom m endation of the m anufacturer of the equipm ent being used should be carefully followed to
attain proper results.
A SSEM B LY
1. Insert a valve in the proper port.
2. Assem ble the valve spring and related parts as follows:
a. Install valve spring shim on valve spring seat then install a new valve stem oil seal.
Valve Stem Oil Seal/Or Valve Spring
To replace a worn or broken valve spring w ithout removing the cylinder head proceed as follows:
REM O VA L
1. Remove rocker arm assemblies.
2. Rotate engine so piston is at top dead center for each cylinder, or install air line adapter to glow pJ«g£port and
apply compressed air to hold valves in piace.
. '*■
*
3. Install Tool J-5892-1 or J-26513 and compress the valve spring until valve keys are accessible; then remove keys,
valve cap or rotator, springs and seals. If valve spring does not compress, tap tool with a mallet to break bind at
rotator and keys.
INSTA LLA TIO N
1. Install seal, valve spring and cap rotator. Using Tool J-5892-1 or J-26513, compress the valve spring until the valve
keys can be installed.
2. Install rocker arm assemblies.
2-19
2. Engine Systems and Construction
Piston Construction (Figure 2-17)
Pistons (See Figure 2-17) are cast alum inum with:
• A ni-resist full top ring groove.
• 2-piece oil control ring.
• “ Full floating piston pin” .
The full ni-resist insert-molded cast iron full groove
protector is for high temperature strength and
improved fatigue life. Ni-resist is a m etallurgical term
describing a cast iron consisting of graphite in a
matrix of austenite. Austenite is a non-magnetic solid
solution of carbon in gamma-iron. This version „
contains significant am ounts of nickel and chromium.
It has high resistance to growth, oxidation and
corrosion. It has a high bonding ability to aluminum,
and thermal ability (high dissipation rate of aluminum).
The “ full-floating ’ piston pin concept is used to
elim inate pin-to-boss scuffing and to promote uniform
pin loading through pin rotation. This happens by
using the film thickness of the oil, that the pin is
suspended by, and rotating in to increase loading and
surface area. The film thickness is also used to absorb
some of the downward thrust.
PISTO N R IN G S
The top ring (See Figure 2-18) is a com pression ring
made of keystone high strength iron w ith a
molybdenum face.
It is a keystone design, w hich is a tapered ring fitting
into the tapered land of the Ni-resist insert-molded cast
iron full groove insert.
The second ring is also a com pression ring; cast iron
construction and chrome faced. Two rings are used to
reduce the pressure drop across each ring. The third
ring is an oil control ring and tw o types are utilized
depending on em issions application: Lt. duty (under
8.500 lbs. GVWR) uses a 3-piece. Heavy duty (over
8.500 lbs. GVWR) uses a 2-piece. The 3-piece design is
made up of 2 segment rails w hich wipe the cylinder
wall and one expander w hich controls the 2 segment
rails.
In 1983 and later both Lt. and Heavy duty w ill use the
tw o 2-piece. This improves high mileage durability.
2-20
2. Engine Systems and Construction
This piston has a half-clover shaped identation on the
piston face, which at T.D.C. outlets to the pre-chamber,
Figure 2-19. As the piston rises during.the compression
stroke, the air swirl begins in these tw o indentations.
When the piston reaches the pre-chamber opening, the
air swirl is increased in the spherical pre-chamber. This
is a Ricardo Turoidal Piston design and is used with
the Ricardo COMET V Pre-Chamber for more complete
mixing of the air and fuel.
INDENT
Figure 2-19, Piston Top.
The 6.2L piston is m atch fitted to each cylinder bore of the engine. This is accom plished by measuring the internal
diam eter of the cylinder bore and stam ping the corresponding size code on the pan rail of the case. The piston
outside diam eter is measured and the size code stamped on the piston face. When the piston is assembled to the
cylinder case, these size codes are matched to insure that proper fit and clearance between the cylinder and piston
is maintained. There are six m atching cylinder bore sizes. Size codes A, B, C, D, E, G are used to match the piston
and cylinder bore. “ A ” size pistons are assembled to “ A ” size cylinder bores, “ B” size pistons to “ B” size cylinder
bores and so forth.
Piston Selection
A. The size codes (A, B, C, D, E, G) are stamped on the cylinder case pan rail and beside the proper cylinder.
B. Sen/ice pistons w ill be available in std., high lim it std., and .030 in. (.75mm) O.S. An “ S6” or “ S7” w ill be stamped
on the piston face.
C. Stamped Size
56-100.914-100.940mm
57-100.914-100.965mm
.030 in. (.75mm) O.S.
Part #
14053377 Standard
14053378 High Lim it Standard
14053379 Oversize
-
NOTE -
Pistons in cylinders number 7 and 8 are fit .013mm (.0005 in.) looser.
This is done because #7 and #8 run hotter, and piston scuff may occur.
2-21
2. Engine Systems and Construction
1. Check USED piston to cylinder bore clearance as follows:
a. Measure the “ Cylinder Bore Diameter” w ith a telescope gage 2 V2 " (64mm) from the top of cylinder bore.
b. Measure the “ Piston Diameter” (at skirt across center line of piston pin). (Fig. 2-10).
c. Subtract piston diam eter from cylinder bore diam eter to determine “ Piston to Bore Clearance” .
d. For
For
For
For
Bohn Pistons
Zollner Pistons
Bohn Pistons
Zollner Pistons
#1
#1
#7
#7
thru
thru
and
and
6 .089-.115mm (.0035-.0045 in.)
6 .112-.138mm (.004-.005 in.)
8 .102-.128mm (.004-.005 in.)
8 .125-.151mm (.0049-.0059 in.)
2. If used piston is not acceptable, determine if a new piston can fit cylinder bore.
3. If cylinder bore must be reconditioned, measure new piston diam eter (across center line of piston pin) then hone
cylinder bore to correct clearance.
4. Mark the piston to identify the cylinder for w hich it was fitted.
There will be tw o different suppliers of pistons used in the 6.2L; and you may encounter either one, they differ in
finish on the exterior of the piston, so there are tw o different piston to bore clearance values. Bohn Pistons
identified by the word “ Bohnna Lite” near the pin boss, w ill have a clearance of .089-.115mm (.0035-.0045 in.).
Zollner Pistons identified by the letter Z w ith a circle around it, also near the pin boss. It carries a clearance of
.112-. 138mm (.004-.005 in.)
Piston Inspection
Clean the varnish from piston skirts and pins with a cleaning solvent. DO NOT WIRE BRUSH ANY PART OF THE
PISTON. Clean the ring grooves w ith a groove cleaner and make sure oil ring holes and slots are clean.
Inspect the piston for cracked ring lands, skirts or pin bosses, wavy or worn ring lands, scuffed or damaged skirts,
corroded areas at top of the piston. Replace pistons that are damaged or show signs of excessive wear.
Inspect the grooves for nicks or burrs that m ight cause the rings to hang up.
Measure piston skirt (across center line of piston pin) and check clearance.
PISTON PINS
The piston pin is a free floating piston pin. It is im portant that the piston and rod pin hole be clean and free of oil
when checking pin fit.
Whenever the replacement of a piston pin is necessary, remove the ring retaining the pin. Then remove pin. Using
tool J-29134 install piston pin retaining ring.
It is very im portant that after installing the piston pin retaining rings, that the rings be rotated to make sure they are
fully seated in their grooves.
RING GAP
All com pression rings are marked on the upper side of the ring. When installing com pression rings, make sure the
marked side is toward the top of the piston. The top ring is treated with molybdenum for m axim um life.
1. Select rings com parable in size to the piston being used.
2. Slip the com pression ring in the cylinder bore; then press the ring down into the cylinder bore about V* " (6.5mm)
(above ring travel). Be sure ring is square with cylinder wall.
3. Measure the space or gap between the ends of the ring with a feeler gage.
4. If the gap between the ends of the ring is below specifications, remove the ring and try another for fit.
5. Fit each com pression ring to the cylinder in w hich it is going to be used.
6. If the pistons have not been cleaned and inspected as previously outlined, do so.
7. Slip the outer surface of the top and second compression ring into the respective piston ring groove and roll the
ring entirely around the groove to make sure that the ring is free. If binding occurs at any point, the cause should
be determined. If binding is caused by ring groove, correct by dressing w ith a fine cut file. If the binding is
caused by a distorted ring, check a new ring.
2-22
2. Engine Systems and Construction
RING INSTALLATION
For service ring specifications and detailed installation instructions, refer to the instructions furnished w ith the
parts package.
Piston Related Cylinder Case Operations
CLEANING AND INSPECTION
1. Wash cylinder block thoroughly in cleaning solvent and clean all gasket surfaces.
2. Remove oil gallery plugs and clean all oil passages.
3. Clean and inspect water passages in the cylinder block.
4. Inspect the cylinder block for cracks in the cylinder walls, water jacket, valve lifter bores and main bearing webs.
5. Measure the cylinder w alls for taper, out-of-round or excessive ridge at top of ring travel. This should be done
with a dial indicator. Set the gage so that the thrust pin must be forced in about V (6.5mm) to enter gage in
cylinder bore. Center gage in cylinder and turn dial to “ 0” . Carefully work gage up and down cylinder to
determine taper, and turn it to different points around cylinder wall to determine the out-of-round condition. If
cylinders were found to exceed specifications, honing or boring will be necessary.
CONDITIONING
The performance of the follow ing operation is contingent upon engine condition at tim e of repair.
If the cylinder block inspection indicated that the block was suitable for continued use except for out-of-round or
tapered cylinders, they can be conditioned by honing or boring.
If the cylinders were found to have less than .005" taper or wear, they can be conditioned with a hone and fitted
w ith the high lim it standard size piston. A cylinder bore of less than .005" wear or taper may not entirely clean up
when fitted to a high lim it piston. If it is desired to entirely clean up the bore in these cases, it w ill be necessary to
rebore for an oversize piston. If more than .005" taper or wear, they should be bored and honed to the smallest
oversize that w ill permit com plete resurfacing of all cylinders.
When pistons are being fitted and honing is not necessary, cylinder bores may be cleaned w ith a hot water and
detergent wash. After cleaning, the cylinder bores should be swabbed several tim es with light engine oil and a
clean cloth and then wiped w ith a clean dry cloth.
BORING
If boring is necessary, an oversize gasket w ill be required.
1. Before using any type boring bar, the top of the cylinder block should be filed off to remove any dirt or burrs.
This is very important. If not checked, the boring bar may be tilted which would result in the rebored cylinder wall
not being at right angles to the crankshaft.
2. The piston to be fitted should be measured w ith a micrometer, measuring at the center of the piston skirt and at
right angles to the piston pin. The cylinder should be bored to the same diameter as the piston and honed to
give the specified clearance.
3. The instructions furnished by the m anufacturer of the equipment being used should be carefully followed.
HONING
1. When cylinders are to be honed, follow the hone m anufacturer’s recommendations for the use of the hone and
cleaning and lubrication during honing.
2. O ccasionally during the honing operation, the cylinder bore should be thoroughly cleaned and the piston
selected for the individual cylinder checked for correct fit.
3. When finished honing a cylinder bore to fit a piston, the hone should be moved up and down at a sufficient
speed to obtain very fine uniform surface finish marks, in a cross-hatch pattern of approxim ately 45° to 65°
included angle. The finish marks should be clean but not sharp, free from imbedded particles, and torn or
folded metal.
4. Permanently mark the piston for the cylinder to w hich it has been fitted and proceed to hone cylinders and fit
the remaining pistons.
2-23
2. Engine Systems and Construction
-
NOTE -
Handle the pistons with care and do not attempt to force them through the cylinder
until the cylinder has been honed to correct size as this type piston can be distorted
through careless handling.
5. Thoroughly clean the bores with hot water and detergent. Scrub well with a s tiff bristle brush and rinse
thoroughly with hot water. It is extremely essential that a good cleaning operation be performed. If any of the
abrasive material is allowed to remain in the cylinder bores, it w ill rapidly wear the new rings and cylinder bores
in addition to the bearings lubricated by the contam inated oil, the bores should be swabbed and then wiped with
a clean dry cloth. The cylinder should not be cleaned with a kerosene or gasoline. Clean the remainder of the
cylinder block to remove the excess material spread during the honing operation.
Rod and Piston
INSTALLATIO N
1. Install the connecting rod bolt guide hose over rod bolt threads.
2. Lightly coat pistons, rings and cylinder w alls with light engine oil. Depression on top of piston to be assembled
toward outside of engine.
3. Install each connecting rod and piston assembly in its respective bore. Install w ith connecting rod bearing tang
slots on side opposite cam shaft. Use Tool J-8037 to compress the rings. Guide the connecting rod into place on
the crankshaft journal. Use a hammer handle and light blows to install the piston into the bore. Hold the ring
com pressor firm ly against the cylinder block until all piston rings have entered the cylinder bore.
4. Install the bearing caps and torque nuts to specifications 65 N.m. (45 ft. lbs.). Be sure to install new pistons in
the cylinders for which they were fitted and used pistons in the cylinder from w hich they were removed. Each
connecting rod and bearing cap should be marked, beginning at the front of the engine. Cylinders 1, 3, 5 and 7 in
the left bank and, 2, 4, 6 and 8 in the right bank. The numbers on the connecting rod and bearing cap must be
on the same side when installed in the cylinder bore. If a connecting rod is ever transposed from one block or
cylinder to another, new bearings should be fitted and the connecting rod should be numbered to correspond
with the new cylinder number.
Crankshaft
The 6.2L crankshaft (Figure 2-20) is made of nodular
iron w ith deep rolled fillets. Nodular iron, also called
ductile iron, is one of three com m on types of cast iron.
The others are grey iron and malleable iron.
Nodular iron is made by treating a low-sulfur, grey-iron­
like alloy w ith magnesium. Addition of the magnesium
forms the free carbon into the spheroids — or nodules
— w hich give nodular iron the best com bination of
du ctility and strength of the three com m on cast irons.
Depending on the application, nodular iron castings
can be used as cast (without heat treatment), annealed
for greater d u ctility as required or heat-treated to
higher hardness for greater strength and wear
resistance.
It has 5 main bearing journals. These main bearing
journals are classed by O.D. into 3 classes so that the
main bearing can be matched to the proper size
bearing insert in the main bearing cap. The diameter of
the main journals is controlled to the follow ing total
range #1 through 4 — 74.917/74.941 mm and #5 —
74.912/74.936 mm. Each of these ranges is divided into
3 sizes. The pin journal diam eter range is 60.913/60.939
mm. This range is divided into 2 sizes.
2-24
2. Engine Systems and Construction
UPPER ROPE SEAL ASM.
NOTE: END PLAY TO BE
0.05/0.18mm
GROOVE. ENDS OF SEAL MUST BE CUT
CLEAN AND FLUSH WITH CYLINDER AND
CASE AND BEARING CAP MOUNTING
SURFACE.
BEARING
OIL SLINGER
CRANKSHAFT
ASBESTOS ROPE SEAL ASM.
BEARING CAP—^
MACHINED ANULUS
APPLY DROP OF SEALER TO
BEARING CAP AND CYLINDER
AND CASE GROOVE PRIOR TO
INSTALLING ROPE SEAL.
1, Rear Mainseal.
Crankshaft Rear Main Seal
The crankshaft rear main seal is an asbestos “ rope” seal. A slot is machined the bearing at the rear which bleeds
o ff excess oil. An oil slinger is part of the crankshaft. It prevents excessive oil from going past this area.
(Figure 2-21).
Immediately behind the slinger is a knurled surface which is positioned in a way to push oil away from the rope
seal during engine rotation. The rope seal is at the rear of the sealing system.
2-25
2. Engine Systems and Construction
Upper Rear Main Seal Repair
Tools are available to provide a means of correcting
engine rear main bearing upper seal leaks w ithout the
necessity of removing the crankshaft. The procedure
for seal leak correction is listed below.
1. Drain oil and remove oil pan and rear main bearing
cap.
2. Insert Packing Tool J33154-2 against one end of seal
in cylinder block and drive the old seal gently into
the groove until it is packed tight. This varies from
1/4 " to 3/4", depending on the am ount of pack
required. (Figure 2-22).
3. Repeat this on the other end of the seal in the
cylinder block.
4. Measure the am ount the seal was driven up on one
side; add 1/16", then cut this length from the old
seal removed from the main bearing cap with a
single edge razor blade. Measure the am ount the
seal was driven up on the other side. Add 1/16" and
cut another length from old seal. Use main bearing
cap as a holding fixture when cutting seal as shown
in Figure 2-23.
5. Place a drop of 1052621 sealer or equivalent on
each end of seal and cap as indicated.
(Equivalents are Loctite 414 or Fel-Pro 361.)
-
IMPORTANT -
Install the seal pieces within one minute,
as this material sets up very quickly.
, Cutting Section of Rope Seal.
2. Engine Systems and Construction
6. Work these tw o pieces of seal into the cylinder
block (one piece on each side) with tw o small
screwdrivers. Using Packing Tool, pack these short
pieces up into the block. Use Seal Trim m ing Tool
BT-6436 or sharp blade to trim seal flush with block
as shown in Figure 2-24.
Place a piece of shim stock between seal and
crankshaft to protect bearing surface before
trimming.
7. Form a new rope seal in the rear main bearing cap.
— NOTE —
In order to prevent the possibility of
cylinder block and/or main bearing cap
damage, the main bearing caps are to be
tapped into their cylinder block cavity
using a brass or leather mallet before
attaching bolts are installed. Do not use
attaching bolts to pull main bearing caps
into their seats. Failure to observe this
information may damage a cylinder
block or bearing cap.
8. Lubricate the cap bolts with engine oil.
9. Assemble the cap to the block and torque to
specifications.
Lower Rear Main Oil Seal
Replacement
REM OVAL
1. Remove oil pan.
2. Remove the rear main bearing cap.
3. Remove rear main bearing insert and old seal.
4. Clean bearing cap and seal grooves and inspect
for cracks.
AFTER CORRECTLY POSITIONING
SEAL, ROTATE TOOL SLIGHTLY
AND CUT OFF EACH END OF SEAL
FLUSH WITH CAP.
Figure 2-25, Installing Rear Main Lower Oil
Seal.
2-27
2. Engine Systems and Construction
IN STA LLA TIO N
1. Coat seal groove w ith 1052621 sealer or equivalent (Loctite 414 or Fel-Pro 361).
2. W ithin one minute, install seal into bearing cap, packing by hand. Using seal installer J33153, drive seal into
groove. (Figure 2-25).
To check if seal is fully seated in the bearing cap, slide the tool away from seal. W ith tool fully seated in the
bearing cap, slide tool against the seal. If undercut area of tool slides over the seal, the seal is fully seated. If
tool butts against the seal, the seal must be driven further into the seal groove. Rotate tool before cutting off
excess seal packing.
3. W ith tool slightly rotated, cut seal flush w ith m ating surface. W ith screwdriver, pack seal end fibers towards
center, away from edges. Rotate seal installer when cutting seal to avoid damage to tool.
4. Clean bearing insert and install in bearing cap.
5. Place a piece of plastic gaging material on the rear main journal. Install the rear main bearing cap and torque
to 95 N-m (70 ft. lbs.).
6. Remove the rear cap and check the plastigage for bearing clearance (.0022"-.0037"). If it is out of specification,
recheck the ends of the seal for fraying, that may be preventing the cap from fully seating.
7. Clean crankshaft bearing journal and seal contact. Install sealer 1052756 or equivalent on cap as shown in
Figure 2-25.
-
NOTE -
In order to prevent the possibility of cylinder block and/or main bearing cap damage,
the main bearing caps are to be tapped into their cylinder block cavity using a brass or
leather mallet before attaching bolts are installed. Do not use attaching bolts to pull main
bearing caps into their seats. Failure to observe this information may damage a cylinder
block or bearing cap.
8. Install bearing caps, lubricate bolt threads with engine oil and install. Torque bolts to inner 135 N-m (100
Ft. Lbs.), outer 150 N-m (110 Ft. Lbs.).
9. Install pan w ith new gaskets.
10. Install flywheel lower cover.
Main Bearings
Main bearings are of the precision insert type and do not utilize shims for adjustm ent. If clearances are found to
be excessive, a new bearing for both the upper and lower halves, will be required. Service bearings are available
in standard size, .013mm (.0005 in.) U.S. and ,026mm (.001 in.) U.S.
Selective fitting of main bearing inserts is necessary in production in order to obtain close tolerances. For this
reason you may find one half of a standard insert w ith one half of a .001" (.026mm) undersize insert w hich will
decrease the clearance .0005" (.013mm) from using a full standard bearing.
IN S P E C T IO N
In general, the lower half of the bearing (except #1 bearing) shows a greater wear and the most distress from
fatigue. If upon inspection the lower half is suitable for use, it can be assumed that the upper half is also
satisfactory. If the lower half shows evidence of wear or damage, both upper and lower halves should be
replaced. Never replace one half w ithout replacing the other half.
C H E C K IN G C LE A R A N C E
To obtain the most accurate results with “ Plastigage” (or its equivalent) a wax-like plastic material which will
com press evenly between the bearing and journal surfaces w ithout damaging either surface, certain
precautions should be observed.
2-28
2. Engine Systems and Construction
If the engine is out of the vehicle and upside down, the crankshaft w ill rest on the upper bearings and the total
clearance can be measured between the lower bearing and journal. If the engine is to remain in the vehicle, the
crankshaft m ust be supported upward to remove the clearance from the upper bearing. The total clearance can
then be measured between the lower bearing and journal.
To assure the proper seating of the crankshaft, all bearing cap bolts should be at their specified torque. In addition,
preparatory to checking fit of bearings, the surface of the crankshaft journal and bearing should be wiped clean
of oil.
1. W ith the oil pan and oil pump removed, and starting with the rear main bearing, remove bearing cap and wipe
oil from journal and bearing cap.
2. Place a piece of gaging plastic the full w idth of the bearing (parallel to the crankshaft) on the journal. Do not
rotate the crankshaft w hile the gaging plastic is between the bearing and journal.
3. Install the bearing cap and evenly torque the retaining bolts to specifications. Bearing cap MUST be torqued to
specifications in order to assure proper reading. Variations in torque affect the com pression of the plastic gage.
4. Remove bearing cap. The flattened gaging plastic w ill be found adhering to either the bearing shell or journal.
5. On the edge of gaging plastic envelope there is a graduated scale w hich is correlated in thousandths of an
inch. W ithout removing the gaging plastic, measure its compressed w idth (at the widest point) with the
graduations on the gaging plastic envelope. Norm ally main bearing journals wear evenly and are not out-of­
round. However, if a bearing is being fitted to an out-of-round (.001" max.), be sure to fit to the maximum
diam eter of the journal. If the bearing is fitted to the m inim um diam eter and the journal is out-of-round .001",
interference between the bearing and journal w ill result in rapid bearing failure. If the flattened gaging plastic
tapers toward the m iddle or ends, there is a difference in clearance indicating taper, low spot or other
irregularity of the bearing or journal. Be sure to measure the journal w ith a m icrom eter if the flattened gaging
plastic indicates more than .001" difference.
6. If the bearing clearance is w ithin specifications #1, 2, 3, 4 (.0018"-.0032") and #5 (.0022"-.0037"), the bearing
insert is satisfactory. If the clearance is not w ithin specifications, replace the insert. Always replace both upper
and lower inserts as a unit.
7. A standard, .013mm (.0005"), or ,026mm (.001") undersize bearing may produce the proper clearance. If not, the
crankshaft may be ground up to .010". But bearings in that size range are not available at this writing.
8. Proceed to the next bearing. After all bearings have been checked rotate the crankshaft to see that there is no
excessive drag. When checking #1 main bearing, loosen accessory drive belts so as to prevent tapered reading
with plastic gage.
9. Measure crankshaft end play (.05-.18mm) by forcing the crankshaft to the extreme front position. Measure at the
front end of the rear main bearing w ith a feeler gage.
10. Install a new rear main bearing oil seal in the cylinder block and main bearing cap.
REPLACEMENT
Main bearings may be replaced w ith or w ithout removing the crankshaft.
-
NOTE -
Main bearing cap bolt torque instruction: With crankshaft, bearing and bearing caps
installed and bolts started, thrust crankshaft rearward to set and align bearing caps. Then
thrust crankshaft forward to align rear faces of center main bearings. Torque bolts as
specified. The above procedure is mandatory.
2-29
2. Engine Systems and Construction
Connecting Rod Bearings
The connecting rod bearings are of the precision insert type and do not utilize shim s for adjustment. DO NOT
INTERCHANGE RODS OR ROD CAPS. If clearances are found excessive a new bearing w ill be required.
Service bearings are available in standard size and ,013mm (.0005") and .026mm (.001") under size for use w ith new
and used standard size crankshafts.
IN S P E C T IO N A N D R E P L A C E M E N T
1. W ith oil pan and oil pump removed, remove connecting rod cap and bearing. Before removing connecting rod
cap, mark the side of the rod and cap with the cylinder number to assure matched reassembly of rod and cap.
2. Inspect the bearing for evidence of wear or damage. (Bearings showing the above should not be installed.)
3. W ipe both upper and lower bearing shells and crankpin clean of oil.
4. Measure the crankpin for out-of-round or taper w ith micrometer. If not w ithin specifications replace or recondition
the crankshaft. If w ithin specifications and a new bearing is to be installed, measure the maxim um diam eter of
the crankpin to determine new bearing size required.
5. If w ithin specifications measure new or used bearing clearances with Plastigage or its equivalent. If a bearing is
being fitted to an out-of-round crankpin, be sure to fit to the maximum diam eter of the crankpin. If the bearing is
fitted to the m inim um diam eter and the crankpin is out-of-round .001" interference between the bearing and
crankpin w ill result in rapid bearing failure.
a. Place a piece of gaging plastic, the length of the bearing (parallel to the crankshaft), on the crankpin or
bearing surface.
Plastic gage should be positioned in the middle of upper or lower bearing shell. (Bearings are eccentric and
false readings could occur if placed elsewhere.)
b. Install the bearing in the connecting rod and cap.
Install the bearing cap and evenly torque nuts to specifications. Do not turn the crankshaft with the gaging
plastic installed.
Remove the bearing cap and using the scale on the gaging plastic envelope, measure the gaging plastic width
at the w idest point.
6. If the clearance exceeds specification (.0018"-.0039"), select a new, correct size, bearing and remeasure the
clearance. Be sure to check what size bearing is being removed in order to determine proper replacement size
bearing. If clearance cannot be brought to w ithin specifications, the crankpin w ill have to be ground undersize. If
the crankpin is already at m axim um undersize, replace crankshaft.
7. Coat the bearing surface w ith oil, install the rod cap and torque nuts to specifications 65 N-m (45 ft. lbs.).
8. When all connecting rod bearings have been installed tap each rod lightly (parallel to the crankpin) to make sure
they have clearance.
9. Measure all connecting rod side clearances (.063-.17mm) between connecting rod caps.
Rod Assembly
If a rod is tw isted or bent, a new rod must be installed. NO ATTEMPT SHOULD BE MADE TO STRAIGHTEN
CONNECTING RODS.
The connecting rods are forged heat-treated steel. They are balanced to w ithin ± 10 grams to avoid engine
imbalance.
The connecting rod w rist pin bronze bushing is not serviced. If the clearance between the wrist pin bushing and the
w rist pin exceeds .030mm (.0012") the rod must be replaced.
2-30
2. Engine Systems and Construction
Torsional Damper 6.2L
The 6.2L damper is made of nodular iron. It is press-fit
assembled to the front end of the crankshaft and
bolted on. (Figure 2-26).
The function of the torsional damper is to counteract
the tw isting or torsional vibration caused by force
variations on the piston and thus on the crankshaft.
Torsional vibration is an oscillation w hich occurs
w ithin every power stroke. The application of force and
its removal a split second later causes the crankshaft
to be alternately twisted out of alignm ent and snapped
back in place. If a preventive measure is not taken
against this action, the engine w ill run rough and the
crankshaft may break.
The damper consists of two parts: A small inertia
inner ring, or damper flywheel, and an outer ring. These
are bonded together by a rubber insert that is
approxim ately seven mm thick. It is mounted to the
front end of the crankshaft. As the engine tends to
Figure 2-26, Torsional Damper.
speed up or slow down, it acts much like a flywheel by
imposing a dragging effect due to its inertia. This
effect slightly flexes the rubber insert and tends to hold the crankshaft at a constant speed. Thus, it tends to check
the twist, untw ist or torsional vibration of the crankshaft. This tw ist m ight be as much as 10 tons and w ithout a
damper, the crankshaft could break.
The vibration damper, like the crankshaft and flywheel, must be properly balanced prior to assembly to the engine.
Since torsional vibration differs w ith engine design, vibration dampers are designed to suit specific engines.
Also on the outer diam eter is a tim ing groove. We use this groove to statically tim e the diesel engine during
assembly. This groove can also be used w ith a mag-tach to measure RPM’s during engine operation. Remove
torsional damper using tool J-23523 and suitable pilot. Install damper using a mallet. Assemble key as shown in
Figure 2-26. Tap damper far enough on crankshaft so attaching bolt may be installed. Torque bolt to specifications
205 N-m (150 ft. lbs.).
Camshaft
The 6.2L has a forged steel carburized cam shaft for durability. (Figure 2-27). There are 5 bearing journals which
position and support the cam shaft. The cam shaft has 16 lobes. There is an eccentric lobe imm ediately rear of the
number one journal. This eccentric changes rotary motion of the cam shaft to linear m otion of the fuel pump push
rod, thus the mechanical fuel pump is operated through a push rod off the camshaft.
There is also a helical gear at the rear of the cam shaft, this gear mates with another gear w hich drives the vacuum
pump and the oil pump.
2-31
2. Engine Systems and Construction
Camshaft Bearings
CK TRUCK, G VAN
• REMOVAL (FIGURE 2-28)
Cam shaft bearings can be replaced w hile engine is
disassem bled for overhaul.
1. W ith cam shaft and crankshaft removed, drive
cam shaft rear plug from cylinder block.
2. Using Tool J-6098 with nut and thrust washer
installed to end of threads, index pilot in cam shaft
front bearing and install puller screw through pilot.
3. Install remover and installer tool J-6098-11 for #2, 3,
4 bearing w ith shoulder toward bearing, making sure
a sufficient am ount of threads are engaged.
4. Using tw o wrenches, hold puller screw while turning
nut. When bearing has been pulled from bore,
remove remover and installer tool and bearing from
puller screw (Figure 2-28).
5. Remove remaining bearings (except front and rear)
in the same manner. It will be necessary to index
pilot in cam shaft rear bearing to remove the rear
interm ediate bearing.
Figure 2-28, Removing or Replacing
Camshaft Bearings
6. Assem ble remover and installer tool J-6098-11 for #1
and J-6098-12 for #5 bearing on driver handle and
remove cam shaft front and rear bearings by driving
towards center of cylinder block (Figure 2-29).
• INSTALLATION
The cam shaft front and rear bearings should be
installed first. These bearings w ill act as guides for the
pilot and center the remaining bearings being pulled
into place.
1. Assem ble remover and installer tool on driver handle
and install cam shaft front and rear bearings by
driving towards center of cylinder block.
2. Using Tool Set J-6098 w ith nut then thrust washer
installed to end of threads, index pilot in cam shaft
front bearing and install puller screw through pilot.
3. Index cam shaft bearing in bore (with oil hole aligned
as outlined below), then install remover and installer
tool on puller screw with shoulder toward bearing.
All five bearings must have an oil hole at the
approxim ate 4 o ’clock position when viewed from the
front w ith the block in an upright position.
The seam in the bearing must always be located in the
upper half of the block face.
The front bearing has an additional oil hole w hich w ill
be located between the 12 and 1 o ’clock position. This
bearing also has a notch w hich m ust be positioned
towards the front of the block.
This procedure w ill ensure that the oil supply to the
bearings w ill enter prior to the high load zone which is
near the bottom of the bore.
Figure 2-29, Replacing Camshaft Front
Bearing
2-32
2. Engine Systems and Construction
CLUTCH PLATE
PRESSURE
PLATE
BOLT/SCREW
BOLT/SCREW
3/8-16 x 1.00
WASHER
FLYW HEEL-AU TO M ATIC
MANUAL
Figure 2-30, Flywheel.
Flywheel
The 6.2L diesel engine has 2 flywheels, one to be used for autom atic transm issions and one for manual
transm issions. The autom atic flywheel is made of a heavy steel stamping and the manual flywheel is made of cast
iron. See Figure 2-30.
It reduces vibration by sm oothing out the power strokes of m ulti-cylinder engines. Each cylinder delivers power only
every fourth stroke. It is absorbing power the other 3 strokes. During the other 3 strokes, the engine tends to slow
down. The flywheel resists any effort of the engine to change its speed of rotation because of its inertia. Thus, the
flywheel minimizes the effect of the engine trying to slow down or to speed up by absorbing power during the
power stroke and then gives it back to the engine during the outer 3 strokes. Thus, the flyweel acts to smooth out
the peaks and valleys of power from the engine.
The autom atic flywheel (flex plate) should be examined for any signs of cracking. And the ring gear should be
checked for worn or broken teeth.
2-33
2. Engine Systems and Construction
Front Cover
See Figure 2-31. The 6.2L diesel engine front cover is a
die cast of alum inum . This compares with the metal
stamped front covers of most gasoline engines. This
front cover:
• Covers tim ing gears and chain.
• Retains front crankshaft seal.
• Covers injection pump drive and driven gears.
Provides m ounting for injection pump and drive
components.
• M ounts T.D.C. tim ing pointer.
Sealed to cylinder case w ith anaerobic sealant to
prevent oil leaks. Pt. #1052357 or 1052756
Provides m ounting for water pump and backing
plate.
There is a baffle in the upper half of the tim ing cover,
and the purpose of baffle is, to keep the oil in the
bottom of the cover area and not allow too large a
quantity to accum ulate in the gear and chain area.
This prevents oil aeration. Also the upper half of the
cover contains the oil fill pipe where venting blow-by
gases go to the CDR valve. This area must have a
baffle to prevent oil from being drawn into the
CDR valve.
It is necessary to m aintain .040 in clearance between
the baffle and the pump drive gear, or noise could
result.
Exhaust Manifolds
The 6.2L diesel has 2 exhaust m anifolds made of
nodular cast iron, Figure 2-32. Exhaust gases are
forced out when a lobe on the cam shaft causes the
exhaust valve to open and the piston forces the
exhaust gases through this opening to the exhaust
manifold. Using dual exhaust improves efficiency of
the engine by allow ing freer exhaust of gases, thus
leaving less burned gases for the cylinder at the
beginning of the intake stroke.
The m ounting flanges are m achined to seal the
exhaust ports to the cylinder head. It is extremely
im portant that these surfaces be flat, since no gasket
is used.
2-34
2. Engine Systems and Construction
Lubrication System
Lubrication System
See Figure 2-33. The lubrication system of the 6.2L diesel engine is composed of:
•
•
•
•
Oil pan reservoir
Filter
Pump
Galleries
Seven quarts of oil are required for this engine. The oil pan acts as a reservoir for holding the oil waiting to be
circulated through the engine. The oil pan is attached to the bottom side or pan rail of the engine.
The lubricating system of this engine is a pressure feed type which means that a pump forces oil through the
galleries to the necessary parts. The pump is mounted to the bottom side of the number five main bearing cap.
Extending down from the pump and into the oil is a pick-up tube with a screen cover to filter out foreign material.
Oil is picked up by this tube and pumped through the oil pump. The pump is a gear type w hich uses 2 meshing
gears. As these gears rotate in opposite directions, the spaces between the gear teeth and the housing fill w ith oil
from the inlet side of the pump. Then as the teeth mesh, the oil is forced out through the outlet tube. The pump is
driven from the engine cam shaft by means of an intermediate shaft. The oil is next pumped through a cooler
located in the radiator (Figure 2-34) which cools the oil and thus helps to remove engine heat.
From the cooler the oil passes through a filter. This filter is a cartridge type and all oil going to the engine should
pass through this filter. The cartridge is made of materials that trap foreign materials to prevent it getting to engine
2-35
2. Engine Systems and Construction
components. The filter used in this engine is called a full flow filter, because all engine oil normally flow s through
it. If this full flow filter becomes clogged, the engine is equipped w ith a by-pass valve w hich is spring loaded. This
valve protects the engine from oil starvation by opening when increased pump pressure tries to pump oil through a
clogged filter. When the pressure causes the by-pass valve to open, the oil by-passes the filter and the engine
continues to receive lubrication. Replacement of the filter periodically w ill prevent damage to the engine due to a
clogged filter.
From the filter the oil is pumped through the drilled galleries in the crankcase to the various moving metal parts in
the engine. The rear crankshaft bearing is fed by a hole drilled from the rear main bearing bore to main gallery from
filter to cylinder case. Oil is pumped further through the main gallery to a drilled oil gallery w hich has been drilled
the full length of the left side of the case. Oil from this gallery feeds the cam shaft babbit bearings and another
gallery which runs the full length of the right side of the case. All other engine com ponents are provided lubrication
by these 2 oil galleries. Holes are drilled from cam shaft bore to provide oil for main bearings #1 through #4. Lifters
on the right side receive oil from the right side main oil gallery and lifters on the left side receive oil from the left
side oil gallery. The lifters contain a check ball which meters oil through the hollow push rods and to the rocket
arm and valve stem in the cylinder head. After a small accum ulation of oil is in the head, it begins to drain back to
the crank case. As mentioned before, the first four main bearings receive oil from vertical holes drilled from the
cam bores to crank bores. This oil flow s onto the crankshaft main bearings and provides lubrication for the
crankshaft to rotate freely in its bearings. This oil also flow s around the groove in each bearing to holes drilled in
the crankshaft to the crankpin journals to provide lubrication there, to allow the crankpins to rotate freely in the
connecting rod bearings. As the crankshaft rotates, it slings oil off the crankpins to cover cylinder walls, pistons,
piston pin and piston rings. Oil drains off these parts and back to the engine.
There is also one other by-pass valve which has not yet been discussed. This is the oil cooler by-pass valve. It
works much the same as the oil filter by-pass valve and opens to allow an alternate route for the oil if the cooler
should become clogged.
There is an oil pressure sw itch w hich is assembled to the top rear of the cylinder case to sense oil pressure in the
oil cavity.
OIL PRESSURE
Hot idle 10 PSI
Max. Cold Start 80 PSI
Average Pressure at stable
C onditions 40-45 PSI @ 2000 RPM
2-36
2. Engine Systems and Construction
Engine and Transmission Oil Cooler Diagnosis, All Models
When radiator oil coolers are suspected of leaking, they should be thoroughly checked before the radiator is
removed for repair. This can be done by testing the cooler with air pressure while the radiator is still in the vehicle.
BT-8316-A or J-34111 are available tools that can be used to test the oil coolers.
TESTING
1. Allow the engine to cool down.
2. Disconnect the negative battery cable(s).
3. Remove the radiator cap. Check coolant level in the radiator and add as necessary.
— CAUTION —
Never remove the radiator cap on a warm engine. Removing the cap immediately
lowers the boiling point of the liquid and can cause violent overflow. The result could
be a large coolant loss and possible personal injury.
4. Place a drain pan under the vehicle to catch lost oil.
5. Disconnect the lower pipe or hose from the oil cooler to be tested. Install the correct plug from the Tool Kit into
the open radiator fitting.
6. Disconnect the upper pipe or hose from the oil cooler. Install the correct adapter from the Tool Kit into the
radiator oil cooler fitting.
7. Apply 345 kPa (50 psi) adapter valve.
8. W atch for bubbles in the coolant. If bubbles appear, remove radiator for repair.
9. If no bubbles, increase the air pressure to 690 kPa (100 psi) and watch for bubbles. If still no bubbles, increase
the air pressure to 1,034 kPa (150 psi) and again watch for bubbles.
If no bubbles appeared, the oil cooler is not leaking. If bubbles did appear, remove the radiator for repair.
10. Reconnect the cooler lines (or hoses using new “ O” rings) and torque to specifications.
11. Connect the negative battery cable(s).
12. Start the engine and check for leaks.
13. Check and add coolant, engine oil, or transm ission fluid as necessary.
2-37
2. Engine Systems and Construction
Oil Filler Tube (Figure 2-35)
During late 1983 Model Year production, a vented oil fill tube (14071059) replaced the non-vented tube (Figure 2-35).
The vented tube w ill prevent the possibility of some oil entering the air intake system during oil additions. This
vented oil fill tube is available through sen/ice as P/N 14071059.
Oil which has entered the intake m anifold can cause damage if the amount is sufficient to cause hydraulic lock-up
of a piston.
The vented tube should always be used in service when replacing the tube for any reason.
When replacing the fill tube on vehicles equipped w ith air-conditioning, a clearance m odification must be made to
the A/C hose support bracket (or use new P/N 14074317).
2-38
2. Engine Systems and Construction
OIL PAN SEAL
6.2L diesel uses R.T.V. around most of the perimeter of the pan, except at the rear, where a neoprene seal is used.
See Figure 2-36.
RTV part #1052734, 1052914, or 1052915.
DIRECTIONS FOR RTV APPLICATION
1. Surface m ust be clean and dry. Remove all traces of oil and old gasket material. Clean w ith a chlorinated solvent
such as carburetor spray cleaner. Don’t use petroleum cleaners such as mineral spirits. They leave a film which
R.T.V. w on’t stick to.
2. Cut the tube extension to approxim ately 1/8".
3. Apply R.T.V. (1052734 or 1052915) to one of the clean surfaces. Circle all bolt holes.
4. Assem ble w hile R.T.V. is still wet. Don’t w ait for R.T.V. to skin over (within 3 minutes).
5. Torque bolts to 10 N-m (7 Ft. Lbs.) except the 2 rear bolts (2 rear bolts 22 N-m 16 Ft. Lbs.). Don’t over torque.
6. R.T.V. w ill skin over in 15 minutes, w hich is sufficient to allow for testing and operation of vehicle. No need to
w ait for the R.T.V. to cure.
2-39
2. Engine Systems and Construction
Vacuum Pump
The vacuum pump (Figure 2-37) is required because the
diesel engine does not develop vacuum in the
unrestricted air intake manifold.
Since the air crossover and intake m anifold are
unrestricted, no vacuum source is available as found in
gasoline engines. To provide vacuum, a vacuum pump
is mounted in the location occupied by the distributor
in the gasoline engine. This vacuum pump supplies the
air conditioning sen/os, cruise control servo, and
transm ission vacuum m odulator where required.
It is a diaphragm pump w hich needs no periodic
maintenance. It is driven by a cam inside the drive
assem bly to w hich it mounts. The pum p’s diaphragm
moves back and forth causing air to flow into the inlet
tube, through the pump, and exhaust out the rear port.
The drive housing assem bly has a drive gear on the
lower end w hich meshes w ith the cam shaft gear in the
engine. This drive gear causes the cam in the drive
housing to rotate. The drive gear also powers the
engine oil lubricating pump.
Figure 2-37, Vacuum Pump.
Figure 2-38 illustrates the vacuum pump in sectional
view. Lubrication of the vacuum pump is via a passage
from the rear of the right lifter oil gallery.
See Figure 2-39 for removal and installation of the
assem bly and Figure 2-40 for general diagnosis.
-
NOTE -
The engine will run without the
vacuum pump installed, but in that case,
there would be no oil circulation in the
engine since the oil pump shaft has no
gear to the camshaft. So, you should
never run the engine without the vacuum
pump installed.
Figure 2-38, Vacuum Pump Drive.
2-40
2. Engine Systems and Construction
VACUUM HOSE
1. REMOVE AND INSTALL
DRIVE & VACUUM
PUMP ASSEMBLY
REMOVE
1. Remove hose from
pump inlet.
2. Remove bolt and
bracket holding pump
to engine block.
BOLT
BRACKET
3. Remove pump.
INSTALL
1. Insert pump in engine,
making sure the gears
on the pump mesh
with the gears on the
engine camshaft.
2. Rotate the pump into
position so the
bracket and bolt can
be installed.
View showing assembly from
rear of engine.
3. Install vacuum hose.
Removing assembly from engine.
Figure 2-39, Repair Procedures.
CONDITION
POSSIBLE CAUSE
CORRECTION
1. Loose screws between pump
assy, and drive assy.
1. A - Tighten screws to spec.
B - Replace pump assy.
2. Loose tube on pump assy.
2. Replace pump assy.
Hooting noise.
Valves not functioning properly.
Replace pump assy.
Pump assy, loose on drive assy.
Stripped threads
Replace pump assy.
Oil around end plug.
Loose plug.
1. Seat plug.
Excessive noise or clattering noise.
2. Replace drive assy.
Oil leaking out crimp.
Bad crimp.
Replace pump assy.
Install hose and vacuum gage to pump,
engine running, gage should have
reading of 20 inches vacuum minimum.
With engine off, vacuum level loss should
not drop from 20 inches to 19 inches in
less than 1Vfe seconds.
1. Defective valves.
Replace pump assy.
2. Defective diaphragm.
3. Worn push rod seal.
4. Loose tube.
Figure 2-40, Vacuum Pump Diagnosis.
2-41
2. Engine Systems and Construction
EXCESSIVE BRAKE PEDAL EFFORT, BRAKE WARNING LIGHT ON
(BRAKES WITH VACUUM ASSIST).
AUTOMATIC TRANSMISSION (VACUUM MODULATED)
WILL NOT SHIFT OUT OF FIRST (LOW) GEAR
CONNECT VACUUM GAGE TO VACUUM PUMP INLET. AT ENGINE IDLE,
VACUUM SHOULD REACH 70 kPA (21" Hg) MINIMUM AT SEA LEVEL
W ITHIN 30 SECONDS (SEE GRAPH FOR VACUUM AT OTHER ELEVATIONS).
CHECKS OKAY. LEAK IN
SYSTEM OTHER THAN VACUUM
PUMP
GO TO STEP 2
VACUUM PUMP DIAGNOSIS
LOW VACUUM OR
FLUCTUATING GAGE
READING
1. CHECK GAGE AND CONNECTIONS
FOR LEAKS.
2. IF BELT DRIVEN, CHECK BELT
TENSION AND PULLEY FIT TO SHAFT.
3. CHECK IDLE RPM.
RECHECK VACUUM GAGE
VACUUM O.K.
LOW VACUUM
REPLACE PUMP
I
GO TO STEP 2
GO TO STEP 1
VACUUM PUMP, NO-LEAK VACUUM
MINIMUM ACCEPTABLE vs. ALTITUDE
VACUUM, (INCHES Hg)
Figure 2-40, Vacuum Pump Diagnosis.
2-42
2. Engine Systems and Construction
VEHICLE VACUUM SYSTEM DIAGNOSIS
VACUUM PUMP
VACUUM GAGE
Figure 2-40 Cont’d, Vacuum Pump Diagnosis.
2-43
2. Engine Systems and Construction
On applications w ith an engine mounted Model 80 fuel filter, a belt driven vacuum pump is used. This appears on
1984 and later units. See Figure 2-41.
Units w ith belt driven vacuum pump use an oil pump
drive in place of the gear driven vacuum pump. See
Figure 2-42.
2-44
2. Engine Systems and Construction
Cooling System
The engine cooling system is sim ilar to that used in a
gasoline engine, except that it is larger capacity. (See
Figure 2-43).
The purpose of the cooling system is to dissipate heat
arising from com bustion and to keep the engine at its
most efficient operating temperature at all engine
speeds and all driving conditions. During com bustion
of the air fuel mixture in engine cylinder, the burning
gases may reach temperature as high as 4,000 °F.
Some of this heat is absorbed by the wall of the
cylinder, the heads and the pistons. These parts must
be cooled so that they are not damaged from
excessive temperature.
W hile it is critical that the engine not overheat, it is
desirable that the engine operate as close as possible
to the limits. This is because the engine is less
efficient when it is cold. Therefore, the cooling system
includes devices that prevent normal cooling action
during warm-up of the engine. These devices are called therm ostats and only allow flow of the coolant after the
engine reaches normal operating temperature.
The cooling system in m ost all autom obile and truck applications is a liquid coolant system. The liquid coolant
system is made up of w ater jackets in both the cylinder head and in the cylinder case, a pump, an engine fan
and a radiator.
GM 1825 M Spec. Coolant is used in the 6.2L Diesel. It is a new specification with modified form ulations to lessen
alum inum transport deposition (cavitation erosion). When engines with alum inum com ponents are used w ith
coolants not form ulated for aluminum, plugging of radiators and engine overheating has been observed. Alum inum
com pounds in the radiator tubes caused the plugging.
Both service and owners manuals call for GM 1825 M Spec. Coolant. The new coolant (1052753) conform s to
GM 1825 M.
2-45
2. Engine Systems and Construction
Cooling System Diagnosis
A.
PROBLEM S NOT REQUIRING D ISA SSE M B LY OF COOLING SYSTEM —
1. LARGE OBSTRUCTIONS BLOCKING RADIATOR OR CONDENSER
a. AUXILIARY OIL COOLERS— i
b. LICENSE PLATES
— relo cate
c. SPARE TIRES
- 1
d. ICE, M UD OR SN O W OBSTRUCTING GRILLE — REMOVE
2. ENGINE OIL OVERFILL — CHECK ENGINE OIL DIPSTICK
3. W RONG RADIATOR FOR APPLICATION
4. LOOSE, DAM AGED OR M IS S IN G AIR SEALS
5. M IS S IN G OR DAM AGED LOWER AIR BAFFLE
6. WRONG TIM ING
B.
PROBLEM S REQUIRING D ISA SSEM B LY OF COOLING SYSTEM —
1. INCORRECT OR DAM AGED FAN
2. PRESSURE CHECK COOLING SYSTEM
3. DEFECTIVE WATER PUM P
a. ERODED OR BROKEN IMPELLER VANES
b. FAILED BEARING OR SEAL — CHECK FOR SHAFT OR BEARING PLAY
4. PLUGGED RADIATOR TUBES — SEND TO RADIATOR REPAIR SHOP FOR FLOW CHECK
5. INTERNAL SY STEM LEAKS
a. HEAD GASKET
b. CRACKED BLOCK
c. TIM ING CHAIN COVER
6. PLUGGED COOLANT P A SSA G ES IN CYLINDER HEADS — REMOVE HEADS AND CHECK VISUALLY
Figure 2-44, Cooling System Diagnosis Check List.
VISCOUS FAN DRIVE
The 6.2L Coolant Fan is not directly driven. The engine fan is mounted on the water pump shaft and is driven by
the same belt that drives the pump. The purpose of this fan is to provide a flow of air thru the radiator. It
incorporates a therm ostatically operated fluid clutch in the fan hub. This allows the fan to turn less slow ly when
the engine is cold or when down-the-road driving supplies enough cooling air to control coolant temperature. As
coolant temperature rises, the hot air passing through the radiator causes the bim etallic spring at the front of the
hub to expand. The spring moves a plate, allowing the working fluid to pass into the working chamber. The fluid
resists the free rotation of the fan hub and the fan turns faster. See Figure 2-45.
STUD 8 N-m (6 FT. LBS.)
BOLT 23 N-m (17 FT. LBS.)
BLADE ASM.
NOTE: DO NOT ALLOW
CLUTCH ASM TO REST ON
MOUNTING FLANGE AS LOSS
OF DRIVE FLUID MAY OCCUR.
CLUTCH
ASM
NUT 26 N-m
(19 FT. LBS.)
Figure 2-45, Viscous Fan Drive.
2-46
2. Engine Systems and Construction
DRIVING AND DRIVEN MEMBERS
There are tw o viscous clutch members (Figure 246).
The clutch plate is splined to the pulley shaft and
becomes the driving member.
The driven member is integral w ith the drive housing,
which is bolted to the fan. Both members have circular
grooves that are closely mated.
Figure 2-46, Fan Drive Members.
SILICONE FLUID
The viscous drive medium is silicone fluid, which is
stored in a reservoir chamber in front of the pump
plate (Figure 2-47). A bi-metallic coil or therm ostat
controls the fluid flow.
BI-METAL CONTROL
The bi-metallic coil senses the air temperature directly
behind the radiator to engage or disengage the drive
as required.
Figure 2-47, Fluid Reservoir and Thermostat.
DRIVE UNCOUPLED
When the radiator air stream is cold, the silicone fluid
remains trapped in the reservoir. W ith little or no fluid
in the working chamber, the clutch members are
uncoupled, and there is little or no fan rotation
(Figure 2-48).
Figure 2-48, Drive Uncoupled.
2-47
2. Engine Systems and Construction
DRIVE COUPLED
As the bi-m etallic coil gets hot (around 165 degrees), it
moves an arm to uncover an opening in the pump
plate and let the fluid flow into the working chamber.
The fluid viscosity causes the members to couple and
drive the fan, whenever there is enough fluid to fill the
spaces between the grooves.
When the drive is in the coupling phase, the fluid
continually circulates between the reservoir and the
working chamber. It is again trapped in the reservoir
when the bi-m etallic coil cools and the fan is
uncoupled. See Figure 2-49.
Fan Clutch Diagnosis
1. NOISE
Fan noise is som etim es evident under the follow ing normal conditions:
a. When clutch is engaged for maxim um cooling.
b. During first few m inutes after start-up until the clutch can re-distribute the silicone fluid back to its normal
disengaged operating condition.
2. LOOSENESS
Under various temperature conditions, there is a visible lateral movement that can be observed at the tip of the
fan blade. This is a normal condition due to the type of bearing used. Approxim ately 1/4" maxim um lateral
movement measured at the fan tip is allowable. This is not cause for replacement.
3.
SILICONE FLUID LEAK
The operation of the unit is generally not affected by small fluid leaks w hich may occur in the area around the
bearing assembly. However, if the degree of leakage appears excessive, proceed to item 4.
4.
ENGINE OVERHEATING
a. Start w ith a cool engine to insure com plete fan clutch disengagement.
b. If the fan and clutch assem bly free-wheels w ith no drag (revolves over 5 tim es when spun by hand), the clutch
should be replaced. If clutch performs properly w ith a slight drag go to Step C.
Testing a fan clutch by holding the small hub with one hand and rotating the alum inum housing in a
clockw ise/counterclockw ise m otion will cause the clutch to free-wheel, which is a normal condition when
operated in this manner. This should not be considered a test by w hich replacement is determined.
c. Position therm om eter so that it is located between the fan blades and radiator. This can be achieved by
inserting the sensor through one of the existing holes in the fan shroud or fan guard, or by placing between
the radiator and the shroud. On some models, it may be necessary to drill a 3/16" hole in the fan shroud to
insert thermometer.
2-48
2. Engine Systems and Construction
-
NOTE -
Check for adequate clearance between fan blades and thermometer sensor before starting
engine, to prevent damage to thermometer, fan or radiator.
d. with therm om eter in position, cover radiator grille sufficiently to induce a high engine temperature. Start
engine and turn on A/C if equipped, operate at 2,000 rpm.
e. Observe therm om eter reading when clutch engages. It w ill take approximately 5 to 10 minutes for the
temperature to become high enough to allow engagement of the fan clutch. This w ill be indicated by an
increase or roar in fan air noise and by a drop in the therm om eter reading of approxim ately 5-15°F (3-9 °C). If
the clutch did not engage between 150-195°F (66-91 °C) the unit should be replaced. Be sure fan clutch was
disengaged at beginning of test.
If no sharp increase in fan noise or temperature drop was observed and the fan noise level was constantly
high from start of test to 190°F (88°C), the unit should be replaced.
f. As soon as the clutch engages, remove the radiator grille cover and turn off the A/C to assist in engine
cooling. The engine should be run at approxim ately 1500 rpm.
g. After several m inutes the fan clutch should disengage, as indicated by a reduction in fan speed and roar.
If the fan clutch fails to function as described, it should be replaced.
— CAUTION —
If a fan blade is bent or damaged in any way, no attempt should be made to repair
and reuse the damaged part. A bent or damaged fan assembly should always be replaced
with a new assembly.
2-49
2. Engine Systems and Construction
Figure 2-50, Water Pump.
Water Pump
The water pump (Figure 2-50) is mounted at the front end of the engine between the block and the radiator. The
pump consists of a housing, w ith a water inlet and water outlet. Internally there is an impeller which rotates, forcing
the coolant through the pump. The inlet of the pump is connected by a hose to the bottom of the radiator and
coolant from the radiator is drawn thru the pump. The impeller shaft is supported on bearings and a ceramic type
seal prevents coolant from leaking out around the bearing. The pump is driven by a belt on the drive pulley
mounted on the front end of the end of the engine crankshaft.
The water pump discharge (flow) rate is 70 G.P.M. and the average coolant capacity is 6.2 gallons with 3.2 gallons
in the engine.
2-50
2. Engine Systems and Construction
Radiator
------------ RADIATOR
T
PRESSURE CAP
RADIATOR
.^ ^ --D R A IN COCK
12 N-m (9 FT. LBS.)
Figure 2-51.
2-51
FOR CORRECT
INSTALLATION TURN
RADIATOR CAP
CLOCKWISE UNTIL
ARROW ON CAP
ALIGNS WITH VENT
TUBE ON RADIATOR.
See Figure 2-51. The radiator holds a large volume of
coolant in close contact with flow ing air. This allows
the radiator to transfer heat from the coolant to
outside air. Many cooling system s today have a
separate expansion tank outside the radiator. The
expansion tank is partly filled w ith coolant and is
connected to the radiator cap. The coolant expands in
the engine as it heats up. This sends part of the
coolant into the expansion tank. Then when the engine
reaches operating temperature a valve in the radiator
cap closes which seals the coolant system. The
pressure in the cooling system increases and thus
prevents boiling. This increased pressure allows a
higher coolant temperature and thus a more efficient
cooling system.
2. Engine Systems and Construction
RADIATOR CAP
A pressure-vent cap is used on the cross-flow radiator
to allow a buildup of 103 kPa (15 psi) in the cooling
system. This pressure raises the boiling point of
coolant to approxim ately 125°C (262 °F) at sea level.
DO NOT REMOVE RADIATOR CAP TO CHECK
ENGINE COOLANT LEVEL; CHECK COOLANT
VISUALLY AT THE SEE-THROUGH COOLANT
RESERVOIR. COOLANT SHOULD BE ADDED ONLY
TO THE RESERVOIR.
The pressure-type radiator fille r cap contains a blow off
or pressure valve (Figure 2-52) and a vacuum or
atm ospheric valve (Figure 2-53).
The pressure valve is held against its seat by a spring
of pre-determined strength w hich protects the radiator
by relieving the pressure if an extreme case of internal
pressure should exceed that for w hich the cooling
system is designed.
Figure 2-52, Radiator Cap With Pressure
Valve Open.
A vacuum valve is used w hich perm its opening of the
valve to relieve vacuum created in the system when it
cools o ff and w hich otherwise m ight cause the radiator
to collapse. It also perm its transfer of coolant from
the reservoir.
The design of the radiator cap is to discourage
inadvertent removal. The finger grips have been
removed so the cap is round in shape. It must be
pushed downward before it can be removed. A rubber
asbestos gasket is added to the diaphragm spring at
the top of the cap. Also, embossed on the cap is a
caution against its being opened, and arrows
indicating the proper closed position.
TEMPERATURE SWITCH
FROM
RECOVERY
BOTTLE
Figure 2-53, Radiator Cap With Vacuum
Valve Open.
A temperature sw itch (Figure 2-54) activates a warning
lamp in the instrum ent cluster should excessive
coolant temperatures prevail in the engine. W ith
optional instrum entation, a temperature gage replaces
the warning lamp and the temperature sw itch is
replaced w ith a transducer.
2-52
2. Engine Systems and Construction
TH ER M O STA T
ARROWS POINT TO
COOLANT FLOW
The therm ostat Figure 2-55 is placed in the coolant
passage between the cylinder head and the top of the
radiator. Its purpose is to close off this passage when
the engine is cold so that coolant circulation is
restricted. This allows the engine to reach normal
operating temperature more rapidly. The therm ostat is
designed to open at a specific temperature (180 °F).
When the engine is cold and the therm ostat is closed
and coolant recirculates thru the cylinder head and
case. When the therm ostat opens, the coolant
circulates through the radiator.
1982 - Early 1983 Engines 180°
1983 and Later
190°
Figure 2-55, Thermostat.
THERMOSTAT RANGE CHART
2-53
190°F Stat.
Temperature Range 187°Fto 194 °F
Fully Open @212°F
180°F Stat.
Temperature Range 175°F to 182°F
Fully Open @202 °F
2. Engine Systems and Construction
THERMOSTAT OPERATION
A pellet-type therm ostat (Figure 2-56) is used in the
coolant outlet passage to control the flow of engine
coolant, to provide fast engine warm-up and to regulate
coolant temperatures. A wax pellet element in the
therm ostat expands when heated and contracts when
cooled. The pellet is connected through a piston to a
valve. When the pellet is heated, pressure is exerted
against a rubber diaphragm w hich forces the valve to
open. As the pellet is cooled, the contraction allows a
spring to close the valve. Thus, the valve remains
closed w hile the coolant is cold, preventing circulation
of coolant through the radiator. At this point, coolant is
allowed to circulate only throughout the engine to
warm it quickly and evenly.
As the engine warms, the pellet expands and the
therm ostat valve opens, perm itting coolant to flow
through the radiator where heat is passed through the
radiator walls. This opening and closing of the
therm ostat perm its enough coolant to enter the
radiator to keep the engine w ithin operating limits.
See Figure 2-57 for therm ostat diagnosis and Figure
2-61 for general cooling system diagnosis.
Figure 2-56, Thermostat Construction.
•NOTE THE T E M P E R A T U R E ST IC K IS A P E N C IL L IK E D E V IC E W HICH H A S A W A X M A T E R IA L C O N T A IN IN G C E R T A IN C H E M IC A L S W HICH M E L T AT A
G IV E N T E M P E R A T U R E . T H E M P E R A T U R E S T IC K S C A N BE U SE D TO D E T E R M IN E A T H E R M O ST A T 'S O P E R A T IN G T E M P E R A T U R E BY R U B B IN G 188°F A N D
206°F S T IC K S ON THE T H E R M O ST A T H O U S IN G THE M A R K S M A D E BY THE S T IC K S SH O U L D M E L T W HEN C O O LA N T T E M P E R A T U R E S OF 188°F A N D
206°F A R E R E A C H E D . R E S P E C T IV E L Y TH ESE T E M P E R A T U R E S A R E THE N O R M A L O P E R A T IN G R A N G E OF THE T H ER M O ST A T , T H E R E F O R E , IF THE
C O O LA N T FLOW S A S IN D IC A T E D ON THE D IA G N O S IS CH A R T . THE T H E R M O ST A T M A Y BE D E F E C T IV E .
Figure 2-57, Thermostat Diagnosis.
2-54
2. Engine Systems and Construction
Cooling System Schematic
GOES TO
HEATER
• COOLANT FLOW
NOTE: HEATER RETURN
GOES TO RADIATOR
A. Coolant is drawn from the radiator by the water
pump.
BY PASS
B. The pump pushes the coolant into both sides of the
block.
C. Coolant flow s around the cylinders and up into:
D. The heads where it circulates around the exhaust
passages and fire deck areas of the head and flows
out the front into:
Figure 2-58, Cooling System Flow.
E. The therm ostat housing w hich stops the main flow
when the temperature is below about 180°F
directing a small portion (bypass) back to the pump.
When the therm ostat is open the coolant flows to
the top tank of the radiator to be cooled.
BOLT
SUPPORT CLAMP
CLAMP
Nm
(3 N-m (2 FT. LBS.)
<2 FT- LBS-
NOTE: CLAMP ATTACHES
TO OUTSIDE OF
RADIATOR SHROUD. TOP
OF CLAMP SLIDES INTO
SLOT IN SHROUD
FRAME SIDE MEMBER
CLAMP
3 N-m (2 FT. LBS.)
GUARD OUTLET
HOSE
Z SEE UPC OA (C/K) GENERAL INFORMATION
HOSE CLAMPING INSTRUCTIONS.
Figure 2-59, Pressure Coolant Recovery Tank (Bottle).
1985 Cooling System
• The 1985 6.2L cooling system has a pressurized coolant recovery tank.
2-55
2. Engine Systems and Construction
Figure 2-60.
LOW COOLANT INDICATOR
A low coolant indicator system is used in 6.2L applications. See Figure 2-60. This system consists of a:
• Module
• Probe
• Low coolant dash light
• Related wiring
There is an electronic module located in the cab. It w ill turn on a light in the I.P. when the coolant drops below a
specified level. The probe w hich signals low coolant level is located in the right side of the radiator. The module is
located on the upper left side of the pedal bracket.
2-56
2. Engine Systems and Construction
Low Coolant Lamp Inoperative
NO TEST AT KEY ON OR DOES NOT INDICATE LOW COOLANT
LOW COOLANT LAMP INOPERATIVE
NO TEST AT KEY ON OR
DOES NOT INDICATE LOW COOLANT
Figure 2-61, Low Coolant Lamp Inoperative.
2-57
2. Engine Systems and Construction
Low Coolant Lamp “On” All the Time
LOW CO OLANT LAMP “ O N ” ALL THE TIM E
CCOOLANT LEVEL OK?
OK
DISCONNECT TERMINAL ON
RADIATOR PROBE AND GROUND
END OF TERMINAL
LIGHT STILL ON
1
LIGHT OFF
DISCONNECT CONNECTOR
AT LOW COOLANT MODULE
REMOVE PROBE, CLEAN
AND REINSTALL
1 LIGHT O N I
LIGHT OFF
1
REPAIR SHORT TO
GROUND IN CIRCUIT
931
1
CHECK FOR OPEN IN
CKT. 68
OK
NOT OK
OK
REPAIR OPEN
= c
REPLACE MODULE
NOT OK
REPLACE PROBE
Figure 2-62, Low Coolant Lamp Remains “On”.
2-58
CJl
CD
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c
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ro
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5*
CD
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CHECK BULB
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CHECK PRESSURE CAP
Use Pressure Cap Tester Per
Chassis Service Manual
REPLACE
O.K.
CD
CQ
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5'
3
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COOLANT LOSS
CHECK AIR DAM
MISSING OR DAMAGED
REPLACE
ADD |
ANTI-FREEZE
PROTECTION
TO SPEC.
CHECK SENDING
UNIT CONNECTOR
CHECK SENDING UNIT
o
O.K.
CHECK COOLANT LEVEL
"O FF”
OR LOW
TEMP?
a.
SEE THERMOSTAT
DIAGNOSTIC CHART
T ---TIGHTEN TO SPEC.
FAN BELT TENSION
O.K.
REPLACE
REPLACE
1. LEAKS — Check Hoses, Radiator, Clamps,
Water Pump, Thermostat Housing, Rad.
Drain, Soft or Core Plugs, Heater Water
Valves, Heater Core.
“O N ” OR
HOT TEMP.
ON CAR THERMOSTAT CHECK
j= E
BAD
VISUAL SYSTEM CHECK
HOT LIGHT
(or Temp. Gage)
3 *
0)
CHECK PRESSURE CAP
Use pressure Cap Tester Per
Chassis Service Manual
2. FOAMING COOLANT — Observe in filler
neck after engine warmup.
3. OVERFLOW SYSTEM — (Semi-Sealed
System)
A. Check for Gasket in Pressure Cap.
B. Check for Leaks — Hoses, Clamps, Over­
flo w B o ttle , F ille r N e c k N ip p le .
C. Check for Obstructions or Plugging in
Hose Between Radiator and Bottle.
COLLAPSED UPPER OR
LOWER RADIATOR HOSE?
NO
DIRT. BUGS, BENT FINS, ETC.
BLOCKING RADIATOR OR
A/C CONDENSER?
If none of the above required repair, the problem is
out of the ordinary or of a major nature.
REPAIR OR
REPLACE DEFECTS
PRESSURE CHECK SYSTEM
Install Pressure Cap Checker on
Radiator Filler Neck and
Pressurize System to Rated
Pressure.
If System Does not Hold Pressure,
Look for Leak Location.
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3
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3
2. Engine Systems and Construction
Base Engine Troubleshooting
COMPRESSION TEST — DIESEL ENGINES
To determine if the valves or rings are the cause of low compression, a test should be made to determine the
cylinder com pression pressure.
When checking compression, the cranking speed must be at least 180 RPM and the engine fully warmed-up (Engine
Oil Hot). The lowest reading should not be less than 80% of the highest and no cylinder reading should be less
than 2622 KPA (380 PSI)
1. Remove air cleaner then install intake m anifold cover J29664-1.
2. Disconnect the wire from the fuel solenoid terminal of the injection pump.
3. Disconnect wires from glow plugs then remove all glow plugs.
4. Screw the com pression gage J-26999-10 into the glow plug hole of the cylinder that is being checked.
5. Crank engine.
Allow six “ puffs” per cylinder.
NORMAL — Compression builds up quickly and evenly to specified compression on each cylinder.
LEAKING — Compression low on first stroke tends to build up on following strokes but does not reach normal.
-
NOTE -
Do not add oil to any cylinder during a compression test as extensive
engine damage can result.
-
NOTE -
6.2L V-8 Diesel compression should be in the 380-400 PSI Range.
2-60
2. Engine Systems and Construction
DIESEL ENGINE NOISE
A noise is possible in diesel engines that is throttle conscious. It is most noticeable when the engine is warm. The
cause of the noise may be a worn w rist pin pushing in the connecting rod.
DIESEL ENGINE WITH STUCK PISTON RINGS
If you encounter a diesel engine that exhibits excessive oil consum ption, low com pression or excessive blowby and
you suspect stuck piston rings as the cause, the follow ing procedure may be an effective correction:
1. Remove the glow plugs from all 8 cylinders.
2. Equally divide the contents of one can of top engine cleaner, part number 1050002, into each cylinder. (Allow the
engine to soak for 24 hours).
3. Crank the engine w ith the glow plugs removed to expell the top engine cleaner.
4. Reinstall the glow plugs and start the engine.
DIESEL ENGINE HOT HARD START
Diesel engines may exhibit hard starting characteristics when they are shut down for some period of tim e after
being fully warmed up. The cause is alm ost always lack of fuel or lack of heat to ignite the fuel.
The first step is to determ ine if it is a heat related condition or a fuel related condition. Normally this can be
determined by looking at the exhaust when the engine is being cranked.
Large quantities of w hite or light blue smoke com ing out the exhaust is fuel vapor that did not ignite. If you see
lots of fuel vapor, the condition is most likely insufficient heat. If there is little or no white or black smoke, there is
insufficient fuel.
The Service M anuals contain inform ation regarding the diagnosis of diesel engines that are hard to start. Review
the appropriate manual for diagnosis inform ation. The follow ing are items that are the most often overlooked. This
listing is by no means a comprehensive list of all items that affect starting.
• INSUFFICIENT HEAT
The follow ing item s affect the heat and must be correct. Refer to the Service Manual for procedures:
1. Cranking speed is extrem ely critical for a diesel to start, either hot or cold. Some tachom eters may not be
accurate at cranking speeds. A way to determine cranking speed and check tachom eter accuracy is to perform
the follow ing procedures:
a. Install J-26999-10 com pression gage into any cylinder.
b. Disconnect the injection pump fuel shut off solenoid lead at the injection pump or harness connector.
c. Install a tachometer.
d. Depress the pressure release valve on the compression gage.
e. W ith the aid of an assistant, crank the engine for tw o or three (2 or 3) seconds to get the starter up to speed,
then w ithout stopping, count the number of “ puffs” at the compression gage that occur in the next 10
seconds. M ultiply the number of “ puffs” in the 10 second period by 12 and that w ill be the cranking
RPM (speed).
Example — 10 seconds = 1/6 of a m inute
1 “ p u ff” = 2 RPM
RPM = (x) “ puffs” x 2 x 6 or
RPM = (x) “ puffs” x 12
Tests conducted show that diesel engines start hot at around 180 RPM which is below the 240 specified in the
Service Manual.
2. Dynamic Tim ing — If tim e is retarded beyond specifications, hard starting may be experienced.
3. Compression — Low com pression may be experienced as a result of stuck rings. Stuck rings can be freed up
w ith the use of a top engine cleaner. Refer to “ Diesel Engine W ith Stuck Piston Rings” .
• INSUFFICIENT FUEL
1. Cranking speed — If it cranks too slowly, high injection pressures w ill not be reached.
i
2. Engine Systems and Construction
ENGINE OIL CONDITIONS TROUBLESHOOTING
CONDITION
Excessive oil loss.
POSSIBLE CAUSE
CORRECTION
A. External oil leaks.
1. Tighten bolts and/or
replace gaskets and
seals as necessary.
B. Improper reading of
dipstick.
1. Check oil with car on a
level surface and allow
adequate drain down
time.
C. Improper oil viscosity.
1. Use recommended
S.A.E. viscosity for
prevailing temperatures.
D. Continuous high speed
driving and/or severe
usage such as trailer
hauling.
1. Continuous high speed
operation and/or severe
usage will normally
cause decreased oil
mileage.
E. Crankcase ventilation.
1. Service as necessary.
F. Valve guides and/or
valve stem seals worn,
or seals omitted.
1. Ream guides and install
oversize service valves
and/or new valve stem
seals.
G. Piston rings not seated,
broken or worn.
1. Allow adequate time for
rings to seat.
2. Replace broken or worn
rings as necessary.
H. Piston improperly
installed or misfitted.
1. Replace piston or repair
as necessary.
2-62
2. Engine Systems and Construction
ENGINE OIL CONDITIONS TROUBLESHOOTING (CONT’D)
CONDITION
Low oil pressure.
POSSIBLE CAUSE
CORRECTION
A. Slow idle speed.
1. Set idle speed to specs.
B. Incorrect or malfunctioning oil
pressure switch.
1. Replace with proper switch.
C. Incorrect or malfunctioning oil
pressure gage.
1. Replace with proper gage.
D. Improper oil viscosity or
diluted oil.
1. Install oil of proper viscosity for
expected temperature.
2. Install new oil if diluted with
moisture or unburned fuel
mixtures.
E. Oil pump worn or dirty.
1. Clean pump and replace worn
parts as necessary.
F. Plugged oil filter.
1. Replace filter and oil.
G. Oil pickup screen loose or
plugged.
1. Clean or replace screen as
necessary.
H. Hole in oil pickup tube.
1. Replace tube.
1. Excessive bearing clearance.
1. Replace as necessary.
J. Cracked, porous or plugged oil
galleys.
1. Repair or replace block.
K. Galley plugs missing or
misinstalled.
1. Install plugs or repair as
necessary.
L. Excessive valve lifter to bore
clearance caused by wear.
Wear is in the upper end of the
bore, and towards the center
line of the engine.
1. Measure the lifter in 2 spots,
where it contacts the bore
parallel with the roller and 90°
to the roller.
2. Wear in the area of .005-.008"
can cause low oil pressure.
The lifter should be replaced.
3. Measure the lifter bore in the
block. Any wear not exceeding
.003" should be satisfactory. If
necessary to replace lifters,
stone the sharp edges on the
bearing shoulder area of the
new lifters.
2-63
2. Engine Systems and Construction
NOISE TROUBLESHOOTING
CONDITION
Valve train noise.
Engine knocks on initial
start up but only lasts a few
seconds.
POSSIBLE CAUSE
CORRECTION
A. Low oil pressure.
1. Repair as necessary.
(See diagnosis for low oil
pressure.)
B. Loose rocker arm shaft
attachments.
1. Inspect and repair as
necessary.
C. Worn rocker arm and/or
pushrod.
1. Replace as necessary.
D. Broken valve spring.
1. Replace spring.
E. Sticking valves.
1. Free valves.
F. Lifters worn, dirty or
defective.
1. Clean, inspect, test and
replace as necessary.
G. Camshaft worn or poor
machining.
1. Replace camshaft
H. Worn valve guides.
1. Repair as necessary.
A. Fuel pump.
1. Replace pump.
B. Improper oil viscosity.
1. Install proper oil viscosity
for expected
temperatures.
C. Hydraulic lifter bleed
down.
1. Clean, test and replace
as necessary.
D. Excessive crankshaft
end clearance.
1. Replace crankshaft
thrust bearing.
E. Excessive main bearing
clearance.
1. Replace worn parts.
2-64
2. Engine Systems and Construction
NOISE TROUBLESHOOTING (CONT’D)
CONDITION
Engine knocks cold and
continues for two to three
minutes. Knock increases
with torque.
2-65
POSSIBLE CAUSE
CORRECTION
A. Flywheel contacting
splash shield.
1. Reposition splash shield.
B. Loose or broken
balancer or drive
pulleys.
1. Tighten or replace as
necessary.
C. Overfueling.
1. With the engine off to
assist in the diagnosis,
retard the injection pump
timing as far as the slot in
the pump flange will
allow. This will quiet
down a combustion
knock. If the knocking is
not substantially
reduced, the noise is
most likely a mechanical
problem.
D. Improper timing.
1. Adjust pump timing.
E. No fuel.
1. See Section 4, Fuel
System.
F. Air leak.
1. See Section 4, Fuel
System.
G. Excessive piston to bore
clearance.
1. Replace piston.
H. Bent connecting rod.
1. Replace bent connecting
rod.
2. Engine Systems and Construction
NOISE TROUBLESHOOTING (CONT’D)
CONDITION
Engine has heavy knock
hot w ith torque applied.
Engine has light knock hot
in light load conditions.
POSSIBLE CAUSE
CORRECTION
A. Broken balancer or
pulley hub.
1. Replace parts as
necessary.
B. Loose torque converter
bolts.
1. Tighten bolts.
C. Accessory belts too tight
or nicked.
1 Replace and/or tension
to specs as necessary.
D. Exhaust system
grounded.
1 Reposition as
necessary.
E. Flywheel cracked.
1 Replace flywheel.
F. Excessive main bearing
clearance.
1. Replace as necessary.
G. Excessive rod bearing
clearance.
1. Replace as necessary.
A. Air leak.
1. See Section 4.
B. Improper timing.
1. Check engine tim ing.
C. Loose torque converter
bolts.
1. Tighten bolts.
D. Exhaust leak at
manifold.
1. Tighten bolts and/or
replace gasket.
E. Excessive rod bearing
clearance.
1. Replace bearings as
necessary.
2-66
2. Engine Systems and Construction
NOISE TROUBLESHOOTING (CONT’D)
CONDITION
Engine knocks at idle hot.
2-67
POSSIBLE CAUSE
CORRECTION
A. Loose or worn drive
belts.
1. Tension and/or replace
as necessary.
B. Compressor or
generator bearing.
1. Replace as necessary.
C. Fuel Pump.
1. Replace pump.
D. Valve train.
1. Replace parts as
necessary.
E. Improper oil viscosity.
1. Install proper viscosity
oil for expected
temperature.
F. Excessive piston pin
clearance.
1. Replace as necessary.
G. Connecting rod
alignment.
1. Check and replace rods
as necessary.
H. Insufficient piston to
bore clearance.
1. Hone and fit new piston.
1. Loose crankshaft
balancer.
1. Torque any or replace
worn parts.
3. Charge Air System
Air Flow To Combustion Chamber
Air moves w ithout restriction through the air cleaner and intake m anifold (Figure 3-1 and 3-2) to the com bustion
chamber. The cham ber is filled w ith air, then the air is compressed to a temperature that w ill ignite the diesel fuel
when it is injected.
The intake m anifold provides a mount for the air cleaner and EGR valve. Since the intake “ bridges” the injection
pump, it must be removed when the injection pump requires removal.
The air cleaner assem bly has a tuning cham ber on the air inlet snorkel, called a resonator. It reduces air intake
noise.
Figure 3-3 shows the available option K46 pre-cleaner chamber.
-
NOTE -
Whenever the air cleaner assembly is removed, manifold cover J29664-1 should be
installed. Manifold covers J29664-2 should be installed when the intake
manifold is removed.
Figure 3-4 shows the air cleaner arrangement on the G-Van.
3-1
3. Charge Air System
3-2
3. Charge Air System
RESONATOR
CLAMP
DUCT
CLAMP
AIR CLEANER
Figure 3-4, G-Van Air Cleaner LH6/LL4.
3-3
3. Charge Air System
Figure 3-5, 6.2L Intake Manifold.
INTAKE MANIFOLD
See Figure 3-5. A com bination intake m anifold and cross over is used. It is a splider air plenum type which allows it
to be com pletely separated from the coolant system. This permits removing the intake m anifold w ithout disturbing
the coolant system.
The intake m anifold is sym m etrical, meaning it is proportionally the same, either from the front or the rear, so it is
possible to install the intake m anifold backwards. The engine would run, however the mounting boss for the
secondary fuel filte r w ould be in the wrong location for filter installation. The secondary fuel filter is at the rear of
the intake m anifold at the cowl.
This m anifold is free standing and doesn’t see any oil splash or heat from the crankcase. Also it contains no
coolant passages. This feature adds 5 to 10 lb. ft. of torque to the performance.
3-4
3. Charge Air System
PRE-COMBUSTION CHAMBERS
See Figure 3-6. A design feature is the Ricardo Comet
V pre-com bustion cham ber w hich has a spherical
cham ber w hich mixes the air and fuel by air swirl. This
assists in prom oting high turbulence. This is an ante-or
divided com bustion chamber, having the m ajor
cham ber in the cylinder head and only a small space
between the piston and the cylinder head. Close piston
clearance produces high turbulence in the ante
cham ber and prom otes rapid com bustion. The charge
is forced out of the throat'area, agitating the entire
m ixture and resulting in more com plete com bustion.
This design has a broad speed operating range. It also
provides low noise and effective em ission control. The
pre-chamber is installed in the cylinder head flush to
+ .050mm (.002 in.).
See Figure 3-7. The 1982-1984 LH6 and LL4 pre­
cham ber was cast from nichol base (nim onic 80 alloy)
stainless steel and is nonm agnetic and marked
M, N, P. The late 1984 and 1985 LH6 pre-chamber is
cast from iron base high carbon alloy and is m agnetic
and marked W, X, Y on the outer area.
The 1985 LL4 pre-chamber is a reversed throat type,
w ith a different locating notch.
The pre-chamber is pressed into the cylinder head.
Orientation is provided by a locating tab on the pre­
cham ber and a m ating slot in the cylinder head. Figure
3-7 provides a detailed view of the pre-chamber.
BROKEN GLOW PLUG TIP
A burned out glow plug tip may bulge then break off
and drop into the pre-chamber when the glow plug is
removed. When this occurs the nozzle should be
removed, and the broken tip removed through the
nozzle hole. In some cases, it may be necessary to
remove the cylinder head.
Cylinder Head.
3-5
3. Charge Air System
PRE-CHAMBER CRACKS
During the service of 6.2L diesel cylinder heads, the observance of hairline cracks may be noted in the pre-chamber
area.
Cracks on the face of the pre-chamber start at the edge of the fire slot. From the edge, the cracks proceed toward
the circular im pression of the head gasket bead.
These cracks are a form of stress relief and are com pletely harmless up to a length of 5mm (3/16")- Cracks longer
than this are approaching the head gasket sealing bead and should be replaced with the proper part number.
See Figure 3-8. This illustration of a pre-chamber displays both acceptable and nonacceptable cracks.
SERVICE PRE CHAMBERS
Service pre-chambers are available for the 6.2L diesel engine. If replacement pre-chambers are required, the correct
pre-chamber for the specific application should be procured per the follow ing parts information:
Application
Standard
.010 Over-Size O.D.
1982 Light Duty LH6-Vin Code C
14067526
14069540
1982 Heavy Duty LL4-Vin Code J
14067527
14069541
1983-84 All 62L
14067526
14069540
1984-85 LH6-Vin Code C
23500082
1985 LL4 Vin Code J
Reverse Throat
23500250
-
NOTE -
Oversize pre-chambers are stamped “OS”.
It should be noted that all 1983 and 1984 6.2L diesel engines, both light duty and
heavy duty emission, use a common pre-chamber which is the same part number
used in the 1982 light duty application.
3-6
3. Charge Air System
EGR VALVE
Build up of soot (carbon) or contam ination of the air filte r element is a result of exhaust gases em itted from the
EGR valve.
During normal operation of the EGR valve, some soot w ill occur in the intake m anifold below the EGR valve. A soot
deposit w ill also occur on the inner surface of the air cleaner element and housing. This is normal. The air filter
element air flow w ill not be affected, and should last the specified change interval.
Should soot build-up be excessive, and/or evidence of filter deterioration occurring, the follow ing may
have occurred:
1. M a lfu n c tio n o f the EGR s yste m (evidenced by e xce ssive b la c k exhaust).
2. M a lfu n c tio n or s e ttin g o f th e TPS (th ro ttle p o s itio n sw itch ). Refer to S e ctio n 4B.
3. M ode o f v e h ic le o p e ra tio n . If th e v e h ic le is idled fo r long periods, or long d o w n h ill o p e ra tio n w ith clo se d
th ro ttle , the bu ild -u p m ay be excessive.
To direct the EGR exhaust gas directly into the intake m anifold, a baffle, P/N 25042774, has been released for
service. The installation of this baffle w ill prevent the sooting of the filter element. M alfunctions or improper
settings of the EGR/TPS system w ill still cause excessive black smoke and poor performance. Conditions in these
areas should be corrected promptly.
To install this baffle, refer to Figure 3-9 below and use the follow ing steps:
1. Remove air filter housing from engine. (Disconnect
EGR hose at EGR valve and at solenoid.
2. Clean housing and cover.
3. Inspect air cleaner gasket on m anifold. If it is torn or
missing, install a new gasket.
4. Install air cleaner housing.
5. Replace element if required.
6. Install baffle and element. Assure proper seating of
both. (Attach vacuum hose to EGR valve and
solenoid.)
7. Install cover and tighten wing nuts.
Figure 3-9, Baffle.
3-7
3. Charge Air System
NOTES
3-8
4. Fuel System
4A. Low Pressure Fuel Delivery System
4B. High Pressure Fuel Delivery System
Fuel System Components
The diesel fuel system (see Figure 4-1) consists of the follow ing components:
• Low Pressure: Fuel tank, fuel (lift) pump, fuel filter or filters, fuel lines.
A. Low Pressure Fuel Delivery System.
The system consists of:
•
•
•
•
•
•
•
Tank filter sock.
Mechanical lift pump.
1982-83 Primary fuel filter.
Fuel Line Heater.
1982-83 Secondary fuel filter.
1983 G-P Truck Secondary fuel filter.
1984 Model 80 fuel filte r (1984).
B. High Pressure Fuel Delivery System.
The system consists of:
• Fuel injection pump.
• High pressure lines.
• Nozzles.
Fuel is pulled from the fuel tank by the Mechanical pump w hich is located on the right side of the engine. It is
driven by an eccentric lobe on the cam shaft through a push rod. Fuel is pulled through the primary filter (1982-83
only), by the Mechanical pump. Fuel is then pumped through the secondary or model 80 filter mounted on the inlet
manifold. Both filters remove foreign material w hich could damage the injection pump or clog the injector nozzle.
From the filter, the fuel is pumped to the injection pump.
Fuel Return System
A fuel return system routes excess fuel from the injection pump and leak-off type nozzles.
Figure 4-2, Fuel Return Systems.
4-1
4A. Low Pressure Fuel Delivery System
Fuel Recommendations
General M otors Corporation recommends that owners of 1985 and subsequent Model Year diesel engine vehicles
use Number 2-D diesel fuel above 2 0 °F (-7°C) am bient temperature. If the am bient temperature is expected to be
below 20°F, Num ber 1-D diesel fuel is recommended. (Figure 4-3). A “ winterized” blend of Num ber 2-D and Number
1-D fuels may be used if Num ber 1-D is unavailable.
General Motors w ill not recommend the use of Number 2-D diesel fuel below 20 °F unless it is “ winterized” .
Temperatures below 2 0 °F w ill cause the “ non-winterized” fuel to thicken w hich may keep the engine from running.
FUEL AND ENGINE OIL RECOMMENDATION
• FUEL TYPE — ABOVE 20°F (-7°C) USE NO. 2-D FUEL.
BELOW 2 0 °F (-7°C) USE NO. 1-D (OR WINTERIZED NO.
2-D) FUEL.
• OIL CHANGE INTERVAL AND OIL TYPE — EXTREMELY
IMPORTANT
- CHANGE OIL AND FILTER EVERY 5000 MILES (8000 km)
- USE ONLY ENGINE OILS LABELED SF/CD (PREFERRED)
OR SF/CC.
• OIL VISCOSITY - SELECT THE SAE GRADE OIL BASED
ON THE EXPECTED TEMPERATURE RANGE BEFORE
NEXT OIL CHANGE.
- USE SAE 30 GRADE WHENEVER POSSIBLE.
- DO NOT USE SAE 10W-40 GRADE OIL, OR ANY OTHER
GRADE NOT RECOMMENDED.
- USE SAE 10W-30 or 15W-40 FOR COLD OPERATION
ONLY.
The colder temperatures w ill cause number 2 diesel
fuel to thicken or cause a wax build-up. This wax build­
up could plug the fuel filter and keep the engine from
running. However, if the car is towed in and sets in a
warm garage, the wax w ill disappear. On no start
com plaints in cold weather, ask w hich grade of diesel
fuel is in the tank.
For the best fuel economy, use Number 2-D fuel
whenever temperatures w ill permit.
-
NOTE -
Do not try to use home heating oil or
gasoline in the diesel engine. Heating oil
may cause engine damage. Gasoline may
cause engine damage and may keep the
engine from running.
Figure 4-3, Fuel Recommendation On Visor.
- NOTE The fuel injection pump, injection nozzles or other parts of the fuel system and engine can
be damaged if you use any fuel or fuel additive other than those specifically recommended
by DDAD. To help avoid fuel system or engine damage, please heed the following:
• Some service stations mix used engine oil with diesel fuel. Some manufacturers of large
diesel engines allow this; however, for your diesel engine, DO NOT USE DIESEL FUEL
WHICH HAS BEEN CONTAMINATED WITH ENGINE OILS. Besides causing engine
damage, such fuel will also affect emission control. Before using ANY diesel fuel, check
with the service station operator to see if the fuel has been mixed with engine oil.
• Do not use any fuel additive (other than as recommended under “Biocide” in this
section). At the time this manual was printed, no other fuel
additive was recommended.
• Take care to not run out of diesel fuel. If you do run out of fuel, you may need to crank
the engine longer to re-start it after fuel has been added. To protect the cranking motor
(starter), do not crank the engine for more than 10-15 seconds at a time. Allow a one
minute cooling off period between crankings. This will allow the cranking motor to cool
and any trapped air in the fuel system to bleed off. However, if air is TRAPPED in the
system and the engine does not re-start after a total of 30 seconds of cranking air must be
purged from the system. See “Fuel Exhaustion” information in this section.
4-2
4A. Low Pressure Fuel Delivery System
COLD WEATHER OPERATION (DIESEL ENGINES)
Diesel fuel is sensitive to temperature. All diesel fuel has a certain am ount of heavy paraffin-like components,
w hich are high in energy value and help improve fuel economy. But, when temperatures are less than about - 7 ° C
(20°F), these heavy paraffin com ponents begin turning into wax flakes. If temperatures are low enough, these flakes
can build up on the fuel tank filte r or the engine fuel filte r and stop fuel from reaching the engine.
At low temperatures, wax flakes are more likely to form in Number 2-D fuel than Number 1-D (or a “ winterized” 2-D)
fuel. For best operation at tem peratures below - 7 ° C (20°F) use Number 1-D, or Number 2-D w hich has been
blended w ith Num ber 1-D for w inter use.
If you are driving in temperatures less than - 1 8 °C (0°F) and do not have Num ber 1-D or “ w interized” Number 2-D
fuel in the fuel tank, kerosene can be added to reduce waxing. Kerosene should be added at a ratio of one gallon
of kerosene to tw o gallons o f diesel fuel. Because of the lower energy value of kerosene (and reduced fuel
economy) it should be added only when anticipated tem peratures are less than - 1 8 °C (0°F). Once kerosene has
been added the engine should be run for several m inutes to mix the fuel.
The addition of kerosene w ill not unplug a filte r plugged w ith wax. Warming a “ w axed” filte r 0 °C to 10°C (32°F to
5 0 °F) w ill return the wax to solution. Filter replacement is not norm ally required.
To improve cold weather operation, an engine block heater and fuel heater are on your diesel engine. (See “ Cold
Weather S tarting” under “ Starting the Diesel Engine” in Section 1 of this manual for inform ation on the block
heater.) The fuel heater is designed to com e on when the fuel temperature is less than 4°C (40 °F). It warm s the fuel
and helps stop wax flakes from building up in the fuel filter.
Fuel Tank Components
FILLER CAP
The filler cap contains a 2-way check valve. This w ill allow air to escape during the day when the tank heats up. In
the event of a rollover, the valve w ill prevent spillage. Under pressure, no greater than 2 psi w ill exist. The valve
m ust also allow air to enter the tank to replace the fuel used by the engine. A vacuum of no more than about one
inch of mercury can accum ulate in the tank and a slight hissing sound when removing the cap is normal. The fuel
system is calibrated w ith the cap in place and any alterations w ill effect performance. Diesel fuel tank caps are
specific to Diesels. Gasoline tank caps may fit in the diesel tank filler neck but should not be used.
FUEL PICKUP AND SENDING UNIT
See Figure 4-4. The fuel pick up, com m only known as the “ sock” has three functions:
1. Strain out large solids.
2. Act as a strainer to prevent entry of water.
3. Act as a w ick to drain fuel down to the bottom of the tank since all pickup pipes do not reach the very bottom
of the tank.
The tank filte r is a Saran (Polyvinylidene Chloride) sock and is fastened to the fuel inlet line of the in-tank fuel filter
and fuel pick-up assembly.
The fuel tank filte r sock has a bypass valve w hich opens when the filter is covered w ith wax allowing fuel to flow to
the fuel heater.
W ithout this sock fuel line heater w ould be ineffective because the fuel would be trapped in the tank. Since the
bypass valve is located at the upper end of the sock, fuel w ill only be drawn into the waxed sock if the tank
contains more than approxim ately 4 gallons of fuel. Therefore, it is im portant to m aintain a m inim um of 1/4 tank of
fuel when tem peratures are below 20 degrees F.
The Saran sock material has a nominal pore size of 130 microns. In addition to acting as a particle filter for the
m echanical lift pump, the Saran tank filte r acts as a w ick to pick up fuel from the bottom of the tank and as a
water filter; water is excluded on the basis of the difference in surface tension between the water and the sock
material on the one hand and the fuel and the sock material on the other.
4-3
4A. Low Pressure Fuel Delivery System
By law in many states, water in fuel should be no more than 1/2 of 1%. That quantity of water w ill be absorbed by
the fuel. Periodically, station operators check for water by putting a special gel on the dip stick. If it turns color,
then water is present and it can be pumped out. Unfortunately, not all station operators are responsible and this
prompted the use of the Saran sock.
The fuel pickup tube doesn’t reach the bottom of the tank. However, since the sock acts as a “ w ick” the fuel level
can actually be lower than the level of the tube and fuel w ill be drawn out right down to empty. Also, with this
design, the level of water in the tank can be much higher before water enters the fuel system. This is about five
gallons. W ater that gets into the tank w ill eventually be absorbed by good fuel and w ill pass harm lessly through the
fuel system. W ater w ill be absorbed at a rate of about one gallon per 1000 miles.
— IMPORTANT —
The 6.2L diesel fuel tank sending unit is a 3-pipe assembly (main fuel, fuel syphon, and fuel
return). The 4.3L V-6 and 5.7L diesel sending unit is a 2 pipe (main fuel and return). The
gasoline fuel tank sending unit is a two pipe assembly (main fuel and canister). The
canister pipe has a .055'" orifice in the end of the pipe. It is important that these two units
not be interchanged. If the gas unit is installed on a diesel, it will cause intermittent
problems with idle and power loss. If the diesel unit is installed on a gas car, the fuel
vapors to the canister will be uncontrolled.
The ground wire on a diesel sending unit is a different color than on a gas unit for
identification purposes. The tubes are also different sizes: main fuel 3/8 inch, gasoline fuel
tank sending unit canister tube is 5/16 inch and the diesel sending unit return
tube is 1/4 inch.
4-4
4A. Low Pressure Fuel Delivery System
WATER IN FUEL WARNING SYSTEM
The 1982-83 units used a tank unit mounted water in
fuel (W.I.F.) warning-system. It w ill detect the presence
of water when it reaches the 1-2 gallon level. The water
is detected by a capacitive probe. An electronic
module provides a ground through a wire to a light in
the instrum ent cluster that reads “ water in fuel” . The
W.I.F. also contains a bulb check. When the ignition is
turned on, the bulb w ill glow from tw o to five seconds
and then fade away.
Owners w ith water in fuel lights have been instructed
to drain the water from the tank if the light com es on
im m ediately after filling. There could be enough water
in the system to get into the fuel system and shut the
engine down after driving for a short distance. If
however it com es on during a cornering or braking
maneuver, there is less than a gallon and a shut down
w ill not occur, however, the water should be removed
w ithin one or tw o days. This system w ill not detect
bacteria contained in the water. Figure 4-5 contains
diagnostic inform ation on the tank sending unit
mounted W.I.F.
FUEL
PICK-UP
PIPE
FUEL
RETURN
PIPE
/
CHECK
VALVE
FUEL LEVEL
FLOAT
WATER
IN FUEL
DETECTOR
DIESEL FUEL
GAGE WITH
WATER IN FUEL
DETECTOR
FUEL PICK UP
FILTER AND BYPASS
VALVE ASSEMBLY
FUEL RETURN
PIPE EXTENSION'
Figure 4-4, Fuel Pickup/Sending Unit With
Water-in-Fuel Warning.
A check valve is provided at the upper end of the return pipe to allow fuel to return in the event that frozen water
plugs the end of the pipe.
All vehicles using diesel engines have a sock w ith a bypass valve in the top end. This bypass valve is designed to
open up in the event that high cloud point fuels are used in cold weather and the sock gets plugged w ith wax
crystals. The fuel level should be kept at a 1/4 tank, to make sure you do not run out of fuel.
The W.I.F. detector can be serviced separately from the tank unit assembly when it requires replacement. It can be
bench checked by using the test setup shown in Figure 4-6.
The module in the detector probe m ust remain submerged in water for approxim ately a 15 to 20 second delay
period. The indicator lamp w ill then come on and stay on until the 12V signal is removed. This feature w ill
accom m odate large am ounts of water.
In 1983, the water in fuel sensitivity was increased to trigger at 1 to 3 liters (.26 to .80 gals.). The tim e delay was
changed from 15-20 seconds to 3-6 seconds.
4-5
4A. Low Pressure Fuel Delivery System
WATER IN FUEL DETECTOR
DIAGNOSIS
OPERATION
WATER IN FUEL LIGHT
ON AT ALL TIMES
WATER IN FUEL
LIGHT DOES NOT COME ON
DURING BULB CHECK
The Diesel “Water in Fuel" system uses an electronic
water detector mounted inside the fuel tank on the fuel
gage sender. The detector will warn the driver when 1 2 Vi gallons of water are present in the fuel tank by
lighting a “Water in Fuel” light on the instrument panel
The light will also come on for 2-5 seconds each time the
ignition is turned on. This bulb check assures the driver
the light is working.
W ith ignition o n discon nect 2
w ire (yel/blk-p nk)
connector* a tr ear of fuel tank
and check w at er in fuel light.
W ith ignition on discon nect 2
wire (yel blk-pink) c onn ec­
tor* at rear of fuel tank and
ground the yel/blk w ire in the
body harness. Check w ater in
fuel light.
When water is detected it can be drained through the
fuel return line without removing the fuel tank.
•TORONADO HAS A 3 WIRE CONNECTOR.
LIGHT ON
LIGHT OFF
♦
J
*
*
Purge fuel tank per
purging instructions.
C onnect 2 w ire
connector* and check
w ater in fuel light.
R em ove fuel gage
tank unit and check
yel/blk wire for opens.
Check connections to
w ater in fuel detector
and m ounting screwm ust be tight. If OK,
replace w ater in fuel
detector.
Check w ater in fuel
bulb. If OK, check for
open circuit in yel/blk
w ire from 2 w ire
connector at rear of
tank to IP w ater in fuel
lamp socket.
Locate and repair
short to ground in
yel/blk w ire from 2
w ire conn ector to IP
w ater in fuel lamp.
LIGHT ON
LIGHT ON
LIGHT OFF
♦
I
R em ove tank unit.
C heck w ires for short
circuits. If OK, replace
detector.
Norm al - fuel had
w ater in it.
TESTING
WATER IN FUEL DETECTOR
C onnect w ater in fuel detecto r as show n using a 12 V 2
C.P. bulb. T h ere m ust be a ground circuit to the w ater
for the detecto r to w ork. The light will turn on for 2-5
seconds then dim out. It will then turn back on (after
15-20 second delay) w hen about 3/8 of the detector
probe is in the water. Refer to illustration for test set-up.
FUEL TANK PURGE PROCEDURE
Cars which have a “ W ater in Fu el” light m ay have the water
rem oved from the fuel tank with a pum p or by siphoning. The pump
or siphon hose should be hooked up to the 1/4 inch fuel return
hose (sm aller of the tw o fuel hoses) above the rear axle or under
the hood near the fuel pum p. Siphoning should continue until all
w ater is rem oved from the fuel tank. Use a clear plastic line or
observe filter bowl on draining equipm ent to determ ine when clear
fuel begins to flow . Be sure to rem ove the cap on fuel tank while
using this purge procedure. R eplace the cap w hen finished. The
sam e precautions for handling gasoline should be observed when
purging diesel fuel tanks.
TO IGNITION
CAVITY IN
FUSE BLOCK
12 VOLT
2 CANDLE POWER
BULB
WATER IN FUEL
DETECTOR
r G R O U N D -1
TERMINAL
IDENTIFICATION
NEG.
POS.
fe d
WATER MUST
BE GROUNDED'
WATER
LIGHT OFF
P*
~ f< * j
ON SENDING
UNIT
WATER IN FUEL
INDICATOR IN
I.P. CLUSTER
-------Y E L / B L K ---------
NEAR FUSE
BLOCK
AT REAR
OF FUEL
TANK
^
WATER IN
FUEL DETECTOR
TOP VIEW OF
DETECTOR
TEST SET-UP
Figure 4-5, Water In Fuel Detector Diagnosis: 1982-1983.
GNDTHROUGH
FUEL GAGE
SENDER
WATER IN FUEL DETECTOR
CIRCUIT
4A. Low Pressure Fuel Delivery System
1982-1983 Water Drain Syphon Valve (Figure 4-5)
A siphoning system starting at the tank and going to the rear spring hanger, (on some models) and at the midway
point of the right frame rail on other models, permits the user to attach a hose at the shut-off and siphon out the
water.
-
NOTE —
This system was deleted after 1983.
4-7
4A. Low Pressure Fuel Delivery System
Diesel Fuel Contamination
Various m alfunctions in diesel engines often lead to injection pump replacement. Before replacing the injection
pump, determ ine if water or an excessive am ount of gasoline is the cause of the m alfunction. If water or gasoline
is found to be the cause of the m alfunction, injection pump and injection nozzle replacement may not be
necessary. The follow ing procedure should help to elim inate unnecessary pump and nozzle replacement in the
event of fuel contam ination.
• First, remove the engine fuel filte r and inspect the contents for the presence of water or gasoline. If water or
gasoline is found, flush the system as outlined on the follow ing page.
• Fuel contam ination should be expected if the car stalls, performance is poor or in the case of gasoline, the
engine w ill knock loudly.
• If gasoline is suspected, remove the fuel fill cap and check for the presence of gasoline fumes.
• Gasoline w ill not harm the injection system. Flush the gasoline out of the system as outlined. Do not remove any
injection equipm ent unless engine operation is unsatisfactory after the system has been flushed.
• For water, remove the engine fuel filter and inspect the contents for the presence of water. If water is found,
remove the injection pump cover. If the pump is full of water, flush as outlined on the next page.
• Small quantities of surface rust in the injection pump w ill not create a problem. If the vehicle stalls as a result of
contam ination, remove the metering valve and polish it lightly w ith 600 grit paper to remove the contam inant. If
the advance piston is stuck as evident by poor performance, smoke or noise, it may be necessary to remove the
pump to free it up.
• O ccasionally contam ination may enter the system that becomes so severe that physical damage has occurred to
the springs and linkage in the pump. These pumps that require part replacement should be returned to a
Stanadyne shop for repair.
BIOCIDES
In warm or humid weather, fungi and/or bacteria may form in diesel fuel if there is water in the fuel. Fungi or
bacteria can cause fuel system damage by plugging the fuel lines, fuel filters or injection nozzles. They can also
cause fuel system corrosion.
If fungi or bacteria have caused your fuel system problems, have your authorized dealer correct these problems.
Then, use a diesel fuel biocide to sterilize the fuel system (follow the biocide m anufacturer’s instructions). Biocides
are available from your dealer, service stations, parts stores and other such places. See your authorized dealer for
advice on using biocides in your area, and for recom m endations on which biocides to use.
DIESEL FUEL QUALITY TEST
The diesel fuel hydrometer J34352 can be used to measure specific gravity of fuel at a nominal temperature (75 °F
to 9 5 °F). Fuel specific gravity is an indication of the cetane number, and thus, the quality of a fuel. A poor quality
fuel can im pair diesel engine performance. The follow ing procedure outline how to measure diesel fuel quality:
1. Fill a clean container 3A full of diesel fuel.
2. Fill the glass hydrometer container w ith fuel until the hydrometer floats.
3. Gently spin the tool to break the surface tension.
4. Read the scale where the fuel level contacts the hydrometer float.
Scale Code
Green
Yellow
Red
Approx. Cetane Range
46-50 plus
41-45
38-40
-
Possible Fuel Quality
High quality fuel
Medium quality fuel
Low quality fuel
NOTE -
The glass hydrometer, including float portion, is very delicate, thus extreme care must
be utilized when using this tool.
4-8
4A. Low Pressure Fuel Delivery System
-
NOTE -
You should remove the fuel tank for cleaning when water is detected, because of the
current understanding that a small amount of water or slurry is potentially damaging
to the fuel system. The syphon does not remove it all.
Diesel Fuel System Cleaning Procedure
— CAUTION —
Never drain or store diesel fuel in an open container due to possibility of fire or explosion.
CLEANING PROCEDURE: WATER IN FUEL SYSTEM
1. Drain the fuel tank.
2. Remove the tank gage unit.
3. Thoroughly clean the fuel tank. If the tank is rusted internally, it should be replaced. Clean or replace the fuel
pickup filte r and check valve assembly.
4. Re-install the fuel tank but leave the lines disconnected at fuel tank area (above the rear axle).
5. Disconnect the main fuel hose at the fuel pump. Using low air pressure, blow out line towards rear of vehicle.
Disconnect the return fuel line at the injection pump, w ith low air pressure, blow out the line towards the rear of
the vehicle.
-
NOTE -
If rust is present in these pipes, they must be replaced.
6. Re-connect the main fuel and return line hoses at the tank. Fill the tank at least 1/4 full with clean diesel fuel.
Re-install fuel tank cap.
7. Remove and discard the fuel filter.
8. Connect the fuel hose to the fuel pump.
9. Re-connect both battery cables.
10. Purge the fuel pump and pump to filte r line by cranking the engine until clean fuel is pumped out, catching the
fuel in a closed metal container.
11. Install a new fuel filter.
12. Install a hose from the fuel return line (from the injection pump) to a closed metal container w ith a capacity of
at least tw o gallons.
13. If the engine tem perature is above 125 degrees F (52 degrees C), activate the Injection Pump Housing Pressure
Cold Advance (H.P.C.A.). This can be done by disconnecting the tw o lead connectors at the engine temperature
sw itch (located at the rear of the right cylinder head), and bridging the connector w ith a jumper.
4-9
4A. Low Pressure Fuel Delivery System
14. Crank the engine until clean fuel appears at the return line. Do not crank the engine for more than 30 seconds
at one time. Repeat cranking if necessary w ith 3 minute intervals between crankings.
15. Remove the jum per from the engine tem perature sw itch connector and reconnect the connector to the switch.
16. Crack open each high pressure line at the nozzles using tw o wrenches to prevent nozzle damage.
17. Disconnect the lead to the H.P.C.A. solenoid (on the injection pump).
18. Crank the engine until clean fuel appears at each nozzle. Do not crank for more than 30 seconds at one time.
Repeat cranking if necessary, w ith 3 m inute intervals between crankings.
CLEANING PROCEDURE: GASOLINE IN FUEL SYSTEM
1. Drain fuel tank and fill w ith diesel fuel.
2.
Remove fuel line between fuel filte r and injection pump.
3. Connect a short pipe and hose to the fuel filte r outlet and run it to a closed metal container.
4. Crank the engine to purge gasoline out of the fuel pump and fuel filter. Do not crank engine more than 30
seconds w ith tw o m inutes between cranking intervals.
5.
Remove the short pipe and hose and install fuel line between fuel filter and injection pump.
6. A ttem pt to start engine. If it does not start, purge the injection pump.
7.
Purge the injection pump and lines by cranking the engine with accelerator held to the floor, crank until the
gasoline is purged and clear diesel fuel leaks out of the fittings. Tighten fittings. Lim it cranking to 30 seconds
w ith tw o m inutes between cranking intervals.
8. Start engine and run at idle for 15 minutes.
-
NOTE -
If gasoline is inadvertently pumped into the tank, there will be no damage to the fuel
system or the engine. The engine will not run on gasoline. Gasoline has a feature called
Octane which defined is the ability of the fuel to resist ignition under high temperatures.
Gasoline is a fuel that has high Octane and it resists ignition under high heat, it will only
ignite by a spark. Gasoline in the fuel at small percentages, 0-30%, will not be noticeable
to the driver. At greater percentages the engine noise will become louder. Gasoline at any
percentage will make the engine hard to start hot. In the summer time, this could
be a cause of a hot start problem.
4-10
4A. Low Pressure Fuel Delivery System
Fuel Lines and Lift Pump
Although the injection pump has capabilities to pull
fuel from the tank, an engine mounted fuel pump is
included in this system as an additional assist in the
event of air in the lines such as running out of fuel,
fuel line air leaks or air from occasional fuel tank
service. (Figure 4-7).
The fuel pum p’s main job is to supply 51/2 lbs. to 6 Vi
lbs. of pressure through the fuel filter to the Injection
pump.
Fuel is drawn from the fuel tank through the tank filter
by the fuel pump. The fuel pump is driven by an
eccentric on the crankshaft. The injection pump drive
system uses the end of the cam shaft where the fuel
pump eccentric is usually located in a gasoline engine.
See figure 4-8. The diesel fuel pump is located on the
right side of the engine between the fuel tank and fuel
filter. The design of this pump is quite sim ilar to the
gasoline engine pump: however, the tw o com ponents
are not interchangeable.
All 1982 and later m odels w ill be equipped with GM
SPEC. 6031 hoses which are made of “ V iton” and
contain a non-permeable tube inside.
HIGH PRESSURE FUEL LINE
DIESEL FUEL
DISTRIBUTION
SYSTEM
INJECTION PUMP
LOW
PRESSURE FUEL
LINE
Ln_
SUCTION
LINE
____ £
FUEL PUMP
Figure 4-7, Mechanical Lift Pump and
Fuel Lines.
The hoses w ill include a yellow stripe and the words
“ Fluro Elastom er” on the outside. Their purpose is to
reduce em issions when hydro-carbons pass through
the hose material.
Figure 4-8, Mechanical Lift Pump Location.
4-11
4A. Low Pressure Fuel Delivery System
Mechanical Fuel Pumps
INLET VALVE
OUTLET
How the Mechanical
Fuel Pump Works
A mechanical fuel pump is m echanically actuated by a
rocker arm or push rod w ithout electrical assistance.
Figure 4-9 shows a typical mechanical fuel pump.
The rocker arm spring holds the rocker arm in constant
contact w ith the cam shaft or eccentric.
As the end of the rocker arm moves upward, the other
end of the arm pulls the fuel diaphragm downward.
The vacuum action of the diaphragm enlarges the fuel
chamber drawing fuel from the fuel tank through the
inlet valve and into the fuel chamber.
The return stroke starting at the high point of the cam
releases the compressed diaphragm spring, expelling
fuel through the outlet valve.
When the immediate fuel needs of the engine are
satisfied, pressure builds in the fuel line and pump
chamber. This pressure forces the diaphragm /piston to
make shorter and shorter strokes, until more fuel is
needed in the engine.
Figure 4-9, Typical Mechanical Fuel Pump.
4-12
4A. Low Pressure Fuel Delivery System
Fuel Pump Service
Mechanical Fuel Pump Tests
PRELIMINARY INSPECTION
— NOTE —
Perform following tests or inspections before removing pump.
Step 1
Check fitting s and connections to insure tightness. If insufficiently tight, leaks of air and/or fuel may
occur.
Step 2
Check for fuel line bends or kinks in hoses.
Step 3
W ith engine idling look for:
a. Leaks at pressure (outlet) side of the pump.
b. A leak on suction (inlet) side w ill reduce the volume of fuel on the pressure side of the pump and suck
in air.
c. Also check for leaks at diaphragm, flange, and at breather holes in pump casting.
d. Check fuel pump steel cover and its fittings for leaks. Tighten or replace fittings as necessary. If fuel
pump leaks (diaphragm, flange, steel cover, or pump casting breathing holes), replace pump.
FUEL FLOW TEST
Step 1
Disconnect fuel line at the filte r inlet.
Step 2
Disconnect pink wire at the fuel injection
pump electric shut-off (ESO) solenoid.
Place a suitable container at end of pipe and
crank engine a few revolutions (Figure 4-10). If
little or no fuel flow s from open end of pipe,
then fuel pipe is clogged or pump is
inoperative.
4-13
4A. Low Pressure Fuel Delivery System
Step 3
Before removing fuel pump, disconnect fuel line at tank and blow through it with air hose. Do not blow
through fuel line w ithout disconnecting it becasue it is possible to blow strainer o ff tank unit or to rupture
it. Then reconnect fuel lines to pump and tank. Also, reconnect fuel lines at filter. Start engine and check
for leaks.
If fuel flow s in a good volume from pipe at filter 1 pint @ 30-45 seconds, fuel delivery pressure may be checked.
This test is necessary because a weak pump can still produce an adequate volume of fuel when it is not under
pressure. Fuel pressure should be in the 5.5 to 6.5 psi range.
VACUUM TEST, FUEL PUMP INLET
(DEAD HEAD)
Low vacuum or com plete loss of vacuum provides
insufficient fuel to the injection pump to operate the
engine throughout normal speed range. The vacuum
test w ill determine if the pump has the ability to pump
fuel and is the best indication of the quality
performance of the pump (Figure 4-11).
TO FILTER INLET
Step 1
Disconnect hose from fuel tank to fuel pump
at fuel pump. Plug or position hose to insure
no fuel leakage.
Step 2
Connect one end of a short hose to fuel
pump inlet and attach a vacuum gage to the
other end.
Step 3
Start engine. W ith engine idling (using fuel in
the filter assembly), check vacuum gage. If
vacuum is less than 12 inches Hg (2.98 kPa)
replace fuel pump.
Figure 4-11, Fuel Pump Vacuum Test.
Avoiding Air Intake
An im portant function of all hoses, lines and fittings is to carry fuel with maximum absence of air.
When the fuel tank cap is in place and the injection pump and fuel pump are drawing fuel through the lines a low
vacuum of 0-1 lb. mercury is created. This occurs because the fuel w hich the engine uses m ust be replaced by air.
During this vacuum condition, the slightest leak, which may not leak fuel externally, could draw air into the system
and depending on the volum e of air, a wide variety of engine m alfunctions are possible. These may show up as
M.P.G. com plaints, smoke com plaints, performance com plaints and hard starting or not starting conditions.
For example, suppose the inlet fitting was slightly loose at the engine fuel filter. This would probably have an
external leak and be a com plaint of fuel leak or smell of diesel fuel accompanied by a “ starts but then dies and
can’t re-start” com plaint. It is possible that when the engine is shut down the fuel could syphon out of the lines
and fuel pump and back into the tank. It is then replaced by air which entered at the loose fitting. The fuel system
is now em pty and as a result the engine must be cranked until the lines are full again.
4-14
4A. Low Pressure Fuel Delivery System
Diagnosing Air In Fuel Lines
Shop manual diagnosis charts should be referred to when diagnosing for air problems to determine the presence of
air. First install a short clear plastic hose into the return line at the top of the injection pump (Figure 4-12). Start the
engine and observe for air bubbles or foam in the line. If foam or bubbles are present, proceed as follows:
1. Raise vehicle and disconnect both fuel lines at the tank unit.
2. Plug the sm aller disconnected return line.
3. Attach a low pressure (preferably hand operated pump) air pressure source to the larger 3/8 fuel hose and apply
8-12 P.S.I.
a. Diagnosing trucks equipped with dual tanks will require a check of the right fuel lines w ith the dash sw itch in
the right tank position and a check of the left fuel lines with the dash switch in the left tank position. The
sw itching valve could be a source.
4. Observe the pressure pump reading of 8-10 P.S.I. A decrease in pressure w ill indicate the presence of a leak. The
pressure w ill push fuel out at the leak point indicating the location of the leak.
5. Repair as necessary.
In checking for air problems, the proper size clam ps on all hoses should be checked. Also, a burr on the edge of a
pipe could rip the inside of a line and create air ingestion. Particular attention should be given to improper
installation or defective auxiliary filters or water separators.
Since operation of the hydraulic advance mechanism is dependent on transfer pump pressure and pump housing
pressure, any deviation from pre-set tolerances can affect the advance mechanism and therefore, the injection
tim ing. Fuel pump delivery less than 5 1/2 lbs. to 6 Vi lbs. pressure, for example, w ill reduce total advance directly
proportional to pressure loss. Leaks, plugged filters, air ingestion restriced lines etc. w ill all reduce pressure
delivery. Return line restriction can raise housing pressure to as high as transfer pump pressure depending on the
degree of restriction and eventually stall the engine by upsetting the balance of transfer pump and housing
pressures.
4-15
4A. Low Pressure Fuel Delivery System
1982-83 Primary Fuel Filter
The primary fuel filte r is mounted on the bulkhead in the engine compartment. It is the same type of filter that is
used on larger trucks. (Figure 4-13).
At the bottom of the filter, a water drain valve permits draining water that is caught by the filter. This filter is an AC
fibrous depth elem ent of the spin-on type. The filter case includes the drain petcock.
PRIMARY FUEL FILTER-WATER DRAIN
See Figure 4-13. If it should become necessary to drain water from the fuel tank, also check the primary fuel filter
for water. This can be done as follows:
1. Open the petcock on the top of the primary filter housing.
2. Place a drain pan below the filter and open the petcock on the bottom of the drain assembly. (A length of hose
is attached to the petcock to direct drained fluid below the frame.)
3. When all water is drained from the filter, close the petcock lightly.
-
NOTE -
If filter is completely drained, remove filter and refill with clean fuel
to prevent engine stalling.
4. Close upper petcock tightly.
5. Start the engine and let it run briefly. The engine may run roughly for a short tim e until the air is purged from the
system.
6. If engine continues to run roughly, check that both petcocks at the primary filter are closed tightly.
The primary filter was used in 1982-83 only.
4-16
4A. Low Pressure Fuel Delivery System
Line Heater
A Diesel cold weather package is used. This package
consists of an in-line diesel fuel heater and the engine
block heater. (Figure 4-14).
The purpose of the heater is to heat the fuel so that
the filter does not plug with paraffin wax crystals. This
allows the use of more efficient #2 Diesel fuel at
temperatures substantially below its cloud point.
The heater is electrically powered from the ignition
circuit and is placed on the fuel filter inlet line a short
distance up stream from the filter.
Following are some of the qualities designed into this
system:
The heater is in-line, and in fact, a com ponent of fuel
pipe assem bly between fuel lift pump and filter. It does
not have any additional seals or joints that increase
the possibility of fuel leaks.
Figure 4-14, Fuel Line Heater Installation.
The heater is therm ostatically controlled to work when waxing of the fuel is expected. Thermal feedback from the
heating elem ent to the bimetal actuator protects the element from burning out if for any reason fuel is not flowing
through the fuel heater.
OPERATION
The device can be divided into tw o m ajor functional
components, the heater and the power control
assemblies. (Figure 4-15).
BIMETAL
ACTUATOR
The heater is 7/8 inches in diam eter and approxim ately
5 1/2 inches long and consists of an electric resistance
strip spiral wound and bonded around the fuel pipe. To
minimize the heat loss to the environment, heating
element is surrounded by an insulating fiber.
The power control assembly senses fuel temperature
and responds by closing an electrical circuit to the
heater. The sensing element is a bim etal switch. The
internal bimetal sw itch turns on at 20 degrees F. and
shuts o ff at 50 degrees F. Power consum ption is 100
watts. The heat w ill only be on until the under hood
temperature gets hot enough to warm the fuel.
The fuel tank filter sock has a bypass valve which
opens when the filte r is covered w ith wax allowing fuel
to flow to the heater. W ithout this bypass valve fuel
line heater would be ineffective because the fuel would
be trapped in the tank. Since the bypass valve is
located at the upper end of the sock, fuel w ill only be
drawn into the waxed sock if the tank contains more
than approxim ately 4 gallons of fuel. Therefore it is
im portant to m aintain a m inim um level of 1/4 tank of
fuel when temperatures are below 2 0 °F.
FRAME
END CAP
HEATER
ELEMENT
CONTACT
POINTS
END CAP
SPRING
Figure 4-15, Diesel Fuel Heater Components.
HEATER SERVICEABILITY/DIAGNOSIS
The heater cannot be sen/iced. However, it can be checked by using an ammeter connected in series. Checking
m ust take place below 20° am bient temperature. Proper operation w ill draw approxim ately 7 amps.
4-17
4A. Low Pressure Fuel Delivery System
Secondary Fuel Filters
INTAKE MANIFOLD
/
The 1982 C, K & P, and the 1983 C, K trucks use an
intake m anifold mounted secondary fuel filter, before
the fuel enters the pump. This filte r is an AC 10 micron
paper replaceable element of the spin-on type. It is
mounted to the rear of the intake manifold. See
Figure 4-15.
FUEL INJECTION
PUMP
SECONDARY FILTER
Figure 4-15a, Secondary Fuel Filter
(C-K Series).
SECONDARY FUEL FILTER C-K SERIES
REMOVAL:
1. Remove fuel filter lines from adapter.
2. Remove fuel filter.
3. Remove filter.
INSTALLATION:
1. Install filter to adapter, tighten 2/3 turn after contacting gasket.
2. Install adapter to intake manifold.
3. Install the fuel filter inlet line only.
Anytim e the secondary filter is removed or replaced, air must be purged from the filter to prevent engine stalling or
excessive cranking tim e to restart.
4. W ith the secondary fuel line disconnected, disconnect the pink electrical wire from the fuel injection pump to
prevent the engine from starting.
5. Place an absorbent towel under the filter outlet.
6. Crank engine (for 10 seconds max.) until fuel is observed at the outlet port.
7. If fuel is not observed after 10 seconds, w ait 15 seconds, repeat Step 6.
8. When fuel is observed at the outlet port, install the outlet line.
9. Reconnect pink wire at injection pump, and reinstall air cleaner.
10. Start engine and allow to idle for several m inutes to purge remaining air.
11. Check all fitting s and filte r for leakage; remove absorbent towel.
4-18
4A. Low Pressure Fuel Delivery System
1983 G-P TRUCK MODEL 75 FILTER
The G-P series uses a Stanadyne Model 75 secondary
fuel filter in 1983. See Figure 4-16. It is fastened using
tw o bail clips. It is particularly im portant to place
absorbent tow els under the filter when changing it to
improve cylinder and case valley drain and prevent fuel
oil contam ination of the clutch driven disc.
The Model 75 filter is a two-stage pleated paper type
filter. (Figure 4-16). The first stage consists of
approxim ately 400 sq. inches of filtering area and will
remove 94% of particles 10 m icrons and larger. The
second stage is made of the same paper material and
consists of approxim ately 200 sq. inches of filtering
surface. The second stage is 98% effective in filtering
the fuel already filtered by the first stage.
Particles w hich are larger than 10 m icrons may
damage the pum p’s internal components. Figure 4-17
w ill com pare various micron sizes and will ultim ately
show the filte r’s effectiveness.
Figure 4-16, G-P Model 75 Secondary
Fuel Filter.
SECONDARY FUEL FILTER G-P SERIES
REMOVAL:
1. Engine must be turned off.
2. Remove engine cover.
3. Remove air cleaner.
4. Place absorbent cloth or towel under filter.
5. Unstrap the lower bail first to relieve fuel pressure in the filter.
6. Unstrap the upper bail and remove filter.
INSTALLATION:
1. Insure that both filter m ounting plate fitting s are free of dirt.
2. Install new filter; snap on the upper bail clamp only.
Anytim e the secondary filter is removed or replaced, air m ust be purged from the filter to prevent engine stalling
or excessive cranking tim e to restart.
3. Disconnect the pink electrical wire from the injection pump to prevent the engine from starting.
4. Crank engine (for 10 seconds max.) until fuel is observed at the lower filter fitting.
5. If fuel is not observed after 10 seconds, wait 15 seconds, repeat Step 4.
6. When fuel is observed at the lower fitting, connect the lower bail clamp.
7. Reconnect the pink wire on injection pump — and install air cleaner.
8. Start engine and allow to idle for several m inutes to purge remaining air, — check for fuel leaks.
9. Remove absorbent towel from filter area — reinstall engine cover.
4-19
4A. Low Pressure Fuel Delivery System
RELATIVE SIZE OF M ICRON PARTICLES
M A G NIFICATIO N 1000 TIM ES
1 MICRON = .000039
LOWEST VISIBILITY RANGE = 44 MICRONS (.0017)
HUMAN HAIR = .003
Figure 4-17, Relative Size of Micron Particles.
FUEL HEATER
CONNECTOR
Com bination Fuel Heater
Fuel Filter
Water Separator
W ater Sensor
Filter Change Signal
FUEL FILTER
ELEMENT
FUEL
INLET
ELEMENT
CLAMP
FUEL
OUTLET
OPTION
L or R
FILTER
CHANGE
SIGNAL
CONNECTOR
OPTIONAL
WATER DRAIN
LOCATION
WATER DRAIN
“WATER IN FUEL”
SIGNAL CONNECTOR
OPTIONAL WATER DRAIN
LOCATION
Figure 4-18, Model 80 Fuel Filter and
Base Assembly.
4-20
1984 & LATER MODEL 80 FUEL SENTRY
FILTER SYSTEM (FIGURE 4-18)
» FUEL HEATER
See Figure 4-19. The purpose of the heater is to heat
fuel, so that the filter does not plug with parafin wax
crystals. This will allow the use of fuels at
temperatures substantially below the cloud point
of the fuel.
The heater is electrically powered from the ignition
circuit 39. It is placed in the filter inlet passage in the
filter base.
The heater is therm ostatically controlled to work when
waxing of the fuel is expected. It is self-protected (by
thermal feedback from the heating element to the bi­
metal actuator) against overheating resulting from the
lack of fuel flow. Because it is located w ithin the filter
base, it is 50% more heat efficient than a line heater.
The device can be divided into tw o major functional
components, the heater and the power control
assemblies.
4A. Low Pressure Fuel Delivery System
The heater is 7/8 inches in diam eter and consists of an electric resistance strip spiral wound.
The power control assem bly senses fuel temperature and responds by closing an electrical circuit to the heater.
The sensing element is a bim etal switch. The internal bimetal sw itch turns on at 20 degrees F and shuts off at 46
degrees F. Power consum ption is 110 w atts @ 14 volts D.C. The heat w ill only be on until the under hood
temperature gets hot enough to warm the fuel.
The heater can be sen/iced. However, it is retained in the filter base by the vent valve and an “ 0” ring. To remove it;
1. Remove the vent valve.
2. Disconnect the electrical connector.
3. Grasp the heater and remove it.
It can be checked by using an am m eter connected in series. Checking m ust take place below 20 degrees ambient
temperature. Proper operation w ill draw approxim ately 8.6 amps.
Fuel Filter
The engine fuel filter is a two-stage pleated paper type
filte r (Figure 4-20). The first stage consists of
approxim ately 350 sq. inches of filtering area and w ill
remove 96% of particles 5-6 m icrons and larger. The
second stage is made of the same paper material with
glass particles and consists of approxim ately 100 sq.
inches of filtering surface.
The second stage is 98% effective in filtering the fuel
already filtered by the first stage. Particles which are
larger than 10 m icrons may damage pum p’s internal
components. The rectangular design of this filter
allows the use of these 2 different elements.
Figure 4-17 compares various m icron sizes and will
ultim ately show the effectiveness of the filter.
4-21
4A. Low Pressure Fuel Delivery System
WATER SEPARATOR
The bottom of the filte r is a hollow water collector. (See Figure 4-19). Because of the greater density of the water,
the water droplets w ill separate from the fuel oil. It will hold approximately 260 cubic centim eters of water
(approx. 3-10%).
A nylon fiberglass coalescent is used to blend the small water droplets into larger ones.
“ One m icron” water droplets collect in the coalescent fibers, and when the droplets get large and heavy enough
they drop into the filter bottom.
The coalescing increases the water concentration from 20-30 ppm to 100 ppm. This allows for more efficient water
collection.
WATER SENSOR
The 6.2L uses a water in fuel warning system, which
allows the user to guard against water in the fuel.
The water is detected by a capacitive probe located in
the filter base. Electronics w ithin the probe will
connect a ground (circuit 150) to the ground side of the
water in fuel lamp (circuit 508). This lamp is in the
center of the instrument panel next to the glow plug
lamp. In 1984 (4 wire water sensor module) a bulb
check was made any tim e the ignition sw itch was in
the start position. A B + signal on the purple wire at
the “ A ” test sw itch (Figure 4-21) causes pin “ D” to pull
low, grounding the “ water-in-fuel” bulb. In 19841/2 and
1985 (3 wire water sensor module) when the ignition is
turned on, the lamp will glow from 2 to 5 seconds, and
fade away. This is done as a bulb check.
The probe material is iron ferrite, which is not subject
to electrolysis. The sensor will turn on at a 50cc level.
Figure 4-21, 1984 Filter Base Wiring.
-
NOTE -
The 1984 water sensor is an IC chip, 4 wire, 4 wire male connector voltage transient
module. The 19841/2 water sensor has discrete components, 3 wire module, 4 wire male
connector. The 1985 and later water sensor has discrete components, 3 wire module and a
3 wire “female” connector.
4-22
4A. Low Pressure Fuel Delivery System
PRESSURE SWITCH
A pressure w ill be incorporated in the filter base. It will be used to indicate filte r blockage. The pressure differential
value is set at 14 in. Hg. ± 2 in.
Fuel Flow
See Figure 4-22. Fuel enters at top right inlet and flow s into heating chamber. Heater is activated at 8 degrees C (46
degrees F) and below. Heated fuel enters element at top and flow s down thru the tw o stage fuel filter media pack.
W hile passing through the third stage, water coalesces out and drops to a sump holding area. Clean fuel returns to
the base and exits to the fuel injection pump. An electrical signal is obtained from the filter change sensor located
in the return path.
4-23
4A. Low Pressure Fuel Delivery System
FUEL FILTER MOUNTING
MODEL 80
FILTER
The Model 80 is cowl mounted on the C-K. See
Figure 4-23.
FUEL FEED
HOSE
WIRE ASM.
It is mounted at the rear of the intake m anifold on a G
or P Truck. Also because of space the G & P w ill use a
belt driven vacuum pump. See Figure 4-24.
Water in Fuel
\
DRAI
HOSE
FUEL
RETURN
HOSE
Figure 4*23, C-K Model 80 Mounting.
G AND P TRUCK FUEL FILTER
INLET
MANIFOLD
43 N m
\
(31 FT. LBS.)
'
During refueling, it is possible for water to be pumped
into your fuel tank along w ith the diesel fuel. Your
vehicle has a water separation system in the fuel filter.
It also has a “ WATER IN FUEL” light in the instrument
cluster which is designed to come on if water has
accumulated in the fuel filter and if the fuel filter
becomes plugged (a low pressure sensor will activate
the light). (The “ WATER IN FUEL” light is also
designed to come on during engine starting to let you
know the bulb is working. If the light does not come
on, check the fuse and the bulb.)
PIPE
ASM-INLET
/
/
CONNECTOR
(FILTER ASM.)
MODEL 80
FILTER ASM.
CONNECTOR
(FILTER ASM.)
FUEL
INJECTION
PUMP
PIPE ASM.
WATER
DRAIN
N m (9 IN. LBS.)
Figure 4-24, G-P Model 80 Mounting.
Figure 4-25, G-P Truck Remote Fuel Filter Water Drain.
4-24
4A. Low Pressure Fuel Delivery System
The G & P Truck have a remote mounted water drain valve near the water outlet.
FUEL FILTER - WATER DRAIN (FIGURE 4-23, 4-24 OR 4-25)
The diesel equipped truck has a m ultifunction filter for solid contam inants and water. The filter is mounted on the
front of the dash.
To drain water:
1. Remove the vehicle fuel tank cap.
2. Place a container below the filte r drain hose located below the filter.
3. W ith the engine off open water drain valve 2-3 turns.
4. Start engine — allow it to idle for about 1-2 m inutes or until clear fuel is observed.
5. Stop engine and close water drain valve.
6. Install fuel tank cap.
If the “ WATER IN FUEL” light com es on again after driving a short distance or the engine runs rough or stalls — a
large am ount of water has probably been pumped into the fuel tank. The fuel tank should be purged.
FUEL TANK PURGE PROCEDURE
An authorized dealer can remove (purge) water from the fuel tank. However, you can purge the fuel tank by using
the follow ing procedure.
-
CAUTION -
If you choose to purge the fuel tank yourself, use caution when working on or near the
fuel tank or other parts of the fuel system. Use the same safety precautions you would
normally use with gasoline when handling and disposing of the purged mixture.
(To dispose of purged fuel, contact a waste oil facility, your dealer or a service station.)
Remember that improper or incomplete service could lead to the vehicle itself not working
properly, which may result in personal injury or damage to the vehicle or its equipment. If
you have any questions about carrying out this service, have the service done
by a skilled technician.
TO PURGE THE FUEL TANK:
1. Park vehicle in a level position. The fuel pick up is in the approximate center of the tank.
2. Place a large container under the filte r drain hose. Open the drain 3 4 turns.
3. Disconnect fuel return hose at injection pump.
4. W ith the fuel tank cap properly installed, apply a low pressure 20.6-34.4 kPa (3-5 psi) maxim um air through the
fuel return hose. The fuel tank cap is designed to retain 20.6-34.4 kPa (3-5 psi) pressure, allowing water to be
forced out of the tank via the filte r drain hose.
5. Continue to drain until only clear fuel is observed — the com plete contents of the tank may have to be drained.
6. Close drain valve tightly. Reinstall the fuel return hose.
FUEL EXHAUSTION - ENGINE STOPS
Care should be taken not to run out of fuel; however, if the engine stalls and you suspect fuel exhaustion the
follow ing procedure will facilitate restarting.
First, determine if engine stall is due to fuel exhaustion. Open the filter air bleed valve — if air is present then the
vehicle is probably out of fuel.
To restart the engine:
1. Add at least 2 gallons of fuel if the vehicle is parked on a level surface; as much as 5 gallons may be required if
the vehicle is parked on a slope.
2. Disconnect the fuel injection pump shut off solenoid wire (pink wire). (See illustration).
4-25
4A. Low Pressure Fuel Delivery System
3. W ith the air bleed open crank the engine 10 to 15 seconds. Wait one minute for the starter to cool. Repeat until
clear fuel is observed at the air bleed.
4. Close air bleed and reconnect injection pump solenoid wire.
5. Repeat cranking 10-15 seconds until engine starts.
FUEL FILTER -
REPLACEMENT (FIGURE 4-23, 4-24 OR 4-25)
The fuel filter is easily removed and installed w ith the use of a screwdriver. To prevent fuel spillage — drain fuel
from the filte r by opening both the air bleed and water drain valve allowing fuel to drain out — into an appropriate
container.
To remove the filter:
1. Remove fuel tank cap. This releases any pressure or vacuum in the tank.
2. Disengage both bail wires w ith a screwdriver.
3. Remove the filter.
4. Clean any dirt off the fuel port sealing surface of the filter adapter and the new filter.
5. Install the new filter — snap into position w ith bail wires.
6. Close the water drain valve — and open the air bleed. Connect a 1/8" I.D. hose to the air bleed port and place
the other end into a suitable container.
7. Disconnect fuel injection pump shut off solenoid wire. (See illustration).
8. Crank engine for 10-15 seconds and then wait one minute for the starter m otor to cool. Repeat until clear fuel is
observed com ing from the air bleed.
9. Close the air bleed, reconnect the injection pump solenoid wire and replace fuel tank cap.
10. Start engine and allow it to idle for 5 minutes.
11. Check fuel filte r for leaks.
If the “ WATER IN FUEL” light illum inates the follow ing chart (Figure 4-26) may help pinpoint a specific problem.
“WATER IN FUEL” LIGHT CHART
PROBLEM
• Light com es on interm ittently.
RECOMMENDED ACTION
Drain water from fuel filter.
• Light stays on — engine running
1) Temperatures above freezing.
Drain fuel filter immediately. If no water is drained
and light stays on — replace fuel filter.
2) Temperatures below freezing.
Drain fuel filter immediately. If no water can be
drained — water may be frozen. Open air bleed to
check for fuel pressure. If no fuel pressure
replace filter.
• Light comes on at high speed or heavy
accelerations.
Fuel filter plugged — replace.
• Light stays on continuously — engine stalls, will
not restart.
1) After initial start-up.
Fuel filter or fuel lines may be plugged. See your
dealer.
2) Immediately after refueling — Large amounts of
water probably pumped into the tank.
Fuel tank purging required. See “ Fuel Tank Purge”
procedure found in Section 4 of this manual.
Figure 4-26, “W.I.F.” Light Chart.
4-26
4A. Low Pressure Fuel Delivery System
Model 80 Fuel Filter Seal Leakage
Leakage of fuel and/or air past the drain and/or vent seal(s) can occur in the base of a Model 80 fuel filter. The two
Model 80 assem blies involved are part numbers 14071933 and 14071064. The specific sym ptom s of this leakage are:
1. External fuel leakage from the vent or drain plugs.
2. A hard starting problem where the engine starts normally, then stalls, and is d ifficu lt to re-start.
A new seal (P/N 15529641) has been released to repair fuel and/or air leakage. The new seal has a slightly sm aller
outside diameter, enabling it to bottom in the bore and seal properly.
Seal replacement can be accom plished w ith the filter assembly removed from the vehicle as outlined in the
follow ing steps:
1. Remove the air vent plug located at the top of the filter base.
2. Loosen the drain plug on C/K model trucks and drain the fuel from the filter. On G and P models, open the
remote drain valve to drain the filter.
-
NOTE -
G and P model trucks do not have a filter drain plug or seal, and only the air vent plug seal
will require replacement.
3. Disconnect fuel hoses and wire connections from the filter assembly. Remove the assembly from the vehicle.
4. Unclip and remove the filter/separator element from the base.
5. A paper clip or short length of m echanic’s wire can be formed into a tool for seal removal. Using the tool,
remove the air vent and drain plug seal (if applicable) from the filter base.
6. Visually inspect the bore(s) for evidence of seal particles. If particles are present, compressed air can be blown
into the filte r base outlet to remove small particles in the bore(s).
7. A short length of 1A " bar stock or equivalent w ith square ends can be used to install the new seals in the base.
Apply a sm all amount of Synkut lubricant or equivalent, such as STP, to one end of the rod. Attach a new seal
(P/N 15529641) to the rod’s end. Insert the seal into the air vent plug bore until it seats firm ly in the bottom of
the bore. Visually inspect the seal to ensure it is squarely bottomed. Install the air vent plug.
8. Repeat the above procedure to install a new seal in the drain plug bore, but do not install the drain plug.
9. Prior to installing the drain plug, measure the length of the drain plug bore boss. If the boss is V long, install
the drain plug and tighten until it bottoms. If the boss is 1/8" long, install plain washer (P/N 561890) on the drain
plug and then thread the plug in until it bottoms. The drain plug washer prevents threading the drain plug in too
far and damaging the seal.
10. Attach the element to the base.
11. The filter assembly can be pressure checked with air by plugging the fuel inlet, outlet, and drain outlet (if
applicable). Using a m axim um of 10 psi air pressure, open and close the air vent and drain plug (if equipped)
several tim es to ensure the valve(s) are sealing.
12. Reinstall filter assem bly on vehicle and attach all fuel hoses and wire connections.
13. Vent and prime the fuel system as outlined in the Service Manual or Owner’s and Driver’s Guide.
4-27
4A. Low Pressure Fuel Delivery System
Fuel Filter/Water Separator
SERVICE INSTRUCTIONS TO CORRECT A “WATER IN FUEL” LIGHT INDICATED PROBLEM
When a problem is indicated by the “ WATER IN FUEL” signal light, first follow the diagnostic procedure outlined in
the vehicle sen/ice manual. If this procedure fails to locate the problem and the light continues to stay on, the fault
may be in the fuel filter/w ater separator assembly electrical sensors.
To determine w hich sensor may be at fault, first disconnect the vacuum sensor. To distinguish the electrical leads,
refer to Figure 4-27. The vacuum sensor has tw o wire leads w ith a black connector. (The “ WATER IN FUEL” sensor
C,K MODELS
G,P MODELS
Figure 4-27, Electrical Connections, Fuel Filter/Water Separator.
If the indicator light goes off, then the vacuum sensor is probably defective and should be replaced according to
the follow ing instructions.
1) Prior to removal of the defective vacuum sensor, obtain a new vacuum sensor and connect to the wire leads in
the vehicle. The light should remain off. This is to ensure the new sensor has not been damaged during
shipment.
2) Drain the fuel filter/w ater separator assem bly into a container according to the instructions in the vehicle service
manual, then disconnect and remove the entire assembly from the vehicle.
3) Remove the filter/separator element from the base assembly.
4) Using a sm all screwdriver, pry the vacuum sensor retaining clip from the base (Reference Figure 4-27). Take care
to prevent damage to the bore. It is suggested that initially prying the clip upwards at
the wire lead protective tab w ill cause the least am ount of scoring to the base bore.
5) Remove the vacuum sensor by pulling up on the sensor wire leads and by sim ultaneously prying under the
sensor opposite the leads using a small screwdriver.
6) After the sensor is removed, check the bore by running your finger around the inside of the bore and visually
inspect for sharp edges or raised metal burrs caused by removal of the retaining clip.
7) If burrs are present, use a fine (300) grit paper or round stone to remove any sharp metal burrs or scratches in
the bore. This is to prevent harm to the sensor “ 0” ring seal during installation. Take care to prevent debris from
entering the hole at the bottom of the bore when performing this service.
— CAUTION Do not sand or scratch the lower machined “0” ring sealing surface while deburring.
4-28
4A. Low Pressure Fuel Delivery System
8) Using a lint-free cloth and solvent, wipe off any debris from the bore area that may have been generated during
the deburring process, then blow o ff the area with compressed air.
9) Remove the sensor retaining clip from the new sensor using a knife blade or screwdriver to pry the clip upward
at the wire lead area.
10) Apply a liberal am ount of vaseline, grease or STP to the sensor “ 0” ring seal. Also apply a small amount of
lubricant to the base sensor bore.
11) See Figure 4-28 for proper vacuum sensor installation. To prevent cutting of the “ 0” ring seal, insert the sensor
into the bore at an angle w ith wire lead portion inserted first. Insert the new sensor (less the retaining clip) into
the base, using finger pressure until it is seated or nearly seated at the bottom of the bore.
12) Assure the cellular air filter is in place atop the sensor, then place the sensor retaining clip in position w ith the
protective tab over the wire lead. Holding the retaining clip in position w ith one finger placed at the center of
the clip, work the retainer into place by forcing each tab downward uniform ly and in small increm ents using a
screwdriver. The retainer w ill be in proper position when no further downward movement is felt and the top of
the retainer is approxim ately flush w ith the lip of the bore.
— NOTE Current versions of the vacuum sensor have a rubber button at the center of the retaining
clip. This button should be in place prior to installation of the sensor retaining clip to the
base and prior to installation of the filter/separator element.
13) Install filter/separator element to the base assembly.
14) Reinstall fuel filter/w ater separator assembly to the vehicle. Connect all electrical leads and the fuel inlet line.
Leave the fuel outlet line (smaller) disconnected.
15) Follow the engine startup procedure outlined in the vehicle service manual under “ Fuel Filter — Replacement
(Diesel Engine)” . When clear fuel is observed com ing from the outlet fitting, connect the outlet fuel line and
com plete the engine startup procedure.
4-29
4A. Low Pressure Fuel Delivery System
Modifications To Model 80 Fuel Sentry For DDA (G & P) Applications
*SDS #
TITLE
DESCRIPTION
1984
27108
W ater Sensor
IC chip, 4 wire, 4 wire male connector, voltage transient module
24831
Vacuum Switch
2 wire male connector
24270
Fuel Heater
2 wire female connector
1984V2
27284
W ater Sensor
Discrete components, 3 wire, 4 wire male connector
24831
Vacuum Switch
Same as 1984
24270
Fuel Heater
Same as 1984
1985
27285
W ater Sensor
Discrete components, 3 wire, 3 wire female connector
24290
Vacuum Switch
2 wire female connector
27530
Fuel Heater
2 wire female connector
27517
W ire Harness Bracket
All connectors are attached to this bracket at final assembly
*SDS — Stanadyne Diesel Systems
Functional Difference:
Discrete circuit (1984V2 & 1985) water sensor w ill lamp test for approximately 2-5 seconds each tim e the key is
turned on.
1984 unit lamp tests only during cranking.
4-30
4A. Low Pressure Fuel Delivery System
14071933 ASSEMBLY C-K TRUCK MODEL 80 PARTS LIST
GM PART NUMBER
STANADYNE NUMBER
Bracket, W iring Harness
15593335
24838
Clip, Vacuum Switch Retainer
15593306
24835
Seal, “ 0” Ring (Vacuum Switch)
15596608
24275
Switch, Vacuum
15593308
24831
Seal, Drain Plug
15596611
24266
Seal, “ 0” Ring (Fuel Heater)
15596600
15349
Plug, Vent
15596612
24267
Screw, Thd Forming V2-20
15596607
24437
Bracket, Mtg.
15593336
34522
Clamp, Filter
15596613
24265
Heater Assembly, Fuel
15593337
24870
Screw, Thd Forming
15596603
24322
Sensor, W ater
15596610
24269
Base Assem bly
15593338
24521
14075347
24262
DESCRIPTION
* Element, Filter
*Part of Filter Element
14071064 ASSEMBLY G-P TRUCK MODEL 80 PARTS LIST
GM PART NUMBER
STANADYNE NUMBER
Bumper, Vacuum Switch
15593305
27129
Clip, Vacuum Switch Retainer
15593306
24835
Seal, “ 0” Ring Vacuum Switch
15593307
24834
Switch, Vacuum
15593308
24831
Screw Thd Forming (V*-20)
15596607
24437
Clamp, Filter
15596613
24265
Bracket, Filter Mtg.
15593309
24527
Seal, Drain Plug
15596611
24266
Plug, Vent
15596612
24267
Seal, “ 0” Ring
15596600
15349
Heater Assembly, Fuel
15596609
24270
Screw, Thd Forming (8-32)
15596603
24322
Sensor, W ater
15593310
27108
* Element, Filter
14075347
24262
DESCRIPTION
‘ Part of Filter Element
4-31
4A. Low Pressure Fuel Delivery System
High Pressure Fuel Delivery System
• Injection distributor pump.
• High pressure lines.
• Fuel injection nozzles.
The 6.2 liter injection pump is mounted on top of the
engine under the intake manifold. It is gear driven by 2
gears — one attached to the front end of the cam shaft
w hich drives the second gear that is attached to the
end of the injection pump shaft. These 2 gears are the
same size and have the same number of teeth; thus,
the injection pump shaft turns at the same rate as the
cam shaft and one-half the speed of the crankshaft.
The pump will turn in the opposite direction to that of
the cam shaft and crankshaft. See Figure 4-29.
The injection pump is a high pressure rotary type
pump that directs a metered pressurized fuel through
the high pressure tubes to the eight injector nozzles.
The eight high pressure lines are all the same length
although their shape may be different. This prevents
any difference in tim ing, cylinder to cylinder. See
Figure 4-30.
The lines are all 600mm long. The I.D. is 2.5mm, and
the O.D. is 6.3mm on C, K, and P series. The G-van I.D.
is 2mm and the O.D. is 6mm.
Figure 4-30, High Pressure Lines.
4-32
4B. High Pressure Fuel Delivery System
Fuel Injection Pump
The 6.2L diesel engine uses the Stanadyne DB2, distributor-type, fuel injection pump (Figure 4-31).
The function of the fuel injection pump is to meter the fuel according to engine power requirements and to inject it
at high pressure through nozzles into the com bustion chambers of the engine at the correct tim ing intervals. The
metering calls for careful design and construction, as it has to be carried out at a high speed and with great
precision, in order to ensure even fuel distribution with sm ooth running, and sensitive response to power control.
The tim ing of the injections must also be done w ith perfect precision, or high efficiency is im possible to achieve,
and since the operating pressure may be as high as 6,000 PSI, the pump itself must be constructed w ith the utm ost
care, em ploying high-grade m aterials and the finest of working tolerances for the pump elements.
The em ploym ent of a separate pum ping element for each cylinder, together w ith suitable means of output control,
has been the general practice of fuel injection pump m anufacture for some time. The idea of using one pump barrel
and a set of plungers to supply all cylinders in turn is a natural one, as it offers obvious savings; the pumping
elem ent operates more often (according to the number of cylinders), and is provided with a distributor or means of
connecting the pump delivery to each of the injectors in turn.
The distributor type pump is thus an attractive proposition, since the number of pumping elements is reduced to
one in all cases.
4-33
4B. High Pressure Fuel Delivery System
Injection Pump Description
The main rotating com ponents (Figure 4-32) are the drive shaft, the distributor rotor, the transfer pump blades and
the governor.
The drive shaft engages the distributor rotor in the hydraulic head. The drive end of the rotor incorporates tw o
pumping plungers.
The plungers are actuated toward each other sim ultaneously by an internal cam ring through rollers and shoes
which are carried in slots at the drive end of the rotor. The number of cam lobes equals the number of engine
cylinders.
The hydraulic head contains the bore in which the rotor revolves, the metering valve bore, the charging ports and
the head discharge fittings. The high pressure injection lines to the nozzles are fastened to these discharge fittings.
The DB2 Pump is an inlet metering pump. That is, it has a pumping period with a variable beginning, and a
constant ending.
4-34
4B. High Pressure Fuel Delivery System
Injection Pump Operation
The general operating principal of the pump may be
easily understood by follow ing the fuel circuit through
the pump.
FUEL FLOW
First, the fuel is drawn into the pump inlet, and
through the inlet filter screen by the transfer pump.
Excess fuel is bypassed through the pressure regulator
assembly, and back through the suction side. The fuel,
w hich is under transfer pump pressure, flow s through
the rotor and head. (Figure 4-33).
Figure 4-33, Fuel Intake.
From here, the fuel is routed in a number of different
directions. Some of the fuel is sent through the head
locating screw to the autom atic advance. The majority
of the fuel is sent into a connecting annulus to the top
of the hydraulic head. (Figure 4-34).
Figure 4-34, Fuel Flow To Hydraulic Head.
From this point fuel is sent to the transfer pump test
tap and the vent wire assembly. The remaining fuel is
sent through a connecting passage to the metering
valve. (Figure 4-35).
Figure 4-35, Fuel Flow To Transfer Pump and
Metering Valve.
4-35
4B. High Pressure Fuel Delivery System
M E TE R IN G VALVE
The metering valve, which is controlled by the
governor, regulates fuel flow into the head charging
ports. (Figure 4-36). It is the equivalent of a throttle
plate in a carburetor. It controls the flow area to the
pumping plungers. Figure 4-37 shows m inim um flow
area, and Figure 4-38 shows maxim um flow area.
Figure 4-36, Metering Valve.
Figure 4-38, Metering Valve Full Load.
Figure 4-39 shows the vertical straight edge and hole
type metering valves. The 6.2L uses the vertical straight
edge type.
STRAIGHT EDGE
Figure 4-39, Metering Valve Designs.
4-36
4B. High Pressure Fuel Delivery System
PUMPING MECHANISM
As the rotor revolves, the tw o rotor inlet passages
register w ith charging ports in the hydraulic head.
(Figure 4-40).
Figure 4-40, Charging Ports.
This allow s fuel to flow into the pum ping chamber.
(Figure 4-41). For improved roller retention, the 6.2L
engine w ill use a new roller shoe. It w ill provide
increased shoe wrap-around by positioning the roller
deeper into the shoe. Due to the lower profile of these
shoes and rollers, the part number of their com panion
leaf spring has been changed. The shoes are identified
by a - 1 0 marking.
CHARGING
ROLLER BETWEEN
CAM LOBES
PLUNGER
/
METER|NG
VALVE
CIRCULAR
FUEL PASSAGE
LEAF
SPRING
DISTRIBUTOR
ROTOR
PUMPING
CHAMBER
CAM
SHOE
INLET
PASSAGES
CHARGING
PASSAGE
TRANSFER
PUMP
Figure 4-41, Pumping Chamber.
As the rotor continues to revolve, the inlet passages
move out of registry, ending charging. Discharge
begins when the discharge port of the rotor registers
w ith one of the head discharge outlets. (Figure 4-42).
DISCHARGING
R 0 L ^C?MCLO b £ CTS
DISTRIBUTOR
roto r
DISCHARGE
FITTING
PUMPING
CHAMBER
DELIVERY
DISCHARGE VALVE
PASSAGE
d is c h a r g e p o r t
Figure 4-42, Fuel Discharge.
4-37
4B. High Pressure Fuel Delivery System
PUMPING UNDER PRESSURE TO NOZZLE
W hile the discharge port is open, the movement of the
rotor causes the rollers to contact the cam lobes,
forcing the plungers together. The fuel is thus
pressurized until the rollers pass over the top of the
injection cam, when the pressure starts to drop.
(Figure 4-43).
The fuel then flow s through the discharge outlet and
discharge port to the injection nozzle. (Figure 444).
DISCHARGING
PASSAGE
DISCHARGE PORT
Figure 4*45, Delivery Valve Control.
4-38
The magnitude of this pressure drop is controlled by
the delivery valve which retains a definite residual
pressure in the discharge circuit. This pressure is low
enough to assure prompt nozzle closing yet high
enough to prevent cavitation of the fuel between
injections. (Figure 4-45).
4B. High Pressure Fuel Delivery System
TRANSFER PUMP
Now for a closer look at some of the system s and
com ponents mentioned earlier in the program. Where
model year design differences exist they w ill also be
pointed out.
Let’s begin w ith the com ponent that supplies and
pressurizes the fuel: The Transfer Pump.
The positive displacem ent vane type transfer pump
consists of a stationary liner and four spring loaded
blades. Since the inside diam eter of the liner is
eccentric to the rotor axis, inlet and discharge cavities
are formed by the blades as they rotate. (Figure 4-46).
-
NOTE —
A positive displacement pump discharges
a certain amount of liquid for each
revolution of the rotating element.
As a blade passes over the inlet slot it enlarges the
inlet volume, creating suction. The cavity between this
and the second blade fills w ith fuel until the second
blade passes the end of the inlet slot. (Figure 4-47).
This volum e of fuel is carried around until the leading
blade uncovers the end of the discharge slot as shown
in the next illustration.
As the leading blade continues to pass over the
discharge slot it is followed by the second blade which
pushes the captive volume of fuel ahead of it. Since
the blades are moving into a decreasing volume in the
liner, the captive fuel is squeezed out through the
discharge slot by the follow ing blade as shown in
Figure 4-48.
This sequence takes place four tim es every revolution
of the rotor, producing a continuous discharge.
4-39
4B. High Pressure Fuel Delivery System
REGULATOR ASSEMBLY OPERATION
REGULATING SLOT
REGULATING PISTON
REGULATING SPRING
INLET SIDE
REGULATOR
THIN PLATE
In order to understand how designed fuel pressures
are maintained over a broad range of conditions w e’ll
now take a closer look at regulator assembly
operation.
This illustration shows the operation of the pressure
regulator assembly while the pump is running. Fuel
output from the discharge side of transfer pump forces
the piston in the regulator assembly against the
regulating spring. (Figure 4-49).
ORIFICE
SPRING ADJUSTING PLUG
DISCHARGE SIDE
Figure 4-49, Regulator Assembly.
REGULATING SLOT
Since the fuel pressure on the piston is opposed by
the regulating spring, the pressure curve of the transfer
pump is controlled by the spring rate and the size of
the regulating slot. This results in pressure being
increased as engine speed increases. (Figure 4-50).
Figure 4-50, Regulator Control.
VISCOSITY COMPENSATING DEVICE
Another unique and very sim ple feature of the DB2
automotive pump is a viscosity com pensating device.
This com ponent ensures proper transfer pump
pressure regardless of the ambient temperature or
grade of fuel used. (Figure 4-51).
Figure 4-51, Viscosity Compensating Device.
4-40
4B. High Pressure Fuel Delivery System
When fuel “ th in s ” out due to heat, pressure loss will
occur. The thin fuel, however, perm its increased
leakage past a loose fit at the regulating piston
causing an increase o f pressure in the spring cavity.
This aids the spring and moves the piston to restrict
spill, thus correcting the pressure. (Figure 4-52).
REGULATING
SLOT
Figure 4*52, Thin Fuel Correction.
When fuel is cold it “ thickens,” and due to the better
sealing this affords: fuel pressure increases. Also due
to better sealing, leaking past the regulating piston
diminishes. This causes a reduction of spring cavity
pressure allow ing transfer pump pressure to move the
regulating piston outward. This increases spill and
corrects the pressure. (Figure 4-53).
Figure 4-53, Thick Fuel Correction.
A short sharp edged orifice in the adjusting plug
controls the leakage from the spring cavity.
This orifice is not sensitive to viscosity variation.
Consequently, as input to the spring cavity, past the
piston, varies w ith viscosity, pressure in this cavity will
also change. This biases the position of the regulating
piston over the spill slot and m aintains the correct
transfer pump pressure. (Figure 4-54).
THIN PLATE
_
1
1
1
I -
ORIFICE
Figure 4-54, Orifice Control.
4-41
4B. High Pressure Fuei Delivery System
RETURN OIL SYSTEM
The return oil system (Figure 4-55) performs the
follow ing functions. 1.) A controlled flow through the
housing m aintains stable conditions for the internal
parts. 2.) The fuel flow cools and lubricates the pump.
3.) It provides autom atic air venting of the system.
TRANSFER PRESSURE
ANNULUS
The return oil vent passage is fed, from the transfer
pressure annulus.
Figure 4-55, Return Oil System.
Fuel under transfer pump pressure is discharged from
the transfer pressure annulus into a vent passage in
the hydraulic head (Figure 4-56). Flow through the
passage is restricted by a vent wire assembly to
prevent excessive return oil and undue pressure loss.
The assem bly is made of a hollow screw, into w hich a
“ J ” wire is installed.
The am ount of return oil is controlled by the size of
wire used in the vent wire assembly, i.e., the smaller
the wire the greater the flow and vice versa. The vent
wire assembly is available in several sizes in order to
meet the return oil quantities called for on the
specification.
Note that this assem bly is accessible by removing only the governor cover. The vent passage is located behind the
metering valve bore and connects w ith a short vertical passage containing the vent wire assem bly and leads to the
governor com partm ent.
Should a sm all quantity of air enter the transfer pump, it im m ediately passes to the vent passage as shown. Air and
a small quantity of fuel then flow from the housing to the fuel tank and via the return line.
Housing pressure is m aintained by a spring loaded ballcheck return fitting in the governor cover of the pump.
4-42
4B. High Pressure Fuel Delivery System
ELECTRIC SHUTOFF SOLENOID
All Stanadyne Diesel Systems DB2 Autom otive
pumps are equipped w ith electrical shut-off solenoids.
(Figure 4-57).
Illustrated here is an energized to run solenoid. When
this is de-energized, an arm on the solenoid is moved
out by spring force and physically closes the metering
valve. This action interrupts injection, and stops the
engine.
AUTOMATIC ADVANCE SYSTEMS
The speed advance device (Figure 4-58) is used to
achieve best engine performance through the operating
speed range of the engine. Tim ing advance is needed
to com pensate for the tw o delay periods: 1) the
injection pressure wave traveling the length of the
injection line, 2) the ignition delay period.
The injection tim ing advance system controls the start
of injection proportional to pump speed. This is done
by moving the cam ring opposite the direction of rotor
rotation. The plunger rollers w ill then com e in contact
with the lobes on the cam ring earlier in the cycle.
The power advance piston engages the cam ring
through the cam advance pin and moves the cam. Fuel
under transfer pump pressure is fed through a passage
in the hydraulic head, through the cam advance pin to
the servo advance piston valve chamber. As transfer
pump pressure is increased the servo advance piston
valve uncovers a port w hich is connected to the
advance piston, w hich advance the cam ring.
Secondary control of the cam ring advance is by a mechanical connection from the throttle shaft thru a face cam
and rocker lever to the servo advance piston valve spring seat. This secondary tim ing control results in injection
tim ing better suited to engine demand.
4-43
4B. High Pressure Fuel Delivery System
ADVANCE
DIRECTION
CAM
DISTRIBUTOR
ROTOR
RETARD
DIRECTION
HOUSING
SPRING
PISTON
TRIMMER
SCREW
ADVANCE
PISTON
AUTOMATIC ADVANCE LOADING FORCES
When the pump is operating, the force required to
displace the plungers inward plus the m omentum of
the rotor assembly transm itted by the rollers, produces
the cam loading force. This tends to turn the cam in
the direction of rotor rotation. (Figure 4-59). This
movement retards the pum p’s tim ing.
This cam loading plus spring force is transm itted to
and opposes the power side forces. The com bination
of forces positions the advance m echanism at a
definite point for each full load speed. At part load the
reactive forces dim inish and are not as effective in
opposing power side forces. As a result the cam
assumes a more advanced position.
SLIDE
WASHERS
ADVANCE
SPRING
m
TRANSFER PUMP PRESSURE
□ HOUSING PRESSURE
CAM ADVANCE
SCREW
Figure 4-59, Power Side Forces.
LIGHT LOAD (PART THROTTLE) TIMING
The inlet metered DB2 pump (Figure 4-60) has a pumping period w ith a variable beginning and a constant ending.
That is, at m inim um throttle positions the metering valve is only open a small amount, so the plungers only move a
small amount. And the rollers have to ride a great distance up the cam ramp before they can cause the plungers to
pressurize the fuel. This causes retarded injection tim ing as compared to wide open throttle position (maximum
metering valve opening). Because at WOT; plunger pressurization begins as the rollers start up the cam ramp, and
peaks at the lobe. Therefore, tim ing must be advanced at light loads (part throttle) to com pensate for this injection
tim ing lag. The am ount of light load retard is compensated by an inherent light load advance obtained from the
mechanical light load advance.
ROLLER
ROTOR
ROTATION
ROTOR
ROTATION
ADVANCE
DIRECTION
LEAF
SPRING
ROLLER
ADVANCE
DIRECTION
LEAF
SPRING
CAM
LOBE
CAM
LOBE
METERING VALVE AT WOT (MAXIMUM)
Figure 4-60, Cam Positioning.
4-44
METERING VALVE AT MINIMUM THROTTLE
4B. High Pressure Fuel Delivery System
SPEED AND LIGHT LOAD ADVANCE SYSTEMS
As noted previously, inlet metered pum ps characteristically retard the start of pumping at light loads.
To correct this condition, several form s of light load advance have been developed, two of w hich are described
below.
• The first of these, used in speed advance (used only in the 78-81 5.7L diesel), uses a sm aller diam eter advance
piston to retard the full throttle advance curve w ith respect to the light load advance curve. The actual advance
position at full throttle depends on the difference between the flow into the power piston chamber between
pumping events and the reverse flow through the bleed orifice during the pumping event. The sm aller diam eter
advance piston raises advance cham ber pressure during the pumping event because of its small area. The flow
rate through the bleed orifice is therefore increased. The sm aller piston area also increases the advance motion
for a given orifice flow change.
MECHANICAL LIGHT LOAD ADVANCE SYSTEM, 6.2L DIESEL
A second light load advance system, shown in Figure 4-61, is available for autom otive applications that use
min-max governing. In addition to the normal speed advance, light load advance is furnished as a function of
throttle angle.
The mechanical light load advance system is used on autom otive pumps. It relies on tw o systems to provide
advance. The first system is a servo advance mechanism that is operated by transfer pump pressure and which
positions the cam ring in response to throttle setting and engine load.
The second system is com posed of a mechanical link between the throttle shaft and the servo plunger. This link is
composed of a face cam connected to the end of the throttle shaft and a rocker lever assembly connected to the
side of the pum p housing by a pivot pin. A roller is attached to the upper end of the lever and rides on the surface
of the face cam. The lower end of the lever contacts the protruding end of the servo advance plunger.
4-45
4B. High Pressure Fuel Delivery System
MECHANICAL LIGHT LOAD ADVANCE OPERATION
As w ith the previous advance system, the rotor’s force
is transferred to the cam ring during injection. This
force continually urges the piston toward the retard
position. However, an opposing force is supplied by
transfer pump pressure acting on one end of the servo
advance piston. (Figure 4-62).
TRANSVERSE
PASSAGE
S.
LONGITUDINAL
PASSAGE
The position of the servo valve in the advance piston
bore regulates this force, and determines the degree of
advance achieved at any throttle setting or load.
(Figure 4-63).
SERVO
VALVE
Figure 4-63, Servo Valve Movement.
Additional advance at low throttle settings is provided
by the face cam to rocker lever action w hich changes
the reference point of the spring. (Figure 4-64).
This allows the servo-advance valve to open further
and provide a greater degree of advance at low throttle
settings. The end result of both of these advance
m echanisms is a vast improvement in the driveability
of diesel equipped vehicles.
Figure 4-64, Face Cam To Rocker Lever
Action.
4-46
4B. High Pressure Fuel Delivery System
INTEGRAL ORIFICE ADVANCE PISTON
See Figure 4-65. The advance piston orifice screw has
been elim inated, and the orifice is now m achined into
the piston. The orifice size in 1984 and later is .030 in.
1982-83 orifice size was a .040 in. orifice screw.
Stanadyne part #24433 (2443405).
©■>
''t®
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
P O W E R SID E PLU G
" O ” R ING SE A L
P ISTO N A S S E M B L Y
S ER V O A D V A N C E V A LV E
M E C H A N IC A L LIG H T LO AD
“ O ” RING SEA L
S P R IN G SID E PLUG
W A SH ER
SE R V O A D V A N C E P LU N G E R
C AM A D V A N C E PIN
11. H EA D LO C A TIN G S C R E W
A N D FILTER
12. S ER V O A D V A N C E A D JU S TIN G
S C R E W (DO N O T A D JU S T)
13. R E TA IN IN G RING
14. R O C K E R LE V ER PIN
15. R O C K E R LE VER
16. R O LLER
17. S C R E W
18. “ O ” RING
19. C AM A D V A N C E PIN H O LE PLUG
Figure 4-65, Advance Piston.
HEAD LOCATING SCREW
AND FILTER ASSEMBLY
A new head locating screw (#24566) w ith nylon filter
has been introduced to prevent contam inants from
reaching the advance piston area. See Figure 4-66. The
filte r is installed into the body of the screw, the end of
which is crim ped over. The screw is only available as
an assembly, as shown on the right, and is identified
by a groove around the head of the screw. Suitable for
use in all mechanical light load advance-type pumps.
Figure 4-66, Head Locating Screw With Filter.
4-47
4B. High Pressure Fuel Delivery System
HOUSING PRESSURE COLD ADVANCE (H.P.C.A.)
All pumps are equipped w ith a Housing Pressure Cold Advance solenoid. (Figure 4-67).
This com ponent has been designed to allow more advance during engine warm-up. It consists of a solenoid
assembly and a ball check return connector, both in a redesigned governor cover. The electrical signal which
controls the operation of the solenoid is generated by a sensing unit mounted on the rear of the right cylinder head.
1984 and later H.P.C.A. is controlled by a cold advance circuit (C.A.C.) relay.
FAST IDLE/H.P.C.A. TEMPERATURE
CONTROL COOLANT SENSOR SWITCH
OPENS ABOVE 95°F
CLOSES BELOW 85°F
GROUND
Figure 4-67, H.P.C.A. Solenoid Installation.
The sw itch is calibrated to open the circuit at 9 5 °F for 83 and later (115° on 1982). Below the sw itching point,
housing pressure is decreased from 8-12 psi to zero which advances the tim ing 3°. Above, the sw itch opens de­
energizing the solenoid and the housing pressure is returned to 8-12 psi. The fast idle solenoid is energized by the
same switch. The sw itch again closes when the temperature falls below 8 5 °F (95°F on 1982).
PURPOSE:
1. Emission Control device.
2. Better cold starts.
3. Improves idle, reduces w hite smoke and noise when cold.
4-48
4B. High Pressure Fuel Delivery System
H.P.C.A. OPERATION
During cold warm-up conditions, the plunger moves up
and the rod contacts the return connector ball. (Figure
4-68). W hen the ball is moved off of its seat, the
housing pressure is reduced due to an increased flow
through the connector. Because of lowered housing
pressure, the resistance to the advance piston
movement is less, and thus the piston can move
further in the advance direction.
(4) RETURN CONNECTOR
BALL OFF ITS SEAT
(1)
SOLENOID
ENERGIZED
(3)
ROD
EXTENDED
(2) PLUNGER
Figure 4-68, Solenoid Energized.
When the engine reaches normal operating
tem perature the electrical signal to the solenoid
ceases, and the plunger is returned to its initial
position. (Figure 4-69).
(4) RETURN CONNECTOR
1984 H.P.C.A. Terminal w ill be changed (24669) because
of 84 California System.
Figure 4-69, Solenoid De-Energized.
— NOTE —
When changing the fuel filter, injection pump or when the car has run out of fuel,
disconnect the connector from the temperature switch and jumper connector
terminals. This will aid in purging air from the pump by allowing more fuel to pass to the
return line. (This procedure is necessary only on a hot engine, as the circuit will
always be closed when the engine is cold.)
4-49
4B. High Pressure Fuel Delivery System
MIN-MAX GOVERNOR
Now for a look at the operation of the assem bly that controls the engine speed at low idle and high speed. The
Min-Max governor.
Illustrated here (Figure 4-70) are the main com ponents of the governor. They are the governor weights, the governor
arm, the low idle spring, the idle spring guide, the main governor spring, the main governor spring guide
and the guide stud.
4-50
4B. High Pressure Fuel Delivery System
Low Idle
Figure 4-71 shows the relationship of the parts when
the pump is running at low idle. The low force
developed by the governor weights is balanced by the
low idle spring. Thus, only a small am ount of fuel is
delivered by the metering valve.
THROTTLE SHAFT
(LOW IDLE THROTTLE POSITION)
GUIDE STUD
LOW IDLESPRING
GOVERNOR
ARM
GOVERNOR
WEIGHTS
METERING
VALVE
DRIVE SHAFT
Figure 4-71, Governor at Low Idle.
Mid-Range
In Figure 4-72, the throttle is in a mid-range position.
The idle spring is fully collapsed, and the governor
weights have moved out partially. The main governor
spring is designed such that the governor weight force
cannot overcome the spring’s preload until the engine
reaches the m axim um rated speed. Thus, at partial
throttle, the assem bly acts as a solid link against the
governor arm. This permits the driver to control the
metering valve position w ith the throttle over the entire
mid-range speed.
Figure 4-72, Governor at Mid-Range Throttle.
Full Load
W ith the throttle in the full load position, the engine
speed and the pump speed increase until the governor
w eights have generated enough force to deflect the
main governor spring. This movement turns the
metering valve to the shut-off position, thereby
preventing an engine overspeed condition. (Figure 4-73).
Figure 4-73, Governor at Full Load.
4-51
4B. High Pressure Fuel Delivery System
IDLE SPRING
EXTERNAL
IDLE SPRING
IDLE SPI ING
IN TE R N A L IDLE SPRING
The 1984 and later 6.2L C alifornia applications use an
internal idle spring, which controls the gap between
the sleeve and the washer. (Figure 4-74). The close
tolerance will result in a more accurate input to the
engine throttle position sensor, w hich regulates the
exhaust gas recirculation and exhaust pressure
regulator functions.
INTERNAL
IDLE SPRING
Figure 4-74, Internal Idle Spring Design.
HOT FUEL IDLE SPEED DROP
When idle speed drops due to hot fuel, a bi-metal strip
on the governor arm deflects. This creates a “ spring
load” on the governor arm causing it to rotate slightly,
thus repositioning the metering valve to pass more fuel
and increase speed slightly. (Figure 4-75).
Figure 4-75, Bi-Metal Operation.
G O V E R N O R ARM 1982-84
See Figure 4-76. The 6.2L uses a ball-pivot governor
arm which has a slot below the bi-metal strip. This
prevents interference with the ball pivot conical
extrusion. All governor arms of this style now have a
tab at the bottom of the conical extrusion, for better
retention. The bi-metal strip is covered by a .012" thick
back-up leaf for wear resistance.
Figure 4-76, Ball Pivot Governor Arm.
4-52
4B. High Pressure Fuel Delivery System
Injection Pump Rotor
The final com ponent that we w ill examine is the heart
of the diesel injection pump; the rotor. (Figure 4-77).
Due to the extrem ely close tolerances of the rotor and
head assemblies, a thermal relief groove has been
incorporated into the rotor design. Thermal shock can
cause a head assem bly to contract, resulting in the
seizure of the head and rotor. To lessen the possibility
of this happening, a reduction in the rotor diam eter at
the area between the ports has been added.
Figure 4-77, Rotor.
The rotor in 1980 through 1984 pum ps incorporates residual pressure balancing ports. These small vent ports
operate by sim ultaneously registering w ith the head discharge outlets shortly after each injection. This operation
allows a balance of the residual pressures between injection lines and helps smooth out the operation and the
sound of the engine.
ROTOR SEIZURES
A rotor seizure can be due to a loss of clearance between the hydraulic head and rotor during the transient (or
warm-up) condition. Heat generated by shearing the oil film at the hydraulic head to rotor interface causes heating
of the hydraulic head and rotor. Because the mass of the rotor is less than that of the hydraulic head, it heats and
expands at a faster rate. The clearance at the interface of the hydraulic head and rotor is thereby reduced and the
possibility of rotor seizure is introduced.
The rotor seizures in a test series occurred at the m idpoint of the rotor length indicating that the maximum rotor
heating and expansion occurred at the midpoint. Therefore, a relief groove was added to the diameter of the rotor,
as shown in Figure 4-77 to minim ize the potential for rotor seizure follow ing a cold, high speed acceleration.
DELIVERY VALVE
The delivery valve rapidly decreases injection line pressure after injection to a predetermined value lower than that
of the nozzle closing pressure. This reduction in pressure permits the nozzle’s valve to return rapidly to its seat,
achieving sharp delivery cu to ff and preventing improperly atomized fuel from entering the com bustion chamber.
4-53
4B. High Pressure Fuel Delivery System
DELIVERY VALVE OPERATION
A single, spring loaded, delivery valve (Figure 4-78) is
located in the center of the DB2 pump rotor. It serves
as a one way check valve to seal the pumping
chamber from the injection line and also controls
residual line pressure by providing volume unloading.
At the beginning of pumping, the delivery valve is
displaced into its spring chamber until, at a valve lift
equal to the dim ension “ H” , fuel flow s from the
plungers to the discharge port. At the end of the
pumping cycle, the plungers travel outward allowing
the delivery valve to move toward its seat. As the valve
closes and the retraction volume (Valve Area H) is
removed from the delivery valve spring chamber, a
negative pressure wave is propagated toward the
nozzle. The negative pressure wave lowers the injection
line pressure to allow rapid nozzle closure and
prevents secondary injection.
The delivery valve operates in a bore in the center of
the distributor rotor. The valve requires no seat — only
a stop to lim it travel. Sealing is accom plished by the
close clearance between the valve and bore into which
it fits. Since the same delivery valve performs the
function of retraction for each injection line, the result
is a sm ooth running engine at all loads and speed.
Figure 4-78, Delivery Valve.
When injection starts, fuel pressure moves the delivery valve slightly out of its bore and adds the volume of its
displacem ent to the delivery valve spring chamber. Since the discharge port is already opened to a head outlet, the
retraction volum e and plunger displacem ent volume are delivered under high pressure to the nozzle. Delivery ends
when the pressure on the plunger side of the delivery valve is quickly reduced, due to the cam rollers passing the
highest point on the cam lobe.
Following this, the rotor discharge port closes com pletely and a residual injection line pressure is maintained. Note
that the delivery valve is only required to seal w hile the discharge port is opened. Once the port is closed, residual
line pressures are m aintained by the seal of the close fitting head and rotor. It is possible that the residual pressure
may vary between injection lines.
4-54
4B. High Pressure Fuel Delivery System
TRAILING PORT SNUBBER
A damper orifice is located after the delivery valve.
This dam per is called a trailing port snubber (Figure
4-79).
The trailing port snubber is used to prevent secondary
injections and cavitation errosion of the high pressure
system by weakening reflected pressure waves. This
port trails the discharge port radially and resonates the
fuel back into the delivery valve cavity.
Figure 4-79, Trailing Port Snubber.
The snubber is drilled directly into the rotor bore and is reduced to .018" in diam eter at the bottom of the hole.
Since it is located radially behind the discharge port, reflected pressure waves w ill re-enter the rotor after each
injection. The flow rate into the delivery valve bore is then restricted by the .018" orifice.
Phasing of the rotor snubber port in relation to the other port sequences m ust be carefully designed. This is
especially true for an eight cylinder distributor pump where rotor angular space is at a premium.
The discharge cycle at each port is about 20 degrees. At the 15 degree point in the injection the snubbing begins
for approxim ately 22 degrees.
In the oscilloscope traces (Figure 4-80) the reflected waves cause a needle lift in a system w ith a standard rotor.
W ith an .018" snubber port rotor, the pressure waves are reduced and the nozzle valve remains seated between
injection.
This reduces the cavitation erosion potential. In addition, pressure waves reflected from the nozzle are partially,
rather than totally, reflected as they pass through the snubber orifice.
TRAILING PORT SNUBBER OPERATION
PINTLE TYPE NOZZLES
WITHOUT
SNUBBER VALVES
WITH .018 ORIFICE
SNUBBER PORT
INJECTION
PRESSURE
NEEDLE
LIFT
Figure 4-80, Trailing Port Snubber Graph.
4-55
4B. High Pressure Fuel Delivery System
Injection Pump Repairs
— NOTE —
The following procedure is not intended as a guide for complete overhaul. It does not
include repairs which would involve calibration on a test stand. For operations which
require re-calibration, the pump must be sent to an authorized Stanadyne agency.
Figure 4-81 shows a typical test stand installation. The test stand incorporates a 2 to 15 H.R electric motor,
depending on the particular model used, w hich drives the injection pump. The stand’s m otor sim ulates the
autom otive engine w ith the rpm controlled on the machine by the operator and not by the throttle opening. Various
tests and adjustm ents are performed. Some are: Electric solenoid pull-in voltage, housing pressure cold advance
solenoid operation, face cam position, min-max governor, return oil volume, housing pressure, transfer pump
pressure and autom atic advance adjustm ents. Actual calibration of fuel delivery is not adjustable w ithin the head
and rotor assem bly but is affected directly by some of the above adjustm ents. Various rpm ranges and throttle
openings are used to check output of the pump.
TRANSFER PUMP PRESSURE GAUGE
— IMPORTANT —
It should be understood
that the injection pump is
designed to deliver a
metered amount of fuel at
the proper time and is
therefore incapable of
delivering a rich or lean
mixture. It should also be
understood that other
than a failure of the
governor weight retainer
ring or the correction of
the min-max governor,
the injection pump will
have very little to do with
a rough idle condition
and therefore generally
should not be sent to the
local Roosa Master shop
for rough idle.
Figure 4-81, Typical Test Stand Installation.
4-56
4B. High Pressure Fuel Delivery System
GOVERNOR WEIGHT RETAINER RING FAILURES
Background inform ation of failed governor weight retainer ring: diesel fuel that is contam inated w ith excessive
water or the presence of alcohols found in some additives not normally present in recommended diesel fuels may
accelerate failure of the Poly-urethane (Pellethane) governor w eight retainer ring in the injection pump. Failure of the
ring is heat related and w ill most likely result in a rough idle condition and, in some instances, the engine may not
run. A failed ring w ill break apart into small black particles plugging the fuel return check valve. Remove the check
valve if small particles are observed. Confirm the findings by removing the pump cover and rotating the governor
weight retainer in both directions (Figure 4-82) using a suitable tool or screwdriver. If the retainer moves more than
1/16" and does not return, the retainer ring has failed. Norm ally a failed ring w ill allow 1/4" free movement.
If a failed ring is found, the pump w ill require removal from the engine. Follow the procedures listed in this manual
for replacement.
Figure 4-82, Failed Governor Weight Retainer Ring Checking Procedure.
SERVICE OPERATIONS ON-VEHICLE
Operations which can be performed individually without removing the pump from the engine are as follows:
• Cover seal replacements
• Guide stud seal replacements
• Throttle shaft seal replacements
• Governor weight retainer ring checking procedure
• Min-Max governor service
The procedure that follow s include disassembly, various seal replacements, installation of the pellethane governor
w eight retainer ring, and a bench leak test.
4-57
4B. High Pressure Fuel Delivery System
Mounting in Holding Fixture
Mount the pump in the holding fixture, Tool #J-29692B
(BT 8046). Always use the fixture to avoid damage to
the pump. NEVER MOUNT THE PUMP DIRECTLY IN A
VISE. (Figure 4-83).
Figure 4-83, Mounting Pump in Fixture.
See Figure 4-84. Rotate the throttle lever to the low idle
position and install Tool J-29601 over the throttle shaft
with slots of tool engaging pin. Put the spring clip over
the throttle shaft advance cam and tighten the wing
nut. W ithout loosening the wing nut, pull the tool off
the shaft. (This provides the proper alignm ent on
reassembly).
4-58
4B. High Pressure Fuel Delivery System
GOVERNOR COVER
Unscrew the three governor cover hold down screws
and remove the governor control cover and cover
gasket. (Figure 4-85).
Figure 4*85, Removing Governor Cover.
SOLENOIDS
Examine the electric shut o ff solenoids (Figure 4-86)
and the housing pressure cold advance solenoid if so
equipped, for damage or debris. Clean the solenoids
w ith compressed air. Solenoid plungers should move
freely in their bores.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
SHUTDOWN SOLENOID ASSEMBLY
COLD ADVANCE SOLENOID
GOVERNOR CONTROL COVER GASKET
GOVERNOR CONTROL COVER
TERMINAL INSULATING WASHER
PLAIN WASHERS
LOCKWASHERS
NUT
NUT, TERMINAL CONTACT
TERMINAL GROUNDING STRAP
GOVERNOR CONTROL COVER SCREW
Figure 4-86, Solenoids.
4-59
4B. High Pressure Fuel Delivery System
Remove the drive pin from the throttle shaft using the
appropriate drift punch. (Figure 4-87).
LIGHT LOAD ADVANCE ROCKER ARM
AND FACE CAM
All mechanical light load advance pumps are equipped
w ith a rocker arm, which contact the servo advance
plunger at one end and a face cam w hich is located
on the throttle shaft at the other end. (Figure 4-88).
4-60
4B. High Pressure Fuel Delivery System
Pry o ff the retaining rings from the rocker lever pin and
discard the rings. (Figure 4-89).
Figure 4-89, Removing Retaining Rings.
Push out the pin and remove the lever assembly.
(Figure 4-90).
Figure 4-90, Removing Lever Assembly.
Face Cam Removal
Loosen the face cam screw, using a 5/32" hex bit, or
#27 Torx bit. The screw m ust be fully withdraw n to
allow for removal of the face cam. (Figure 4-91).
Figure 4-91, Removing Face Cam.
4-61
4B. High Pressure Fuel Delivery System
Guide Stud
Using a 7/16" open end wrench or a V \" Allen, loosen
and w ithdraw the guide stud. (Figure 4-92).
Observe position of metering valve spring over the top
of the guide stud. This position m ust be exactly
duplicated during reassembly. Remove guide stud
and washer.
Figure 4-92, Loosening Guide Stud.
-
NOTE -
Two types of guide stud and washer combinations are in use:
• The current combination is a guide stud with a 1/4 inch internal hex and utilizes a steel
washer with trapped elastomer.
• The other combination has a 7/16 inch external hex and an aluminum washer. This type
of washer must be replaced during reassembly. The correct guide stud and washer
combination must be used to prevent fuel leakage.
4-62
4B. High Pressure Fuel Delivery System
Governor Spring Components
W hile holding the Min-Max assem bly between the
thum b and forefinger, rotate the throttle and lift out the
governor spring components. (Figure 4-93).
MIN-MAX GOVERNOR
ASSEMBLY__ „
IDLE GOVERNOR SPRING
/
Figure 4-93, Removing Governor Spring.
Throttle Assembly
Now, sim ply pull the throttle shaft assem bly through
the housing. Remove the mylar washer and O ring
seals from the throttle shaft. (Figure 4-94).
Linkage Hook
W hile depressing the metering valve assem bly raise
the linkage hook from the metering valve arm.
(Figure 4-95).
Figure 4-95, Disengaging Linkage Hook.
4-63
4B. High Pressure Fuel Delivery System
Governor Arm and Linkage (Late Model)
The governor arm and linkage assembly may be
removed as a single unit. (Figure 4-96).
Linkage (Late Model).
Metering Valve
Remove the metering valve assembly. (Figure 4-97).
Vent Wire Assembly
Remove the vent wire screw assembly, using a 1/8"
Allen wrench. (Figure 4-98).
Figure 4-98, Removing Vent Wire Assembly.
4-64
4B. High Pressure Fuel Delivery System
End Cap Locking Screw
Loosen and remove the transfer pump end cap locking
screw, plate and seal from the hydraulic head.
(Figure 4-99).
Screw.
— NOTE —
The following 4 procedures are optional,
and are used to replace the end cap seal,
if it is found to be leaking.
Transfer Pump End Cap
In a counterclockw ise direction, loosen and remove the
transfer pump end cap assembly, using the appropriate
end wrench. (Stanadyne Tool #20548, Figure 4-100).
Figure 4-100, Removing End Cap.
Regulator Assembly
See Figure 4-101. W ith the end cap assem bly removed,
remove the transfer pump regulator assembly.
— NOTE —
Do not remove the transfer pump blades
and liner, unless they fall out.
Figure 4-101, Regulator Components.
4-65
4B. High Pressure Fuel Delivery System
Transfer Pump Blades and Liner
See Figure 4-102. If the liner and blades fall out, note
on which side the “ potm ark” is located on the liner.
Also identify w hich slots in the rotor each blade comes
from and mark them w ith Dykem stain, Stanadyne Part
#18836.
Figure 4-102, Removing Transfer Pump
Blades and Liner.
End Cap Seal
Remove the transfer pump end cap seal. (Figure 4-103).
Figure 4-103, Removing Seal.
Head Screws
Loosen the head locking screws and remove one screw. (Figure 4-104, left).
Carefully invert the pum p and holding fixture in the vise, and remove the head locating screw. (Figure 4-104, right).
Figure 4-104, Removing Head Screws.
4-66
4B. High Pressure Fuel Delivery System
Servo Advance Plunger and Piston — M echanical Light Load Advance
Remove the servo advance plunger. (Figure 4-105, Left).
Using a one inch socket and breaker bar, loosen and remove the spring side piston hole plug. (Figure 4-105, Right).
Figure 4-105, Removing Servo Advance Plunger and Piston Hole Plug.
Remove the m echanical light load advance spring and servo advance valve from the advance piston. (Figure
4-106, Left).
Next, remove the power side advance piston hole plug. (Figure 4-106, Right).
4-67
4B. High Pressure Fuel Delivery System
Using needle nose pliers, carefully remove the cam advance pin from the advance piston. (Figure 4-107, Left).
Now remove the advance piston from its housing bore. (Figure 4-107, Right).
Figure 4-107, Removing Cam Advance Pin and Advance Piston.
Hydraulic Head Assembly
Return the pump and holding fixture to its initial
position w ith the rear of the hydraulic head tilted
slightly downward, and remove the remaining head
locking screw. Remove the hydraulic head assembly by
grasping w ith both hands and w ithdraw ing with a
slight rotary motion. (Figure 4-108).
Figure 4-108, Removing Hydraulic Head
Assembly.
4-68
4B. High Pressure Fuel Delivery System
Governor Weights
To disassem ble the governor, sim ply invert the
hydraulic head and let the weights, governor thrust
sleeve and washer fall into your hand. (Figure 4-109).
Weight Retainer
Carefully invert the head and rotor assembly,
supporting it on the discharge fittings. Use care to
avoid dropping the rotor from the hydraulic head. Using
Stanadyne tool #13337 07 Tru-Arc Snap Ring Pliers,
remove the snap ring holding the retainer assembly to
the rotor. (Figure 4-110, Left).
Then remove the w eight retainer assem bly from the
rotor. (Figure 4-110, Right).
— NOTE The pump drive shaft is retained with
either an “O” ring or a retaining clip
(ring). Drive shafts with “0 ” rings, on late
1984 and later, use a rotating motion and
pull out the shaft. Make certain that no
pieces of the “O” ring have broken off
and still remain in the pump. Remove
and discard all drive shaft seals.
4-69
4B. High Pressure Fuel Delivery System
-
NOTE -
The pump drive shaft is retained with either an “0 ” ring or a retaining clip (ring). Drive
shafts with “O” rings, on late 1984 and later, use a rotating motion and pull out the shaft.
Make certain that no pieces of the “O” ring have broken off and still remain in the pump.
Remove and discard all drive shaft seals.
1982,1983 And Early 1984 Drive Shafts With A Retaining Clip (Ring).
Rotate drive shaft until one of the raised portions of the retaining ring (immediately below the ball pivot stud), is
accessible.
Use a long, thin hook-shaped tool, such as a dental tool, or bent wire, or a snap-on GA467. Reach into the housing
through the governor arm opening, hook the ring, and pull it slightly to the rear. Grasp the ring w ith needle nose
pliers and pull it straight up and out of the housing. Discard the ring, it cannot be used again.
— NOTE —
The early drive shaft Stanadyne Part # is 23098. The late drive shaft Part # is 24623.
The O-Ring Part # is 22937. The retaining clip (ring) Stanadyne Part # is 23209.
4-70
4B. High Pressure Fuel Delivery System
INSPECTION OF PUMP COMPONENTS
Remember, keep the work area clean. Dirt is the major enemy of the diesel fuel injection pump.
• Discard all “ O ” rings, seals and gaskets. Replace gaskets and “ O ” rings during re-assembly.
• Check all springs that you have removed for fretting, wear, corrosion or breakage.
• Check all bores, grooves and seal seats for damage, wear or obstructions of any kind.
• Inspect all components for excessive wear, rust, nicks or scratches.
Drive Shaft Inspection
Measure the distance across the flats of the drive tang.
The measurement must not be less than .305" or 7.75
mm. The drive shaft seal area m ust be free of nicks
and scratches. (Figure 4-112).
Vent Wire Inspection
Next, check the vent wire assem bly for freedom of
movement. If the vent wire is sticking or damaged,
replace the assem bly w ith the same number vent wire.
(Figure 4-113).
4-71
4B. High Pressure Fuel Delivery System
PUMP REPAIR PROCEDURE — ASSEMBLY
Head Seal
Install a new seal onto the hydraulic head.
Cam Ring
If the cam ring was removed, place the cam ring onto
the head and rotor assembly, w ith the arrow indicating
the direction of pump rotation showing. (Figure 4-114).
Pump rotation is expressed as viewed from the
drive end.
Checking Proper Direction of Rotation
If you are servicing a pump in these series, place the
cam ring on a table in the same position as Figure
4-115. (Note the hold in relation to the tim ing line.)
Check to be sure the arrow is pointing in the same
direction as shown in the illustration.
Weight Retainer Ring (Using Tru-Arc Snap Ring Pliers)
Install a new flexible retaining ring onto the weight
retainer. Use number 13337 Snap Ring Pliers as shown
in Figure 4-116, or use the follow ing procedure with
tool BT-8209-A.
Figure 4-115, Cam Ring Timing Line.
With “Tru-Arcs”.
4-72
4B. High Pressure Fuel Delivery System
Installing Weight Retainer Ring — Using the BT 8209-A
See Figure 4-117.
1. Slide seal over tapered locating pin and into groove
on sm all sleeve.
2. Place indexer ring on bench and insert end of
tapered locating pin into hole in top of seal retaining
post.
3. Position tool vertically and push down firm ly in one
continuous m otion until it bottom s out.
4. Repeat above operation for all locations.
Figure 4*117, Installing Ring With Tool BT
8209-A.
Weight Retainer to Rotor
Assem ble the w eight retainer onto the rotor.
(Figure 4-118).
Next, assem ble the snap ring to it’s groove using
Stanadyne #13337 Pliers 07 Tru-Arc #22 Pliers.
Carefully hold the assem bly so the rotor w ill not fall
out. Invert the entire assem bly so that it rests on the
w eight retainer.
4-73
4B. High Pressure Fuel Delivery System
Transfer Pump End Cap Seal
Install a new transfer pump end cap seal into it’s
groove in the hydraulic head. This seal has an oval
cross section, and can be identified by rolling it
between your fingers. (Figure 4-119).
Transfer Pump Liner
Insert the transfer pump liner w ith the slot in line with
the hole that the regulator roll pin enters. (Figure 4-120).
— NOTE —
Utmost cleanliness is required during
this operation.
Transfer Pump Blades
Assemble the springs to the transfer pump blades and
install the blade sets in their rotor slots. The blades
must be fully compressed, and care m ust be exercised
that the sharp edge of the liner does not score the
blade ends. (Figure 4-121).
— NOTE —
Put the blades in the exact rotor slots,
you removed them from, which were
marked during disassembly.
Blades.
4-74
4B. High Pressure Fuel Delivery System
Transfer Pump Regulator
Now, install the transfer pump regulator assembly,
beginning w ith the filte r screen seal. (Figure 4-122).
REGULATOR ASSEMBLY
SCREEN SEAL
Figure 4-122, Installing Filter Screen Seal.
Piston Free M ovement Check
Check the movement of the regulating piston by
inserting a brass rod through the unthreaded end of
the regulator assem bly and applying a moderate
am ount of pressure to the rod. The piston should move
in it’s bore. (Figure 4-123). If it does not, the pump must
be sent to an authorized pump repair station.
Figure 4-123, Checking Piston Movement.
Regulator, Pressure Plate and Screen
Assem ble the regulator to the liner. Make certain that
the locating pin is in the correct position for proper
pump rotation. (Figure 4-124, Left).
Install the assembled pressure plate and screen onto
the transfer pump regulator assembly. (Figure 4-124,
Right).
RIGHT
LEFT
INLET FILTER
SCREEN
LINER
REGULATING
ASSEMBLY
PRESSURE
PLATE
'LOCATING
PIN
Figure 4-124, Installing Regulator and
Pressure Plate/Screen.
4-75
4B. High Pressure Fuel Delivery System
Transfer Pump End Cap
Coat the beveled surface of the pressure plate and the
threads on the outside diam eter of the end cap w ith
lubriplate or equivalent. (Figure 4-125).
Install the transfer pump end cap by applying slight
pressure on the top of the cap. Rotate the cap counter­
clockw ise until a slight click is heard. Now, turn the
cap clockwise by hand until it is tight.
End Cap.
Hydraulic Head and Rotor
Support the head and rotor in Stanadyne Tool #18332
or a used T.H.M. 350 Transmission Sun Gear and Shell.
(Figure 4-126).
Assembly.
GOVERNOR WEIGHTS AND THRUST WASHER
Install the governor weights into the governor weight
retainer. (Figure 4-127, Left).
1982 and later pumps do not have a chamfered thrust
washer. The washer may be installed either side up.
(Figure 4-127, Right).
On 1978-1981 pumps, install the thrust washer w ith the
chamfered side up.
4-76
4B. High Pressure Fuel Delivery System
GOVERNOR THRUST SLEEVE
Next, insert the governor thrust sleeve into the lower
slots of the governor weights. (Figure 4-128).
Sight across the tops of the assembled weights. All
weights should be level and collapsed against the
thrust sleeve.
Checking Weights.
LUBE HEAD AND HOUSING
The hydraulic head and rotor assem bly are now ready
to be placed into the housing. First, apply grease onto
the hydraulic head, and apply a light film of Synkut
(J-33198) lubricant around the inside edge of the
housing. In order to aid assembly, tilt the housing
slightly downward. (Figure 4-129).
CAM POSITIONING
See Figure 4-130. Rotate the cam ring so that the
honed hole in the cam is 180 degrees opposite the
metering valve bore. This w ill ensure proper positioning
of the cam ring. The sm allest hole in the cam ring
should be at the bottom . To determ ine w hich hole is
the smallest, use a head locking screw. The screw w ill
enter the large holes, but not the sm all one. Position
the governor thrust sleeve w ith the flat edge and two
lugs up, and round edge down.
4-77
4B. High Pressure Fuel Delivery System
HEAD INTO BORE
Grasp the hydraulic head firm ly in both hands and
insert it into the housing bore using a slight rotary
motion. (Figure 4-131).
-
CAUTION -
Do not force: If the assembly should jam
during insertion, withdraw and start over.
— NOTICE —
Be careful not to insert the head
assembly too far into the housing.
Pushing the head too far will cause the
seal to tear in the vent wire opening. It
will damage the seal on the hydraulic
head and cause leakage.
Rotate the head assembly until the head locking screw
holes line up with their corresponding holes in the
housing. Insert the tw o head locking screws, finger
tight. (Figure 4-132).
Screw.
4-78
4B. High Pressure Fuel Delivery System
DRIVE SHAFT AND SEALS
Lubricate the seal installer tool. Polish seal tools with
#400 grit paper before first use. This w ill aid
installation of seals.
To prevent the governor weights from becoming
dislodged from the retainer, the drive shaft should be
installed. Begin by installing new seals onto the drive
shaft using seal installation tool part #22727 or
J-29745A. Apply a liberal coating of Synkut lubricant,
part #22204, or J-33198 to the seals and the surface of
the tool, to facilitate assembly.
— CAUTION —
Excessive stretching of the center drive
shaft seal may cause it to tear.
(Figure 4-133)
Figure 4-133, Drive Shaft Seal
Installation Tool.
Install one black seal, cup tow ards tim ing gear drive flange.
Relubricate the seal installation tool, and install the red seal, cup towards the tang rotor end.
Install the last black seal, cup towards the tang rotor end.
O-ring retained drive shafts require installation of the O-ring or wire retaining ring onto the shaft at this point.
Or install new retaining ring on drive shaft (if so equipped).
— CAUTION —
Do not spread ring far enough so that it becomes loose in the drive shaft retaining slot.
Install the drive shaft to the pump so that the tim ing spot on the drive shaft tang registers with the tim ing spot in
the rotor tang slot. (Figure 4-134).
Figure 4-134, Installing Shaft in Pump.
4-79
4B. High Pressure Fuel Delivery System
Governor Arm: Late Pump
Next, place the governor arm in position in the
housing. In later model pumps, the arm sim ply rests on
a rounded pin cast into the pump housing. Let the
linkage hang over the side. (Figure 4-135).
Vent Wire Assembly
Now, install the vent wire screw assembly (Figure
4-136). 2.8-3.4 N-m (25-30 in. lbs.).
Metering Valve
Place the metering valve assembly into it’s bore and
depress and rotate the valve several tim es to ensure
freedom of movement. If the valve sticks, rinse it off
with clean calibrating oil. (Figure 4-137). Never use an
abrasive or the specially treated surface w ill be
damaged. However, it may be polished w ith 600 grid
sand paper, but only five turns.
It is possible for the metering valve arm on some
injection pumps to contact and bind on the housing
after the head and rotor have been removed and
reinstalled. If this condition is encountered when
checking for metering valve free movement, rotate the
head to provide clearance for the metering valve arm.
4-80
4B. High Pressure Fuel Delivery System
Then position the opposite end of the linkage
assembly onto the metering valve arm, making certain
that the spring is not twisted. Remember to check all
governor parts for freedom of movement. (Figure 4-138).
- NOTE All throttle shaft seals (1984 and later)
are made from an improved Viton
material, and identified by a green color.
This was done to lessen the effects of
cold temperatures on the sealing area.
Throttle Shaft (and Clip on Speed Advance Pump)
1. Install the throttle shaft, w ith throttle shaft spacer,
new seals and mylar washer. (Figure 4-139 Left).
A. Install throttle shaft spacer (22900 if removed).
Figure 4-138, Linkage To Metering Valve Arm.
B. Install new seals on the throttle shaft.
C. Install the throttle shaft.
D. Install m ylar washer.
and Clip.
4-81
4B. High Pressure Fuel Delivery System
Governor Assembly
MIN-MAX GOVERNOR
ASSEMBLY
IDLE GOVERNOR SPRING
Rotate the throttle to the wide open throttle position,
and holding the entire assembly between the thum b
and forefinger, fit the block onto the throttle shaft. Hold
the assembly in place and rotate the throttle back to
the low idle position until the other end of the governor
assembly bears against the governor arm. (Figure
4-140).
THROTTLE SHAFT
Figure 4-140, Installing Governor Assembly.
Install the guide stud, w ith a new guide stud washer
into the housing. (Figure 4-141). The guide stud must
be installed beneath the metering valve spring, and
engage the min-max assembly w ithout binding. Torque
the guide stud to 9-10 N-m (80-90 in.-lbs.).
Check the governor com ponents for proper installation
by rotating the throttle shaft assembly to the rear. This
should cause compression of the min-max assembly.
There should be no evidence of binding.
Figure 4-141, Installing Guide Stud.
4-82
4B. High Pressure Fuel Delivery System
Head Locating Screw
See Figure 4-142. Invert the pump in the vise, and
assemble the seal onto the head locating screw. Apply
a light film of grease to the head locating screw. Insert
the screw and tighten hand tight. Then using a 5/16"
hex socket, torque to 20-25 N-m (180-220 in.-lbs.).
Make sure that the seal is not sheared during
tightening.
- NOTE —
The head locating screw will contain a
filter to reduce advance piston sticking
caused by contamination. WDDGM part
#14067415 - Stanadyne part #24566.
Figure 4-142, Installing Head Locating Screw.
Head Locking Screws
See Figure 4-143. At this time, torque the tw o head
locking screws to 20-25 N-m (180-220 in.-lbs.).
Automatic Advance
Begin the autom atic advance assem bly of mechanical
light load equipped pumps by installing the advance
piston. Make certain that the transfer pump pressure
port is facing the head locating screw, and that the
servo-valve bore faces the rocker arm side of the
pump. (Figure 4-144).
Figure 4-144, Installing the Advance Piston
on Mechanical Light Load
Pump.
4-83
4B. High Pressure Fuel Delivery System
Then, insert the cam advance pin into its bore, making
certain that it properly engages the cam ring. (Figure
4-145).
Figure 4-145, Inserting Cam Pin.
Install the servo valve and spring into the advance
piston. (Figure 4-146).
Install the advance hole plugs. (Figure 4-147).
4-84
4B. High Pressure Fuel Delivery System
Now, torque both piston hole plugs to 34.7-42.4 N-m
(307-375 in.-lbs.). (Figure 4-148).
Figure 4-143, Tightening Piston Hole Plug.
Complete the assembly of the auto advance
m echanism by fitting the advance boss plug w ith a
new seal, and torque to 8.5-11.3 N-m (75-100 in.-lbs.)
using a Va inch hex socket. (Figure 4-149).
Servo Advance Plunger
In m echanical light load advance pumps, you should
now install the servo advance plunger. (Figure 4-150).
Then, invert the pump in the vise.
Figure 4-150, Installing Servo Advance
Plunger.
4-85
4B. High Pressure Fuel Delivery System
Face Cam
Next, install the face cam and a new mylar washer
onto the throttle shaft. (Figure 4-151). Secure it by
tightening the face cam screw hand tight. Install a new
vacuum module drive pin.
Figure 4-151, Installing Face Cam Screw.
Install tool J-29601 to position face cam and insert a
.005" feeler gage between throttle shaft washer and
housing. (Figure 4-152). Push throttle shaft into housing
and squeeze the advance cam to remove clearance.
Torque face cam screw to 3-4 N-m (28-32 in.-lbs.).
Figure 4-152, Feeler Gage to Position Cam.
Rocker Arm
Then, assemble the rocker arm to the housing by
installing the rocker arm pin. Secure w ith the rocker
arm pin clips. (Figure 4-153).
Figure 4-153, Installing Rocker Arm Pin.
4-86
4B. High Pressure Fuel Delivery System
Governor Cover Gasket
Complete the governor assem bly by placing a new
gasket on the governor cover. (Figure 4-154)...
1
2
3
4.
5
6
7.
8
9.
10.
11
SHUTDOWN SOLENOID ASSEMBLY
COLD ADVANCE SOLENOID
GOVERNOR CONTROL COVER GASKET
GOVERNOR CONTROL COVER
TERMINAL INSULATING WASHER
PLAIN WASHERS
LOCKWASHERS
NUT
NUT, TERMINAL CONTACT
TERMINAL GROUNDING STRAP
GOVERNOR CONTROL COVER SCREW
Figure 4-154, Gasket on Governor Cover.
Governor Cover
...and placing the governor cover slightly to the rear of
its correct m ounting position. (Figure 4-155). Now, slide
the cover forward. This prevents the electric shut off
solenoid arm from accidently locking the linkage in the
run position.
4-87
4B. High Pressure Fuel Delivery System
Governor Cover Screws
Install the flat washers, and lock washers onto the
cover screws, and torque to 4-5 N-m (35-45 in.-lbs.).
(Figure 4-156).
1
2
3.
4.
5.
6
7.
8.
9.
10.
11.
SHUTDOWN SOLENOID ASSEMBLY
COLD ADVANCE SOLENOID
GOVERNOR CONTROL COVER GASKET
GOVERNOR CONTROL COVER
TERMINAL INSULATING WASHER
PLAIN WASHERS
LOCKWASHERS
NUT
NUT, TERMINAL CONTACT
TERMINAL GROUNDING STRAP
GOVERNOR CONTROL COVER SCREW
Figure 4-156, installing Governor Cover
Screws.
Transfer Pump End Gap
Tighten the transfer pump end cap to 41-50 N-m
(360-440 in.-lbs.). (Use Stanadyne Tool #20548, Figure
4-157).
Figure 4-157, Installing the End Cap.
4-88
4B. High Pressure Fuel Delivery System
End Cap Locking Plate
Assemble the end cap locking plate, seal and screw to
the head and tighten to 8-9 N-m (70-80 in.-lbs.).
(Figure 4-158).
Figure 4-158, Installing End Cap Locking
Plate, Seal and Screw.
Pressure Testing Of Fuel Injection Pump On the Bench
1. Drain all fuel from the pump.
2. Connect an air line to the pump inlet connection. Be certain that the air supply is clean and dry.
3. Seal off the return line fitting and com pletely immerse the pump in a bath of clean test oil.
4. Raise the air pressure in the pump to 137.9 kPa (20 PSI). Leave the pump immersed in the oil, to allow any
trapped air to escape.
5. W atch for leaks. If the pump is not leaking, reduce the air pressure to 13.8 kPa (2 PSI) for 30 seconds. If there is
still no leak, increase the pressure to 137.9 kPa (20 PSI). If still no leaks are seen, the pump is ready for use.
4-89
4B. High Pressure Fuel Delivery System
GUIDE STUD
HEAD LOCKING SCREWS
PISTON HOLE PLUG
(POWER SIDE)
PISTON HOLE PLUG
(TRIMMER SIDE)
ADVANCE SCREW HOLE PLUG
Figure 4-159, Injection Pump Components Location.
4-90
HEAD LOCATING SCREW
4B. High Pressure Fuel Delivery System
TORQUE VALUES ARE GIVEN IN POUND FORCE-INCHES (TOP)
AND NEWTON METERS (BOTTOM)
BOLD FACE ITEMS ARE CRITICAL TORQUE VALUES
80 M INIMUM AT
POSITION SHOWN
9.0
^ 0 \ _______________ _
28-32
3.2-3.6
1
TO BE W ITHIN ± 2 ° OF
TRUE POSITION SHOWN
307-375
34.7-42.4
75-100
Figure 4-160, Torque Values.
4-91
4B. High Pressure Fuel Delivery System
High Altitude Adjustment, 1982 “C-K” Trucks With 6.2L Diesel Engine and LH6
(Light Duty Emissions)
These adjustm ents are considered altitude performance adjustm ents and apply only to in-use vehicles. They should
not be used to m odify vehicles prior to sale.
1982 trucks equipped w ith the 6.2L diesel engine for low altitude operation may be m odified if operation is changed
to high altitude for an extended period or permanently. Dealers in high altitude areas should encourage owners who
have moved to high altitude counties to purchase the service adjustm ent procedure outlined below, which is
considered an owner maintenance expense. High altitude is defined as 4,000 feet and above. Vehicles designed for
principal use at low altitude can be identified by P/N 14050587, injection pump, on light duty emission
(LH6) vehicles.
Operation of the 6.2L diesel at high altitudes w ithout m odification can result in excessive em ission of black
exhaust smoke due to low air density. M odification involves the recalibration of the fuel injection pump to a
different fuel rate w hich w ill compensate for the lower air density at high altitudes.
The injection pump cannot be modified on the vehicle. The follow ing procedure should be used:
1. Remove the injection pump per service manual procedures. Be sure to note the relationship of the tim ing marks
on the pump and front housing. The pump must be reinstalled to its exact previous position.
2. Send the pump to an ADS (Association of Diesel Specialists) Service Center for the altitude performance
adjustm ent. The ADS service centers w ill be advised by Stanadyne Corporation Bulletin as to injection pump
recalibration procedures.
3. Reinstall the pump per service manual procedure. The pump must be installed to its original tim ing setting. If the
original tim ing relationship was not retained, refer to Bulletin number 82-B-59 detailing the tim ing procedure.
ALTITUDE ADJUSTMENT LABEL
When LOW ALTITUDE vehicles are adjusted for high altitude operation, a SUPPLEMENTAL em ission control
inform ation label must be placed next to the existing underhood emission control inform ation label. Wash off the
area w ith soap and water, dry thoroughly, and apply the new label, P/N 14057201.
The label should be ordered as regular parts and accessories through the General Motors Warehousing and
Distribution Division system. When ordering these labels via rapid entry, use order type CSD. Orders also may be
placed on a PC 66 and mailed directly to GMWDD, 6060 West Bristol Road, Flint, Michigan 48554, attention Ship
Direct Department.
After perform ing these adjustm ents, dealers should advise custom ers that, IF THE VEHICLE IS RETURNED TO
CONTINUOUS, LOW ALTITUDE OPERATION, THE PUMP MAY BE RECALIBRATED TO LOW ALTITUDE
SPECIFICATION PER THE ABOVE PROCEDURE AMD THE SUPPLEMENTAL LABEL REMOVED.
Vehicles designed for principal use at high altitude (RPO NA6 — fuel injection pump, P/N 14050526, LH6 engine)
perform satisfactorily at low altitude w ithout excessive smoke levels and need not be adjusted for extended
operation at low altitude.
HEAVY DUTY DIESEL ENGINE (LL4)
No adjustm ents are applicable. Engine performs satisfactorily at low and high altitudes.
4-92
4B. High Pressure Fuel Delivery System
High Altitude Adjustment, 1983 and Later “C-K-P-G” Trucks With 6.2L Diesel
Engine and LL4 (Heavy Duty) or LH6 (Light Duty Emissions)
These adjustm ents are considered altitude performance adjustm ents and apply only to in-use vehicles. They should
not be used to m odify vehicles prior to sale.
1983 trucks equipped w ith the 6.2L diesel engine for low altitude operation may be m odified if operation is changed
to high altitude for an extended period or permanently. Dealers in high altitude areas should encourage owners who
have moved to high altitude counties to purchase the service adjustm ent procedure outlined below, which is
considered an owner m aintenance expense. High altitude is defined as 4,000 feet and above. Vehicles designed for
principal use at high altitude are identified by option number NA6 on Service Parts Identification label. All other
vehicles are designed for principal at low altitude.
Operation of the 6.2L diesel at high altitudes w ithout m odification can result in excessive emission of black
exhaust smoke due to low air density. M odification involves the recalibration of the fuel injection pump to a
different fuel rate w hich w ill com pensate for the lower air density at high altitudes.
The injection pump cannot be m odified on the vehicle. The follow ing procedure should be used:
1. Remove the injection pump per Service Manual procedures. Be sure to note the relationship of the tim ing marks
on the pump and front housing. The pump m ust be reinstalled to its exact previous position.
2. Send the pump to an ADS (Association of Diesel Specialists) Service Center for the altitude performance
adjustm ent. The ADS Service Centers w ill be advised by Stanadyne Corporation Bulletin as to injection pump
recalibration procedures.
3. Reinstall the pump per Service Manual procedure. The pump m ust be installed to its original tim ing setting. If the
original tim ing relationship was not retained, refer to bulletins detailing the tim ing procedure to follow.
ALTITUDE ADJUSTMENT LABEL
When LOW ALTITUDE vehicles are adjusted for high altitude operation, a SUPPLEMENTAL em ission control
inform ation label must be placed next to the existing underhood emission control inform ation label. Wash off the
area w ith soap and water, dry thoroughly, and apply the new label, (P/N 14057201).
The label should be ordered as regular parts and accessories through the General Motors W arehousing and
Distribution Division system. When ordering these labels via rapid entry, use order type CSD. Orders also may be
placed on a PC 66 and mailed directly to GMWDD, 6060 W est Bristol Road, Flint, Michigan 48554, attention Ship
Direct Department.
After perform ing these adjustm ents, dealers should advise custom ers that, IF THE VEHICLE IS RETURNED TO
CONTINUOUS, LOW ALTITUDE OPERATION, THE PUMP MAY BE RECALIBRATED TO LOW ALTITUDE
SPECIFICATION PER THE ABOVE PROCEDURE AND THE SUPPLEMENTAL LABEL REMOVED.
Vehicles designed for principal use at high altitude (RPO NA6 — fuel injection pump, P/N 14050526, LH6 engine)
perform satisfactorily at low altitude w ithout excessive smoke levels and need not be adjusted for extended
operation at low altitude.
4-93
4B. High Pressure Fuel Delivery System
Static Timing
FUEL SYSTEM ADJUSTMENT “MARKING TDC”
ON FRONT HOUSING 6.2L DIESEL ENGINE:
1. Turn engine to TDC #1 cylinder (firing).
2. Install tim ing fixture (J-33042) in F.l. pump location
(Figure 4-161). Do not use gasket.
3. Slot of F.l. pump gear to be in vertical 6 o’clock
position — (if not, remove fixture and rotate engine
crankshaft 360 degrees). The tim ing marks on
gears w ill be aligned. See Figure 4-162.
4. Fasten gear fixture w ith one 8mm bolt, and tighten.
5. Install on 10mm nut to housing upper stud to hold
fixture flange nut to be “ finger” tight.
6. Torque large bolt (18mm head) counterclockwise
(towards left bank) to 50 ft. lbs. Tighten 10mm nut.
Figure 4-161, Tool #J33042.
7. Insure crankshaft has not rotated (and fixture did
not bind on 10mm nut).
8. Strike scriber w ith mallet to mark “ TDC” on front
housing.
9. Remove tim ing fixture.
10. Install fuel injection pump with gasket.
11. Install on 8mm bolt to attach gear to pump hub
and tighten to specifications.
DRIVEN GEAR
12. Align tim ing mark on F.l. pump to front housing
mark. Tighten to specification (3) 10mm attachm ent
nuts.
13. Rotate engine and install remaining (2) pump gear
attaching bolt and tighten to specifications.
Figure 4-162, Slot of F.l. Pump Gear.
4-94
4B. High Pressure Fuel Delivery System
Checking Probe Holder Alignment For Timing Accuracy
ENGINES DISASSEMBLED
1. Balance #3 and #5 piston positions to establish T.D.C. #1 cylinder firing (Figure 4-163).
WITH #1 PISTON AT T.D.C. AS
DETERMINED BY BALANCING
THE POSITION OF #3 PISTON
C, OF ENGINE AND #5 PISTON, “0” REF
LINE OF POINTER MUST ALIGN
WITH CENTER OF TIMING
NOTCH ON TORSIONAL
W ITHIN ± 0 .5 DEGREES.
CENTER OF TIMING NOTCH
Figure 4-163, T.D.C. Mark.
2. W ith crankshaft fixed (locked) at T.D.C. #1 cylinder firing:
A. Install tim ing pointer at 0 position w ith respect to mark on torsional damper.
B. Install tim ing gear fixture and housing marking fixture. Apply a torque to 50 ft. lbs. to fixture gear in clockw ise
direction (looking at front of engine, i.e., toward #1 cylinder). Mark tim ing line on housing. Remove fixtures.
3. Position reference pin on fuel injection pump hub w ith respect to tim ing line on pump.
4. Install fuel injection pump through rear of front housing. Align housing and pump tim ing marks, tighten
fasteners.
— NOTE —
Determining cylinder #1 TDC position on an assembled engine
for probe holder alignment.
4-95
4B. High Pressure Fuel Delivery System
• Remove valve rocker cover.
• Rotate crankshaft until desired cylinder is at or near TDC.
• Remove valve spring retainers, cap, and spring from the inlet valve and allow valve to drop on to head of piston.
• Set up a dial indicator to record the displacem ent of the valve tip as the crankshaft is rotated.
• Attach a degree wheel to the front of the crankshaft or attach a piece of “ calibrated” tape on the damper
circum ference (.070 inches per degree for an 8 inch diam eter damper) to provide accurate reading of at least ± 1 0
degree crankshaft rotation from an assumed TDC reference on a stationary pointer.
• Turn the crankshaft in the direction opposite normal rotation such that the damper mark is approxim ately 18
degrees BTDC.
• Turn crankshaft in the direction of rotation to 10 degrees BTDC. (To remove any gear/chain lash in tim ing system).
Record dial indicator reading.
• Continue to rotate crankshaft in 2 degree increm ents and take dial indicator readings thru 10 degrees ATDC.
• Plot the data on a graph. If the assumed TDC was correct, the plot w ill be symm etrical about that point, i.e., a
given valve tip displacem ent w ill occur at the same number of degrees before and/or after TDC.
• An alternative to a graph would be to record the number of degrees before TDC and after TDC that a given valve
tip displacem ent occurs; then average those 2 numbers. The resulting number w ill be the number of degrees thru
TDC is from the selected valve tip displacement.
Checking Or Adjusting Pump Timing (Static)
For the engine to be properly timed, the marks on top of the engine front cover and the injection pump flange must
be aligned.
-
NOTE -
The engine must be off when the timing is reset.
ADJUSTING
If marks are not aligned, adjustm ent is necessary. See
Figure 4-164.
1. Loosen the 3-pump retaining nuts (ENGINE MUST
BE OFF).
2. Align mark on injection pump w ith mark on front
cover and tighten nuts to 40 N-m (30 ft. lbs.). Use
Tool J-29872 to aid in rotating the pump to align the
marks.
Figure 4-164, Aligned Timing Marks.
4-96
4B. High Pressure Fuel Delivery System
Pump Timing Mark Location And White Smoke At Idle
A condition of w hite exhaust smoke at idle when the engine is at normal operating temperature may be due to
slightly retarded injection tim ing. The follow ing steps must be adhered to in order to properly diagnose the
condition and take corrective action.
1. Determine if retarded tim ing is the cause of w hite smoke.
A. Engine should have a m inim um of tw o hundred (200) miles.
B. Operate engine to normal temperature (thermostat open).
C. Check engine RPM and set if required to six hundred and fifty (650) RPM in park (auto) or neutral (manual).
Also set fast idle speed to 800 RPM.
D. W ith engine at proper idle speed, check for em ission of white smoke.
E. If w hite smoke is evident, connect a lead from battery plus ( + ) terminal to the cold advance solenoid terminal
on the injection pump (Figure No. 1). A noticeable change in engine sound w ill be evident. Activating the cold
advance solenoid increases the tim ing approxim ately three (3) degrees.
F. Check for w hite smoke. If no white smoke is evident or has reduced considerably, a change in tim ing setting
is required. If the smoke does not dim inish, check for other causes of w hite smoke. (Assure each cylinder is
firing — start w ith a com pression check.)
2. Adjustm ent of Tim ing. See Figure 4-165A.
A. The pump/engine flanges may or may not have a w hite alignm ent tape attached, w hich was used on some
early production engines for tim ing adjustment.
B. Obtain locally a piece of w hite tape and draw a 1mm offset line as shown in Figure 4-165B.
C. To correct the w hite smoke condition on this engine, add a new tape w ith a 1mm offset over the old tape (or
bare flange(s) if tape is missing). Cut the tape between the flanges. Loosen the three (3) pump attaching bolts
and rotate the pump to line up the offset lines. The pump must be rotated clockw ise as viewed from the front
of the vehicle. Do not exceed 1mm of pump movement. Retighten the three (3) pump attaching nuts to a
torque of 25-37 ft. lb. (34-50 N-m).
D. NOTICE: Do not make tim ing adjustm ent w ith engine running. Do not start engine until pump attaching nuts
are torqued securely.
4-97
4B. High Pressure Fuel Delivery System
TIM ING ADJUSTMENT PROCEDURE
1. Obtain w hite tape approxim ately one (1) inch wide by one (1) inch long.
2. Draw a center line.
3. Draw a perpendicular line downward from the center line.
4. Measure from this line 1mm to the left along the center line.
5. Draw a perpendicular line from this point in the other direction.
6. Remove tape backing.
7. Install on pum p/flange interface with center line on joint.
8. Cut tape.
9. Loosen pump attaching nuts, move pump to align the offset lines.
10. Retighten pump attaching nuts.
SERVICE INJECTION PUMP STATIC TIM ING SETTING
See Figure 4-166. Any service on the 6.2L Diesel engine w hich requires replacement of the injection pump requires
the static tim ing mark to be at the correct setting.
During the 1982 model year a change to the procedure for marking the pump was made. Injection pumps built
during the first half of the 1982 model prior to the change, required the pump tim ing mark to be offset from the
housing flange mark. To facilitate these settings a piece of tape was used w hich had offset lines. By lining up the
tape lines the correct setting was achieved. W hite tape was used on light duty engines and yellow on heavy duty.
Since service pum ps may be of a different vintage than the removed pump, the follow ing m ust be adhered to for
correct tim ing setting whenever installing a replacement injection pump:
1. All injection pum ps have a model identification plate w hich is attached to the pump housing just below the
throttle linkage. The plate includes the (1) model number, (2) serial number and (3) the part number —
(Figure 4-166).
2. Remove and install injection pump per service manual procedure.
3. Refer to Figure 4-116 w hich displays the location of the tim ing marks which are stamped into the injection pump
flange and the front housing.
4. Remove any tim ing tape that is over the stamped marks.
5. Refer to the model identification plate on the pump that is being installed. Use the follow ing chart to determine
the tim ing mark alignm ent setting:
MODEL NUMBER
ENGINE/RPO
PUMP PART NUMBER
TIMING MARK OFFSET
DB2-4090
Light Duty (LH6)
14050587
1.5mm (.059")
DB2-4091
Heavy Duty (LL4)
14050588
2.5mm (.098")
DB2-4126
Light Duty (LH6)
14050587
Aligned
DB2-4153
Heavy Duty (LL4)
14050588
Aligned
6. If the pump is DB2-4090 or 4091 always have the mark on the pump toward the left side (driver’s) of the mark on
the housing. This is the advance direction.
7. If an injection pump is to be removed and then reinstalled, it should be first paint marked at the pump to
housing flange to allow reinstallation at the original setting.
8. Do not make tim ing adjustm ent w ith the engine running. Do not start engine until pump attaching nuts are
torqued securely.
4-98
4B. High Pressure Fuel Delivery System
TIMING MARKS
YELLOW
TAPE
CENTER LINE
FLANGE JOINT
TIM ING LINE
INJECTION
PUMP
HOUSING
ADJUST FROM
4 mm TO 2Vimm
MARK ON PUMP'
FLANGE (DAB PAINT
OVER AFTER ADJUST)
ADD NEW MARK
AFTER ADJUST
FLANGE JOINT
MARK ON HOUSING
FLANGE
Figure 4-166, Timing Adjustment, Heavy Duty 6.2L Diesel Engine.
4-99
4B. High Pressure Fuel Delivery System
6.2L Diesel California Engine Timing “C-K” With YF5 California Emissions
Light Duty 6.2L Diesel
Any service on the 6.2L light duty diesel engine (built to California specifications) w hich necessitates removal or
replacement of the injection pump, requires a different static tim ing procedure.
Light duty engines built to C alifornia specifications have been tim ed w ith a microwave process. After tim ing with
the microwave, an additional mark “ O” is stamped over the pump flange/housing interface.
When viewing the C alifornia tim ed engine, the tw o (2) tim ing marks (as on Federal engines) w ill be visible. These
may or may not be lined up. In addition, an “ O ” w ill be visible, stamped on the flange interface. The “ O” should be
round. Any deviation of the tim ing w ill result in tw o (2) half circles not matching.
If the pump is removed for service and is replaced on the same engine, be sure to match the “ O” for correct
tim ing setting.
If a new pump or a pump that was not previously on the engine is installed, do not use any “ O ” marks. Instead, use
the normal tim ing marks and align according to the inform ation previously detailed.
Timing Meters
Diesel engine tim ing meters have the capability of checking engine tim ing and RPM. These meters can be used to
perform diagnostic checks on the 6.2 liter diesel engine. The 6.2 liter engine’s injection pump tim ing must be set to
static specifications outlined in this manual.
TIM ING METERS AND DIAGNOSTIC PROCEDURES
The tim ing m eter’s tim ing capability and tachom eter can be used to check the injection pum p’s housing pressure
cold advance and rocker arm mechanical light load advance functions for operation. These checks may indicate if
the pum p’s advance solenoid, advance piston assembly and cam ring are functioning and not binding or seized.
PROCEDURE
1. Place the transm ission selector in park, apply the parking brake and block the wheels.
2. Start the engine and let idle until fully warmed up. Then shut o ff engine.
3. Clean any dirt from the engine probe holder (RPM counter) and crankshaft balancer rim.
4. Using a snap-on MT95 (bracket qualifier) qualify the tim ing indicator.
5. Attach the tim ing meter, follow ing m anufacturer’s instructions.
6. Start engine and adjust idle to 650 RPM. Note engine tim ing and RPM readings.
HOUSING PRESSURE COLD ADVANCE CHECK
Disconnect advance solenoid’s terminal wire at the injection pump. Attach a jum per wire to the battery positive
terminal and touch injection pum p’s advance solenoid terminal. Note engine tim ing and RPM readings.
When the advance is functioning properly, the engine’s tim ing w ill advance approxim ately 3 to 5 degrees and RPM
w ill increase when the solenoid is energized.
ROCKER ARM MECHANICAL LIGHT LOAD
ADVANCE CHECK
See Figure 4-167. Using a ten-inch long screwdriver,
push the injection pum p’s rocker arm (at lower end)
towards injection pump. Note engine tim ing and RPM
readings.
When the rocker arm mechanical light load advance is
functioning properly, the engine’s tim ing w ill retard
approximately 3 to 5 degrees and RPM w ill decrease.
Injection pump removal is normally required to repair
the pum p’s internal m echanical advance.
Engine RPM may require readjustment to emission
label specifications when diagnostic procedures are
completed.
4-100
4B. High Pressure Fuel Delivery System
Injection Nozzles
6.2L NOZZLE A N D HIGH PRESSURE FUEL LINES
See Figure 4-168. The fuel from the injection pump is directed through the 8 high pressure lines to the fuel injection
nozzles. To a large degree, the successful operation of the engine depends on these eight injection nozzles.
Figure 4-168, 6.2L High Pressure Fuel Lines.
Metered fuel, under pressure from the injection pump,
enters the nozzle and pressurizes the nozzle body
(Figure 4-169).
HIGH PRESSURE INLET
LEAK-OFF PORT
SHIM
PRESSURE
SPINDLE
NOZZLE NUT
PRESSURE
SPRING
INTERMEDIATE
PLATE
NEEDLE
VALVE
PINTLE NOZZLE
HEAT SHIELD
WAVE WASHER
Figure 4-169, 6.2L Nozzle.
4-101
4B. High Pressure Fuel Delivery System
When the pressure in the nozzle body overcomes the
spring force, the valve lifts off its seat allowing fuel to
spray into the pre-chamber.
During injection a small amount of fuel leaks through
the clearance of the valve guide. This fuel flow s
through the fuel drain back nipple at the top of the
nozzle and is returned to the fuel tank through the fuel
return line.
PRESSURE SPRING
PRESSURE SPINDLE
«>-
INTERMEDIATE PLATE
—
PINTLE NOZZLE
----- HEAT SHIELD
NOZZLE NUT
Figure 4-170, Nozzle Holder Assembly,
Exploded View.
The nozzle also has a bleed back path for bleeding
excess fuel back to the gas tank. The nozzle allows
only the amount of fuel to pass that is needed for
engine operation.
Model #KCA18450
Bosch #DNOSD193
See Figure 4-170. The nozzle is a pintle type
#DNOSD248 having an initial rota-flow value of 680
cm 3/m inute at 0.1mm lift, and overlap length of 0.7mm
and a maximum lift of 97mm. The nominal opening
pressure is 130 bars (1885 psi).
A pintle nozzle has a special type of a needle valve
where in an integral tip from the lower end of the
needle is so formed as to influence the flow rate
and/or spray. It is a tiny projection at the end of the
valve (pintle) which extends through the single large
orifice.
The main purpose of the nozzle is to direct and to atomize the metered fuel into the pre-combustion chamber. Fuel
from the injection pump enters and pressurizes the supply passages in the injector. When the force on the lift area
is greater than the spring pressure on the needle valve spindle, the needle valve is lifted off its seat and rests with
its upper shoulder against a stop.
Fuel is forced out into the pre-combustion cham ber while the needle valve is lifted. The pressure required to open
this injector needle valve is approxim ately 1700 psi.
As the fuel sprays into the pre-combustion chamber, the pump continues to turn and instantaneously closes off
fuel to the nozzle. This action causes a rapid drop in fuel line pressure and spring pressure forces the needle valve
to close and seat again, sealing off fuel from the pre-combustion chamber.
The injector nozzle injects fuel once for every 2 revolutions of the crankshaft. This means that under normal driving
conditions it w ill open and close about 1,000 tim es for every mile driven. In a 10-mile drive to and from work each
day, each injector nozzle would open and close approxim ately 10,000 times. In relation to tim e if you are driving
60 MPH, each injector nozzle w ill open and close 1,000 times/m inute.
Tool J-29873, a 30mm socket, is used for R & R. There is a copper washer used to seal the outside from the
com bustion area.
It must be replaced anytim e the injector is removed. Maxim um pop-off is 135 bars (1960 psi), m inim um pop-off 125
bars (1810 psi), leakage 105 bars (1520 psi).
Opening pressure used nozzle; should not fall below 105 bars (1500 psi) on used nozzles.
• Thread size — M24 x 1/5mm fin.
• Length — 84mm
• Needle valve diam eter — 6mm
• Line O.D. — 6.3mm
• Line I.D. — 2.5mm
• Line length — 600mm
4-102
4B. High Pressure Fuel Delivery System
The G-series has a nozzle w hich is 10mm shorter than
the C-K-P model (Figure 4-171).
Changes in fuel injection nozzle design in the 6.2L
diesel from the 1982 to the 1983 and later models
require that correct replacement nozzles are used in
service.
A ttem pts to use the incorrect nozzle w ill damage the
cylinder head and nozzle threads. The nozzle used in
1983 and later is sim ilar in appearance to the 1982
nozzle except for a different thread pitch size for the
C-K-P Truck only.
When replacing nozzles, reference should be made to
the nozzle part number (stamped on the side of the
nozzle).
Comparison.
— NOTE —
When installing nozzle threads, use Anti-Seize Compound #1052771.
The follow ing chart displays the nozzle applications for 1982 and later models:
1983 AND LATER
1982
USAGE
NOZZLE
THREAD
LENGTH
NOZZLE
THREAD
LENGTH
C-K-P
0430211051*
M24 x 2 (coarse)
84mm
0430211058*
M24 x 1.5 (fine)
84mm
G
—
--
--
—
M24 x 1.5 (fine)
74mm
-
*NOTE -
The nozzle part numbers shown are vendor part numbers and should not be used
for ordering. Use GM part numbers for ordering.
The G-series nozzle also has a 5mm needle valve diameter. The I.D. of the G-series lines are 2mm. The C-K-P needle
valve O.D. is 6mm and line I.D. is 2.5mm. Both lines are 600mm in length.
4-103
4B. High Pressure Fuel Delivery System
Nozzle Testing
Test is com prised of the follow ing checks:
•
•
•
•
Nozzle Opening Pressure
Chatter
Leakage
Spray Pattern
-
NOTE -
Each test should be considered a unique test, i.e., when checking opening pressure;
do not check for leakage.
If all the above tests are satisfied, the nozzle holder assembly can be again installed in the engine w ithout any
changes. If any one of the tests is not satisfied, the com plete nozzle holder assembly must be replaced or repaired.
Use the follow ing steps.
1. Test Lines — 6 x 2 x 400mm (1.5mm bore).
2. Test fluid per ISO 4113 (example Sheel V1399, Viscor 1487c).
3. Kinetic V iscosity at 40 degrees C per ISO 3104: 2.45-2.75mm 2/second.
4. Test oil tem perature during test: 20-25 degrees C (room temperature).
5. Refer to the equipm ent m anufacturers instructions for exact test procedures.
— CAUTION —
When testing nozzles, DO NOT place your hands or arms near the tip of the nozzle. This
high pressure atomized fuel spray from a nozzle has sufficient penetration power to
puncture flesh and destroy tissue and may result in blood poisoning. The nozzle tip should
always be enclosed in a receptacle, preferably transparent, to contain the spray.
TEST S E Q U E N C E
• PREPARATION
1. Connect the nozzle holder assembly to the test line.
2. Install tw o clear plastic lines (approximately 1 to 1.5 in. long) over the leak-off connections.
3. Close the shutoff valve to the pressure gauge.
4. Fill and flush the nozzle holder assembly with test oil by activating the lever repeatedly and briskly. This will
apply test oil to all functionally important areas of the nozzle and purge it of air.
4-104
4B. High Pressure Fuel Delivery System
• OBTAINING PRESSURE CHECK
1. Open shutoff valve at pressure 1A turn.
2. Depress lever of tester slowly. Note at what pressure the needle of the pressure gauge stopped, indicating an
increase in pressure (nozzle does not chatter) or at w hich pressure the pressure dropped substantially (nozzle
chatter). The m axim um observed pressure is the opening pressure. Some nozzles may drip slightly before they
fully open. This is not to be considered a leakage fault, because this is not a leakage test.
3. The opening pressure should not fall below the lower lim it of 105 bar (1500 psi) on used nozzles.
4. Replace or adjust nozzles w hich fall below the lower lim it.
5. A djust the pressure by changing the adjustm ent shim. The opening pressure is increased by increasing shim
thickness and decreased by decreasing shim thickness. It can be changed at the rate of 5 bar (68 psi) for every
.04mm (.0016 in.) thickness change.
• LEAKAGE TEST
1. Further open shutoff valve at pressure gauge (V2 -IV 2 turns).
2. Blow-dry nozzle tip.
3. Depress lever of manual test stand slow ly until gauge reads a pressure of 95 bar (1400 psi). Observe tip of nozzle.
A drop may form but not drop off w ithin a period of 10 seconds.
4. Replace the nozzle holder assem bly if a droplet drops off the nozzle bottom w ithin the 10 seconds.
• CHATTER TEST
When testing for chatter, it should be noted that the sound (chatter) for new or used nozzles may vary.
On used nozzles, carbonized fuel oil deposited on the pintle and on the nozzle tip produces different sound (chatter)
between new and used nozzles on the hand test stand.
W ith some used nozzles, the chatter is d iffic u lt to detect during slow actuation of the hand test stand lever. As long
as there is chatter, the nozzle is acceptable. Use the follow ing steps:
1. Close shutoff lever at pressure gauge.
2. Depress lever of manual test stand slow ing noting whether chatter noises can be heard.
3. If no chatter is heard; increase the speed of lever movement until it reaches a point where the nozzle chatters.
4. The chatter indicates that the nozzle seat, guide, as well as the pintle, have no mechanical defects.
5. Replace nozzles w hich do not chatter.
• SPRAY PATTERN
This nozzle features a longer nozzle overlap, greater pintle to body clearance, and greater needle to body clearance.
This assem bly also features an internal wave washer between the nozzle nut and nozzle. Because of these features,
objective testing in the field is difficu lt. A pop tester w ill not deliver fuel w ith the velocity necessary to obtain proper
spray pattern analysis.
1. Close shutoff valve at pressure gauge.
2. Depress lever of manual test stand downward abruptly and quickly. The spray should have a tight, evenly shaped
conical pattern w hich is well atomized. This pattern should be concentric to the nozzle axis. Stream-like
injections indicate a defect.
4-105
4B. High Pressure Fuel Delivery System
Oscilloscope Pattern, Fuel
Injection Pump
Shown in Figure 4-172 is a typical, unretouched, four
channel oscilloscope photograph of a Stanadyne fuel
injection pump operating at full speed and full load on
a 219CID turbocharged diesel engine.
Trace No. 1 represents the cylinder pressure, in pounds
per square inch, w hich reaches approxim ately 1400 psi
during com bustion. The preignition pressure of 1000
psi results from the added turbocharger boost which
raises the effective com pression ratio.
Trace No. 2 represents the nozzle valve lift of .0135
inches (.34mm).
TYPICAL OSCILLOSCOPE READING
Figure 4-172, Oscilloscope Pattern.
Trace No. 3 shows the nozzle pressure, in pounds per
square inch, at the nozzle fitting. A delay in pressure
rise occurs around 20° BTDC (engine timing) due to
the unseating of the nozzle valve at the preset pressure
of 2500 psi. The pressure continues to rise to a peak of
approxim ately 5000 psi after the valve lifts o ff its seat.
This is a result of the resistance generated when the fuel is forced through the tiny spray orifices in the nozzle tip.
Note that a small pressure rise, or bounce, occurs after the valve strikes its seat upon closing.
Trace No. 4 represents the injection pump output pressure in pounds per square inch. The peak pressure is
approxim ately the same as nozzle pressure (5000 psi).
The m isalignm ent of traces 3 and 4 indicates the tim e (lag) it takes for the pump discharge pressure wave to pass
through the fuel injection lines and reach the nozzle.
The pump discharge begins at 28° BTDC engine tim ing. This is 14° pump tim ing. The advance mechanism was
adjusted to produce an 8° pump speed advance (16° engine) w ith a 12° BTDC static engine tim ing.
Notice the reflected pressure waves (or afterwaves) w hich occur after the nozzle is closed. Fluid flow at the nozzle
is stopped abruptly when the nozzle closes, but the fuel in the line continues to flow and generates the pressure
waves seen in the oscilloscope trace. The pressure waves “ echo” back and forth between the nozzle and the pump
until they are com pletely dissipated by fluid friction prior to the next injection cycle. In order to prevent after­
injection, the peak pressure of the reflected waves is kept below the nozzle opening pressure.
Also notice that a residual line pressure of approxim ately 500-600 psi occurs on the left side of the pressure peaks.
This pressure is required in order to prevent the valleys of the reflected pressure waves from dropping below
atm ospheric pressure w hich could cause cavitation erosion in the pump, fuel line and nozzle.
Cavitation
The injection line is susceptible to a particular kind of corrosion known as cavitation. Cavitation is short of
cavitation-erosion-corrosion, indicating the states of the process. First cavitation, second erosion, third corrosion.
The action of the pum p creates vapor bubbles in a confined space. These bubbles burst and create shock waves.
The shock waves attach nearby metal surfaces, causing them to crumble, or erode. The eroded surface is open to
attach by corrosion, w hich allow s the erosion to continue.
Cavitation erosion is actually damage from these pressure waves “ echoing” back and forth between the nozzle and
pump. It can be compared to the noise or jerk in water pipes w hich occurs when water is shut o ff very rapidly.
4-106
4B. High Pressure Fuel Delivery System
Fast (Cold) Idle Speed System
FAST IDLE/H.P.C.A. TEMPERATURE
CONTROL COOLANT SENSOR SWITCH
OPENS ABOVE 95°F
CLOSES BELOW 85°F
See Figure 4-173. The fast idle speed control system
consists of a throttle solenoid, engine coolant
tem perature sw itch and related control.
During a cold start when the engine coolant
tem perature is below a prescribed value, the control
circuitry energizes (extends) the solenoid and
m aintains a high engine idle speed by holding the
throttle o ff the low idle stop.
When the engine coolant tem perature reaches the
prescribed value, the control circuitry de-energizes the
solenoid, allow ing the throttle to return to the low idle
stop.
The fast idle system s work together w ith the housing
pressure cold advance, except on 1984 and later
C alifornia LH6 systems.
Figure 4-173, H.P.C.A./ldle Circuit.
6.2L DIESEL IDLE SPEED SETTING PROCEDURE
1. All idle speeds are to be set w ithin ± 2 5 RPM of
specified value.
2. Set parking brake and block drive wheels.
3. Engine m ust be at normal operating temperature. Air
cleaner should be on and all accessories should be
turned off.
4. Install a Kent-Moore J-26925 Diesel Tachom eter or
equivalent per m anufacturer’s instructions.
5. Adjust low idle speed screw on fuel injection pump
to an engine speed of 650 RPM in Neutral for
autom atic transm issions and 650 RPM in Neutral for
manual transm issions.
• ADJUST FAST IDLE SPEED AS FOLLOWS:
1. Remove connector from fast idle solenoid. Use an
insulated jum per wire from a 12 volt term inal to
energize solenoid.
Figure 4-174* Idle Adjustment.
— NOTE All fast idle solenoids will have the plunger extending through the rear, with a screw head
on it. This is for easy access to adjust from the front of the engine.
2. Open throttle m om entarily to ensure that the fast idle solenoid plunger is energized and fully extended.
3. Adjust the extended plunger by turning the hex head to an engine fast idle speed of 800 RPM in Neutral.
4. Remove jum per wire and re-install connector to fast idle solenoid.
• REMOVE TACHOMETER.
4-107
4B. High Pressure Fuel Delivery System
NOTES
4-108
5. Emission Systems
5A. General Emission Systems
5B. California Diesel Electronic Control System (DECS)
EPR
VALVE
VACUUM PUMP
EGR VALVE
A IR
EGR
SOLENOID
SOLENOID
CLEANER
EPR
SOLENOu
EGR
VALVE
INJECTION
PUMP
CRANKCASE
DEPRESSION
REGULATOR
VALVE
THROTTLE
POSITION
SWITCH
INJECTION PUMP
THROTTLE POSITION
SWITCH
CRANKCASE DEPRESSION
REGULATOR
Figure 5-1, Emission Systems.
OIL FILL
PIPE
FAST IDLE SOLENOID
Figure 5*2, Emission Systems — Federal CK
(LH6 Engine).
5A. General Emission Systems
See Figure 5-1.
1. Crankcase ventilation system (crankcase depression regulator — CDR) LH6 and LL4.
2. Exhaust gas recirculation (EGR) LH6 only.
3. Exhaust pressure regulator (EPR) LH6 only.
4. (LH6) Throttle position switch/(LL4) Vacuum regulator valve.
• Figures 5-2, 5-3 and 5-4 are the Federal Emission schem atics for various vehicle applications:
ENGINE SPEED
SENSOR
EPR
SOLENOID
CRANKCASE
DEPRESSION
REGULATOR
VALVE
EGR
VALVE
CRANKCASE
DEPRESSION
REGULATOR
VALVE
EPR
VALVE
tu n
SOLENOID
VACUUM
PUMP
VACUUM
PUMP
INJECTION
PUMP
INJECTION PUMP
THROTTLE POSITION
SWITCH
FAST IDLE SOLENOID
OIL FILL
FRONT
PIPE
OF
VEHICLE
Figure 5-3, Emission Systems — Federal G
(LH6 Engine).
VACUUM REGULATOR
VALVE
OIL FILL
PIPE
FAST IDLE
SOLENOID
Figure 5-4, Emission System — LL4 Engine.
5A. General Emission Systems
C r a n k c a s e
CRANKCASE VAPORS
TO INDUCTION
SYSTEM
INLET MANIFOLD
RUNNERS
CRANKCASE
DEPRESSION
REGULATOR
VALVE
(CDR)
BLOWBY LEAKAGE
AT VALVES AND
PISTONS
V e n t ila t io n
S y s t e m
The 6.2L crankcase ventilation system is designed to
reduce crankcase pressure at idle (Figure 5-5). It
consequently reduces the possibility of engine oil
leaks. Crankcase pressure has been highest at idle
and, subsequently, the engines have been more
susceptible to oil leaks at idle. The regulator is located
at the front of the right cylinder head. This, along w ith
the use of large ventilation system tubing w ill lower
crankcase pressure. Crankcase gases now enter the air
crossover on each side of the intake manifold.
CRANKCASE
VAPORS
Figure 5-5, Crankcase Ventilation System.
C r a n k c a s e
CRANKCASE DEPRESSION REGULATOR
INTAKE MANIFOLD
HOSE TO INTAKE
BLOWBY GASES FROM
THE CRANKCASE
OIL FILL PIPE
MOD PIPE HARN ASM
Figure 5-6, CDR Valve Installation.
5-2
D e p r e s s i o n
R e g u la t o r , C D R
The major com ponent in the ventilation system is the
CDR, crankcase depression regulator valve (Figure 5-6).
CDR lim its crankcase vacuum to a maximum of 3 to 4
inches water. This is done as the gases (blow-by and
fresh air) are drawn from the oil fill pipe through the
CDR valve and into the intake manifold. 1985 and later
CDR plum bing incorporates plastic snap clam p
(10019739) for hose retention.
5A. General Emission Systems
Intake vacuum acts against a spring loaded diaphragm
(Figure 5-7) to control the flow of crankcase gases.
Higher intake vacuum levels pull the diaphragm closer
to the top of the outlet tube. This reduces the amount
of gases being drawn from the crankcase and
decreases the vacuum level in the crankcase. As the
intake vacuum decreases the spring pushes the
diaphragm away from the top of the outlet tube
allowing more gases to flow to the intake valve.
C R A N K C A S E DEPR ESSIO N R EG U LA TO R
A diesel engine has little vacuum at idle, because at
slow speed there is more tim e to leak past the rings.
And w ith higher com pression the crankcase can be
pressurized by blowby.
The purpose of the CDR valve is to maintain 3-4 inches
of water (vacuum in the crankcase). Too little vacuum
will tend to force oil leaks. Too much vacuum w ill pull
oil into the air crossover.
■7, CDR Valve Operation.
CDR VALVE TEST
The CDR valve is checked w ith a water m anom eter (Figure 5-8). The U-tube manometer is a primary measuring
device indicating pressure or vacuum by the difference in the height of two colum ns of fluid. The CDR valve can
also be checked w ith a magnehelic gauge (see Section 7).
Connect one end of the m anom eter to the oil dipstick hole . . . the other end is vented to the atmosphere. The air
cleaner m ust be installed . . . then run the engine at idle.
•CDR SPECIFICATIONS
1 inch water pressure @ idle to approxim ately 3-4 inches water vacuum at full load.
NOTE:
ENGINE OIL
Too little vacuum w ill tend to
force oil leaks . . . too much
pulls oil in to the air crossover.
NOTE:
Add am ount colum n travels
up, to am ount colum n travels
down, to obtain to ta l. Psi/Vac.
EXAMPLE:
1/2" + 1/2" Vac. Reading
shown on the m anom eter is
for th is example only.
Figure 5-8, CDR Valve Test with Manometer.
5-3
5A. General Emission Systems
E x h a u s t
G a s
R e c ir c u la t io n ,
EGR
EGR PRINCIPLE
W hen a vehicle operates fo r a substa ntia l part of its tim e at part load — w hich is the norm al co n d itio n in tow n
tra ffic — em issio ns can be reduced by the use of Exhaust Gas R ecirculation. M ixing som e of the exhaust gas
w ith the inlet air at part load reduces the concentratio n of oxygen and lessens the o p p o rtu n ity to produce NOx .
R eduction in NOx o f som e 40% can be obtained w ith o u t increasing HC, CO or sp e cific fuel consum ption.
The increase in the temperature and NOx form ation in the main chamber depend upon the am ount of incom pletely
burned com pounds discharged from the pre-chamber, the oxygen concentration, and the tim ing of the discharge.
EGR is designed to control (Oxides of Nitrogen) NOx. This is done by blending the fuel-air w ith exhaust gases to
reduce the peak temperatures and oxygen concentration. The lack of oxygen lowers the possibility of nitrogen
com bining w ith oxygen to form NOx.
The effect of increasing the EGR on the pollutants shows that as EGR is increased NOx decreases, while both HC
and CO increase. The gradual decrease in NOx continues as EGR increases but the characteristics of HC and CO
change significantly above a value of EGR which varies w ith speed and load. It is possible to establish an amount
of EGR as a function of speed and load. Above 90% fuel no EGR is used. Also since during normal driving in town,
very little tim e is spent above 75% maximum speed, the use of EGR at high speed would have little effect on the
pollutants.
Spent gas is run through an EGR valve to the manifold, and then is part of the air intake (Figure 5-9). This is
introduced into the com bustion chamber. It takes up some of the volume of the incoming charge of air. When
ignition takes place, the spent exhaust gases cannot partake in the com bustion process, since they have already
been used previously, so they add nothing. During the period of “ rapid” com bustion, the temperature increases
quite rapidly. The tem perature rise causes the gases to expand. The temperature in the chamber is much higher
than the exhaust gases. The spent gases now take part in the process. They cannot add to the process because of
lack of oxygen. So the spent or inert gas acts as a sponge and pulls heat into itself causing it to expand. As it
does it absorbs heat of com bustion and drops the temperature approximately 500 °F. Carbon monoxide is not a
significant em ission factor w ith diesels. Hydrocarbons are controlled by the injection nozzles, pump tim ing and
com bustion cham ber design. The EGR valve is used on the LH6 (C) engine only.
5-4
5A. General Emission Systems
VACUUM SWITCHED EGR (FEDERAL EMISSIONS)
W ith vacuum switched EGR, either full flow or no flow of exhaust gas is admitted to the intake manifold, Figure
5-10. At closed throttle the EGR valve is opened. The EGR valve remains fully open to a calibrated throttle position
at w hich point it closes. The throttle position is sensed by a throttle position switch (TPS) mounted on the throttle
shaft. W ith a TPS, as the throttle is opened, the sw itch closes at the calibration point and de-energizes a solenoid
which shuts the vacuum signal to the EGR valve allowing the valve to close.
VACUUM SIGNAL
INLET NIPPLE
CLOSING SPRING
DIAPHRAGM
ROD SEAL
VALVE
(PARTIALLY OPEN)
INTAKE
RUNNER
EXHAUST GASES
VALVE
(CLOSED)
VACUUM SIGNAL
INLET NIPPLE
CLOSING SPRING
DIAPHRAGM
ROD SEAL
VALVE
(PARTIALLY OPEN)
(7
A
INTAKE
RUNNER
INTAKE
RUNNER
VALVE
(CLOSED)
EXHAUST GAS
Figure 5-10, Single Diaphragm EGR Valve.
5-5
5A. General Emission Systems
EPR SOLENOID
EGR SOLENOID
EGR
SOLENOID
EPR
SOLENOID
Figure 5-11, EPR Valve and Solenoid Location.
EXH A U ST
PRESSURE REGULATOR EPR VALVE
An Exhaust Pressure Regulator (EPR) valve is used in the exhaust system to restrict the flow and increase exhaust
gas back pressure. (Figure 5-11). This EPR valve is used in conjunction w ith the vacuum switched EGR valve at the
intake manifold. When the throttle is closed, the EPR valve is closed increasing the recirculation of exhaust gas. As
the throttle is opened the valve would also open decreasing the am ount of exhaust back pressure. The throttle
position is sensed by a throttle position sw itch mounted on the throttle shaft on the injection pump. The throttle
position sw itch de-energizes the EPR solenoid at a calibrated throttle angle.
5-6
5A. General Emission Systems
E P R / E G R
S o l e n o i d s
VACUUM SWITCHED EPR
See Figure 5-12. The EPR solenoid is norm ally closed. When energized by (B + ) from the TPS it is open allowing
vacuum to the EPR, closing it. This occurs at idle. As the throttle is opened, at a calibrated throttle angle the TPS
de-energizes the EPR solenoid, cutting off vacuum to the EPR valve and opening it.
VACUUM SWITCHED EGR
See Figure 5-12. The EGR solenoid is normally open. W ith vacuum switched EGR, either full flow or no flow of
exhaust gas is adm itted to the intake manifold. At closed throttle the EGR valve is opened. The EGR valve remains
fully open to a calibrated throttle position at w hich point it closes. The throttle position is sensed by a throttle
position sw itch (TPS) mounted on the throttle shaft on the injection pump.
W ith TPS, as the throttle is opened the sw itch closes at the calibration point. It energizes a solenoid w hich is
norm ally open. This cuts off the vacuum signal to the EGR valve, allowing the valve to close.
— NOTE The EPR solenoid is de-energized before, or at the same time,
the EGR solenoid is energized.
5-7
5A. General Emission Systems
VACUUM SW ITCHED EGR EPR CONTROL SCHEMATIC
6.2 LITER DIESEL
Figure 5-13, Federal EPR/EGR Schematic
Federal EPR/EGR System Operation
Exhaust gas is recycled through the com bustion cycle by adm itting exhaust gases into the intake manifold.
Exhaust gases are routed from both cylinder heads through internal passages in the m anifold to the EGR valve
(Figure 5-13). Exhaust gas flow is a function of the pressure differential between the exhaust system and the intake
manifold. The EGR valve controls the exhaust flow at the point of discharge into the intake manifold.
The EGR valve is operated by vacuum furnished from a mechanically driven vacuum pump (Figure 5-13). The
vacuum source signal is routed through an electrically operated open/close solenoid to the EGR valve. EGR is
adm itted into the intake m anifold at idle, and light load fueling rates. The EGR valve remains fully open through a
calibrated throttle lever motion. Throttle position is sensed by an electrical sw itch mounted directly to the R.H. side
of the injection pump. As the throttle is opened, the throttle position sw itch (TPS) electrically closes at the
calibration point, energizes the solenoid, and shuts off the vacuum signal, allowing the EGR valve to close.
5-8
5A. General Emission Systems
To increase flow EGR rates an exhaust pressure regulator (EPR) valve is used at the left hand exhaust m anifold to
increase exhaust back pressure. At closed throttle the EPR valve is closed. W ith increasing throttle position the
throttle position sw itch electrically opens causing the EPR valve to open by shutting off vacuum to the valve. The
EPR valve is controlled by its own sw itch point w ithin the throttle position sw itch assembly and its own open/close
solenoid. W ith autom atic transm ission vehicles, the throttle position sw itch has an additional function of applying
and releasing the transm ission converter clutch (TCC), when the throttle is operated to a calibrated point.
THROTTLE POSITION SWITCH
The throttle position sw itch just has 2 contacts inside it: One to send (B + ) at idle on a blue or purple wire to the
EPR solenoid w hich is N.C. and this opens the solenoid valve and vacuum closes the EPR valve. The other contact
w ill send (B + ) on a yellow wire to the EGR solenoid, at a specified throttle angle. The EGR solenoid is N.O. This
current energizes the EGR solenoid closing it, w hich cuts off vacuum, closing the EGR valve. There is a delay on
some sw itches in the tim e when the EPR opens and the EGR closes. There are three different cams used to
change EPR/EGR sw itch points:
• Blue Cam
• Black Cam
• Red Cam
0° Difference
5° Difference
10° Difference
- NOTE —
When DEACTIVATED; the EGR solenoid is normally OPEN, which would allow vacuum to
open the EGR valve; and the EPR solenoid is normally CLOSED, cutting off vacuum
to the EPR valve, opening it.
5-9
5A. General Emission Systems
8 Y E L( S X L)
8 LT B L U / B L K ( S X L | 8 LT B L U ( S X L )
THROTTLE PO SI TIO N
SW ITCH
(AUTOMATIC T R A N S M IS S IO N )
1
8 LT B L U / B L K I S X L ) -
CLOSED
8917548
—
8
8
8
8
LT
LT
LT
LT
O P E N ■- 1 0 %
THROTTLE SET TING
BLU/ B L K-3 82AIS X LIBLU /BLK 382BISXL )BLU-38 3(SX L)GRN-384(SXL|-
. 89 0 52 22
382
-.8 LT B L U / B L K 382 ■ 8 LT B L U - 3 8 3 -.8 LT G R N - 3 8 4 A -
_^ 12010649
RE F
H S T O P LAMP
] — i *— (C O N T A C T S
F R O N T OF D A S H -
BRAKE
SW IT C H
------- 8 B R N 141A —
r - 8 B R N 141 C - '
Pr
A C C FU SED
15 A M P
L P S FUSLL)
5 AMP
2004893
12004215
SOCKET
• 12004885
■8 B lK
8 GRY-8 -
8 LT G R N - 3 8 4 I S X L )
7
'—
12004267-
\
CT
BU S BAR
GR D
150A— - 1
■ 8 B L K - 1 5 0 B -----------------------------
FUSE BLOC K
4 W D S HI F T
I E VER L IGHT
t
C L O SE S WITH
4 TH C L U T C H '
ENGAGED
OPENS
M OM ENTARILY
ON 4 3
D N S HI F T
F L OO R U N D E R '
'
TC C S O L
23.5 O H M S
2 WD
OR NEUT
- V^WD
1201 5792 A S M
RPO M D 8 T R A N S M I S S I O N
!RAN SFER CASE
A U T O M A T IC T R A N S M I S S I O N DIE SE L
R P O M D 8 FE D K T R U C K
Figure 5-14, Wiring Diagram T.C.C. MD-8 K Truck.
The third sw itch incorporated in the throttle position sw itch is used to operate the transm ission converter clutch
(TCC), in the 7Q0-R4 Transm ission (MD8). This sw itch disengages the converter clutch at a throttle angle of less
than 8 degrees.
— NOTE The 1982 models disengaged the converter clutch below, have a 16 degree throttle angle.
See Figure 5-14, w iring schem atic. This sw itch controls (B + ) com ing from the brake sw itch to the T.C.C. solenoid. It
prevents converter clutch operation below 8 degrees of throttle opening.
On a 4-wheel drive (Figure 5-14), Diesel Truck, there is a N.C. relay in the parallel path of current to the T.C.C.
solenoid, at pin B of the connector at the transmission. It is energized by grounding at pin 4 of the relay.
Pin 4 is grounded through the 4 wheel drive indicator switch in the transfer case. It is grounded in either 4 high or 4
low. When the relay is grounded the N.C. relay is switched to open interrupting the B + path to pin B of the
transm ission connector. The only way to have converter clutch operation in 4 wheel drive is, to close the 4th gear
switch in the transm ission allowing B + from the other parallel path at pin A to pass through the now closed
contacts of the 4th gear sw itch to the T.C.C. solenoid.
5-10
5A. General Emission Systems
Figure 5-15 summarizes the EGR/EPR valve and
solenoid operations.
- NOTE —
Heavy black exhaust smpke upon
acceleration generally indicates a
malfunction in the EGR system.
E G R / E P R
P r o b l e m
ENGINE
SPEED
EGR
VALVE
EGR SOL
Not Energized
Idle to 15° Open
Throttle
(Vacuum to Valve)
Not Energized
15° to 20° Open
(Vacuum to Valve)
Throttle
Energized (No
20° to Full Closed
Vacuum to Valve)
Throttle
EPR
VALVE
EPR SOL
Closed
Energized (Vacuum
to Valve)
Not Energized (No
Vacuum to Valve)
Not Energized (No
Vacuum to Valve)
Open
Open
Figure 5-15, EGR Summary.
D i a g n o s i s
1. Start engine and operate to open therm ostat
temperature.
2. Remove air cleaner cover to observe operation of
EGR valve.
3. W ith engine at idle the EGR valve should be open. (Observe valve head in up position and noticeable exhaust
noise intake.) If not, check and correct any electrical and hose connection w hich may be loose and/or
disconnected.
4. Remove vacuum hose from EGR valve. The valve head should drop with a noticeable reduction in noise.
Reconnect hose.
5. At idle the hose to the EGR valve should have approxim ately 20 inches of vacuum. If vacuum is not present,
check output of the vacuum pump at the pump. The pump should produce a m inim um of 20 inches of vacuum.
6. If vacuum is present at the EGR valve but the valve does not open and close as the hose is put on and taken
off, the EGR valve is stuck and should be checked and replaced if necessary.
7. Manually operate the throttle lever at the injection pump through approximately 15° to 20° of travel. The EGR
valve should close when the TPS reaches the calibrated point.
8. Check the pink wire to the TPS for 12 volts (key on.) If 12 volts is not present, check for any loose connections,
open wire, and a blown 20 amp gauge idle fuse.
9. Correct any loose wire connections and change fuse if required. W ith key on, the blue wire from the TPS switch
should also have 12 volts. This blue wire feeds the EPR solenoid. At idle if the pink wire has 12 volts but the
blue one doesn’t, the TPS is inoperative and should be changed as shown in Section 6CG of the Light Duty
Truck Service Manual.
10. W ith engine off but key on, operate the throttle through 20° travel. At approxim ately 15°, the TPS w ill cut out the
12 volts to the blue wire (EPR). At approxim ately 20°, the TPS w ill cut in 12 volts to the yellow wire (EGR). If not,
the TPS is inoperative.
11. Check to see that the electrical connections are made at the EGR-EPR solenoid assembly and that the hoses
are routed correctly and connected to the solenoids.
12. If vacuum is present at the solenoid assembly and the solenoids are receiving an electrical signal as previously
m entioned and operation of the TPS through the calibrated points does not operate the EGR and/or EPR valves,
the solenoid assem bly is inoperative and should be replaced.
DIODE CAUSING EGR SYSTEM (1982 ONLY) MALFUNCTION
A condition exists whereby an excessive electrical feedback load can cause a diode in the EGR and/or EPR
solenoids to short. The diodes are for radio noise suppression only. When the diode shorts it usually w ill blow the
20 amp gauge fuse. A blown fuse will result in no engine electrical accessory feed such as no glow plug operation
or light, no cold advance or fast idle, and the EGR system w ill not operate. When the EGR system becomes
inoperative, full vacuum is supplied to the EGR valve at all speeds resulting in heavy black exhaust smoke and
low power.
To prevent the diodes from shorting due to heavy feedback loads, a jum per harness unit #14048052 is being made
available to install in the EGR-EPR electrical feed circuit at the TPS. This jum per harness has a built in diode to
reduce the feedback load.
5-11
5A. General Emission Systems
If a com m ent of heavy black exhaust smoke is received and the condition can be traced to the EGR/EPR solenoid
assembly diode, the follow ing outlines the procedure to follow to install the jum per harness unit.
1. Have engine stopped and key in off position.
2. Disconnect vacuum and electrical connections to the EGR/EPR solenoid assembly.
3. Remove bolt holding assembly, remove and install new assembly.
4. Reconnect vacuum hose and electrical connections.
5. Disconnect (3) wire connector to TPS and install jum per harness between connectors. (NOTE — The wire colors
blue, pink and yellow should line up.)
6. Install a new 20 amp gauge idle fuse.
LL4 Model—Vacuum Regulator Valve (VRV)
When using the M40 THM 400 Transmission, w ith an LL4-Model, a vacuum regulator valve is used (Figure 5-16). This
valve supplies an engine load vacuum signal to the transm ission vacuum modulator, w hich is proportional to
throttle travel (e.g. at idle m axim um vacuum, at W.OT. m inim um or “ 0” vacuum). This allows the vacuum modulator
to regulate transm ission shift points and line pressure.
5-12
5A. General Emission Systems
- NOTE The 1983 and later LL4*Model is also available with the 700-R4 4 speed automatic
transmission. This application uses a different throttle position switch, which has only one
set of contacts for transmission converter clutch operation. Also a specific adjusting gage
bar J33043-5 is necessary.
Throttle Position Switch Adjustment Tool
• J33043 THROTTLE POSITION SWITCH
GAGE BLOCK (6.2L)
The throttle position sw itch (Figure 5-16A) is properly
adjusted on the throttle shaft using this go-no-go gage
and a powered test light or ohmmeter, J33043 enables
the technician to check and adjust the throttle position
switch on the injection pump.
Figure 5-16A, J33043 Throttle Position Switch
Gage Block (6.2L).
• THROTTLE POSITION SWITCH GAGE BLOCKS
New applications for this engine may require new
throttle position sw itch specifications. New gage
blocks (Figure 5-16B) can be installed on the handle
(J33043-1) of the original gage block:
J33043-2
.646-.668 inch
J33043-4
.602-.624 inch
J33043-5
.771-.773 inch
Figure 5-16B, Throttle Position Switch Gage
Blocks
5-13
5A. General Emission Systems
1982 LH6-MODEL TPS CHART
USAGE
ALTITUDE
TRANS.
MODELS
THROTTLE
POSITION
SWITCH P/N
N a tio n w id e
A ll
M anual
A ll
14050405
0.646"
0.668"
J-33043-2
0.646"
0.668"
J-33043-2
GAGE BAR
SWITCH
SWITCH
CLOSED
OPEN
GAGE TOOL
NUMBER
Federal
A ll
A uto.
A ll
14033943
C a lif.
A ll
A uto.
C/K
14033943
0.646"
0.668"
J-33047-2
C a lif.
A ll
A uto.
C/K
14050408
0.602"
0.624"
J-33043-4
1983 LH6-MODEL TPS CHART
ENG INE
ASM
PART #
BROADCAST
B/C
CODE
THROTTLE
POSITION
SW ITCH P/N
14061529
UHB
14050405
.646
.668
J 33043-2
14061531
UHC
14050405
.646
.668
J 33043-2
14061545
UHD
14050405
.602
.624
J33043-4
14061549
UHF
14050405
.646
.668
J 33043-2
14061550
UHH
14066239
.646
.668
J33043-2
14061552
UHJ
14066238
.602
.624
J 33043-4
14061560
UHN
14066239
.646
.668
J33043-2
14050581
UHA
14050405
.646
.668
J33043-2
14061573
UHS
14050405
.646
.668
J33043-2
.602
.624
J 33043-4
.646
.668
J33043-2
-646
.668
J33043-2
GAGE BAR
SW ITCH
SW ITCH
CLOSED
OPEN
GAGE TOOL
NUMBER
14066299
UHZ
14050405
14061571
UHR
14050405
14061576
UHT
14066239
14061578
UHU
14066238
.602
.624
J33043-4
14061580
UHW
14066239
.646
.668
J33043-2
T
1984 LH6 TPS CHART
5-14
ENG INE
ASM
PART #
BROADCAST
B/C
CODE
THROTTLE
POSITION
SW ITCH P/N
GAGE BAR
SW ITCH
SW ITCH
CLOSED
OPEN
GAGE TOOL
NUMBER
14071011
FHB
14050405
.602
.624
14071019
FHF
14050405
.602
.624
J33043-4
14071018
FHD
14066239
.646
.668
J33043-2
J33043-4
14071022
FHJ
14066239
.646
.668
J33043-2
14071025
FHK
14050405
.602
.624
J33043-4
14050405
.602
.624
J33043-4
14071029
FHN
14071038
FHW
14066239
.646
.668
J 33043-2
14071042
FHY
14066239
.646
.668
J33043-2
5A. General Emission Systems
- NOTE The gage block dimensions were not on the emission label until the 1983 model year. See
gage block tool J33043 chart on page 5-14.
1983 & LATER LL4 TPS CHART
GAGE BAR
SWITCH
SWITCH
CLOSED
OPEN
THROTTLE POSITION
SWITCH
PART NUMBER
14066207
J33043-5
.773
.751
INJECTION PUMP
GAGE
TOOL #
OPTIONAL
TEST
LOCATION
THROTTLE
SHAFT
ROTATION
EPR
BLUE OR VIOLET
WIRE
WIDE OPEN
STOP SCREW
GAGE BOSS
GAGE
BAR
EGR
YELLOW
WIRE
GAGE
BOSS
IGN
PINK
WIRE
POWER TEST LIGHT OR
OHM METER
CLOCKWISE
ROTATION
Figure 5-1 , TPS Adjustment LH6-Model.
DIESEL ENG INE THROTTLE POSITION SWITCH SETTING PROCEDURE
See Figures 5-17 and 5-18.
1. Loose assem ble throttle position sw itch to fuel injection pump w ith throttle lever in closed position.
2. Attach an ohm m eter or powered test light across the IGN (pink) and EGR (yellow) term inals or wires. (Or on an
LL4/710 R4 across the connector terminals.)
3. Insert the proper “ sw itch-on” gage block between the gage boss on the injection pump and the wide open stop
screw on the throttle shaft. (Gage block dim ension listed on em ission label).
4. Rotate and hold the throttle lever against the gage block.
5. Rotate the throttle sw itch clockw ise (facing throttle switch) until continuity pivot occurs (low meter reading)
across the IGN and EGR term inals or wires. Hold sw itch body at this position and tighten mounting screws to 5-7
N-m (4-5 ft. lbs.).
6. Release throttle lever and allow it to return to idle position. Remove the “ switch-on” gage bar and insert the
“ sw itch-off” gage bar. Rotate throttle lever against “ sw itch-off” gage bar. There should no continuity (meter reads
resistance infinity) across the IGN and EGR term inals or wires. If no continuity exists, sw itch is set properly.
However, if there is continuity, then the sw itch m ust be reset by returning to Step 1 and repeating the entire
procedure.
5-15
5A. General Emission Systems
— NOTE —
The gage block dimensions were not on the emission label until the 1983 model year. See
gage block tool J33043 chart on page 5-12.
Transmission Vacuum Regulator Valve Adjustment (LL4)
See Figure 5-19.
1. Attach the vacuum regulator valve snugly, but loosely to the fuel injection pump. The switch body must be free to
rotate on the pump.
2. Attach vacuum source of 67 ± 5 kpa (20" Hg.) to inboard vacuum nipple. Attach vacuum gage to outboard
vacuum nipple.
3. Insert vacuum regulator valve gage bar J33043-2 between the gage boss on the injection pump and the wide open
stop screw on the throttle lever. (Switch on position).
4. Rotate and hold the throttle shaft against the gage bar.
5. Slowly rotate the vacuum regulator valve body clockwise (facing valve) until vacuum gage reads 27 kpa ± 2 kpa
(8" Hg). Hold valve body at this position and tighten m ounting screws to 5-7 N-m (4-5 ft. lbs.).
5-16
5A. General Emission Systems
- NOTE Valve must be set while rotating valve body in clockwise direction only.
6. Check by releasing the throttle shaft allow ing it to return to the idle stop position. Then rotate throttle shaft back
against the gage bar to determ ine if vacuum gage reads w ithin 27 kpa ± 2 (8" Hg.). If vacuum is outside limits,
reset valve.
VACUUM REGULATOR VALVE, 1982 “C-K-P” W ITH 6.2L AND 400 AUTOMATIC TRANSM ISSION
Com m ents regarding high or late upshifts in 1982 “ C-K-P” trucks equipped w ith 6.2L diesel engines and THM 400
autom atic transm issions may be the result of the vacuum regulator valve (VRV) calibration. This condition may be
corrected by replacing the valve w ith a new valve, P/N 14057219.
The new valve entered production at the assem bly plants in March, 1982.
The VRV should be verified as the cause of this condition using the follow ing procedure:
1. Identify w hich valve (old or new) is on the engine.
a. Old valve — rotating CAM is green color. P/N 14033982 is cast into the valve.
b. New valve — rotating CAM is orange color. P/N 14057219 is white lettered on face of valve.
2. If the valve has a green rotating CAM, remove the valve. If the rotating CAM is orange, go to Step 5.
3. Install a new valve. P/N 14057219.
4. Adjust the new valve, as described on Page 5-16 to 27 kpa (8" Hg.).
5. If the valve has an orange rotating CAM (P/N 14057219), check for a correct setting of 27 KPA.
- NOTE When diagnosing high or late transmission upshifts, be sure to check for a proper vacuum
output of approximately 70 kpa (21" Hg.). Check for the correct modulator pipe. The pipe
part #14054204 should be 5/32" I.D. and be approximately 5" long.
5-17
5B. California Diesel Electronic Control System (DECS)
5B. California (NB2) Diesel Electronic
Control System (DECS)
1984-1985 DDAD 6.2L DECS
The 6.2L, LH6 diesel engine w ill use an electronic controlled EGR em ission system for California applications. It is
a lim ited function system, controlling EGR, EPR T.C.C. and system diagnosis.
The 1985 6.2L LH6 DECS is similar, w ith the addition of on-vehicle seIf-diagnostics (10 trouble codes) and a vehicle
speed sensor.
1984-1985 “ C alifornia only” (RPO NB2) LH6 Engine less than 8500 lbs. GVWR.
ABBREVIATIONS USED IN THIS SECTION
• DEC—
Diesel Electronic Control System
• IP—
Instrum ent Panel
• DVM—
Digital Volt — OHM Meter W ith 10 MEG-OHM
Impedence
•T P S —
Throttle Position Sensor
•C E L Check Engine Light
• ECM—
Electronic Control M odule— Diesel
• MAPM anifold Absolute Pressure Sensor
• EGRExhaust Gas Recirculation
• EPR—
Exhaust Pressure Regulator
• V-REF—
ECM Reference Voltage (Approximately 5.3V)
• W OTW ide Open Throttle
• PW M—
Pulse W idth Modulated
• CKT—
Circuit
• DDC—
Diesel Diagnostic Check Tool
• TCC—
Transm ission Convertor Clutch
• ALDLAssem bly Line Diagnostic Link
or
» RPMRevolutions Per M inute
• ALCLAssem bly Line C om m unications Link
1985 DIAGNOSTIC CHARTS
• Diesel system diagnostic check
• DDC tool check
« Code 12
• Code 21
• Code 22
• Code 24
• Code 31
• Code 32
•
•
•
•
•
•
•
Code 33
Code 51
Code 52
Code 53
TCC check
ECM check (no code 12)
TPS check
1984 DIAGNOSTIC CHARTS
• Diesel system diagnostic check
• Engine speed sensor check
• DDC tool check
• EPR electrical check
• ECM check
• EPR vacuum check
• Map sensor check
• TPS check
• EGR/EGR vent check
• Transmission convertor clutch (TCC) check
5-18
5B. California Diesel Electronic Control System (DECS)
Electronic Vacuum Modulated EGR LH6 6.2L California Diesel
Electronic vacuum modulated EGR is a modulated EGR control system involving digital electronics.
In addition to controlling EGR vacuum signal by throttle position as in a mechanical system, the electronic system
also makes use of engine speed and closed loop feedback of EGR control vacuum.
The electronic vacuum m odulated EGR system is shown schem atically in Figure 5-20. It consists of an electronic
control m odule receiving inputs from throttle position, engine speed and absolute pressure sensors. In 1985 from
vehicle speed sensor (VSS).
The electronic control m odule sends out a pulsed signal w hich drives a solenoid to control the signal vacuum on
the EGR valve, and an “ O N /O FF” signal to a solenoid to control vacuum on an exhaust pressure regulator
(EPR) valve.
In operation, engine speed and throttle angle define the desired am ount of EGR. The electronic control module
sends out a pulsed signal to the EGR vacuum control solenoid indicating the vacuum level desired on
the EGR valve.
6.2 DIESEL ELECTRONIC CONTROL SYSTEM
VACUUM H O SE
EGR
VALVE
1985
BATTERY
A5 (1985 C14)
1985-C16
S W IT C H E S C L O S E S
IN 4TH G E A R
MAP
SEN SO R
A11 (1985 A l)
(1985 C10) A1
P W M E G R SOL.
A7 (1985-A12)
THROTTLE
P O S IT IO N
SEN SO R
A10 (1985-A2)
-Q
D IE S E L
ECM
c
A A Al
2K 12 IN
P R O D U C T IO N
V E H IC L E
SPEED SEN SO R
V E N T FILTER
A8 (1985 C 1 )
(1985-C11) A3
A9 (1985)
(1985-C12) B2
E G R V E N T SOL.
E P R SO L.
VAC
A9 (1985-A8)
E N G IN E
SPEED
SEN SO R
A6 (1985-A 10)
B11 (1985-A6)
(M AG. P/U, PART
O F VAC. P U M P ASM .)
ALDL
CONNECTOR
TCC
ALCL
F
E
D
C
(1985-C5)
A2
A12/b12
(1985 C 2 C 3 )
DIAG
EM AR
GND
B
A
□
TCC
S O L E N O ID
BRAKE
S W IT C H
E N G IN E
GROUND
Figure 5-20, Digital Diesel System Schematic.
5-19
5B. California Diesel Electronic Control System (DECS)
NOTES
5-20
5B. California Diesel Electronic Control System (DECS)
An absolute pressure sensor m onitors the vacuum on
the EGR valve and feeds this inform ation back to the
electronic control module. The electronic control
module compares the measured vacuum to the desired
vacuum (as defined by throttle angle, engine speed
and in 1985 vehicle speed), and then trim s the vacuum
control solenoid to provide the desired vacuum on the
EGR valve. A vacuum control bleed (vent) valve
solenoid is also included to quickly relieve vacuum on
the EGR valve during accelerations.
In addition, an EPR system is used and the EPR valve
is either open or closed. The EPR valve sw itch point is
determined by the electronic control module and is a
function of throttle angle and engine speed.
Since the vehicles w hich use the 6.2L engines are not
equipped with a “ Check Engine” light, a Diesel
Diagnostic Check (DDC Tool J34750) is used whenever
the need for service diagnostics (Figure 5-21). This tool
J34750 has 4 sw itch or diagnostic mode positions:
• Normal
CIGAR LIGHTER
PLUG-IN
DIESEL
DIAGNOSTIC
CHECK
TOOL DDC
TOOL J-34750
OR
EQUIVALENT
V
ALDL
CONNECTOR
ALDL
DIAGNOSTIC
MODE SELECTOR
SWITCH
CHECK ENGINE
LIGHT (CEL)
Figure 5-21, DDC Tool #J34750.
— Open or resistance infinity to ALCL
Pin B.
-
NOTE -
ALCL CONNECTOR - LOCATED UNDER LEFT
SIDE OF INSTRUMENT PANEL
/
In this mode of operation all of the ECM
outputs are in control of the ECM.
F
O
• ALCL 1
— A 10K ohm resistor to ground from
ALCL Pin B.
• ALCL 2
— A 3.9K ohm resistor to ground from
ALCL Pin B.
• Diagnostic — 0 ohm s resistance to ground from
ALCL Pin B.
This allow s the ability to quickly recognize that a
driveability problem is due to the ECM being in default
by either the CEL being “ O N ” or one of the selectable
diagnostic modes indicating a fault is present.
E
D
C
B
A
G
TERMINAL IDENTIFICATION
GROUND
E T.C.C.
DIAGNOSTIC
TEST TERMINAL
OTHER TERMINALS
ARE NOT USED
ALCL DATA
Figure 5-22, ALCL Connector (CK Series).
ALCL CONNECTOR
Under the instrum ent panel on a series CK or under the driver’s seat on a series GP is an Assem bly Line
C om m unications Link (ALCL) that is used by the assembly plant for a computerized check-out of the system. This
connector is also used in sen/ice to help diagnose the EGR system and TCC. See Figure 5-22.
5-21
5B. California Diesel Electronic Control System (DECS)
1984 6.2L DIAGNOSTIC MODE CHART
ENGINE SPEED
CHECK
ENGINE
LIGHT
TCC
OUTPUT
EPR
OUTPUT
EGR
OUTPUT
DUMP
SOLENOID
OUTPUT
N/A
Normal
Normal
Normal
Normal
Normal
ALCL 1
> 600 RPM
Send
ALCL Data
Normal
Normal
Normal
Normal
10k to GRD
> 375 RPM
< 800 RPM
Send
ALCL Data
On
On
10" Vacuum
Normal
< 375 RPM
Send
ALCL Data
Off
O ff
Off
Off
ALCL 2
> 800 RPM
Send
ALCL Data
Normal
Normal
Normal
Normal
3.9k to GRD
> 375 RPM
< 800 RPM
Send
ALCL Data
O ff
Off
Off
On
< 375 RPM
Send
ALCL Data
O ff
Off
Off
Off
> 375 RPM
Normal
On
On
10" Vacuum
Normal
< 375 RPM
Normal
On
On
50% DC
On
MODE SELECT
Normal
No resistor or
infinite resistance
Diagnostic
OOto GRD
ALCL
GRD
>
<
DDC
—
—
—
—
—
Assem bly Line Com m unications Link
Ground
Greater Than
Less Than
Diesel Diagnostic Check
-
NOTE -
1984 Diagnostic Modes
ALCL 1 Mode is whenever the ALCL Pin B or ECM Pin B11 is grounded by a
10k Ohm resistor.
ALCL 2 Mode is whenever the ALCL Pin B or ECM Pin or ECM Pin B11 is grounded by a
3.9k Ohm resistor.
Diagnostic Mode is whenever the ALCL Pin B or ECM Pin B11 is grounded
0 Ohms resistance.
SPECIAL SOLENOID CONTROL CO NDITIO NS (1984
DECS SYSTEM)
Under certain conditions the EGR solenoid, the vent solenoid, and the EPR solenoid are controlled independently of
the EGR control programming in the ECM.
These conditions include ECM reset, engine not running, engine at idle, engine above idle, diagnostic mode selec­
tion, ALCL 1 mode selection and ALCL 2 mode selection.
Engine not running is defined such that engine speed is less than 375 RPM. Engine at idle is defined such that
engine speed is greater than 375 RPM but less than 800 RPM. Engine above idle is defined such that engine speed
is greater than 800 RPM.
5-22
5B. California Diesel Electronic Control System (DECS)
NORMAL MODE
The control functions are operating according to ECM programming.
RESET
The EGR solenoid is de-energized (EGR valve fully open) when the ECM is reset.
The EPR solenoid is de-energized (EPR valve open) when the ECM is reset.
The vent solenoid is de-energized (EGR vent disabled) when the ECM is reset.
ALC L 1 M O D E OR ALCL 2 M O D E /E N G IN E N O T R U N N IN G
The EGR solenoid is de-energized (EGR valve fully open) if the engine is not running and either ALCL Mode is
selected.
The EPR solenoid is de-energized (EPR valve open) if the engine is not running and either ALCL Mode is selected.
The vent solenoid is de-energized (EGR vent disabled) if the engine is not running and either ALCL Mode is
selected.
A LC L 1 M O D E /E N G IN E AT IDLE
The EGR solenoid is controlled by the ECM to deliver a calibrated amount (kPa) of vacuum to the EGR valve
whenever the ECM is in the ALCL 1 Mode and the engine is at idle.
The EPR solenoid is energized (EPR valve closed) whenever the ALCL 1 Mode is selected and the engine is at idle.
The vent solenoid is controlled according to the vent determ ination logic in the ECM whenever the ALCL 1 Mode is
selected and the engine is at idle.
ALCL 2 M O D E /E N G IN E AT IDLE
The EGR solenoid is de-energized (EGR valve fully open) if the ALCL 2 Mode is selected and the engine is at idle.
The EPR solenoid is de-energized (EPR valve open) if the ALCL 2 Mode is selected and the engine is at idle.
The vent solenoid is energized (EGR vent enabled) if the ALCL 2 Mode is selected and the engine is at idle.
D IA G N O S T IC M O D E /E N G IN E R U N N IN G
The EGR solenoid is controlled by the ECM to deliver a calibrated amount (kPa) of vacuum to the EGR valve
whenever the ECM is in the Diagnostic Mode and the engine is running. In this way, the EGR control can be
checked out using a vacuum gauge or a dwell meter test.
The EPR solenoid is energized (EPR valve closed) whenever the Diagnostic Mode is selected and the engine is
running.
The vent solenoid is controlled according to the vent determ ination logic whenever the Diagnostic Mode is selected
and the engine is running.
D IA G N O S T IC M O D E /E N G IN E N O T R U N N IN G
The EGR solenoid is pulsed at a 50% duty cycle level if the Diagnostic Mode is selected and the engine is not
running.
The EPR solenoid is energized (EPR valve closed) if the Diagnostic Mode is selected and the engine is not running.
The vent solenoid is energized (EGR vent enabled) if the Diagnostic Mode is selected and the engine is not running.
5-23
5B. California Diesel Electronic Control System (DECS)
1985 6.2L DIAGNOSTIC MODE CHART USING DDC TOOL
ENGINE SPEED
CHECK
ENGINE
LIGHT
TCC
OUTPUT
EPR
OUTPUT
EGR
OUTPUT
VENT
SOLENOID
OUTPUT
o
N/A
Normal
Normal
Normal
Normal
Normal
10k
> 800 RPM
Send Data
Normal
Normal
Normal
Normal
> 375 RPM
< 800 RPM
Send Data
On
On
10" Vacuum
Normal
GMAD Test Mode
> 375 RPM
Send Data
Off
Off
Off
Off
ALCL 2
>
800 RPM
Send Data
Normal
Normal
Normal
Normal
> 375 RPM
< 800 RPM
Send Data
Off
Off
Off
On
GMAD Test Mode
> 375 RPM
Send Data
Off
Off
O ff
Off
ALCL 3
> 800 RPM
Send Data
Normal
Normal
Normal
Normal
> 375 RPM
< 800 RPM
Send Data
Normal
Normal
Normal
Normal
> 375 RPM
Send Codes
On
On
1 0 " Vacuum
Normal
> 375 RPM
Send Codes
On
On
50% DC
On
MODE SELECTION
Normal
co
ALCL 1
3.9k
30k
Diagnostic
OO
Dealer Test Mode
PWM — Pulse w idth m odulation
oo — Resistance infinity
D.C. — Duty cycle
DDC — Diesel Diagnostic Check
> Greater Than
< Less Than
> Greater Than or Equal To
< Less Than or Equal To
Figure 5-23
1985 Diagnostic Modes
• NORMAL
ALCL Line Open (Infinite Resistance)
In this mode of operation all of the outputs are in control of the ECM. The diagnostics w hich have been enabled
are operational and can log a m alfunction if it occurs and issue a remedial action if appropriate.
• ALCL 1
ALCL Line Grounded Thru a 10k Ohm Resistor
In this mode of operation, the ALCL data is transm itted via the check engine light output. This list is intended for
usage by the GMAD assem bly plants.
Additionally, the ECM functions are altered depending upon what engine speed is input to the controller. The ALCL
list transm ission is not altered by engine speed but the data transm itted is.
• ENGINE SPEED GREATER THAN 800 RPM
When the engine is operated at greater than 800 RPM. the ECM functions as it would in the normal mode.
- NOTE 1985 Diagnostic Modes
ALCL 1 Mode is whenever ALCL Pin B or ECM Pin A6 is grounded by a 10k Ohm resistor.
ALCL 2 Mode is whenever ALCL Pin B or ECM Pin A6 is grounded by a 3.9k Ohm resistor.
ALCL 3 Mode is used only by Delco Electronics during manufacture.
Diagnostic Dealer Test Mode is whenever ALCL Pin B or ECM Pin A6 is grounded
with 0 Ohms resistance.
5-24
5B. California Diesel Electronic Control System (DECS)
ENG INE SPEED @ IDLE
When the engine speed is between the ECM run decision RPM w hich is between 375 and 800 RPM, the TCC and
EPR outputs are turned on all the time. Also, the EGR loop is forced to run at a constant vacuum, by setting the
desired (KPA) vacuum am ount equal to the 10" Hg. EGR vacuum in the diagnostic mode. If this diagnostic mode
EGR vacuum of 10 in. Hg. is less than the value in the ECM memory, the vent solenoid will be de-energized. This
operation helps verify that the MAP transducer, vacuum plum bing and EGR solenoid are installed and operating
properly. The TCC solenoid operation is also checked in this mode.
• ENGINE NOT RUNNING
When the engine is not running, all ECM outputs are de-energized.
• ALCL 2 ALCL Line Grounded Thru 3.9k ohm
In this mode of operation the ECM behaves the same as in the ALCL 1 mode except at engine idle.
• ENGINE SPEED AT IDLE
When the engine speed is between 375 and 800 RPM, the TCC, EPR and EGR outputs are de-energized. The vent
solenoid output is energized. This state helps verify that the vent solenoid is installed and operating properly.
• ALCL 3
ALCL Line Grounded Thru 30k ohm
This test mode is intended for usage by Delco Electronics during ECM manufacturing.
• ENGINE SPEED AT IDLE OR ABOVE
When the engine speed is above 375 RPM, the ECM functions as if it were in the normal mode.
• DIAGNOSTIC MODE
ALCL Line Grounded (ALCL Pin B or ECM Pin A6)
This mode is intended to aid field service of the vehicle system. W hile in this mode the ECM will output diagnostic
codes on the check engine light in the typical flash-out three tim es format. In addition ECM operation will be
m odified as follows.
1. ENGINE RUNNING
The TCC and EPR outputs w ill be energized and the EGR loop will be forced to run at 10" vacuum. The
vent solenoid w ill be de-energized if the calibrated value of 10" is less than the current value of the EPR
sw itchpoint table. If ALCL Pin B or ECM Pin A6 is grounded with the engine running the system will display
any stored trouble codes by flashing the “ CHECK ENGINE” light. Each code w ill be flashed three times. The
ignition sw itch is then turned off, engine is re-started and run to see if the code is a “ hard” or “ interm ittent”
failure. If it is a “ hard” failure, a Diagnostic Code Chart is used to find the problem. If it is an “ interm ittent”
failure, the charts are not used. A physical inspection of the applicable system is made.
2. ENGINE NOT RUNNING
When the engine is not running, all outputs except the EGR output are energized. The EGR output is forced to
run at a 50% duty cycle. If ALCL Pin B or ECM Pin A6 is grounded, with the ignition “ O N” and the engine
stopped, the system w ill display a code “ 12” by flashing the “ CHECK ENGINE” light (indicating the system is
operating). A code “ 12” consists of one flash, followed by a short pause, then tw o flashes in quick succession.
Code 12 w ill continue to flash until the “ Test” terminal is ungrounded.
3. SYSTEM RESET
During normal operations the system will only be in reset for the first few m illiseconds of operation. During
this tim e the ECM w ill not process any data flow and all four outputs w ill be energized.
5-25
5B. California Diesel Electronic Control System (DECS)
-
NOTE -
All diagnosis should start with the Diesel Diagnostic Circuit Check.
DDC Tool Check
6.2L LH6
See Figures 5-24, 5-25 and 5-26. The Diesel Diagnostic Check (DDC) Tool is a com bination “ Check Engine” Light
(CEL), and diagnostic mode selector. The tool allow s a check on the ECM’s ability to detect a fault and set a CEL.
The mode selector assists diagnostics if a fault is present, even if there was no C E L
— NOTE —
Prior to any diagnostics, it must be verified that the DDC tool is functioning.
BACK VIEW A
OF
CONNECTOR
I.P. HARNESS
CONNECTOR
488
451
150
ECM SIDE
[ J DIESEL DIAGNOSTIC CH ECK TOOL
DOS TOOL J-34750 OR EQUIVALENT
[2] CH ECK ENGINE LIGHT (CEL)
[3] ALCL DIAGNOSTIC
M ODE SELECTOR SWITCH
[4] ALCL CONNECTOR
[ g CIGAR LIGHTER PLUG IN
I.P.
HARNESS
ECM
C ONN.
ECM
A 12
GROUND
T=
ALCL DATA
DIAGNOSTIC TEST
TERM
— -
150
ENGINE
GROUND
—
B12
—
488
451
—
-----
F E
D C
B A
ALDL CONNECTOR
Figure 5-24,1984 DDC Tool Check Schematic.
1. Check to see if the DDC tool is supplied w ith 12 volts. Light should be “ O N ” w ith only the power cord installed.
See Figures 5-24 and 5-25.
2. Check to see if ALCL circu it is grounded or faulty. Normally when connection is made to ALCL, the CEL should
remain “ O N ” .
3. When ignition is turned “ O N ” , the CEL should remain “ O N” . If CEL goes “ OFF” , ECM may be shorted internally.
-
NOTE -
When using the DDC Tool in any of the diagnostic modes (3.9k or 10k), the CEL will flicker.
This is normal. Also, when going from any diagnostic mode to either normal or ground, the
CEL will come on SOLID for 10 seconds then go “OFF”. This is the normal ECM reset.
5-26
5B. California Diesel Electronic Control System (DECS)
DDC TOOL CHECK
6.2L (LH6) DIESEL (CALIF.)
©
Figure 5-25, DDC Tool Check 1984-85.
5-27
5B. California Diesel Electronic Control System (DECS)
a
B A C K V IE W A
/a ,\
OF
M
CONN ECTOR
I.P. HARNESS
CONNECTOR
488
451
[j]
DIESEL DIAGNOSTIC CHECK (DDS) TOOL
J-34750 OR EQUIVALENT
[2] CHECK ENGINE LIGHT (CEL)
150
ECM SIDE
jjj
ALCL DIAGNOSTIC
MODE SELECTOR SWITCH
[4] ALCL CONNECTOR
24 PIN A B
CO NN ECTOR
[5] CIGAR LIGHTER PLUG-iN
f6l BAT CONNECTOR
GROUND
C2
T=
C3
DIAGNOSTIC TEST
TERM
u—::
HARNESS
CONN.
150
J11
—
150
E N G IN E
•' GROUND
gin
u:
—
488
ALCL DATA
baco
pviewA
^ C O N N E C T O R ------
I.P.
ECM
CONN.
ECM
A
—
451
A6
—
LJ
F
E
D
C
B A
ALCL CONNECTOR
Figure 5-26 1985 DDC Tool Check Schematic,.
Pin Condition
Terminal
CEUCode
Condition
A10 0PN
ALCL
No CEL
OK
No Light — No Code
A 10G N D
ALCL
No CEL
OK
No Light — No Code
A10 OPN
EGR Vent
No CEL
OK
Normal — except vacuum for
EGR doesn’t go to 0.
A 10G N D
Sensor GND
No CEL — No Code
OK
System Normal
5-28
Codes
5B. California Diesel Electronic Control System (DECS)
1984 Diesel Diagnostic Circuit Check
See Figure 5-27.
The ECM provides the diagnostic logic to detect faults in the systems the ECM m onitors or controls. In 1984 the
ECM, when it recognizes a fault, has the capability of turning a “ Check Engine” Light (CEL) “ O N” but does not
store or flash a trouble code. Furthermore, if the condition corrects itself, the CEL signal w ill be turned “ O FF”
im m ediately follow ing the correction.
The ECM recognizes errors in Engine Speed, Vacuum errors in the EGR vacuum loop via the MAP sensor, and
electrical faults involving the 5-volt reference circuit.
1985 DECS with On-Vehicle Self Diagnostics
PURPOSE
The purpose of the system self diagnostics is to detect faults which may occur and then alert the operator. The self
diagnostics also assist service personnel in diagnosing system faults.
The Electronic Control Module (ECM) m onitors its own performance and certain system input and output signals to
determ ine if a system fault has occurred.
TROUBLE CODES
Ten “ 2 d ig it” trouble codes are used to indicate various system faults.
If the DDC tool J34750 is in the diagnostic mode, that is ALCL Pin B or ECM Pin A6 grounded, w ith the ignition
“ O N ” and the engine stopped, the system w ill display a code “ 12” by flashing the “ CHECK ENGINE” light
(indicating the system is operating). A code “ 12” consists of one flash, follow ed by a short pause, then tw o flashes
in quick succession. Code 12 w ill continue to flash until the ALCL line (ALCL Pin B or ECM Pin A6) is ungrounded.
If the ALCL line (ALCL Pin B or ECM Pin A6) is grounded w ith the engine running the system w ill display any
stored trouble codes by flashing the “ CHECK ENGINE” light. Each code w ill be flashed three times. The ignition
sw itch is then turned off, engine is re-started and run to see if the code is a “ hard” or “ interm ittent” failure. If it is a
“ hard” failure, a Diagnostic Code Chart is used to find the problem. If it is an “ interm ittent” failure, the charts are
not used. A physical inspection of the applicable system is made.
Each trouble code has its own set of conditions that m ust be met for that code to be detected. Once a code is
detected, it w ill cause the “ CHECK ENGINE” light to turn on, and a code may be logged in the nonvolatile memory
after meeting the trouble code logging requirements.
The purpose of the trouble code logging requirements is three-fold:
1. To prevent false codes from being logged.
2. To insure that the “ CHECK ENGINE” light when illum inated, w ill remain illum inated for a period of tim e
su fficien t to be seen by the technician.
3. To prevent an interm ittent code from “ flashing” the “ CHECK ENGINE” light.
5-29
5B. California Diesel Electronic Control System (DECS)
1984 DECS
6.2L (LH6)
DIESEL DIAGNOSTIC CIRCUIT CHECK
•
•
•
•
•
Make physical inspection of engine compartment.
Make certain all electrical components are correctly attached.
Check all vacuum lines fo r hoses o ff, pinched or burned through.
Check EGR valve fo r vacuum leak and free movement.
Check fo r plugged EGR vent filte r.
Figure 5-21,1984 Diagnostic Circuit Check.
5-30
5B. California Diesel Electronic Control System (DECS)
The codes are stored in a non-volatile memory, whose storage data is retained if the ignition sw itch power is turned
off. This is com m only known as a long term memory. The trouble codes can be erased by:
1. Disconnecting the large (32 pin) connector for 10 seconds.
2. Disconnecting the battery for 10 seconds.
3. Cycling the ignition sw itch o ff and on 50 times.
THE TROUBLE CODES INDICATE FAULTS AS FOLLOWS:
CODE 12
No Engine RPM Reference Pulses. This code is not stored in the memory and w ill only flash w hile the
fault is present. A normal code w ith the ignition “ O N ” engine not running.
CODE 21
Throttle Position Sensor (TPS) circuit 417 sensor signal voltage high on ECM Pin A-2 (open circuit or
m isadjusted TPS). The engine must run for 2 m inutes to set this code.
CODE 22
Throttle Position Sensor (TPS) circuit 417 sensor signal voltage low on ECM A-2 (grounded circuit). The
engine m ust run at 1250 RPM or above before this code w ill set.
CODE 24
Vehicle Speed Sensor (VSS) is detected when the engine is running. RPM and throttle position indicate
the vehicle should be in motion, w ith inadequate VSS signal (open or grounded circuit). The vehicle
must be operating at road speed for 10 seconds before this code w ill set.
CODE 31
MAP sensor signal voltage too low. Engine m ust run at idle for 10 seconds before this code w ill set.
CODE 32
EGR vacuum circuit has seen improper EGR vacuum (closed loop error). The vehicle m ust be running at
a road speed of approxim ately 30 mph (48 Km/h) for 10 seconds before this code w ill set.
CODE 33
MAP sensor signal voltage too high. Possible vacuum leak — check for a poor connection at the
sensor hose. The engine m ust run at idle for 10 seconds before this code w ill set.
CODE 51
PROM fault — (incorrectly installed in socket). It takes 10 seconds to set this code.
CODE 52
ECM fault analog to digital converter fault. It takes 10 seconds to set this code.
CODE 53
5 Volt Reference (V-REF) circuit overloaded (grounded circuit). It takes 10 seconds before this code
w ill set.
5-31
5B. California Diesel Electronic Control System (DECS)
1985 Diagnostic Circuit Check
The Diagnostic C ircuit Check is the starting point for the diagnostic procedure to be used.
The diagnostic charts are related to the ECM and w ill determine if the ECM is working properly. This section
diagnoses the em issions system controlled by the ECM and has charts to diagnose a circuit when the ECM has
displayed a trouble code.
The way to approach a problem is to follow three basic steps:
1. ARE THE ON-VEHICLE DIAGNOSTICS WORKING? — We find this out by performing the “ Diagnostic Circuit
Check” . Since this is the starting point for the diagnostic procedure, always begin here. If the On-Vehicle
Diagnostics aren’t working, the “ Diagnostic C ircuit Check” w ill lead you to a chart to correct the On-Vehicle
Diagnostics. If the vehicle w ill not start, see “ Engine Cranks Normally W ill Not Start” in Section 7. If the OnVehicle D iagnostics are OK, the next step is:
2. IS THERE A TROUBLE CODE STORED? If a trouble code is stored, go directly to the numbered code chart. If no
trouble code is stored, the third step is:
3. WHAT IS THE DRIVEABILITY SYMPTOM? Section 7 lists various driveability sym ptom s w hich may be found, and
suggests checks of related com ponents, many of w hich are found in Section 7.
This procedure, w hich takes only a short time, w ill help lead you to repair the problem in the least amount
of time.
5-32
5B. California Diesel Electronic Control System (DECS)
1985 DIESEL DIAGNOSTIC CIRCUIT CHECK
6.2L (LH6) DIESEL (CALIF.)
•
•
•
•
•
MAKE PHYSICAL INSPECTION OF ENGINE COMPARTMENT.
MAKE CERTAIN ALL ELECTRICAL COMPONENTS ARE CORRECTLY CONNECTED.
CHECK ALL VACUUM HOSES THAT MAY BE DISCONNECTED, PINCHED OR BURNED.
CHECK EGR VALVE FOR VACUUM LEAK AND FREE MOVEMENT.
CHECK FOR PLUGGED EGR VENT FILTER AND REPLACE IF REQUIRED.
• CONNECT DIESEL DIAGNOSTIC CHECK (DDC) TOOL IN CIGAR LIGHTER
OR BAT TERMINAL ON FUSE PANEL
• DDC TOOL IN “ NORMAL” MODE LIGHT SHOULD BE “ ON” .
• CONNECT DDC TOOL INTO ALCL— LIGHT SHOULD BE “ ON” .
CEL “ OFF”
C E L “ ON”
~ - i ___
X
• IGNITION “ ON” AND ENGINE OFF.
• POSITION DDC TOOL IN “ GROUND” MODE.
• NOTE LIGHT—SHOULD FLASH CODE 12.
GO TO DDC
TOOL CHECK CHART
• FLASHES CODE 12
AND ANY OTHER CODE.
• POSITION DDC TOOL IN
“ NORMAL” MODE.
• START ENGINE.
DOES NOT FLASH CODE 12.
• NO LIGHT— CODE SYSTEM OK.
• IGNITION “ OFF” .
• INSTALL VACUUM GAGE
IN PLACE OF EGR VALVE.
• START AND RUN ENGINE
AT 850 RPM IN PARK OR
NEUTRAL.
• NOTE VACUUM GAGE.
VACUUM STEADY.
• VEHICLE IN PARK OR NEUTRAL.
• QUICKLY FLASH THROTTLE.
• OBSERVE VACUUM GAGE MOVEMENT.
VACUUM GAGE DROPS FROM ABOVE
68 kPa (20") TO NEAR ZERO.
• IGNITION “ OFF” .
• RECONNECT EGR VACUUM GAGE IN
PLACE OF EPR VALVE.
• START ENGINE.
• OBSERVE VACUUM IN “ 3.9k” AND “ 10k”
MODE OF DDC TOOL.
• VACUUM SHOULD BE 0 kPA
(“ 0” ) IN 3.9k AND BETWEEN
50-68 kPa (15 "-20") in 10k.
GO TO ECM
CHECK CHART
FLASHES CODE.
IF THERE IS CODE
51, 52 OR 53, GO TO
THAT CODE CHART FIRST.
FOR ANY OTHER CODE,
START WITH LOWEST
NUMBER CODE CHART
VACUUM PULSES.
GO TO EGR/EGR VENT
CHECK CHART
VACUUM GAGE DROPS ONLY ABOUT
V2 DISTANCE FROM FULL VACUUM.
FULL VACUUM,
NO MOVEMENT.
I
|
GO TO EGR/EGR VENT
CHECK CHART
GO TO TPS
CHECK CHART
NORMAL VACUUM IN 3.9k AND 10k MODES.
VACUUM NOT NORMAL IN EITHER TEST MODE.
• ECM CONTROLS SYSTEM IS OK
AND THERE ARE NO ELECTRICAL
FAULTS.
• SEE SECTION 6-ENGINE DIAGNOSIS
IF DRIVEABILITY PROBLEM EXISTS.
GO TO EPR CHECK CHART.
Figure 5-28,1985 Diesel Diagnostic Circuit Check.
5-33
5B. California Diesel Electronic Control System (DECS)
Electronic Control Module (ECM)
C-K TRUCK ECM
The system electronic control module (ECM) controls
the EGR vacuum signal by m odulating a square wave
electrical signal to the EGR solenoid.
PLENUM
PANEL
The solenoid behaves like an “ O N /O FF” device
responding to the de-energized/energized portion of the
square wave. By m odulating the de-energized/energized
portion of the square wave, the EGR vacuum signal
can be controlled. A bleed portion of the solenoid
improves the EGR m odulation response by bleeding
EGR vacuum to atmosphere whenever the solenoid
closes the source vacuum port.
THE ECM CONTROLS THE FOLLOWING OUTPUTS:
COWL
• Exhaust Gas Recirculation (EGR).
ECM MOUNTING
HOUSING
• Exhaust Pressure Regulation Control (EPR).
• Transm ission Convertor Clutch Control (TCC).
Figure 5-29, C-K Truck ECM Location.
• System Diagnosis.
THE ECM MONITORS THE FOLLOWING INPUTS:
G-TRUCK
• Engine RPM.
ECM
• Absolute Pressure (MAP) used to m onitor EGR
vacuum circuit.
• Throttle Position Sensor (TPS).
• 4th Gear Input (1984 only).
• Vehicle Speed via VSS, 1985 and Later.
The ECM is serviced the same as the Delco ECM in
gas engine vehicles. In 1984 there is only one service
ECM, and 4 different E-PROMS. In 1985, there is one
service ECM and 6 different E-PROMS. During service
replace either the PROM, ECM or both.
Figure 5-30, G-Tmck ECM Location.
The broadcast code (e.g., BRL) on the E-PROM matches the broadcast code on the ECM.
There is a 4 digit E-PROM code on it for identification, and this code is the last 4 digits in the PROM part number.
EG. PROM CODE 9564 BRM
PROM part #10039564
Broadcast code — “ BRM” w ill match “ BRM” code on the ECM label.
5-34
5B. California Diesel Electronic Control System (DECS)
1984 California 6.2L Diesel ECM Usage
• SERVICE ECM P/N — 1226465
VEHICLE USAGE — C10 Suburban
K10 Blazer
C10-20 Pick-up
CALIB. — S8H5M
BROADCAST CODE — BRL
PROM PART #16040980
• SERVICE ECM P/N — 1226465
VEHICLE USAGE — K10 Suburban
G20 (Van) Manual Trans.
CALIB. — S8H7
BROADCAST CODE — BRM
PROM PART #16039564
• SERVICE ECM P/N -
1226465
VEHICLE USAGE — K10 Pick-up
CALIB. — S8B14
BROADCAST CODE — BRN
PROM PART #16039569
• SERVICE ECM P/N — 1226465
VEHICLE USAGE — G20 (VAN) AUTO TRANS.
CALIB. - S8H14
BROADCAST CODE - BRR
PROM PART #16039580
1985 California 6.2L Diesel ECM Usage
SERVICE ECM PART #1226645 (ALL SERIES)
VEHICLE USAGE
• C-Truck Autom atic
• Broadcast Code — DWC
• PROM Part #16044575
• C-Truck Manual
• Broadcast Code — DWD
• PROM Part #16044585
• K-Truck Autom atic
• Broadcast Code — DWF
• PROM Part #160144595
• K-Truck Manual
• Broadcast Code — DWH
• PROM Part #16044605
• G-Van Autom atic
• Broadcast Code — DWJ
• PROM Part #16044615
• G-Van Manual
• Broadcast Code — DWK
• PROM Part #16044625
5-35
5B. California Diesel Electronic Control System (DECS)
ECM REPLACEMENT
-
NOTE —
When replacing a production ECM with a service controller, transfer the Production
Broadcast Code and Production ECM Number to the service controller label. Do not record
on the removable cover. This provides identification of the ECM throughout the service life
of the vehicle.
• REMOVE OR DISCONNECT
— NOTE —
To prevent internal ECM damage, the
ignition must be off when disconnecting
or reconnecting the ECM connector.
See Figure 5-31 and 5-32.
1. ECM mounting hardware.
2. Connector from ECM.
3. ECM
4. Calibrator access cover.
5. Calibrator. Grasp the calibrator carrier and gently
rock from side to side and upward.
• INSTALL OR CONNECT
Record Production Broadcast Code and Production
ECM Number from removed ECM to service controller.
Any tim e a calibrator is installed backwards and the
ignition is turned on, the calibrator w ill be destroyed.
1. Calibrator removed from previous ECM. Position
carrier squarely over the socket and press down
firm ly on the top of the carrier. W hile pressing down
on carrier, use a narrow blunt tool and alternately
pressing down on either end of the calibrator body
to seat into socket.
2. Access cover.
3. Connector to ECM.
4. ECM w ith m ounting hardware.
• PART INFORMATION
PART NAME - GROUP
Controller, ECM — 3.670
Calibrator, PROM — 3.670
5-36
5B. California Diesel Electronic Control System (DECS)
-
NOTE —
To prevent internal damage, the ignition
must be off when disconnecting or
reconnecting the ECM connector.
REFERENCE
EN D
1. Remove ECM mounting hardware.
2. Disconnect the connector from the ECM.
3. Remove ECM.
4. Remove calibrator access cover.
SC R E W
7. If a service controller is to be installed, check the
service part number to make sure that it is the
correct controller for the replaced ECM.
8. Position the carrier squarely over the PROM
socket with the squared off symmetrical end of the
carrier aligned with the small notch in the socket
at the pin 1 end.
ANYTIME THE PROM IS INSTALLED BACKWARDS
AND THE IGNITION SWITCH
IS TURNED ON, THE PROM IS DESTROYED.
PROM
C A R R IE R
REFERENCE
EN D
C A L IB R A T O R
(P R O M ) M O U N T E D
IN A C A R R IE R
P IN 1 O F
PR O M
SOCKET
,T R E F E R E N C E
EN D
5. Remove calibrator. Grasp the calibrator carrier and
gently rock from side to side and upward.
9. Press down firmly on the top of the carrier.
10. While firmly pressing down on the carrier, take a
narrow blunt tool and press down on the body of
the PROM. Try to seat the PROM in the socket
squarely by alternately pressing on either end of it.
•
Replacement ECM (called controller) is supplied
without a PROM. Care should be taken when
removing a PROM from and ECM that is being
replaced as this PROM will be used in a service
controller.
6. A correct PROM in a carrier is where the squared
off symmetrical end of the carrier is at the same
end as the half-rounded molded depression on the
PROM. If a new PROM is to be installed, check to
see that the installation of the PROM to-carrier is
correct. Check for correct PROM part number.
11. Install access cover.
12. Install mounting hardware.
13. Install ECM and connect the connector.
Figure 5-33, Calibrator Replacement.
5-37
5B. California Diesel Electronic Control System (DECS)
1984 ECM Check 6.2L (LH6)
See Figures 5-34 and 5-35. The ECM check is made to determine why the “ Check Engine” light remains “ O N ” after
the engine is started. Normally, the ECM w ill not recognize a fault for at least 10 seconds after start-up. If the CEL
remains “ O N ” , the ECM has lost power, ground or the signal that turns the CEL “ OFF” has been lost. Since the
CEL is remote from the ECM, it can recognize faulty ECM power or ECM.
1. Check for proper CEL signal at ALCL. It should normally be about battery voltage until the vehicle is started.
2. Check for 12 volts to ECM ignition feed terminals. Battery voltage should normally be present at both terminals.
3. Check for good ECM ground. Light should norm ally be “ O N ” . If ECM power and ground term inals are OK, check
for good ECM to connector term inal contact.
4. When the vehicle is started, the ECM turns the CEL “ O FF” and voltage at ALCL should normally drop under 6
volts.
I.P. HARNESS
CONNECTOR
4 3 9 48 8
a
b a c k V IE W
of
CONNECTOR
451
150
[J
DIESEL DIAGNOSTIC CHECK TOOL
DDC TOOL J-34750 OR EQUIVALENT
[2] CHECK ENGINE LIGHT (CEL)
ECM SIDE
[3] ALDL DIAGNOSTIC
MODE SELECTOR SWITCH
[4] ALDL CONNECTOR
ECM
IG N IT IO N
A5
" T
GROUND
IGNITION
ALCL DATA
DIAGNOSTIC TEST
TERM
39
IGN.
150
ENGINE
GROUND
B12
B1
A6
B11
ECM
FUSE
439
IG N .
488
451
I.P.
HARNESS
CONN.
Figure 5-34,1984 ECM Check Schematic.
5-38
GAU/IDLE
FUSE
BULKHEAD
CONN.
B5
A12
T
24 P IN A B
CONNECTO R
[5l CIGAR LIGHTER PLUG IN
ECM
CONN.
F
E
D
C
B A
ALCL CONNECTOR
A
5B. California Diesel Electronic Control System (DECS)
1984 DECS
6.2L (LH6)
ECM CHECK
• CEL remains “O N” after engine start-up.
• Check PROM for proper installation.
Figure 5-35, ECM Check.
5-39
5B. California Diesel Electronic Control System (DECS)
A
43 9 48 8
451
150
ECM SIDE
2_ CHECK ENGINE LIGHT (CEL)
3_ ALCL DIAGNOSTIC
MODE SELECTOR SWITCH
£_ ALCL CONNECTOR
CIGAR LIGHTER PLUG-IN
ECM
CONN.
ECM
IGNITION
C14 39
D14
GROUND
ECM 1
FUSE
BULKHEAD
CONN.
150
I,
BATTERY
- ill ECM B
'
FUSE
C16
ALCL DATA A10
DIAGNOSTIC TEST
TERM
ENGINE
1«#GROUND
C2
C3
A6
488
451
F
HARNESS
CONN.
Figure 5-36,1985 ECM Check Schematic.
5-40
bacofiewA
------ ^C O N N E C T O R /------
I.P. HARNESS
CONNECTOR
E
D
C
B A
ALCL CONNECTOR
5B. California Diesel Electronic Control System (DECS)
1985 DECS
ECM CHECK
CEL DOES NOT FLASH CODE 12
6.2L (LH6) DIESEL (CALIF)
• CEL REMAINS “O N ” AND NO CODE.
• CHECK PROM FOR PROPER INSTALLATION.
Figure 5-37,1985 ECM Check Chart.
5-41
5B. California Diesel Electronic Control System (DECS)
CODE 51
PROM PROBLEM
• CHECK THAT ALL PINS ARE FULLY INSERTED IN SOCKET.
• IF OK, REPLACE PROM AND RECHECK.
• IF PROBLEM NOT CORRECTED, REPLACE ECM.
6.2L (LH6) DIESEL (CALIF.)
9
THE IG NITIO N SHOULD ALWAYS BE OFF WHEN INSTALLING OR REMOVING THE ECM CONNECTORS
El
1.
2.
L
Remove or Disconnect (Figures 1 and 2)
Inspect (Figure 3)
For correct indexing of reference end of the PROM
Carrier and carefully set aside. Do not remove PROM
from carrier to confirm PROM correctness.
Connectors from ECM
ECM mounting hardware.
Important
PROM
liAH*
ELECTRONIC CONTROL MODULE (ECM) MOUNTING
HARDWARE NOT ILLUSTRATED.
3. ECM from passenger compartment
4. ECM Access cover
r
ACCESS COVER
s
Figure 3
PROM CARRIER
NOTCH IN PROM REFERENCED
TO SMALLER NOTCH IN
CARRIER AND THE PIN END.
Important (Before installing new PROM)
ANYTIME THE PROM IS INSTALLED
BACKWARDS AND THE IGNITION SWITCH
IS TURNED ON, THE PROM IS DESTROYED.
Figure 1
Install or Connect (Figures 1 and 3)
1.
5.
PROM in PROM socket.
PROM removal
Important
Important
Using the rocker-type PROM Removal tool, engage
one end of the PROM carrier with the hook end of the
tool. Press on the vertical bar end of the tool and
rock the engaged end of the PROM Carrier up as far
as possible. Engage the opposite end of the PROM
Carrier in the same manner and rock this end up as
far as possible. Repeat this process until the PROM
Carrier and PROM are free of the PROM Socket. The
PROM Carrier with PROM in it should lift off the
PROM socket easily. PROM Carrier should only be
removed by using the pictured PROM removal tool
(Figure 2). Other methods could cause damage to thfi
PROM or PROM socket.
fa .
Figure 2
Figure 5-38, Code 51.
5-42
DO NOT press on PROM — ONLY CARRIER.
Small notch of carrier should be aligned with small
notch in socket. Press on PROM carrier until it is
firmly seated in the socket. Do not press on PROM;
only the carrier.
2.
Access cover on ECM.
3.
ECM in passenger compartment.
4.
Connectors to ECM.
Functional Check
1.
Turn ignition on
2.
Enter diagnostics
A. Code 12 should flash four times. (No other
codes present.) This indicates the PROM is
installed properly.
B. If trouble code 51 occurs or if the check
engine light is on constantly with no codes,
the PROM is not fully seated. Installed
backwards, has bent pins or is faulty.
5B. California Diesel Electronic Control System (DECS)
CODE 52
6.2L (LH6) DIESEL (CALIF.)
•
•
•
•
•
CHECK THAT ECM CONNECTOR ARE FULLY INSERTED.
CLEAR MEMORY.
DDC TOOL CONNECTED AND IN “ NORMAL” MODE.
START ENGINE AND CHECK FOR LIGHT.
IF LIGHT REAPPEARS AND DDC TOOL INDICATES
CODE 52, REPLACE ECM.
• CLEAR MEMORY AFTER REPAIR TO CONFIRM
NO “ CEL” .
Figure 5-39, Code 52.
CODE 53
Y REF OVERLOAD
Figure 5-40, Code 53.
5-43
5B. California Diesel Electronic Control System (DECS)
Engine Speed Sensor (RPM)
9
E NG. SPEED
S ENSOR
a
ABC
M A P /T P S
CONNECTOR
(F R O N T V IE W )
B A C K VIE W
A
OF
/ di\
p O N N E C T O R / ------
B A C K V IE W
OF
CO N N ECTO I
E NG. SPEED
SENSOR C O N N
A B
E N G IN E SPEED
SEN SO R C O N N E C T O R
(F R O N T V IE W )
24 P IN A-B
CONNECTOR
ECM
CONN.
ECM
5V REFERENCE
A/
SEN S O R G R O U N D
A8
E N G IN E SPEED
S EN SO R
5V 9 — y\Zv'---------
A9
416
452
121
------------------------------ *» B
B
|<►
| AA
A | B | C
C| B |A
M AP
TPS
# 0
i m c
c d p i r n
E Ni iGh IN
E SPEED
SENSOR
Figure 5-41,1984 Engine Speed Sensor Check Schematic.
See Figure 5-41.
The ECM m onitors engine RPM through a permanent magnet (P.M.) generator. It is located in the top of the vacuum
pump, or oil pump drive. Engine RPM is one of the inputs to the ECM to calculate the duty cycle of the EGR. It is
500 m illi-volt peak to peak. There are 4 reference pulses per revolution.
1984 ENGINE SPEED SENSOR CHECK
The Engine Speed Sensor is a cam shaft driven pick-up mounted at the center rear of the engine.
It is sourced by 5 V-reference and allows the ECM to measure engine RPM by the number of tim es the voltage is
pulsed. The Engine Speed Sensor pulses 4 tim es per revolution.
See Figure 542:
1. Checks for a good 5 V-reference. Normally, the ECM should be at about 5 volts for fully charged batteries.
2. Checks for proper ECM voltage to the Engine Speed Sensor. If the circuit to the ECM is complete, normal voltage
w ill be about 5 volts w ith the harness disconnected from the sensor.
3. Checks for a good sensor ground circuit (CKT 452) from sensor to ECM. Since Step 2 indicated an open, the
results of this step indicates whether the open is in the wire or at the ECM.
5-44
5B. California Diesel Electronic Control System (DECS)
1984 DECS
6.2L (LH6)
ENGINE SPEED SENSOR CHECK
•
C E L " O N " a fte r 15 seconds at idle.
Figure 5-42,1984 Engine Speed Sensor Chart.
5-45
5B. California Diesel Electronic Control System (DECS)
ENG. SPEED
SENSOR
A
BACK VIEW
A
A B C
MAP/TPS
CONNECTOR
(FRONT VIEW)
□c
□G
ENG. SPEED
SENSOR CONN
□c
□c
□□
PC
□
1C
A B
ENGINE SPEED
SENSOR CONNECTOR
(FRONT VIEW)
ECM
CONN.
ECM
5V REFERENCE
SENSOR GROUND
ENGINE SPEED
SENSOR
5V
--------
416
A12
452
C1
A8
A 1B |C
452
121
— •
B
MAP
IIA
c
|
b
|a
TPS
451
A6
I
MCL I B I A |
N f t l N P SPEED
QDPCn
ENGINE
SENSOR
Figure 5-43,1985 Engine Speed Sensor Schematic.
CODE 12, NO REF PULSE
M alf Code 12 is detected when the ECM detects an “ engine not running” condition.
Code is not to be stored in nonvolatile memory. Operation is the same as the gas controller.
Pin Condition
Terminal Name
CEL/CODE
Vacuum Condition
Codes
A6G ND
Diag. Term.
Yes — 12
10"/Full (Flutters)
Code 12 at all tim es
A8 0PN
RPM
Solid CEL — 12
NO/NO
Code 12 immediate
A 8G N D
RPM
Solid CEL — 12
NO/NO
Code 12 immediate
C1 OPN
Sensor GND
Solid CEL — 12
NO/NO
Immed. CEL — 12
None/None
Engine Speed Sensor
5-46
—
5B. California Diesel Electronic Control System (DECS)
CODE 12
NO REFERENCE PULSE
6.2L (LH6) DIESEL (CALIF)
Figure 5-43A, Code 12.
5-47
5B. California Diesel Electronic Control System (DECS)
Exhaust Gas Recirculation Control
(EGR)
E C M (UNDER
^D A S H )
-A LC L C O N N EC T O R
lIO LD A D V A N C E J & C O N T R O Li ^ r ~ TCC S O LE N O ID
/
R ELA Y Q m ___________
VENT FILTER
M AP S E N S O R
M A N IFO LD
EGR VENT
SO LE N O ID
VACUUM PUMP
A N D EN G IN E SP E E D
SEN SO R
EPR VALVE
EGR SO LE N O ID
EGR VALVE
EPR S O LE N O ID
C R AN K C A SE
D E P R E SSIO N
REGULATO R VALVE
THRO TTLE PO SITIO N
SE N S O R
IN JECTIO N PUMP
FAST IDLE SO LE N O ID
OIL FILL PIPE
See Figure 5-44.
The exhaust gas recirculation system provides a
means to direct exhaust gases from the exhaust
m anifold to the intake manifold.
This is accom plished using a vacuum powered EGR
valve. The opening of this valve, and therefore the
amount of exhaust gas flow, is increased as the
am ount of vacuum routed to the EGR valve is
increased. The amount of vacuum regulated to the
EGR valve is controlled by an electrically operated
solenoid valve w hich is supplied w ith a relatively
constant am ount of vacuum. The solenoid valve then
controls the am ount of vacuum to the EGR valve by
means of oscilating on and off at a frequency of 25 Hz,
w ith a variable pulse width, controlled by the ECM. The
EGR MAP sensor m onitors the regulated vacuum to
the EGR valve as the feedback parameter of the
control function.
Figure 5-44, Emission Systems — California
CK (LH6 Engine).
TO EPR
TO MAP
TO EGR
EGR VENT
SOLENOID
PULSE WIDTH MODULATED EGR
VACUUM CONTROL SOLENOID - 6.2L
(CALIFORNIA) DIESEL
See Figure 545.
A pulse width modulated solenoid (pulsed solenoid)
controls the vacuum signal to the EGR valve in the
electronic vacuum modulated EGR system. This
vacuum control is via an electronic pneum atic servo
loop based primarily on load (throttle angle) engine
RPM inputs and vehicle speed.
Vacuum is supplied at #8 from the vacuum pump and
the vacuum is m odulated between #2 (vent to
atmosphere) and #4 (vacuum output to EGR valve) as a
result of a pulsed electrical signal from the controller.
FROM VACUUM
PUMP
Figure 5-45, EGR, EPR, Vent Solenoid
Assembly.
5-48
At 0% duty cycle, the output vacuum signal is 0 " hg.
At 100% duty cycle, the output vacuum signal is equal
to the input vacuum from the supply pump.
In 1984 the solenoid is grounded at ECM Pin B2 on
C ircuit 538. In 1985 it is grounded at ECM Pin C10 on
Circuit 435.
5B. California Diesel Electronic Control System (DECS)
The d u ra tio n (tim e) o f the p ulse s (p ulse s per
second) o f th e d u ty c y c le (0-100%) fo r th e EGR
s o le n o id is d e te rm in e d by e ng ine pa ra m e te rs such
as RPM and the T h ro ttle P o s itio n Sensor.
OUT PUT VACUUM SIG NAL
ABS.
PRESS
kPa
ABS.
PRESS
IN HG.
VAC.
IN
HG.
• DUTY CYCLE IS DETERM INED BY:
0
0
29.92
DUTY CYCLE =
5
1.48
28.44
10
2.96
26.96
15
4.44
25.48
20
5.92
24.00
25
7.40
22.52
30
8.88
21.04
35
10.36
19.56
40
11.84
18.08
45
13.32
16.60
50
14.80
15.12
55
16.28
13.64
60
17.76
12.16
65
19.25
10.67
70
20.72
9.20
75
22.20
7.72
80
23.68
6.24
85
25.16
4.76
90
26.65
3.27
95
28.12
1.80
100
29.61
.31
101
29.92
—
105
30.09
—
D .c. =
t-tim e on
T -tim e o ff
10 m sec. = 25%
40 m sec.
It w o u ld o n ly be on 25% o f th e tim e.
F re q u e n cy 25Hz (25 x @ sec.) 25-40 m sec. tim e
periods.
5-49
SB. California Diesel Electronic Control System (DECS)
A B
SOLENOID
CONNECTORS
(FRONT VIEW)
EGR/EPR
SOLENOID ASSY.
BULKHEAD CONNECTOR
39
EPR/VAC
VALVE
TO
VACUUM
PUMP
ECM
CONN.
VAC
HOSE
ECM
PWM
EGR SOL.
ECM #1
FUSE
EGR
VALVE
- [ “I VENT
FILTER
IH
EGR
VENT SOL.
MAP
SENSOR
39
EPR SOLENOID
(C12-1985)
VAC
HOSE
B2
538
EPR SOL.
VAC
HOSE
EPR VAC
VALVE
Figure 5-46, EPR Valve Circuit (1984 & 1985).
EPR Valve
The system also incorporates an exhaust pressure regulator (EPR) valve, which is closed by control of the ECM
whenever the ECM control logic determines that the EGR valve is open. (Figure 5-46).
When the EPR valve is closed, it sim ply makes a restriction in the exhaust system which causes the pressure
inside of the exhaust m anifold to rise, thereby increasing the exhaust gas flow through the EGR valve. The EPR
valve is also a vacuum actuated valve, w hich is either supplied vacuum or not, as directed by the EPR solenoid,
which is energized or de-energized by the ECM.
An EGR vent solenoid valve is also used in the system. This solenoid valve is controlled by the ECM and upon
request of the EGR vent control logic, the vent solenoid valve allows the regulated vacuum supply to the EGR valve
to be vented to barom etric pressure. This very fast rise in EGR pressure allows the EGR valve to close much more
quickly than is attainable w ith the normal EGR feedback control.
5-50
5B. California Diesel Electronic Control System (DECS)
Desired EGR Pressure Calculation
The am ount of controlled EGR flow is determined by the calculated value of the desired EGR valve pressure. The
desired EGR pressure is calculated in the follow ing manner:
The desired EGR pressure is calculated by sum m ing the required am ount of EGR pressure value obtained from one
of the desired kPa ECM memory tables, altitude compensated pressure value is obtained from the Table for EGR
Altitude Com pensation and vehicle speed m odification value, unless one of the follow ing conditions exist:
• If the ECM is in either the Diagnostic Mode or the ALCL 1 Mode, the desired EGR pressure value is calculated to
be the difference of the barom etric pressure value minus the calibration constant value of 10 in. Hg.
• If the initialization routine is forcing the barometric pressure value to be updated, the desired EGR pressure value
is set equal to the calibration parameter.
• If the successive calculated values of desired EGR pressure have been increasing and the value is presently
greater than the EPR sw itchpoint value obtained from table, the desired EGR pressure value is set equal to the
calibration constant.
• If the calculated values of desired EGR pressure have been decreasing and this value is presently greater than or
equal to the EPR sw itchpoint value minus the calibration constant, the desired EGR pressure value is set equal to
the calibration value.
— NOTE The EGR vacuum (low pressure kPa) look-up tables are in the read only memory (ROM) of
the E PROM. They are for designated EGR pressure (vacuum to EGR), and are based upon
known engine RPM and throttle position values.
The 1st table is used to determ ine the required am ount of EGR when engine RPM is between 551 and 1349 RPM.
The 2nd kPa table is used to determine the required am ount of EGR when the engine speed is between 1350 and
2650 RPM.
If the engine speed is less than or equal to 550 RPM and greater than or equal to the “ Low RPM threshold for no
EGR” , the required EGR is set equal to a table value corresponding to the m inim um RPM value (550 RPM).
If the RPM is less than the “ Low RPM for no EGR” , the required EGR is set equal to a calibrated value, w hich w ill
fully close the EGR valve.
When the engine speed is greater than 2650 RPM, the required amount of desired EGR pressure is set equal to the
value in the table corresponding to the maxim um RPM value (2650 RPM).
5-51
5B. California Diesel Electronic Control System (DECS)
ALTITUDE COMPENSATION
There is a look-up table for A ltitude Compensation w hich is based upon barometric pressure values.
VEHICLE SPEED MODIFICATION
The EGR am ount is m odified w ith respect to vehicle speed. The EGR am ount w ill be reduced upon reaching a
calibrated vehicle speed.
EPR VALVE CONTROL
This portion of the EGR logic determines whether the EPR valve should be open or closed as controlled by
the ECM.
EGR SWITCHPOINT TABLE
This is a tw o dim ensional table used for determ ining what pressure value is to be used for the EPR switchpoint,
based upon the present atm ospheric pressure value. This table contains 12 look-up values.
EPR OUTPUT DETERMINATION
The EPR solenoid w ill be de-energized (EPR valve open) if the desired EGR pressure value exceeds the EPR
sw itchpoint value obtained from the table.
If the desired EGR pressure value is less than or equal to the EPR sw itchpoint value, then the EPR solenoid w ill be
energized (EPR valve closed).
EGR VENT CONTROL
This portion of the EGR logic determines if the EGR vent solenoid should be controlled to allow the EGR pressure
to quickly reach a m axim um value, equal to atm ospheric pressure.
EGR VENT DETERMINATION
The EGR vent function w ill be enabled, (vent valve open) if the desired EGR pressure value exceeds the EPR
sw itchpoint value obtained from the table.
EGR PULSE WIDTH MODIFICATIONS
Two term s are calculated and used to m odify the EGR output pulse width, which controls the EGR solenoid duty
cycle. One term is called the integral gain and the other term is called the proportional gain. These values are used
to calculate an EGR pressure error, w hich is the difference between desired EGR pressure, minus the actual EGR
pressure.
In 1984 a 4th gear sw itch is located in the 700-R4 4th gear pressure circuit, and a m echanical sw itch on the shifter
linkage of manual transm issions. When these switches close, this input to the ECM cuts o ff EGR at all throttle
angles.
5-52
m
5B. California Diesel Electronic Control System (DECS)
NOTES
5-53
5B. California Diesel Electronic Control System (DECS)
AB
A
™ A
------ 'C O N N E C T O R /-------
-3p
-□c
JSrlycc
□c
□c
□c
□c
CCf
-x-
-nc-
EGR
VALVE
(1984, A-3)
Figure 5-47, EGR/EGR Vent Schematic (1984 & 1985).
EGR/EGR VENT CHECK (1984 & 1985)
The EGR solenoid controls the amount of vacuum to the EGR valve. The signal from the ECM is Pulse W idth
Modulated (PWM) w hich varies the cycle (“ O N ” time) from 0% to 100%.
As the EGR solenoid cycles, vacuum to the EGR valve is controlled. When the EGR solenoid is “ O N ” , there is no
EGR vacuum.
The EGR Vent Solenoid operates to allow rapid venting of EGR vacuum to improve driveability and performance
when the ECM recognizes the operating range for no EGR. When the solenoid is “ ON” , EGR vacuum is vented.
Both solenoids operate on 12 volts supplied by ignition. The ECM supplies the ground to turn the solenoids “ O N” .
See Figure 547.
• Checks for EGR vacuum at idle. Normally, there should be full EGR vacuum at idle (above 68 kPa/20" vacuum).
• Checks for a ground in the circuit that would energize either solenoid. At idle, neither solenoid should be “ ON” . A
test light “ O N” indicates a faulty ground in the circuit.
• Checks for com plete circuits to both solenoids. The test light should be “ O N ” normally.
• Using the DDC tool in the 3.9k mode should turn the vacuum “ OFF” to the EGR valve by ECM activation of the
EGR vent solenoid. If vacuum is present, the ECM was not able to energize the EGR vent solenoid.
5-54
5B. California Diesel Electronic Control System (DECS)
1984 & 1985 DECS
EGR/EGR VENT CHECK
6.2L (LH6) DIESEL (CALIF.)
From Diesel Diagnostic C irc u it Check
•
Check fo r plugged EGR vent filte r.
If less than 20 ohms, replace solenoid also.
Figure 5-48, EGR/EGR Vent Check, 1984-1985.
5-55
5B. California Diesel Electronic Control System (DECS)
A
A
A\
EGR SOlENOiC
BACK VIEW A
OF
/lA
CONNECTOR
'T 'A
^p O N N E C T O R /------
in
=ip
3C:
¥■
A B
SOLENOID
CONNECTORS
(FRONT VIEW)
1’
□c
□c
□c
T
EGR/EPR
SOLENOID ASSY
BULKHEAD CONNECTOR
EPR/VAC
VALVE
39
TO
VACUUM
PUMP
ECM
CONN.
VAC
HOSE
ECM
PWM
EGR SOL.
r?
Hr
Q
EPR SOLENOID
C12
•
O
A
IGN.
VAC
HOSE
1984 GAU/IDLE
FUSE
EGR
VALVE
_ n VENT
^ FILTER
EGR
VENT SO L
39
1985
ECM #1
FUSE
MAP
SENSOR
538
(1984, B-2)
EPR SOL.
VAC
HOSE
EPR/VAC
VALVE
Figure 5*49, EPR Solenoid Schematic (1984 & 1985).
EPR Solenoid Electrical Check (1984 & 1985)
The EPR solenoid controls vacuum to the EPR valve. The EPR solenoid, when energized, allows vacuum pump
vacuum to close the EPR valve and increase exhaust back pressure for proper EGR operation. The solenoid is
supplied 12 volts by the ignition and the ECM com pletes the ground to energize the solenoid and turn EPR “ O N” .
See Figure 5-49.
• Checks for a short to ground or a faulty ECM signal to EPR solenoid. Test light should normally be “ OFF” .
• Checks for signal to energize EPR solenoid w ith engine at idle. If the test light is “ O N” , electrical circuits to the
solenoid are OK.
5-56
5B, California Diesel Electronic Control System (DECS)
1984 & 1985 DECS
EPR SOLENOID
ELECTRICAL CHECK
6.2L (LH6) DIESEL (CALIF.)
• Perform Diesel Diagnostic Check First.
• Check for plugged EGR vent filter.
Figure 5-50, EPR Solenoid Electrical Check (1984 & 1985).
5-57
5B. California Diesel Electronic Control System (DECS)
1985
ECM #1
FUSE
(1984, B-2)
Figure 5-51, EPR Solenoid Schematic (1984 & 1985).
EPR Vacuum Check (1984 & 1985)
The EPR Solenoid controls vacuum to the EPR valve. The EPR solenoid, when energized, allow s vacuum pump
vacuum to close the EPR valve and increase exhaust back pressure for proper EGR operation. The EPR valve is a
com bination vacuum, actuator and exhaust restrictor plate. When vacuum is applied to the actuator, the restrictor
plate closes to increase exhaust system back pressure to allow the EGR valve to function more efficiently. See
Figure 5-51.
• Checks for normal EPR vacuum at idle. Since electrical circuit was verified as OK on prior chart, if no vacuum is
present, it is due to no source vacuum (vacuum pump) or a restriction or leak in vacuum lines to valve including
the solenoid.
• Checks to see if solenoid w ill respond to ECM command. In 3.9k mode, EPR solenoid is de-energized, so no
vacuum should be present if the solenoid did close.
• Checks for normal operation of EPR valve. When vacuum is applied to vacuum, valve actuator should move
and hold.
5-58
5B. California Diesel Electronic Control System (DECS)
1984 & 1985 DECS
6.2L (LH6)
EPR VACUUM CHECK
•
•
P erform EPR Solenoid E lectrical Check firs t.
Check fo r plugged EGR vent filte r.
Figure 5-52, EPR Vacuum Check (1984 & 1985).
5-59
5B. California Diesel Electronic Control System (DECS)
K VIEW
A
OF
/ o '\
D N N E C T O R /------
A B
ENGINE SPEED
SENSOR CONNECTOR
(FRONT VIEW)
TO EGR
SOLENOID
ASSEMBLY
AND VAC
PUMP
VACUUM
HOSE
ECM
ECM
CONN.
5V REFERENCE A12
416
MAP SIGNAL
A1 432
SENSOR GROUND
C1
MAP
SENSOR
C I B I
ABC
MAP/TPS
CONNECTOR
(FRONT VIEW)
EGR
VALVE
MAP
CONN.
a
TPS
ENGINE
SPEED
| b |c
A I B|
452
Figure 5-53,1985 MAP Sensor Schematic.
1985 CODE 32 EGR LOOP ERROR
M alf Code 32 is detected when the engine is running and all of the follow ing are true:
*1. If the difference between calibrated vacuum and actual vacuum is greater than 2 kPa.
2. If the calibrated vacuum is less than the EPR sw itch point (in ECM memory).
3. If the calibrated vacuum is greater than 25 kPa.
4. If Code 31 is not set.
5. If Code 33 is not set.
6. If Code 51 is not set.
7. If Code 52 is not set.
8. If Code 53 is not set.
9. If Code 54 is not set.
10. Ignition is on.
11. In normal mode of operation.
12. If all the above conditions have been present for a period of tim e greater than 10 seconds.
* = Major Condition.
5-60
5B. California Diesel Electronic Control System (DECS)
CODE 32
EXHAUST GAS RECIRCULATION
(LOOP ERROR)
6.2L (LH6) DIESEL (CALIF)
Figure 5-53A, Code 32.
5-61
5B. California Diesel Electronic Control System (DECS)
NOTES
5-62
5B. California Diesel Electronic Control System (DECS)
Strain Gage MAP Sensor
The 6.2L DEC System uses a strain gage type MAP
sensor. This sensor uses a silicone chip w hich is
approxim ately 3 m illim eters square. Along the outer
edges, the chip is approxim ately 250 m icrom eters (1
m icrom eter = 1 m illionth of a meter) th ick but the
center area is only 25 m icrom eters th ick to form a
diaphragm. The edge of the chip is sealed to a pyrex
plate under vacuum thereby form ing a vacuum
cham ber between the plate and the center area of
the silicone chip.
A set of sensing resistors are form ed around the edge
of this chamber. The resistors are form ed by diffusing
a “ doping im purity” into the silicon. External
connections to these resistors are made through wires
connected to the metal bonding pads.
This entire assem bly is placed in a sealed housing
w hich is connected to the vacuum system by a small
diam eter tube. Pressure applied to the diaphragm
causes it to deflect. The resistance of the sensing
resistors changes in proportion to the applied m anifold
pressure by a phenomenon w hich is known as piezoresistivity. Piezo-resistivity occurs in certain
sem iconductors so that the actual resistivity (a
property of the material) changes in proportion to the
strain (fractional change in length).
a. Circuit
Figure 5-54A, Wheatstone Bridge Set*up.
An electrical signal w hich is proportional to the pressure is obtained by connecting the resistors in a circuit called
a “ W heatstone bridge” as shown in the schem atic diagram of Figure 5-54a. The voltage regulator holds a constant
dc voltage across the bridge. The resistors diffused into the diaphragm are denoted R1f R2, R3 and R4 in Figure
5-54a. W hen there is no strain on the diaphragm, all four resistances are equal, the bridge is balanced, and the
voltage between points A and B is zero. When m anifold pressure changes, it causes these resistances to change in
such a way th at R, and R3 increase by an am ount w hich is proportional to pressure and, at the same time, R2 and
R4 decrease by an identical amount. This unbalances the bridge and a net difference voltage is present between
points A and B. The differential am plifier generates an output voltage proportional to the difference between the
tw o input voltages.
5-63
5B. California Diesel Electronic Control System (DECS)
W INDSHIELD
^CO W L
a
ij\
A B
ENGINE SPEED
SENSOR CONNECTOR
(FRONT VIEW)
MAP
CONN.
VAC
HOSE
ECM
ECM
CONN.
5V REFERENCE
MAP SIGNAL - t l
A7
vsH 3
A B C
MAP/TPS
CONNECTOR
(FRONT VIEW)
EGR
VALVE
MAP
SENSOR
416
C |
B |
TPS
A
MAP
CONN.
a
|
b |c
ENGINE
SPEED
a
|
b
|
A11 432
B10
SENSOR GROUND
TO EGR
SOLENOID
^
ASSEMBLY < —
AND VAC
PUMP
VACUUM
HOSE
BACK VIEW A
OF
M
CONNECTOR
452
A8
Figure 5-54,1984 (Only) MAP Sensor Check Schematic.
MAP Sensor
A M anifold Absolute Pressure Sensor is used to m onitor the am ount of vacuum in the EGR circuit. It senses the
actual vacuum in the EGR vacuum line and sends a signal back to the ECM. The signal is compared to the EGR
duty cycle calculated by the ECM. If there is a difference in the ECM command and what is at the EGR valve
sensed by the MAP, the ECM makes m inor adjustm ents to connect.
The system can sense a high or low vacuum error, indicating a vacuum leak or faulty electrical com ponent in the
vacuum control system. Once a gross vacuum error is sensed, like a disconnected vacuum hose, the ECM de­
energizes EGR solenoid. This causes full EGR and excessive smoking.
1984 MAP SENSOR CHECK
See Figure 5-54.
• Check for 5-volt reference signal to MAP Sensor. Normally, about 5 volts should be present w ith the key “ O N ” at
Terminal “ C” .
• Check for a com plete circuit from MAP sensor back through the sensor ground wire. As in Step 1, this should be
about 5 volts.
• Check for normal response from the MAP to an external vacuum signal. There should be an im m ediate voltage as
vacuum is applied.
5-64
5B. California Diesel Electronic Control System (DECS)
1984 DECS
6.2L (LH6)
M AP SENSOR CHECK
F rom Diesel D iagnostic C irc u it Check
Figure 5-55, MAP Sensor Check.
5-65
5B. California Diesel Electronic Control System (DECS)
BACK VIEW
OF
ONNECTOI
H_f l
89
A B
ENGINE SPEED
SENSOR CONNECTOR
(FRONT VIEW)
TO EGR
SOLENOID
ASSEMBLY
AND VAC
PUMP
VACUUM
HOSE
ECM
ECM
CONN.
5V REFERENCE A12
MAP SIGNAL t
l
A1
MAP
SENSOR
C | B | A
416
a
/a i \
BACK VIEW
OF
CONNECTOI
rT £ ? —
c
E3 .
A B C
MAP/TPS
CONNECTOR
(FRONT VIEW)
EGR
VALVE
TPS
MAP
CONN.
a
|
b|c
ENGINE
SPEED
*1®]
432
452
SENSOR GROUND
C1
PWM EGR SOL.
435
B
C10
ECM #1
FUSE
Figure 5-56,1985 MAP Sensor Schematic (Code 31).
CODE 31 MAP SENSOR TOO LOW
Malf Code 31 is detected when the engine is running and all of the following
are true:
*1.
2.
3.
4.
5.
6.
7.
MAP voltage is less than Vi volt (voltage low = vacuum high).
If Code 51 is not set.
If Code 52 is not set.
If Code 53 is not set.
Ignition is on.
In normal mode of operation.
Conditions 1 thru 4 has to be present for a period of tim e greater than 10 seconds.
* = Major Condition.
The engine m ust run at idle for 10 seconds before code w ill set.
-
NOTE -
If Code 31 is detected the EGR duty cycle should be assigned to 0% (off = full vacuum),
the EPR value should be turned off and the dump solenoid should be turned off.
Also the baro term should be forced to 100 kPa.
5-66
5B. California Diesel Electronic Control System (DECS)
CODE 31
MAP SENSOR
(SIGNAL VOLTAGE TOO LOW)
6.2L (LH6) DIESEL (CALIF)
CLEAR CODES AND CONFIRM NO “ CEL” WITH ENGINE RUNNING
Figure 5-57, Code 31.
5-67
5B. California Diesel Electronic Control System (DECS)
A
BACK VIEW
A
COWL
A B
ENGINE SPEED
SENSOR CONNECTOR
(FRONT VIEW)
VAC'
HOSE
^
ABC
MAP/TPS
CONNECTOR
(FRONT VIEW)
" MAP
CONN.
ECM
5V REFERENCE
MAP SIGNAL t
l
SENSOR GROUND
Figure 5-58, MAP Sensor Schematic (Code 33).
CODE 33 MAP SENSOR TOO HIGH
M alfunction Code 33 is detected when the engine is running (REFPER less than KRUNPER) and all of the follow ing
are true:
*1.
2.
3.
4.
5.
6.
7.
8.
9.
If the actual vacuum is greater than EPR sw itch point.
If the calibrated vacuum is less than EPR sw itch point.
If Code 51 is not set.
If Code 52 is not set.
If Code 53 is not set.
If Code 54 is not set.
Ignition is on.
In normal mode of operation.
If all of the above conditions have been present for a period of tim e greater than 10 seconds.
* = Major Condition.
Pin/Condition
Pin Name
CEL/Code
Vacuum/Condition
Remarks
C 10G N D
EGR solenoid
CEL - 33 after 10 sec.
No/to Full
Not throttle sensitive
MAP Vacuum off
10 sec. CEL - 33
V2I FI utters
MAP hose pinched
10 sec. CEL -33
Full
NOTE: A grounded Pin C11 CKT902 EGR vent solenoid may set a Code 33.
5-68
5B. California Diesel Electronic Control System (DECS)
CODE 33
MAP SENSOR
(SIGNAL VOLTAGE TOO HIGH)
6.2L (LH6) DIESEL (CALIF)
CLEAR CODES AND CONFIRM NO “CEL” WITH ENGINE RUNNING
Figure 5-58A, Code 33.
5-69
5B. California Diesel Electronic Control System (DECS)
Throttle Position Sensor, TPS
A throttle position sensor is used to indicate throttle
position, in calculating EGR pressure am ount and
T.C.C. engagement. (See Figure 5-60).
• The TPS is a 4000 to 6000 ohm (4k to 6k
potentiometer) variable resistor. It signals the ECM,
the degree of throttle opening.
• The TPS is connected to a 5-volt reference and has
its highest resistance at closed throttle (idle). At wide
open throttle (WOT), the resistance is lowest and the
output w ill be near 5 volts.
• The TPS is ratio-metric w hich means it measures the
quotient of tw o quantities. It operates by the
balancing of electrom agnetic forces w hich are a
function of the moving element.
Figure 5-59, Throttle Position Sensor.
ECM
(1985 — A12)
(1985 -
C1)
(1985 — A2)
5V REFER EN CE
A7
SENSO R G R O U N D
A8
T H R O T T L E P O S IT IO N A10
S E N S O R S IG N A L
E N G IN E SPEED
CO NNECTOR
NOTE: NOT USED IN 1985
Figure 5-60, TPS Check (1984 & 1985).
1984 & 1985 TPS Check
See Figure 5-61:
• Check for com plete 5-volt reference circuit. If the circuit is com plete from V-ref and back to sensor ground in
ECM, DVM w ill read about 5 volts.
• Check for a shorted or stuck 4th gear switch. When the transm ission shifts to 4th gear, this sw itch w ill close and
signal the ECM to turn “ O FF” EGR. If the 4th gear switch is not faulty, there could be a short to V-ref or a faulty
TPS adjustm ent or switch.
• Check for normal response at ECM from TPS. Voltage should be normally less than 1 volt at closed throttle and
go to about 5 volts at WOT. If voltage change is OK, circuit is complete.
5-70
5B. California Diesel Electronic Control System (DECS)
1984 & 1985 DECS
TPS Check
6.2L (LH6) DIESEL (CALIF)
From Diesel Diagnostic Circuit Check
Figure 5-61, TPS Check, 1984-1985.
5-71
5B. California Diesel Electronic Control System (DECS)
BACK VIEW A
OF
M
CONNECTOR
W
MAP/TPS
CONNECTOR
(FRONT VIEW)
A12
SENSOR GROUND
A
—
DC
MAP
SENSOR
C I B | A
ECM
CONNECTORS
5V REFERENCE
o nnecto r/
□C□ c:
□
A B C
A B
ENGINE SPEED
SENSOR CONNECTOR
(FRONT VIEW)
ECM
3 I
BACK VIEW
24 PIN A B
CONNECTOR
□c
PC
□L
□c3^□c-
MAP
CONNECTOR
416
452
417
THROTTLE POSITION
SENSOR SIGNAL
IB
WO i
|C
TPS
CONN.
IDLE
TPS
B iA
ENGINE
SPEED
ENGINE SPEED
CONNECTOR
Figure 5-62,1985 TPS Schematic.
TPS
Conn. off
A2
No EGR, No EPR for 2 min.
OPN
TPS
Y e s -22
After 2 min. CEL-22 code
Full/off
Full/N one
Vacuum
Pull up resistor — 2 min. code
CODE 21 TPS TOO HIGH
Malf Code 22 is selected when the ECM detects an “ engine running” condition (REFPER less than KRUNPER) and
all of the follow ing are true:
1.
2.
3.
4.
5.
6.
7.
If the throttle angle is greater than 70%
Engine speed less than 1120 RPM
Vehicle speed greater than 0 mph
If Code 51 is not set
If Code 52 is not set
If Code 53 is not set
C onditions 1 thru 6 have been present for a period of tim e greater than 2 minutes.
— NOTE —
If Code 22 exists then the control algorithm is to use the throttle percent of 15 for
all throttle variables. This can cause the controller to deliver full EGR.
Also EPR is to be turned off.
HARDWARE
A pull-up resistor should be used on the TPS input so that an open sensor w ill be a Code 21.
5-72
5B. California Diesel Electronic Control System (DECS)
CODE 21
THROTTLE POSITION SENSOR
(SIGNAL VOLTAGE HIGH)
6.2L (LH6) DIESEL (CALIF)
Figure 5-62A, Code 21.
5-73
5B. California Diesel Electronic Control System (DECS)
A ’“ 5?“ A
L---- V n u u c rrn o /----
1
A B
ENGINE SPEED
SENSOR CONNECTOR
(FRONT VIEW)
A B C
MAP/TPS
CONNECTOR
(FRONT VIEW)
24 PIN A B
CONNECTOR
Figure 5-63,1985 TPS Schematic.
CODE 22 TPS TOO LOW
M alf Code 21 is detected when the engine is running at 375 RPM or more, and all of the below conditions are met:
1.
2.
3.
4.
5.
6.
The throttle angle is less than 40%.
Engine speed greater than 1250 RPM
If Code 51 is not set
If Code 52 is not set
If Code 53 is not set
Conditions 1 thru 5 have existed for greater than KKTAT21 tim e
If Code 22 exists then EPR is to be turned off.
5-74
5B. California Diesel Electronic Control System (DECS)
CODE 22
THROTTLE POSITION SENSOR
(SIGNAL VOLTAGE LOW)
6.2L (LH6) DIESEL (CALIF)
Clear codes and confirm no “ CEL” with engine running.
Figure 5-63A, Code 22.
5-75
5B. California Diesel Electronic Control System (DECS)
Throttle Position Sensor, TPS
Adjustment
1. Remove A ir Cleaner Assem bly and related hoses.
2. Disconnect TPS connector. Install jum per wires
between TPS and harness. Jumpers can be made
using term inals P/N 12014836 and 12014837. Three
jum pers or their equivalent w ill be necessary
(Figure 5-67).
3. Key “ ON” , engine not running.
4. Install TPS/VRV gage block to J-33043-2 or
equivalent using the .646 side of the block.
Position tool between gage boss on injection pump
and the wide open stop screw on throttle shaft
(Figure 5-68).
5. Rotate the throttle lever and hold the wide open
stop screw against the gage block.
6. Using a DVM J-29124 or equivalent, measure
voltage from TPS connector term inals “ A ” to “ C” .
This is V-ref. Record the voltage reading (Figure
5-66).
7. Now measure and record voltage between
term inals “ B” to “ C” . This is the TPS voltage
(Figure 5-66).
8. Compare the voltage recorded in Step 7 under the
corresponding V-ref. recorded in Step 6 against the
data in TPS table (Figure 5-66).
The TPS voltage should be w ithin ± 1 % of voltage
shown. Example: A V-reference of 4.6 — the TPS
voltage may be 2.87 to 2.93 volts and be w ithin
tolerance.
9. If no adjustm ent is necessary, proceed to Step 12.
10. To adjust TPS, loosen the tw o attaching screws
and rotate TPS until the correct TPS voltage is
obtained as per TPS Table (Figure 5-66).
11. When the correct TPS value is obtained, tighten the
TPS attaching screws to 6 N-m (53 in. lbs.).
12. Check TPS voltage by releasing the throttle lever
allowing it to return to the idle stop position
measuring voltage from term inals “ B” to “ C ” .
Return lever against gage block. Voltage should be about 1 volt at closed throttle and return to TPS voltage
within ± 1 % of the adjusted voltage when throttle is again opened against gage block. If voltage does not
return to TPS voltage, repeat Steps 10, 11 and 12. If at closed throttle, voltage is not less than 1 volt or
adjustm ent cannot be made, replace TPS.
V -R E F E R E N C E '
4.5
4.6
4.7
4.8
4.9
5.0
5.1
5.2
5.3
5.4
5.5
T P S V O L T A G E -------------- ►
(w ith gage to o l in sta lled )
2.84
2.90
2.96
3.02
3.09
3.15
3.21
3.28
3.34
3.40
3.47
Figure 5-66, TPS Voltage Table.
5-76
5B. California Diesel Electronic Control System (DECS)
13. Remove gage block tool.
14. Turn ignition “ O FF” .
15. Remove jum per wires and reconnect TPS harness connector.
16. Reinstall A ir Cleaner Assem bly and related hoses.
• REMOVE OR DISCONNECT
1. A ir cleaner and related hoses.
2. TPS connector.
3. TPS attaching screws.
4. TPS
• CONNECT OR INSTALL
1. TPS and attaching screws.
2. Adjust TPS voltage follow ing procedure above.
3. TPS connector.
4. A ir cleaner and related hoses.
MAP SENSOR
Refer diagnosis that checks MAP sensor circuit and replace sensor as required.
EGR/EGR SOLENOID ASSEMBLY
The EGR solenoid, EGR vent solenoid and EPR solenoid are replaced as an assembly. The vent filter can be
replaced as required. If diagnosis has determined that any solenoid does not operate, replace with com plete
assembly.
PARTS INFORMATION
PART N A M E ........................................................................................................................................................................... GROUP
Controller, E C M ........................................................................................................................................................................... 3.670
Calibrator, PROM .......................................................................................................................................................................3.670
Sensor, M A P ................................................................................................................................................................................3.682
Sensor, Throttle P o s itio n ........................................................................................................................................................... 3.440
Sensor, Vehicle Speed ..............................................................................................................................................................3.682
5-77
5B. California Diesel Electronic Control System (DECS)
I.P. HARNESS
CONNECTOR
!R
B
— i—j —
422
f—
TRANSMISSION
CONNECTOR
(FRONT VIEW)
ECM SIDE
(FRONT VIEW)
I.P. HARNESS
CONNECTOR
1984 GAU — IDLE FUSE
1985 G — IGN 1 FUSE
1985 C,K — IGN 2 FUSE
IGN
„
383
39
TCC BRAKE
SW. CONN.
(FRONT VIEW)
(1984-A2)
ECM
A
TCC
BRAKE SW.
TCC
SOLENOID
ALCL
CONNECTOR
F
E D
c
B A
Figure 5-67, Torque Converter Clutch, TCC Circuit.
T o r q u e
C o n v e r t e r C lu t c h
C o n t r o l
The purpose of the autom atic transm ission torque converter clutch feature is to elim inate the power loss of the
torque converter stage when the vehicle is in a cruise condition (Figure 5-67). This allows the convenience of the
autom atic transm ission and the fuel econom y of a manual transm ission. The heart of the system is a solenoid
located inside the autom atic transm ission w hich is controlled by the ECM.
The solenoid is configured m echanically such that when the coil is activated (ON) the torque convertor clutch is
applied w hich results in straight through mechanical coupling from the engine to transm ission output.
Ignition power feed to the solenoid passes through a brake sw itch w hich opens when the brake is applied. The
ECM com pletes the ground to activate the TCC solenoid for clutch engagement.
The ECM com pletes the circuit whenever the TPS exceeds a calibrated valve for throttle opening.
When the transm ission solenoid is de-activated, the torque converter clutch is released w hich allows the torque
converter to operate in the conventional manner (fluidic coupling between engine and transmission).
5-78
5B. California Diesel Electronic Control System (DECS)
I.P. HARNESS
CONNECTOR
i
422
TCC B R A K E
SW. C O N N .
(F R O N T V IE W )
T R A N S M IS S IO N
CONNECTOR
(F R O N T V IE W )
ECM S ID E
(F R O N T V IE W )
1984 24 PIN A-B
ECM CONNECTOR
1985
CONNECTOR
ECM
I.P. H A R N E S S
CONNECTOR
1984 GAU — IDLE FUSE
1985 G — IGN 1 FUSE
1985 C,K — IGN 2 FUSE
__ 39
IGN
1985
422
383
TCC
BRAKE SW.
I
|g|
I
C5
< 1
A2
TCC
SOLENOID
ALCL
CONNECTOR
F
E
D
C
B A
Figure 5-68,1984 and 1985 TCC Check.
1984 AND 1985 TCC CHECK
The ECM com pletes the circuit whenever the TPS exceeds a calibrated valve for throttle opening. (See Figure 5-68).
• Checks for com plete circuit from ignition through solenoid up to test point. Test light should be “ O N” normally
since ECM has not com pleted circu it yet.
• Checks for ECM to com plete circuit to ground to energize TCC solenoid and engage TCC. Test light should
norm ally go out when ECM com pletes circuit.
• Checks for TPS signal. If signal to ECM is correct, fault is in ECM connection or ECM. If TPS signal to ECM is
incorrect (voltage) proper operation w ill not occur.
• Checks for ground in circu it to ECM Terminal A-2. Normally, light should be “ O FF” .
• Checks for ignition voltage to Terminal “ A ” of TCC connection. Light should norm ally be “ O N ” .
• Checks for com plete circuit from ignition to ground via TCC test terminal in ALCL. Normally, light should go
“ O N ” if harness is good.
5-79
5B. California Diesel Electronic Control System (DECS)
1984 & 1985 DECS
TCC CHECK
6.2L (LH6)
•
•
Check fo r pro pe r TPS adjustm ent.
Check fo r p ro pe r brake sw itch ad ju stm e nt.
Figure 5-69, TCC Check (1984 & 1985).
5-80
5B. California Diesel Electronic Control System (DECS)
TCC SOLENOID OPERATION
The TCC solenoid is actuated (clutch applied) by up to tw o separate control devices in series. These devices
consist of:
• Vehicle brake switch.
• Electronic driver in ECM.
TCC OPERATION MODES
1. RESET. When the ECM is reset, the ECM shall activate the TCC solenoid driver clutch ON.
2. ALCL 1 MODE OR ALCL 2 MODE/ENGINE NOT RUNNING. The ECM driver is de activated (clutch OFF) if either
ALCL Mode is selected and the engine not running.
3. ALCL 1 MODE/ENGINE AT IDLE-ALCL LEAD GROUNDED WITH 10K OHMS. The ECM driver is activated
(clutch ON) if the ALCL 1 Mode is selected and the engine is at idle.
4. ALCL 2 MODE/ENGINE AT IDLE-ALCL LEAD GROUNDED WITH 3.9K OHMS. The ECM driver is de activated
(clutch OFF) if the ALCL 2 Mode is selected and the engine is at idle.
5. DIAGNOSTIC MODE — ALCL LEAD GROUNDED. The ECM driver is activated (clutch ON) whenever the
Diagnostic Mode is selected.
TORQUE CONVERTER CLUTCH CONTROL
Provided the ECM is not in any of the 5 special ALCL cases, the TCC control is determined by TCC control ECM
programming.
If the solenoid driver is not activated (TCC released), the ECM w ill control the solenoid driver to activate the TCC
solenoid (clutch ON) when the throttle position is at position greater than the m inim um throttle position for clutch
engagement (12 degrees ± 2 degrees).
If the solenoid driver is activated (TCC ON), the ECM w ill control the solenoid driver to de-activate the TCC solenoid
(clutch released) when the throttle position is less than the maximum throttle position for clutch release. However,
the solenoid w ill remain activated as long as the throttle position remains greater than, or equal to, the “Maximum
Throttle Position for Clutch Release”.
VEHICLE SPEED SENSOR, VSS
In 1985 a vehicle speed sensor (VSS) is used, so the operation of TCC changes slightly w ith vehicle speed. If the
vehicle speed is below the calibration value, the TCC operates as previously described.
If vehicle speed is above this value, the apply and release is also the same as described w ith one exception. The
release of the TCC w ill be delayed by 3 seconds. Re-apply w ill occur as soon as throttle position requirements
are met.
5-81
5B. California Diesel Electronic Control System (DECS)
The speed of the vehicle is sensed by the speed
sensor. The speed sensor consists of a light em itting
diode and a phototransistor both of w hich are
enclosed in one connector. This connector is located
in the back of the speedometer cluster next to the
speedometer cable. A wiring harness connects the
sensor to the ECM (Figure 5-70).
The light em itting diode is lit any tim e the ignition is
turned on. The light given off is in the infrared area of
the light spectrum and is not visible to the human eye.
The diode directs its light toward the back of the
speedometer cup w hich is painted black, and the shiny
drive magnet which is part of the speedometer rotating
parts.
As each bar of the drive magnet passes the light beam
of the diode, the light beam is reflected back to the
photo transistor. The photo transistor generates an
electrical signal to the ECM. This signal is
representative of vehicle speed.
See Figure 5-71. The speed sensor is supplied w ith 12 volts. When a voltm eter is hooked from term inal A9 of the
ECM to ground and the speedometer cable turned, the voltage will swing between 8 volts and som ething under 1
volt rather than going up to 12 volts.
5-82
5B. California Diesel Electronic Control System (DECS)
DRIVEABILITY AND EMISSIONS — DECS
CODE 24
VEHICLE SPEED SENSOR (VSS)
NOTICE; TO PREVENT MISDIAGNOSIS, THE TECHNICIAN SHOULD REVIEW ELECTRICAL SECTION 8A OR THE ELECTRICAL
TROUBLESHOOTING MANUAL AND IDENTIFY THE TYPE OF VEHICLE SPEED SENSOR USED PRIOR TO USING THIS CHART.
DISREGARD CODE 24 SET WHEN DRIVE WHEELS ARE NOT TURNING.
CLEAR CODES AND CONFIRM “CLOSED LOOP” OPERATION AND NO “CHECK ENGINE” LIGHT.
Figure 5-72, Code 24.
CODE 24 VEHICLE SPEED SENSOR
M alf Code 24 is detected when the engine is running at 375 RPM or more, and all of the follow ing are true:
1.
2.
3.
4.
5.
6.
The vehicle speed is less than 5 mph.
The engine speed is above 2000 RPM.
The throttle angle is greater than 60%.
If Code 51 is not set.
Ignition is on.
Conditions 1, 2, and 3 have been present for a period of tim e greater than 10 seconds.
-
NOTE -
This code could be tricked on a “K” truck by putting the transfer case in neutral
and running a load with the PTO pad.
5-83
5B. California Diesel Electronic Control System (DECS)
COLD ADVANCE SOLENOID CONTROL CIRCUIT LH6 + NB2
FAST IDLE SOL.
1. WITH SYSTEM VOLTAGE AT TERMINAL 8, AND
ALTERNATOR NOT OPERATING, COLD ADV.
SOLENOID IS CONTINUOUSLY ENERGIZED.
2. AFTER ALTERNATOR STARTS OPERATING
(SYSTEM VOLTAGE AT ALT. NO. 1 TERM.), THE
C.A. RELAY DROPS OUT 35 ± 4 SECONDS LATER.
Figure 5-73, Cold Advance Solenoid Control Circuit.
G-TRUCK
DASH PANEL
INSULATOR & LH6
Cold Advance Circuit, CAC
The 1984 California LH6 6.2 Diesel uses a cold
advance circuit (CAC) to term inate housing pressure
cold advance (H.P.C.A.) before the temperature sw itch
does (Figures 5-73 and 5-74). It uses a cold advance
control relay, which is activated by generator output.
CAC OPERATION
When the generator is not operating, and the voltage
at relay terminal 8 is system voltage, the H.P.C.A. is
energized.
The generator starts charging and system voltage
(12-14 volts) appears at generator Terminal 1. In 35 ± 4
seconds the CAC relay w ill disengage the H.P.C.A.
Figure 5-74.
5-84
5B. California Diesel Electronic Control System (DECS)
1984-85 DECS
6.2L (LH6) C A LIFO R N IA ONLY
COLD ADVANCE CONTROL (CAC) CHECK
Check fo r blown fuse, repair fo r short if blown.
Engine coolant temperature below 95 °F .
•
•
•
Key "OIM", engine not running.
Connect test light from Cold Advance Solenoid conn, to ground,
(leave harness connected to solenoid).
Note light.
L ig h t " O F F "
L ig h t " O N "
•
•
•
Start engine.
Light should remain "O N " fo r approx. 35
sec. then go "O F F " w ith a drop in engine
•
Remove and jum per Cold Advance Coolant
temperature switch connector.
Note test light at relay Terminal " A " .
Light "O N '
Light "O F F '
N ot OK
OK
•
No trouble found.
Light remains "O N "
or not "O N " fo r
35 sec.
Repair open in
CKT 39 to ign.
or CKT 534 to
CAC relay.
Light goes "O F F ".
No drop in RPM.
•
Remove CAC relay
conn.
Connect test
light across
Terms. " A and G ".
Start engine and
note light.
•
It is a fa u lty temperature
switch connection or
temperature switch.
(Switch should be closed
below 95 °F ).
It is faulty
CAC solenoid.
534
150 531
25
Light "O N '
Light "O F F '
Check fo r open to ground
in CKT 150 or open to
generator in CKT 25.
(CKT 25 w ill have system
voltage on ly while genera­
to r is operating).
•
CAC R E L A Y
CONN.
(F RO NT VIEW)
It is fa u lty relay
connections or relay.
FAST IDLE SOL.
G A U G E 'ID L E
FUSE
COLD
A D V A N C E SOL.
39
TEMP SW.
(OPEN AB OV E 9 5 ° F)
COLD A D V A N C E
C O NT RO L R E L A Y
G EN E RA TO R
Figure 5-75.
5-85
5B. California Diesel Electronic Control System (DECS)
1984 DEC
6.2L (LH6) CALIFORNIA
435
EGR S O L E N O I D
TO
VACUUM < PUMP
PWM EGR SOL.
- 0
EGR
VALVE
V E N T FILTER
z a
EGR V E N T SOL.
902
EGR V E N T S O L E N O I D
VACUUM
HOSE
538
EPR S O L E N O I D
TCC S O L E N O I D
A2
422
I
Uj| t
TCCSO L
i
BRAKE
SW.
0 fcA__ _____
EPR V A C
VALVE
TRANS
A12
150
EN GI NE
GROUND
B12
39
IGN ITION
IGN.
(G O N L Y )
439
I G N IT I O N
IGN.
E C M /I GN
FUSE (C- K O N L Y )
MAP
SENSOR
5V R E F E R E N C E
MAP S IG N A L
tii
SENSOR G R O U N D
T H R O T T L E PO SI TI ON
SENSOR S I G N A L
A7
A1 1 432
BIO
A8
A10
417
bf
4T H G E A R
SW. (N.O.)
E N G I N E SPEED
SENSOR
A
TPS
b a c k
v ie w
of
MN tUI UK /
EL
A L D L DATA
D I A G N O S T I C TE ST
TERM.
E N G I N E SPEED
SENSOR
451
F E D C
B A
A L D L CONNECTOR
1 ECM
CONNECTOR
USED
2 4 PIN A - B
ECM C O N N E C T O R
Figure 5-76,1984 Calif. (DECS) Diesel Electronic Control System Wiring Schematic.
5B. California Diesel Electronic Control System (DECS)
1984 DECS ECM TERMINAL VOLTAGE
6.2L DIESEL (LH6) CALIFORNIA
T H IS EC M VO LTA G E C H A R T IS FO R USE W IT H A D IG ITA L VO LTM E TE R TO FU R TH E R A ID IN D IA G N O S IS . T H E VOLTA G ES YOU G ET MAY
VARY DUE TO LO W BATTERY C H A R G E OR O TH E R R EA SO N S, BUT TH E Y S H O U L D BE VE R Y C LOSE.
TH E FO L L O W IN G C O N D IT IO N S M U ST BE M ET B EFO R E TE S T IN G :
VOLTAGE
KEY
ENG.
“ ON” RUN
•
•
•
•
OPEN
CRT.
E N G IN E AT O PER A TIN G TE M P E R A TU R E
BATTER IES FULLY C H A R G E D A N D G L O W PLUGS N O T C Y C L IN G
TEST T E R M IN A L N O T G R O U N D E D
DDC TO O L N O T IN S TA LLED
CIRCUIT
PIN
PIN
CIRCUIT
KEY
“ ON”
VOLTAGE
ENG. OPEN
RUN CRT.
*1.0
14
*.5
EGR SOLENOID
A1
B1
IGNITION
12
14
*.5
12
14
*.5
TCC SOLENOID
A2
B2
EPR SOLENOID
12
*1.0
*.5
*1.0
14
*.5
EGR VENT
SOLENOID
A3
B3
NOT USED
—
—
—
—
—
—
NOT USED
A4
B4
NOT USED
—
—
—
12
14
*.5
IGNITION
A5
B5
NOT USED
—
—
—
12
*.5
*.5
ALCL DATA
A6
B6
NOT USED
—
—
—
5.01
5.01
5.01
5V REFERENCE
A7
B7
NOT USED
—
—
—
*.5
*.5
SENSOR GROUND
A8
B8
NOT USED
—
—
—
*.5
t ENGINE SPEED
SENSOR
A9
B9
NOT USED
—
—
—
*.5
TPS SIGNAL
A10
B10
NOT USED
—
—
—
B11
DIAGNOSTIC
TEST TERMINAL
5.01
5.01
5.01
B12
NOT USED
—
—
—
*.5
*.5
.57
var.
4.83
var.
*.5
.22
var.
.57
var.
.45
3.0
MAP SIGNAL
A11
*.5
—
GROUND
A12
24 PIN A B
CONNECTOR
t
— AC VOLT SCALE READING
*
— VOLTAGE LESS THAN THAT VALUE
var. — VARIES WITH ENGINE SPEED, THROTTLE POSITION, OR ALTITUDE
Figure 5-77,1984 Calif. (DECS) ECM Terminal Voltage.
5-87
5B. California Diesel Electronic Control System (DECS)
1985
DECS
6.2L (LH6) C A LIFO R N IA
ECM
EGR SOLENOID
C10
PWM EGR SOL.
- a
EGR
VALVE
VENT FILTE R
EGR V EN T SOL.
EGR V EN T SOLENOID
C11
VACUUM
HOSE
EPR SOLENOID
C12
TCC SOLENOID
C5
EPR VAC
VALVE
GROUND
I,.
IG N ITIO N —*
GROUND
ACC. FUSE
39
C14
D14
BATTER Y
IGN 1 (G)
BRAKE
SWITCH
fc N b lN t
'
C16
IGN.
39
ECM 1 FUSE
440
■BATT.
ECM B FUSE
V EH IC LE
SPEED SENSOR
5V REFERENCE
MAP S IG N AL
437
-
A9
_
V EHICLE
SPEED SENSOR
MAP
SENSOR
A
A i\
416
A 12
A1 432
452
SENSOR GROUND
417
T H R O T TLE POSITION
SENSOR S IG N AL
TPS
ENGINE SPEED
SENSOR
ALDA DATA
DIAG N O STIC TEST
TERM.
A8
A10
121
B
El
488
|| A
w > 0
ENGINE SPEED
SENSOR
451
A6
F E D C B A
ALDL CONNECTOR
Figure 5-79,1985 California (DECS) Diesel ECS Wiring Schematic.
b a c k VIEW , ,
OF
/lA
CONNECTOR
5B. California Diesel Electronic Control System (DECS)
1985 6.2L (LH6) CALIFORNIA (DECS)
ECM CO NNECTOR I D E N TI F IC AT IO N
T H IS EC M V O L T A G E C H A R T IS FO R U SE W ITH A D IG IT A L V O L T M E T E R TO F U R T H E R A ID IN D IA G N O S IS . THE V O L T A G E S Y O U
G ET M A Y V A R Y D U E TO LOW B A T T E R Y C H A R G E O R O T H E R R E A S O N S . BU T T H E Y S H O U L D BE V E R Y C LO SE.
THE F O L LO W IN G C O N D IT IO N S M U S T BE M E T B E F O R E T E ST IN G :
• E N G IN E A T O P E R A T IN G T E M P E R A T U R E • B A T T E R IE S F U L L Y C H A R G E D A N D G L O W P L U G S NOT C Y C L IN G •
• T E S T T E R M IN A L NOT G R O U N D E D • A L C L T O O L NOT IN S T A L L E D •
VOLTAGE
©
PIN
4 64
.70
432
MAP SIG NAL
A1
L T GRN
B1
NOT USED
1.01
1.01
417
TPS SIG NAL
A2
BLU
B2
NOT USED
NOT USED
A3
B3
NOT USED
NOT USED
A4
B4
NOT USED
NOT USED
A5
B5
NOT USED
DIAGNOSTIC
TEST T E R M IN A L
A6
B6
NOT USED
NOT USED
A7
B7
NOT USED
5.0
©
ENG. OPEN
RUN CRT.
5.0
451
.01
.02
121
10.72
12.32
437
12.41
.03
488
CIRCUIT
ENGINE SPEED
SENSOR
VEH IC LE
SPEED SENSOR
CIRCUIT
a
B8
NOT USED
A9
PPL
B9
NOT USED
ALC L DATA
A10
TAN
BIO
NOT USED
NOT USED
416
5V REFERENCE
A12
0
0
452
SENSOR GROUND
0
0
150
0
0
150
NOT USED
C4
CtMCCTOR
B 11
NOT USED
BRN
B12
NOT USED
Cl
BLK
D1
NOT USED
GROUND
C2
TA N /B L K
D2
NOT USED
GROUND
C3
TA N /B L K
D3
NOT USED
D4
NOT USED
D5
NOT USED
D6
NOT USED
D7
NOT USED
D8
NOT USED
D9
NOT USED
D 10
NOT USED
NOT USED
TC C SO LENO ID
C5
NOT USED
C6
NOT USED
C7
NOT USED
C8
NOT USED
C9
CIO
MCI V»«»
YEL
\ei MICTI*/
0
34
14.47
435
EGR SOLENOID
1.88
14.47
902
EGR VENT
SOLENOID
C11
LT BLU
D 11
12.40
.87
538
E P R S O L E N O ID
C12
GRN
D12
NOT USED
NOT USED
C13
D13
NOT USED
D14
IG N . - E C M F U S E
D15
NOT USED
D 16
NOT USED
12.40
12.35
14.52
14.32
39
440
IG N . - E C M F U S E
C14
NOT USED
C15
BATT. 12 VOLTS C16
KEY ENG. OPEN
"O N ” RUN CRT.
]o
YEL
D
5.0
422
PIN
WHT
5.0
10.40
WIRE
COLOR
A8
AH
8.88
©
VOLTAGE
WIRE
COLOR
KEY
"O N ”
PINK
©
CttWICTO*
PN K/BLK
RED
PN K/BLK
12.40
14.32
39
Figure 5-80,1985 ECM Connector Identification.
5-89
5B. California Diesel Electronic Control System (DECS)
NOTES
5-90
6. Electrical System
Starting System
Components of these system s are described here. Figure 6-1 shows the 27MT starter used in the 6.2L. Starting
procedures are covered in detail in Section 1.
Starter Motor
Due to the high com pression ratios in the diesel engine, a high torque starter m otor is required for starting.
A heavy duty starter w ith a center armature bearing is used on the diesel. This is needed to handle the higher
com pression ratios and to produce the m inim um cranking speeds needed for starting of 100 rpm when the engine
is cold and 180-200 rpm on a warm engine.
The diesel engine is fitted w ith a heavy-duty 12-volt cranking m otor w ith increased strength pinion and ring gear
teeth. Power is supplied by tw o 12-volt batteries connected in parallel.
This cranking package provided all-weather starting capability.
27MT STARTER MOTOR
DRIVE GEAR
HOUSING
PLUNGER
RETURN
SPRING
SOLENOID
END FRAME
INSULATOR
.COMMUTATOR
END FRAME
THRUST
WASHER
RETAINER
FIBER
WASHER
FIELD FRAME
SNAP RING
CLUTCH AND
DRIVE ASM.
WASHER
CENTER
BEARING
ARMATURE
Figure 6*1, 6.2L • 27MT Starting Motor Exploded View.
6-1
6. Electrical System
STARTER MOTOR NOISE DIAGNOSIS
PROBLEM
C AUS E
GREAT
BETWEEN
HIGH PI TCHED " W H I N E ” A F T E R E N G IN E FIRES, AS KEY
IS BE I NG R E L E A S E D . E N G I N E C R A N K S A N D F I R E S O K A Y .
T H I S I N T E R M I T T E N T C O M P L A I N T IS O F T E N D I A G N O S E D
A S " S T A R T E R H A N G I N ” OR " S O L E N O I D W E A K . "
D I S TA NC E TOO S M A L L
FLYWHEEL.
FLYWHEEL
IN T ERM IT TEN T NATURE.
BETWEEN
RUNOUT
3.
A LOUD " W H O O P " A F T E R THE E NG IN E F IR E S BUT WHILE
T H E S T A R T E R IS S T I L L H E L D E N G A G E D ' S O U N D S L I K E
A S I R E N IF T H E E N G I N E IS R E V V E D W H I L E S T A R T E R
IS E N G A G E D .
M O S T P R O B A B L E C A U S E IS A D E F E C T I V E C L U T C H . A N E W
CL UTC H WILL OFTEN C O R R E C T THI S PR OB LEM .
4.
A " R U M B L E " , " G R O W L " OR (IN S E V E R E
CASES) A
A " K N O C K " A S T H E S T A R T E R IS C O A S T I N G D O W N TO A
S T OP A F T E R S T A R T I N G T H E E N G I N E .
MOST PROBABLE
CAUSE
STARTER
ARMATURE. A
C O R R E C T THIS PROBLEM.
1.
HIGH PITCHED WHINE
ENGINE
FIRES)
BUT
OKAY.
2.
DURING
ENGINE
CRANKING
(BEFORE
CR A N K S AND FIRES
D I S TA NC E TOO
FLYWHEEL'
STARTER
PINION
AND
S T A R T E R PI NION
C O N T R I B U T E S TO
AND
T HE
IS
A B E N T OR
NEW A R M A T U R E
UNBALANCED
WIL L OFTEN
Figure 6-2, Starter Motor Noise Diagnosis.
STARTER NOISE/NO-START CONDITION
1982-83 C-K-P-G WITH 6.2L DIESEL
Starter noise or a no-start condition may result from
inadequate flywheel ring gear to starter pinion
clearance, due to insufficient shimming.
To correct these conditions, proper starter shim m ing
procedures should be followed:
1. Disconnect both battery ground wires.
2. Remove flywheel inspection cover.
3. Inspect for damage to flywheel teeth. Replace
flywheel if teeth are damaged. (The 6.2L engine will
normally stop in one of four positions approxim ately
90 degrees apart where, due to repeated starter
pinion gear engagements, the teeth w ill be more
worn than others. Do not fail to check these four
locations for excessive damage.)
4. Loosen both starter bolts. Remove the outboard bolt.
Remove the shim(s).
5. Check the shim(s) for thickness. Regardless of the
total shim thickness present, add more shim(s) to
bring the total thickness to 3.0 mm. If the shim
thickness is 3.0 mm, add a 1.0 mm shim. Do not
exceed 4.0 mm. 1.0 mm shim is P-n 14028933. (Figure
6-3).
6. Position shim(s) and insert outboard bolt.
6-2
6. Electrical System
- NOTE —
1982-1983 Starter Motor Noise Repair Procedure
Noise during cranking...reduce shim thickness by removing one 2mm
or one 1mm shim or by leaving both shims out.
Noise after engine fires...remove existing 1mm shim and install a 2mm shim
(total 4.0mm) do not exceed 4.0mm.
— NOTE —
1984 only
Install one 2mm shim on every job. Additional shimming or shim removal
is a repair procedure.
Starter Motor Noise Repair Procedure
Noise during cranking...reduce shim thickness by removing existing shim and using
one 1mm shim or by leaving shim out.
Noise after engine fires...add one 1mm or 2mm as required up to a maximum total shim
stack (original shim plus corrective) of 4.0mm. DO NOT EXCEED 4.0mm.
PINION TO FLYWHEEL CLEARANCE
058mm (.020") WIRE GAGE
Pinion to flywheel clearance can be checked, using a
wire gage o f .508mm (.020 in.) m inim um thickness.
Center the pinion tooth between the flywheel teeth and
gage, and not in the corners, where a misleading larger
dimension may be observed.
7. Torque bolts to 40 to 54 N-m (30 to 40 ft. lbs.).
Torque is very important. Do not overtorque.
Overtorque w ill cause the starter housing to crush.
Undertorque can cause the bolts to loosen.
8. If the starter and/or the starter pinion gear has to
be repaired or replaced, remove the bracket bolt
from the front of the starter. Disconnect wires.
Remove both bolts and shims. Be sure to replace
the front bracket bolt on reassembly. Replace
shim s as in Step 5.
9. Reinstall inspection plate.
10. Connect battery wires.
6.355-12.7mm
(1 /4 "-1/2 ")
76.2mm (3")
APPROXIMATE
X -,
SUGGESTED WIRE GAGE
Figure 6-4, Measure Pinion To Flywheel
Clearance
6-3
6. Electrical System
Batteries
The 6.2L diesel engine uses tw o 12 volt batteries. This doubles the amperage output and elim inates the need for a
special double size battery to meet the high amperage requirements of the starter motor and glow plug circuits.
— IMPORTANT The batteries are connected in parallel to provide 12 volts and must never be hooked up
in series. This could produce over 24 volts in the system and cause damage to the
electrical circuits and equipment in the car.
Block Heater
To help assist the diesel w ith cold weather starts, a block heater comes as optional equipm ent w ith this engine.
The heater is built into the right center block core freeze plug and operates off of normal 110 volt house current.
Glow Plugs
NOZZLE
PRE-CHAMBER
GLOW
PLUG
On initial or cold start-up, glow plugs (Figure 6-5)
preheat the air in the diesel engine prechambers. This
along w ith the heat created by compression, makes
the air hot enough to vaporize diesel fuel being
sprayed into the prechambers by the nozzles. Once the
engine starts, the glow plugs cycle to keep the engine
running sm oothly until warm-up tim e is complete.
When the engine obtains proper temperature, the glow
plugs turn off.
Glow plug systems include a network of electrical
com ponents which coordinate the operations of the
plugs themselves with various sensors and controllers.
Figure 6-5, Diesel Engine Glow Plug Location.
The glow plug is energized prior to cranking the engine for a period of tim e called “ pre-glow” . The pre-glow tim e
period is dependent upon engine coolant temperature. Figure 6-5 shows that when the engine coolant temperature
reaches 140 °F (60 °C), pre-glow is not required. At temperatures of 0°F (-1 8 °C ) and below, m axim um pre-glow is
necessary.
When operating, the glow plugs remain on for up to 60 seconds after the engine starts. This m aintains ignition in
all cylinders, improves throttle response and reduces exhaust smoke. This glow plug operating period is called
“ after glow ” .
6-4
6. Electrical System
Two types of glow plugs are used.
• Fast glow 6 volt plug max pre-glow is approxim ately
8 ± 2 seconds.
• Positive tem perature coefficient (PTC) 6 volt glow
plugs, max pre-glow is approxim ately 15 seconds
(CUCV military).
The m axim um operating temperature of the glow plug
is 1800 °F (982 °C).
G.M . DIESEL GLOW PLUG COM PARISON
(1095°C) 2000°F - (927°C) 1700°F
GLOW PLUG - COOLANT TEMPERATURE
RELATIONSHIP REQUIRED TO START
A DIESEL ENGINE
(816°C) 1500°F - -
(538°C) 1000°F - -
(260°C) 500°F - -
ST A M P ED
ENG INE
YEAR
SYSTEM
VOLT
AMP
OHM
TANG
WIDTH
7G
5.7L
(4.3L V-8)
78-79
Slow
Glow
12
7.5
1.8
1/4"
8G
5.7L
(4.3L V-6)
79-83
Fast
Glow
6
15
.7-.8
5/16"
9G
6.2L
82-85
Fast
Glow
6
15
.7-.8
1/4"
12G
5.7L
(4.3L V-6)
84-85
PTC Fast
Glow
6
10
.7
1/4"
13G
CVCV
6 .21-
84-85
PTC Fast
Glow
6
9
.7
3/16"
0°F
20°F
(-18°C)
(-7°C)
40°F
60°F
80°F
100°F
120°F
140°F
(4.5°C) (15.6°C) (26.7°C) (37.8°C)(48.9°C) (60°C)
■COOLANT T E M P E R A T U R E S -
Figure 6-6, Glow Plug Temperature Required
for Engine Start.
FAST GLOW 6 VOLT PLUG
AC STAMPED I.D. #
1/4" TANG
\
— IMPORTANT —
Be sure to use the proper replacement
glow plug(s) for the system you are
working on. If 12 volt glow plugs are
used in the “second type” 6 volt pulsing
system, the plugs will never get hot
enough. If 6 volt glow plugs are used in
the “first type” system, steady current
will cause the glow plugs to quickly burn
out and the tip may break off and drop
into the prechamber. (Figure 6-7).
I
CVCV MILITARY PTC GLOW PLUG
AC STAMPED I.D. #
3/16" TANG
Figure 6-7, Glow Plug Comparison.
COMMERCIAL UTILITY CARGO VEHICLE (CUCV) MILITARY 6.2L APPLICATION (D-TRUCK)
See Figure 6-7.
Glow plugs from the “ D” (military) truck are AC 13G glow plugs. They will fit into any 6.2L head but have a thinner
electrical connection than the normal 6.2L glow plug, AC 9G. Therefore, they could be installed in a non-military
6.2L diesel, but they would not heat up correctly and a hard start condition would occur. The wider electrical tab on
the AC 9G w ill not allow them to be hooked up in a m ilitary unit.
6-5
6. Electrical System
Glow Plug Design Considerations
Figure 6-8 is a typical AC diesel engine glow plug. The Heater Coil Element is a resistance wire centrally positioned
in the sheath. The Heater Coil Element is welded to the Center Terminal Conductor and to the Sheath. The Heater
Coil Element and the Center Terminal C onductor are supported and electrically insulated from the Sheath by
Magnesium Oxide. The entire assembly is joined to a Threaded Shell w hich has a tapered seat and a Hex Section.
Above the Hex Section are an Insulator and Electrical Terminal Blade.
CENTER
TERMINAL CONDUCTOR
TAPERED SEAT
HEATER COIL
ELEMENT
SHEATH
^
- w w w i —i—
□
ELECTRICAL TERMINAL!
BLADE
THREADED SHELL
MAGNESIUM OXIDE
PACK
INSULATOR
Figure 6-8, Typical AC Diesel Engine Glow Plug.
See Figure 6-9. The glow plug is assembled to the
cylinder head and into the pre-chamber. It has only one
purpose and this is to aid the engine in starting in cold
weather.
When the ignition of the vehicle is turned on, the glow
plugs are im m ediately energized. They rapidly heat up
the air in the pre-chamber to approxim ately 1400 °F. In
0°F weather the glow plug can pre-heat the pre­
chamber in only 8 seconds. The engine w ill then start
much easier. A fter the engine starts, the function of the
glow plugs is complete, except for afterglow.
Figure 6-9, Glow Plug Location.
6-6
6. Electrical System
PTC GLOW PLUGS
- NOTE Used in the “D” truck military application, commercial utility cargo vehicle (CUCV).
The CUCV diesel engines w ill incorporate glow plugs that are, temperature self-regulating. These new glow plugs
have PTC (positive temperature coefficient) characteristics (low resistance at low temperature — high resistance at
high temperature) that provide the self-regulating feature.
The PTC plugs offer rapid temperature rise sim ilar to the present fixed resistance plugs, but do not require the
critical shuf-off tim ing and cycling, and can therefore be operated by a sim pler and less costly control. However, the
PTC plugs do require protection from voltages above 13.7 volts.
The glow plugs are self-regulating at 11.5 volts.
PTC GLOW PLUG SPECIFICATIONS
BODY
TIP
Length (mm)
Cold Resistance (Ohms)
Power (Watts)
16.5
6.35
.70
.30
40
93
(133w Total)
Hot Resistance (Ohms)
Power (Watts)
.70
1.3
43
23
(66w Total)
The PTC (Figure 6-10) is a dual coil plug. It is used to aid cold weather starting of the diesel engine. In a typical
installation, the heated sheath of the glow plug extends into the pre-combustion chamber of the engine near the
injection nozzle.
The glow plug is energized prior to cranking the engine for a period of tim e called “ pre-glow” . The pre-glow tim e
period is dependent upon battery voltage and underhood air temperature. For temperatures above 131 degrees F (55
degrees C) pre-glow is not required. At temperatures of 0 degrees F ( - 1 8 degrees C) and below, maximum pre-glow
(10-13 seconds) is necessary.
The PTC duel coil glow plug is so named because it consists of two coils in series. The tip consists of a steady
resistance element. This tip coil is controlled by the body coil. This occurs because the body coil consists of a
positive temperature coefficient (PTC) wire w hich increases in resistance w ith an increase in temperature. As
voltage is applied to the plug, the body coil resistance is very low allowing high current to pass through the tip coil.
As the body coil heats up, its resistance increases 400% to reduce the current through the tip. This allows the tip
to heat up quickly w hile self-regulating itself for various voltage levels less than 14 volts.
The self-regulating nature makes the plug more forgiving of voltage levels w hich allows a simpler, less expensive
controller to be used. In addition, this new plug continues to heat during cranking, thus improving cold starts. (The
earlier quick heat glow plug cooled down during cranking after being superheated to its maximum possible
temperature.)
The dual coil remains on after engine start-up for up to ninety seconds. This m aintains ignition in all cylinders,
improves throttle response and reduces exhaust smoke. This glow plug operating period is called “ after-glow” .
6-7
6. Electrical System
** h i
Figure 6-10, PTC Glow Plug.
Electro-Mechanical Thermal Controller
COOLANT TEMPERATURE SENSOR (D-TRUCK)
1982-84
THERMAL CONTROLLER
CYLINDER HEAD \
SUPPORT
LEFT REAR
OF ENGINE
Figure 6-11, Thermal Controller.
The electro-mechanical thermal controller controls
glow plug temperature, pre-glow time, and after-glow
time. It signals the “ w ait” and “ start” lamp relay. See
Figure 6-11.
It senses ambient temperature and glow plug voltage
to control system operation. The glow plug relay is
pulsed on and o ff by the thermal controller to control
current to the glow plugs and m aintain glow plug
temperature w ithout overheating.
C O O L A N T TEM PER ATU R E SE N S O R
See Figure 6-12. This sensor is used on the m ilitary
CUCV (D-truck) application only. This sensor provides
engine temperature inform ation to the electronic
module glow plug controller.
The sensor is a two-wire therm ister type that lowers its
resistance w ith coolant temperature increase. The
resistance raises as temperature goes down.
Measuring resistance of this sensor, while in the
engine w ill indicate engine temperature condition.
ENGINE COLD
-4 0 °C
-4 0 °F
0°F
130°C
266 °F
Approximate
100,000 OHMS
3200 OHMS
70 OHMS
The resistance of the coolant sensor changes
approxim ately 300 OHMS per degree of water
temperature.
6-8
6. Electrical System
Figure 6-13, Electronic Module Glow Plug Controller (D-Truck).
Electronic Module Glow Plug Controller
W ith the ignition switch in “ run” , the Electronics Module sends constant voltage to the glow plug relay to maintain
proper glow plug temperature (Figure 6-13). It receives feedback signals from the control sensor to control glow plug
and “ w a it” lamp operation. The module also contains circuits which m onitor the system for failures, and keep the
“ w a it” lamp on to indicate a problem in the system.
The “ D” truck (CUCV) m ilitary application also uses a cowl mounted glow plug relay (Figure 6-13). This relay is
turned on and off by the Electronic Module Glow Plug Controller.
6-9
6. Electrical System
GLOW PLUG RELAY
The glow plug relay is pulsed on and off by the controller to control current to the glow plugs and m aintain glow
plug temperature to prevent overheating (Figure 6-14).
— NOTE —
The “D” truck (CUCV) military application relay does not pulse, it is “ON” or “OFF”.
— NOTE 1985 and later C, K, P, G trucks use a combined electronic module controller
and relay in one unit.
6-10
6. Electrical System
GLOW PLUG TEMPERATURE INHIBIT SWITCH
The non-m ilitary glow plug system in 1984 and later
uses a tem perature sw itch in the wire between the
glow plug relay and Pin 3 of the controller (Figure 6-15).
It opens above 125 degrees F and term inates all glow
plug operation. This helps glow plug life, by reducing
needless glow plug cycles. It is located in the rear of
the right cylinder head, across from the glow plug
controller.
GLOW PLUG
CONTROLLER
OIL PRESSURE
SENDER
FILTER
GLOW PLUG
RELAY
TEMPERATURE
INHIBIT
SWITCH
Figure 6-16 illustrates the Temperature Inhibit Switch
Circuit.
Figure 6-15, Temperature Inhibit Switch.
LOCATION OF NEW TEMPERATURE SWITCH IN CIRCUIT
GLOW PLUG
RELAY
Figure 6-16, Temperature Inhibit Switch Circuit.
- NOTE This switch can be fitted to all past models. The procedure is in this section.
6-11
6. Electrical System
CONTROLLER (THERMAL SWITCH) DESCRIPTION
A controller is an electro-thermal device that threads into the engine water jacket to sense engine coolant pressure
and contains small electric heaters to operate three bi-metal switches. There are four electrical heaters that
alternately heat and cool causing the bi-metal sw itches to open and close the glow plug relay circuit. Typical circuit
schem atics are shown in Figure 6-17.
The circuit for heater H-1 is fed by the glow plug side of the glow plug Relay, and gets hot when the glow plugs get
hot. The heater has 300 O HM s resistance. This causes sw itch S-1 to open (at 180°F) and close to pulse the glow
plug Relay coii and the glow plugs. Heater H-2 is energized by generator output and gets hot when the engine runs.
This heater has a 115 OHM s resistance. It opens switch S-3 (at 160°F) and keeps the glow plug Relay de-energized
when the glow plugs are no longer needed. Switch S-2 is acted on by heat from heaters H-3 and H-4. The resistance
of H-3 is 45 OHMs, and H-4 is 32 OHMs.
The operating temperature of sw itch S-2 is about 300°F. Heater H-3 is a low heat unit and heater H-4 only supplies
heat when sw itch S-2 is open. Switch S-2 is also effected by engine coolant temperature so that at engine
operating tem perature in com bination with heat from heater H-3 and water temperature w ill open sw itch S-2. This
will cause heater H-4 to warm up and m aintain sw itch S-2 in the open position.
System Operation, (Engine Cold-Pre-Glow)
When the ignition sw itch is turned to the “ O N ” position, current flows through; gau-idle fuse, 3 0 glow plug relay
coil, closed temperature switch, and closed controller switches S-2, 1 and 3 to ground. This energizes the glow plug
relay, w hich connects battery to the 8 glow plugs. The “ glow plugs” light is wired in parallel w ith the glow plugs, so
when they are “ O N” , the glow plugs “ LIGHT” . It w ill cycle “ ON” and “ OFF” w ith the glow plugs.
When H1 heater of the controller reaches 180°F, S-1 w ill open. This de-energizes the glow plug relay, and turns
“ OFF” the glow plugs. As this heater cools off, if the engine is not started, S-1 will close again and turn “ O N” the
glow plugs. The glow plugs and light will cycle “ O N” and “ O FF” in a controlled heating mode before the engine is
started.
AFTERGLOW
When the engine is running, the glow plugs light may pulse on for a tim e period determined by generator output.
The total after-glow tim e period is controlled by a signal from the alternator to the control system.
Current from generator output entering the controller at Pin 1, w ill cause heater 2 to get hot and open S-3 at 160°F.
This ends the after-glow period.
6-12
6. Electrical System
GLOW PLUG
R ELAY
rwin
IG N
SW
f*r\- o
X
FAST ID LE
SOL
fu el sol
—o
GLOW PLUG
C O N T R O LLER
ic T \ jy 20
START
9
AMP
G A U ID L E
FU SE
T EM PER A T U R E
IN HIBIT SW ITCH
C OLD A D V SOL
NOTE: T E R M IN A L
" 5 ", B L K . GRD.
SPLICES INTO
T E R M IN A L " 6 ",
B L K , A T SPLICE
150. TH E Y THEN
GRD. AT ENG.
F A S T ID L E & C O L D A D V A N C E ~
T E M P . SW. O PE N S A T 9 5 ° F
10 O H M S
|—
vVvV~~i
W /G AU G ES
I > -v
__________ EPR (O N < 14
'C L O S E D
ISO L
GEN
+
~=~
!
—
BAT
T E L L TA LE
I•
*‘-w v *
\
"G LO W
PLUGS"
LAMP /
1/
GLOW
PLUGS
1 -1 5 0
AM PS
%
] W 0 T Je G R ( 0 N < 2 1 °
!/
Is ™
■ t H o 1"
TCC (ON > 8 °
SOL. (
< 550
•
i
______ i
THROTTLE
S W I T C H - L. D. O N L Y
C O N T R O LL ER
T E R M IN A L LO CA TIO N S
N O TE: THE T.C.C. SOL. SWITCH
W IL L OPEN A T W.O.T. O N LY
WHEN THE SWITCH IS NOT
A T T A C H E D TO THE INJ. PUMP
FR O M
BRAKE
SW ITCH
Figure 6-17, Glow Plug Schematic.
6-13
6. Electrical System
General Glow Plug System Diagnosis
Tools for Diagnosis
Successful diagnosis of any condition depends on having the proper tools. This section tells you what tools are
needed and how they must be used.
• DIGITAL MULTIMETER - (TOOL J-29125)
The m ultim eter has become an essential tool for the glow plug system because it measures extremely low
voltages, w ithout burning out the delicate circuits in the electronic module.
• SELF POWERED TEST LIGHT
Necessary for checking glow plug continuity and opens and grounds in circuit checks where no voltage can be
applied.
• 12 VOLT TEST LIGHT
Used to check for opens and grounds in circuit checks requiring 12 volts or more for proper diagnosis.
• VOLT AMPERE TESTER (VAT-40) OR EQUIVALENT (INDUCTION PICK UP TYPE)
Measures current flow (amps). Used in conjunction with Diesel Glow Plug Systems to measure amperage draw
between right and left glow plug banks.
(When using any of these tools, be sure to follow the m anufacturer’s instructions for proper use.)
Preliminary Checks
Make the follow ing preliminary checks before proceeding to diagnosis:
• Check w ait light operation D-Truck (CUCV) m ilitary application — the wait light w ill remain on if there is a
problem in the glow plug system. Usually the engine can still be started, but the glow plug control system must
be repaired.
• Check glow plug light operation — non-military w ith the key in the “ RUN” position, glow plug light should come
“ ON” , and should stay “ O N ” 8 to10 seconds. When it goes out, start the engine. The light should then cycle a
few tim es and go out. If the system doesn’t cycle or continues to cycle, the glow plug system needs repair.
— NOTE —
1984 and later non-military trucks have a temperature inhibit switch which prevents glow
plug operation above a coolant temperature of approximately 125 °F.
• Check all the glow plugs to see that they are working properly — Refer to the preliminary diagnosis flow charts at
the end of this section.
— If the glow plugs are working properly refer to the appropriate Chassis Service Manual for further diagnosis.
— If the glow plugs are not working properly refer to the appropriate flow charts for diagnosis.
• Check all fuses, bulbs and grounds before replacing any components.
• Make sure that all connections are clean, dry and that no wires are exposed.
• Perform am m eter test (next page) to isolate condition to glow plug system.
6-14
6. Electrical System
Glow Plug Controller and Advanced Engine Timing
The glow plug controller has three internal circuits, a pre-glow timer, an after-glow tim er and a circuit breaker.
Failure of the pre-glow tim er w ill cause the circuit breaker to operate. The fact that the circuit breaker is controlling
the glow plugs can be determined on a cold start by observing the glow plug light on the instrument panel. If the
pre-glow tim er is working, the glow plug light w ill continue to cycle “ O N” and “ OFF” w ith the ignition key “ O N”
and the engine “ OFF” . If the pre-glow tim er is not working, the glow plug light w ill only cycle once w ith the ignition
key “ O N ” and the engine “ OFF” .
If it is found that the circuit breaker is controlling the glow plugs, the glow plug controller should be replaced.
Extended operation of the glow plugs with the circuit breaker can cause premature failure of the glow plugs.
— NOTE —
Be sure A, 6.2L diesel controller is IN THE ENGINE, not a 5.7L diesel. The 6.2L controller
has a light gray connector and a silver label. The 5.7L (4.3L V-6) diesel controller has
a black connector, and a gold label. Because of different resistance values between the
two controllers, do not interchange them.
-
NOTE Advanced fuel injection pump timing will cause glow plug failures due to higher than
normal cylinder temperatures. When an advanced timing condition exists, several glow
plugs may not operate; however, usually not all eight.
A normal looking glow plug, w hich is electrically open, or that has a small blister could probably be due to a glow
plug or system fault. Glow plugs however, that have burned off tips are more likely a result of advanced engine
pump tim ing.
6-15
6. Electrical System
Preliminary Diagnosis With Ammeter
The follow ing procedure (Figure 6-18) provides a fast way to determine whether the glow plug system is functioning
correctly or if you have another condition to contend with. It is suggested that this procedure be performed
whenever there is doubt about correct system operation. Then refer to the diagnosis charts that follow to pinpoint
the condition.
Connect an ammeter in series (induction type meter may also be used)* with DK red
wire leading from the Glow Plug Relay to the LH bank of glow plugs. Operate the
system and note the ammeter reading. Repeat the procedure for the red wire
leading from the Glow Plug Relay to the RH bank of glow plugs. Operate the
system and note the reading.
VEHICLE MODEL
NORMAL AMP READINGS
G-Van
50 MIN.
CUCV
35 MIN.
C, K, P
55 MIN.
LH BANK AMMETER READING LESS
THAN NORMAL
AMMETER READING NORMAL
One or more glow plugs on LH bank not
operative. Check individual glow plug
leads by connecting ammeter in series
with GRN wire that feeds glow plug.
Operate the system and note the
reading on ammeter. Repeat procedure
for each glow plug. Each individual wire
should have a reading of approximately: -
Glow plug operating normally.
C, K, P = 14 amps
G-Van = 13 amps
CUCV = 9 amps
One or more glow plugs on RH bank
not operative. Check individual glow
plug leads by connecting ammeter in
series with GRN wire that feeds glow
plug. Operate the system, note the
reading on ammeter. Repeat
procedure for each glow plug. Each
individual wire should have a reading
of approximately:
READINGS NORMAL
READINGS LESS THAN NORMAL
Glow Plugs and harness OK.
On those cylinders with less than
normal readings, check for continuity
through the harness by disconnecting
the lead and connecting a 12 volt test
light from the connector to ground.
Operate the glow plug system.
TEST LIGHT LIGHTS
TEST LIGHT DOES NOT LIGHT WHEN
GLOW PLUGS ARE OPERATING
Harness OK. Replace glow plug
Repair or replace harness. Retest glow
plug for proper operation.
* lf using an in line ammeter read both banks at once. Do not cut wire.
(Snap-on meter MT552, VAT-40, or equivalent)
Figure 6-18, Preliminary Ammeter Diagnosis.
6-16
RH BANK AMMETER READING LESS
THAN NORMAL
6. Electrical System
1982-1984 6.2L Diesel Glow Plug System Diagnosis
1982 C/K/P AND 1983 C/K/P/G 1500 THRU 3500 SERIES TRUCK WITH LH6 (6.2L DIESEL L.D. EMISSIONS)
OR LL4 (6.2L DIESEL H.D. EMISSIONS)
GLOW PLUG CONTROLLER CONNECTOR CIRCUIT CHECKS
PIN 1: (Brown Wire) Should have continuity (0 Ohms resistance) to the brown wire at the alternator w ith the engine
off or alternator voltage w ith the engine running. If there is battery voltage at this pin with the ignition key off, the
alternator has failed a diode (see below).
PIN 2: There is no connection to this pin on 1982 vehicles. On 1983-84 vehicles, there may be a w hite tube or a wire
to this pin, it is only to seal the position in the connector. It is hooked to the wiring harness. DO NOT GROUND
THIS PIN FOR ANY REASON, IT W ILL PROHIBIT NORMAL OPERATION OF THE CONTROLLER AND CAN
DAMAGE GLOW PLUGS.
PIN 3: (Blue Wire) Should have battery voltage with the vehicle ignition key on.
PIN 4: (Orange Wire 82MY, Dark Green Wire 83,84MY) Should have continuity (0 Ohms resistance) to the double red
wire term inal on the glow plug relay.
PIN 5: (Black Wire) Should have continuity (0 Ohms resistance) to Pin 6 (Black Wire) and to ground.
PIN 6: (Black Wire) Same as Pin 5.
-
NOTE -
Complaint of a “no-start — due to no glow plugs heating” where the no-start problem was
a result of a failed delcotron positive diode.
When the diode fails in the delcotron, battery voltage can be supplied to the glow plug controller with the key off
and the engine stopped. This battery voltage is norm ally supplied to pin #1 in the glow plug controller from the
delcotron after the engine starts. This voltage, in effect, tells the controller that the engine has started and shuts off
the glow plug heating cycle.
When a “ no glow plug heating” problem is received, a quick check should be made to see if a diode failure is the
cause.
Follow this procedure:
1. W ith the key o ff and the engine stopped, check for voltage in the brown wire that goes from the delcotron to the
glow plug controller.
2. If a voltage is present, disconnect the wire from the delcotron. Again, check for voltage in the brown wire. There
should be none. (If the key is “ O N ” , a low voltage — approximately 3 volts — w ill be present in a properly
operating system.)
3. Wait for a m inim um of 15 minutes, or sufficient tim e for the controller to cool off.
4. Turn the key on. If the glow plugs heat, the problem was with the delcotron.
- NOTE The only time battery voltage should be present in the brown wire is when the engine is
running. With the key on, and the engine not running, a low voltage (approximately 3 volts)
will be present in the brown wire. This is normal.
GLOW PLUG CONTROLLER CHECK FOR PROPER FUNCTION
ENGINE COLD, IGNITION SWITCH OFF
1. First connect a VOM between the negative side (Blue Wire) of the power relay coil and ground.
6-17
6. Electrical System
- CAUTION —
Do not short the positive terminal to any metal object.
2. M onitor the VOM when the ignition sw itch is turned on. Turn the ignition switch on.
3. The VOM should read about 2 VDC for approxim ately 4 to 10 seconds depending on the engine coolant
temperature. NOTE: If the engine is hot, you may get a continuous voltage reading of about 12 VDC, (the battery
voltage).
4. The VOM w ill then repeat an on-off cycle, about 12 VDC then 2 VDC. NOTE: The power relay should also be
heard turning on and off.
5. If this occurs, the controller is functioning properly. Remove the positive lead of the VOM from the power relay
coil and connect to the relay output.
6. W ith the ignition sw itch still on, the VOM should continue to repeat the on-off cycle of 3 above.
7. If this is occurring, the proper voltage is being applied to the wiring harness connected to the glow plugs.
ASEMBLY PLANT CHECKOUT OF 1983 G-VAN 6.2L DIESEL GLOW PLUG SYSTEM
NORMAL OPERATION
W ith cold engine (below approxim ately 100°F), and good batteries (green eye visible):
1. Ignition sw itch on.
2. Glow plugs light “ O N” for 10 seconds maxim um (engine below 20°F), “ O N ” for 7 seconds maximum with engine
at room temperature.
3. Glow plug light then cycles on-off.
4. Start engine.
5. Glow plug light continues to cycle on-off for up to one minute with cold engine (below 20°F), less tim e if engine
is warmer.
6. Light remains off as long as engine is running.
VISUAL CHECK
If glow plug light does not operate as above, check the following:
1. Check connections on glow plug lamp jum per harness in I.P. area.
a. “ Ground” at bus bar ground terminal.
b. Fuse block.
Two wire connections to bulkhead connector (Orn/Dbl. Blk. stripe and Yel/Dbl. Blk. stripe).
2. Check connections in engine compartment.
a. “ Ground” at stud — power steering brace.
b. Glow plug relay 2-way connector and connections at studs.
c. Glow plug controller.
d. 2-way connector on delcotron.
If all connections are intact, but glow plug system is not operating as stated, proceed with normal diagnostic
procedure. Do not bypass or manually operate the glow plug relay.
6-18
6. Electrical System
GLOW PLUG CONTROLLER CONTAMINATION
On early 1982 production vehicles, the engine w iring harness connector at the glow plug controller has an open
hole at the No. 2 pin connection. Moisture and/or dirt entering this hole can cause deterioration of the pin
connections and result in a controller m alfunction (Figure No. 6-19).
If a com m ent such as poor starting, burned glow plugs, etc. is received, remove the connector from the controller.
Check for m oisture and dirt. Clean the pin area on the controller and the connector. Reinstall the connector.
Apply a small am ount of R.TV. 1052734 or sim ilar silicone sealant over the No. 2 pin hole to prevent water from
entering.
If the controller cycles normally, replacement is not necessary. However, if corrosion of the pins was excessive
and/or the controller does not cycle correctly, it should be changed.
The two (2) wires from No. 5 and No. 6 pin position are ground wires. The ground connection is at the rear of the
right hand head on a stud w hich also grounds the body ground strap. (The stud is on the opposite side of the
engine from the controller.) Make sure the ground connection is secure (Figure 6-19).
6-19
6. Electrical System
THERMAL CONTROLLER CHECK
This should be used when diagnosing the glow plug
system on all 1982-84 model trucks w ith the 6.2L diesel
engine, excluding the m ilitary (CUCV) vehicles.
W ith the connector removed from the glow plug
controller, the controller bim etal heaters may be tested
using a high im pedance digital Ohm meter on the 200
Ohm scale. See Figure 6-20.
CHECK
READING
Pins 2 to 3
0.40 to 0.75 Ohms
Pins 4 to 5
24 to 30 Ohms
Pins 1 to 5
117 to 143 Ohms
Pins 2 to 6
C ontinuity (“ 0” Ohms)
If the controller does not measure w ithin all the above
values, the controller should be replaced.
If the controller checks good to the above
measurements, the harness connector should be put
back on and insure that the controller cycles on and
off more than once w ith the ignition key on (engine not
running). If the controller cycles more than once and
the measurements are correct, the controller is good. If
the controller cycles only once, the controller is bad or
a harness problem exists. Refer to the Glow Plug
Electrical System Diagnosis Chart for testing for a
harness problem.
DIAGNOSTIC PROCEDURE CHARTS
Figure 6-21 is Chart #1, 6.2L Diesel Glow Plug Electrical System Diagnosis. Figure 6-22 describes the relay not
operating diagnostic procedure.
6-20
Figure 6-21, Glow Plug System
Chart #1 — 6.2 L DIESEL GLOW PLUG ELECTRICAL SYSTEM DIAGNOSIS
Current at all 8 wires, but glow,
plugs only come on once.
Current all 8 wires and plugs
cycle on and off. Glow plug
system is OK, check for other
cause of hard starting.
Check for open circuit in GRN.
wire from controller to splice
503.
I
I
No Current
Diagnosis.
-Fuse Blown
•C H E C K 20 AM P FUSE
Disconnect glow plug relay
connector at relay. Install new 20
amp fuse and turn ignition to run.
Fuse OK
Relay Not Operating
Go To Chart
“ RELAY NOT OPERATING ”
Test Light Does
Not Come On
Touch test light to single red wire
term inal (Batt. feed) on glow plug
relay.
I
--------------- }
Relay Operating
♦
Connect 12-volt test light to
ground. Touch the glow plug
relay terminal with 2 fusible links.
Test light should turn on and off
as controller operates relay.
Test Light On Steady
*
Reconnect glow plug relay
----------- )
Fuse Blows
t
Locate and repair short in wire
from relay to connector and
replace diode at glow plug relay.
(No diode in 1982). (If the diode
is shorted or installed backwards
the circuit breaker heater in the
controller may be damaged).
Test Light
Turns On and Off
Touch each glow plug harness
terminal with 12-volt test light
connected to ground. Test light
should pulse on/off.
Fuse OK
♦
Locate and repair interm ittent
short in glow plug relay coil feed
circuit (circuit breaker heater in
controller may be damaged).
Locate and repair open circuit in
red wire from glow plug relay to
battery.
o>
_______ I_______
}
Test Light Comes On,
All 8 Wire Terminals
Test Light Does Not
Come On, One Or
More Terminals
I
Disconnect harness from all glow
plugs. Connect test light to 12volt source and touch each glow
plug terminal. Light should be on.
Replace glow plug if light is off.
t
Repair open circuit in glow plug
harness. If open circuit is caused
by burned wire, glow plug is
shorted and should be replaced.
Electrical System
Test Light Off
I
Replace relay.
(Contacts burned).
*
Locate and repair short circuit in
one of the following:
1. Cold Adv/fast idle temp,
switch, fuel heater, or
solenoid circuits.
2. L.D. only, throttle switch
circuits EPR, EGR, and TCC
solenoids.
Relay contacts shorted. Replace
glow plug relay and all glow
plugs.
----------- }
Test Light On
Fuse OK
Fuse Blows
I________
♦
----------- }
I--------------
Listen for glow plug relay
operation. Should be clicking on
and off if engine is cold.
f--------------------
N>
No current at one or more w ires..
One or more glow plugs not
functional. (Approx. 15 amps per
plug).
Check for glow plug current
using clam p on ammeter. (Snapon MT-552 or equivalent) clam p
around dark green wire leading
to each plug.
If OK, go to chart “THERM AL
CONTROLLER C H EC K ”
_________________
CD
2. Battery voltage is 10 volts
or more when glow plugs
cycle on.
3. Cranking speed OK (100
RPM or more).
Engine does not start cole
“GLOW PLUGS” lamp may or
may not come on.
1. Fuel system checked
and is OK.
.
6. Electrical System
Chart #2
RELAY NOT OPERATING
W ith ignition in run connect 12volt test light to ground and
touch pink/blk wire in glow plug
relay connector
Light On
------------- Light Off
♦
*
Touch light blue wire term inal at
glow plug relay connector
Repair open circu it in pink/blk
wire from glow plug relay to 39
splice.
r -
t
Light Of)
♦
Replace glow
plug relay.
Light On
(1984 models and 1982-83
models w ith shutdow n switch).
(1982-83 models w ithout
shutdown switch).
Disconnect the glow plug
shutdown connector from the
glow plug shutdown sw itch and
touch light blue wire in connector.
r~
Ligh^On
Light Off
t
Reconnect the glow plug
shutdown connector to the glow
plug shutdown sw itch and with
engine coolant temperature less
than 110°F, touch the light
blue/black wire.
Repair open circuit in light blue
wire from connector to glow plug
relay.
-------------------------------------1______________________
f---------------
t
Light On
Light Off
t
t
Disconnect connector at thermal
controller and touch blue wire
terminal in connector.
*---------------
)
Light On
Light Off
\
♦
Connect test light to 12-volt
source and touch pin 5 and pin 6
black wires.
I
Light On Both Wires
I
Go to “ THERMAL
CONTROLLER CHECK” chart.
Repair open circu it in light blue
wire from controller to glow plug
relay.
}
Light Off Either/Or
Both Wires
t
Repair open c ircu it to 150 splice
in black wires or bad ground
connection to engine.
Figure 6-22, Glow Plug System Diagnosis.
6-22
Replace glow plug shutdown
temperature switch.
6. Electrical System
Installation of Glow Plug System Inhibit Switch
1982-83 C/K/G/P TRUCK WITH 6.2L DIESEL RPO LL4 - H. D. EMISSIONS
RPO LH6 - L.D. EMISSIONS
Many tim es a 6.2L diesel w ill not require glow plugs to start, such as a warm engine or warm climate.
To inhibit glow plug system function when engine coolant temperature is above 125°F and lower glow plug usage,
the follow ing parts can be installed.
Inhibit wire assembly; should be assembled per attached drawing (Figure 6-23).
GLOW PLUG INHIBIT TEMPERATURE SWITCH INSTALLATION
1. D isconnect batteries.
2. Replace cover on R.H. rear head (Figure 6-24A) w ith cover 14028949 (same as on L.H. head) (Figure 6-24B). Use
new gasket 14028951. Drain coolant as required.
3. Install new tem perature sw itch 15599010 using appropriate pipe thread sealer. Tighten to 19-27 N-m (13-20 ft. lb.).
Replace any lost coolant.
4. Connect glow plug inhibit wire assem bly to sw itch w ith the light blue (without the stripe) wire terminal mating
with the sw itch terminal.
5. Route the wire assem bly toward the left side of the vehicle, strap to the engine harness as required.
6. Disconnect the 4-way engine harness connector from its mate on the glow plug relay extension harness
12031493 (Figure 6-25).
7. Remove the light blue wire fem ale term inal from the engine harness 4-way connector and install connector body
2977253 on this terminal. Plug m ating connector on new jum per wire assembly (light blue/black stripe)
to 2977253.
8. Insert fem ale term inal of jum per wire assem bly into em pty cavity of 4-way connector. Reconnect 4-way
connectors.
9. Reconnect batteries.
GLOW PLUG INHIBIT WIRE ASSEMBLY
TERMINAL
2965867
♦
506 CKT. LT. BLUE 1.0MM2, 1000MM. LONG (39.4-INCHES)
n
---------------- -—
f
>
^
n
______
.
903 CKT. LT. BLUE/BLK. 1.0MM2, 950 MM. LONG (37.4-INCHES)
t
t
TERMINAL
TERMINAL
2984528
6294828
506 1
I 903 I
I___ n ___
Use with Temperature Switch #15599010 in 6.2L Diesel Engine.
Connector Body #2977253 also required.
Figure 6-23, Glow Plug Inhibit Wire Assembly.
6-23
6. Electrical System
Figure 6-24 A and B, Installation of Temperature Inhibit Switch.
D-Truck (CUCV) Military 6.2L
(LL4) PTC Glow Plug System
The D-Truck (CUCV) System is
Composed of:
• 2 Reducing Resistors
• Electronic Module Controller
• W ait Lamp
• Reducing Resistors
• 8 PTC Glow Plugs
REDUCING RESISTORS
See Figure 6-26. Two 300 w att (.280 Ohm) reducing
resistors are hooked in a parallel circuit to reduce the
24 volts (used for starting) to 12 volts nominal. This
was done to provide voltage to the glow plug system
when using the 24 volt slave (jump) start socket.
Figure 6-25, Harness Connection.
6-24
6. Electrical System
CIRCUIT 39
Figure 6-26, D-Truck Glow Plug System.
GOES HIGH WHEN IGNITION SWITCH IS CLOSED
CKT. 39
n
PINK/BLK
GROUND SIDE OF
POWER RELAY
H
CKT. 503
\
IGNITION SWITCH
i|i— In
,V
V
H I
CKT. 505
LT. B L U E /t ^
ORANGE
GLOW PLUG ^
RELAY
X
f— •
I_______I
TO HIGH SIDE OF GLOW PLUGS (GOES HIGH
WHEN THE GLOW PLUGS ARE ON)
STARTER CIRCUIT
R6
-+
-
INTERFACE CKT. 930
s~ \
PPL/WHT
A ------------------------------------------- ( \-----r r u y
T 0 HlQH S)DE 0 F STARTER RELAY
(GOES HIGH WHEN STARTER IS ENERGIZED)
R10
vC1
C4
L^ I
D
DK-BLUE
COOLANT
SENSOR
CKT. 980 YELLOW
--------- - ^ 2
• ------
CKT. 507
M
CKT. 507 PULLS THIS LINE LOW AND TURNS ON
THE “WAIT LAMP”.
GROUND
CKT. 151 BLK
ELECTRONIC MODULE
Figure 6*27, D-Truck Electronic Module Controller.
6-25
6. Electrical System
System Operation, D-Truck
Refer to Figure 6-27. When turning “ O N ” the ignition, the follow ing occurs:
WAIT LAMP INDICATION
12 volts B + flow s from the Ignition Switch C ircuit 39 to the top pin of the electronic module. This energizes the
Darlington Com pound Q1 and turns “ O N” the second transistor. This transistor grounds the w ait lamp and turns
it “ O N ” .
POWER RELAY ACTIVATION
12 volts flow from Ignition C ircuit 39 to Darlington Compound 02. This turns “ O N ” the second transistor, which
provides a ground for the power relay.
— NOTE —
This system is regulated by voltage and coolant temperature rise.
When the power relay is energized, 12 volts flow to the glow plugs.
The Power Relay and the w ait lamp w ill both turn “ OFF” at the same time.
The system “ On-Time” is about 14.5 seconds. The “ On-Time” is regulated by:
• Coolant temperature
• Battery voltage
• Battery temperature
• Com bustion cham ber temperature
• Glow plug counter voltage
When the pre-chamber temperature is about 1650 °F, w hich is determined by glow plug counter voltage, the glow
plug tim er in the module goes low and turns off 0 2 transistor which removes the power relay ground. This turns
“ OFF” the glow plugs. At the same time, the module lamp turns “ OFF” 01 transistor w hich ungrounds
the w ait lamp.
The plugs w ill be “ O FF” for 4.5 seconds. Then they turn “ O N” for an “ after glow ” period. The “ after glow ” is
controlled by generator output voltage, w hich changes the voltage into the module. The w ait lamp w ill not turn on
during after glow.
If the coolant temperature is above 4 8 °C (118°F), the wait lamp w ill not turn “ O N” .
Anytim e the starter is energized, it will m aintain glow plug operation, engine cold, or energize them if the
engine is hot.
Glow Plug System Troubleshooting Procedure, D-Truck
1. SYSTEM DEFINITION
For troubleshooting purposes, the glow plug system is divided into tw o subsystems; the power system and the
control system. The power system is shown in Figure 6-28. It consists of the glow plugs, the contacts of the
control relay, the series voltage dropping resistor assembly, and associated wiring. The control system is shown
in Figure 6-29. It consists of the electronic controller module, the “ w a it” lamp, the coolant temperature sensor,
and associated wiring.
6-26
6. Electrical System
TO POSITIVE TERMINAL BOARD
Figure 6-28, Glow Plug Power System, D-Truck.
6-27
6. Electrical System
TO SPLICE 39 (GOES HIGH WHEN IGNITION ON)
39 PNK/BLK
505 LT. BLUE
-> >
V v 930 PPL
A- » -
}
GLOW PLUG
CONTROL
RELAY
930C PPL/WT
> >—
—
—
'
139 PK/BLK
507 DK. BLUE
GLOW
PLUG
CONTROLLER
M O DULE
TO HIGH SIDE OF STARTER RELAY
(GOES HIGH WHEN STARTER ENERGIZED)
^
7
TO SPLICE 139 (GOES HIGH
WHEN IGNITION ON)
“WAIT”
39 PNK/BLK
503 ORANGE
H “? >
______ y
A
'
TO SPLICE 39 (GOES HIGH WHEN IGNITION ON)
TO HIGH SIDE OF GLOW PLUGS (GOES HIGH WHEN
GLOW PLUGS ARE ENERGIZED)
980 YELLOW
■ (—
L-7 >
M -V >
151 BLK
V
W
\A
^
THERMISTOR (RESISTANCE
CHANGES WITH COOLANT
TEMPERATURE)
Figure 6-29, Glow Plug Control System, D-Truck.
2. TROUBLESHOOTING THE POWER SYSTEM, D-TRUCK
This procedure is illustrated in flow chart form in Figure 6-30. In this procedure, the low side of the control relay
coil is disconnected from its harness. This is done to prevent the controller from turning the circuit “ O N” and
“ OFF” during the test. A DC voltm eter is connected across the resistor assembly, and the control relay is briefly
turned “ O N” by grounding the disconnected terminal. The voltage across the resistors can be quite useful for
isolating faults in the system. For example:
• OV WITH RELAY “ OFF” . . .
10-15V w ith relay “ O N” . Expected values; relay OK, resistors OK, harness and plugs probably OK (maybe one or
tw o open).
• OV WITH RELAY “ OFF” . . .
22-28V w ith relay “ O N ” . Open resistors.
• 10-15V WITH RELAY “ ON” OR “ OFF” . . .
Stuck relay contacts.
• 22-28V WITH RELAY “ O N” OR “ OFF” . . .
Stuck relay contacts and open resistors (since the resistors are operated at a power level considerably higher
than their rating, continuous duty could cause them to burn open).
• OV WITH RELAY “ ON” OR “ OFF” . . .
No current flow. Defective relay or open circuit (possibly all plugs open).
Depending on the findings in this step, the technician is directed to a fault path in the flow chart w hich w ill isolate
the problem to a particular component.
6-28
6. Electrical System
D ISABLES
RELAY
MEASURES
VOLTAGE
ACROSS
RESISTORS IN
SERIES W ITH
GLOW PLUGS.
Figure 6-30, Troubleshoot Glow Plug Power Circuit, D-Truck.
6. Electrical System
3. TROUBLESHOOTING THE CONTROL SYSTEM
Before testing the control system, the power system w ill be tested and, if necessary, repaired.
Due to the near-nonaccessability of the controller module, no direct measurements w ill be taken. Instead, the
follow ing procedure w ill be used:
1. Connect a DC voltm eter between ground and the orange wire connector on the relay.
2. Disconnect the pink wire from the fuel shut-off solenoid on the injector pump to keep the engine from starting.
3. Turn “ O N ” the ignition switch. Plugs and “ WAIT” lamp should turn “ O N ” and “ OFF” at irregular intervals
lasting several seconds (10-15V displayed on the voltm eter indicates that the plugs are “ O N ” ).
4. When plugs and “ WAIT” lamp are “ O FF” , crank engine. Plugs should come “ O N” and stay on for duration of
cranking. “ WAIT” lamp should be “ O FF” .
5. Plugs should remain “ O N ” for several seconds after cranking. “ WAIT” lamp should be “ O FF” .
If the plugs and lamp act as described during this sequence, the system can be assumed to be OK. Any major
deviation can be assumed to be the fault of the controller module or wiring harness (unless the “ WAIT” lamp never
comes “ O N ” , whereupon the light bulb is suspect).
The technician should first replace the controller module. If this does not solve the problem, the wiring harness
should be replaced. A controller module input-output line description (Figure 6-31) so that, if desired, the technician
can trace continuity or voltage levels on specific lines.
PIN
NO.
CIRCUIT
NO.
WIRE
COLOR
I/O
Pink/Black
I
From splice 39. Goes high when ignition “ O N ” . Serves 3
functions:
1) Provides power to module.
2) When it first goes high, the module starts the glow plug
sequence.
3) Allow s the module to m onitor system voltage level. This
value is one of the factors used to determine the duration
of “ WAIT” light display and “ AFTERGLOW” .
DESCRIPTION
G
39
A
930
Purple
I
From high side of starter relay. Goes high when starter is
energized. When this line is high, the glow plugs are “ O N”
unconditionally.
H
503
Orange
I
From high side of glow plugs. The voltage on this line varies
with glow plug resistance, which varies w ith pre-combustion
chamber temperature. Used to determine “ ON-time” .
L
980
Yellow
I
From therm istor in cooling system. Measures coolant
temperature. Used to determine duration of “ WAIT” light
display.
B
505
Light Blue
0
Norm ally high. Goes low to turn “ O N” glow plug control
relay.
D
507
Dark Blue
0
Normally high. Goes low to turn “ O N” “ WAIT” lamp.
M
151
Black
—
System ground.
Figure 6-31, Glow Plug Controller Module I/O Description, D-Truck.
6-30
6. Electrical System
Chart #1, Glow Plug Trouble Shooting Procedure, D-Truck.
6-31
6. Electrical System
Chart #2, Glow Plug Trouble Shooting Procedure, D-Truck.
6-32
6. Electrical System
»
Chart #3, Glow Plug Trouble Shooting Procedure, D-Truck.
6-33
6. Electrical System
REPLACE BAD
PLUGS AND
TROUBLESHOOT
GLOW PLUG
CONTROL
SYSTEM.
END
END
Chart #4-5, Glow Plug Trouble Shooting Procedure, D-Truck.
1985 6.2L (LH6/LL4) Glow Plug Control System, CKGP-Truck
A new glow plug controller is used in the 1985 CK/G, & P trucks w ith the 6.2L Diesel engine (Figure 6-32). This new
controller is electronic and contains an integral glow plug relay. This single unit installs to tw o 10mm studs at the
rear of the left hand head.
The glow plugs are the same as in 1984 and the operation of the “ Glow Plug” light remains basically unchanged —
that is, it is on wherever the glow plugs are energized.
6-34
6. Electrical System
9G GLOW PLUGS (6 VOLT)
______________________________________________________________________________________________
Figure 6-32, Electronic Glow Plug Control System.
A normal functioning system (Green eye in batteries) operates as follows:
• KEY “ O N” -
ENGINE NOT RUNNING -
VEHICLE AT ROOM TEMPERATURE
1. Glow plugs “ O N” for 4 to 6 seconds, then “ O FF” for approxim ately 4.5 seconds,
2. Then cycle; “ O N” for approxim ately 1.5 seconds, “ OFF” for approxim ately 4.5 seconds, and continue to cycle
1.5 “ O N ” /4.5 “ OFF” , for a total duration (including the initial 4-6 seconds) of about 25 seconds.
• If the engine is cranked during or after the above sequence, the glow plugs w ill cycle “ ON/OFF” for a total
duration of 25 seconds after the ignition sw itch is returned from the crank position, whether the engine starts or
not. The engine does not have to be running to term inate the glow plug cycling. All the “ tim es” shown above are
approxim ate because they vary w ith initial engine temperature.
The initial “ ON” tim e and cycling “ ON/OFF” tim es vary also w ith system voltage. That is, longer “ O N” tim es are
produced by lower voltage and/or temperature. Longer duration of cycling is produced by lower temperature only.
The temperature sw itch in the upper rear of the R.H. head is calibrated to 125°F and above this temperature the
glow plugs are not energized.
If the system does not operate as described, check all connectors to ensure they are fully seated. As in the 1982-84
6.2L diesels, the engine harness ground connection to the engine is critical . . . make sure the nut is tightened to
specifications and the ground ring term inal is tight.
6-35
6. Electrical System
• THE OTHER CONNECTIONS TO CHECK IN THE ENGINE COMPARTMENT ARE:
1. Four-wire connector on controller. If this connector isn’t fully seated and latched, the glow plugs may not
function.
2. Both stud nuts on controller. Tighten to 4-5 N m (35-45 lb.-in.). Do not overtorque.
3. Temperature sw itch connector at top rear of R.H. Head. If this connection is not made, the glow plugs will not
energize (Engine tem perature must be below 110°F for glow plugs to operate).
If the glow plugs function normally, but the “ Glow Plugs” light does not, check all the connections and bulb in the
jum per harness in the IP area.
If all connections are intact, but the glow plug system does not operate as stated, proceed w ith normal electrical
diagnostic procedures (Figure 6-33).
— CAUTION —
Do not manually bypass relay in the glow plug controller. Do not jump start
with more than 12 Volt System.
6 2
LITER DIESEL ELECTRICAL SYSTEM DIAGNOSIS
ENGINE CONTINUES TO RUN
IGNITION KEY OFF
ENGINE STAYS ON FAST IDLE
AT A LL TIMES
ENGINE CONTINUES
TO RUN
Turn A/C off, ignition on and disconnect
fast idle solenoid —dark green wire.
♦
Disconnect pink wire at
injection pump solenoid.
f------------
----------- 1
ENGINE CONTINUES
TO RUN
Stop engine
Remove injection
pum p fo r repair.
ENGINE STOPS
Check ignition switch
adjustment. If OK,
replace ignition switch.
Check ign. sw. assoc,
wiring.
|
Check for loose Bt wire
at generator.
SOLENOID RETRACTS
t
♦
Check throttle linkage
or solenoid plunger for
binding. If linkage is
OK, replace solenoid.
Connect solenoid wire. Open
throttle slightly. Disconnect
2-wire connector at fast idle
temperature sw.
SOLENOID RETRACTS
ENGINE RUNS ROUGH ON COLD START
GLOW PLUGS NOT CYCLING ON AND OFF
AFTER ENGINE STARTS - 20 AMP FUSE OK
(All open circuit in the orn wire from controller
to glow plug relay or an open heater element
between pin 4 and 5 of the controller will cause
this condition)
NO CONTINUITY
Repair open
circuit in orn
wire from
controller to
relay.
Figure 6-33, General Electrical Diagnosis
]
t
Check continuity of
temperature switch with
self powered test light
(KD-125 or equiv):
continuity below 90°F,
no continuity above 122“F.
Replace switch if bad.
WITH IGN OFF
Using self powered test lite
check continuity of orn
wire from pin 4 of
controller, to the glow
plug relay.
CONTINUITY
Disconnect controller
connector and using a
high impedance m illim eters
check pin 4 to pin 5
resistance (should be
27 + f t 3 )
6-36
------------- }
SOLENOID DOES NOT
RETRACT
INCORRECT READING
OR OPEN CIRCUIT Controller is defective.
6. Electrical System
1983 Diesel G-Truck Engine Run-On, 6.2L Diesel with
Base Engine Warning Lights
A condition exists whereby an electrical feedback signal from the alternator can caust the engine to continue
running w ith the key in the “ O FF” position.
The feedback signal prevents the injection pump solenoid from shutting off the fuel supply. This is only in 1983 “ G”
Truck vehicles equipped w ith the 6.2L Diesel and base warning light system (tell-tale lights).
To correct an affected vehicle, install jum per wire harness P/N 12038051 (Figure 6-34). This wire incorporates a
diode w hich prevents a feedback signal. This harness assembly is installed in production vehicles starting
approxim ately March, 1983.
USE THE FOLLOWING PROCEDURE TO INSTALL THIS WIRE ON AFFECTED VEHICLES:
1. Disconnect the negative battery cable from both batteries.
2. Remove the engine harness bulkhead connector.
3. Looking into the term inal end of the bulkhead connector, locate the #25 circuit (brown wire) and remove.
4. Insert the end of the jum per harness into the )ulkhead connector.
5. Using the supplied terminal, connect the other end of the #25 circuit (brown wire) to the jum per harness.
6. Attach the bulkhead connector.
7. Re-connect both negative battery cables.
6-37
6. Electrical System
6.2L Diesel Drive Belts, 1982-1984 C/K/P/G Truck With 6.2L Diesel Engine
BELT USAGE
RECOMMENDED BELT
Alternator
14050449
A/C Belt
14033869
P.S. Belt
14050459
Pre-delivery retensioning of drive belts in 6.2L diesel engines is MANDATORY to m aintain proper adjustm ent
throughout the life of the belt.
A high percentage of belt tension is lost during the first 15 minutes that the engine is run. This occurs when the
initial stretching of the belt fibers relaxes as the belt seats itself in the pulleys. Vibrations unique to diesel engines,
especially at idle, continue to stretch belt fibers throughout the life of the belt, although a m ajority of this occurs
during the first 15 m inutes of running time. Once a belt has accum ulated 15 m inutes running time, it is considered
a used belt, and the parameters of belt tension change accordingly.
During the dealer pre-delivery inspection, the belt tension MUST be checked. If the tension is below 350 N (80
pounds), the tension m ust be reset to 445 N (100 pounds).
It is recommended that when a vehicle is in for service and a NEW belt is installed that the belt be tensioned to the
new belt specification (See attached chart). The engine should then be run for a m inim um of 15 minutes at idle and
the tension rechecked. If below 350 N (80 pounds), retention the belt to 445 N (100 pounds).
A used belt should never be tensioned to more than 445 N (100 pounds). When checking used belt tension, it w ill
be necessary to run the engine 5 to 15 m inutes to assure the belts are hot. Check the belt tension. If under 275 N
(60 pounds) HOT, the belt m ust be retentioned to 445 N (100 pounds) COLD.
— CAUTION —
Avoid over- or under- tightening belts. Loose belts result in slippage which can lead to
belt and pulley “glazing” and inefficient component operation. Once a belt has become
“glazed”, it will be necessary to replace the belt. Loose belts can also place high impact
loads on driven component bearings due to the whipping action of a loose belt. Over
tightened belts can lead to bearing damage and early belt failure.
6-38
6. Electrical System
W h e n a d ju s tin g drive b e lts, use b e lt te n s io n g a g e J-23600-B.
BELT TENSION (ALL BELTS)
IF BELOW:
Newton (Pounds)
RETENSION TO:
Newton (Pounds)
350 (80)
445 (100)
DEALER
(Pre-delivery
inspection)
SERVICE
(New Belt)
Set Tension to 775 N
(175 lbs.)
SERVICE
(New belt after
m inim um of 15
m inutes running
time)
SERVICE
(Used belt — any
mileage over
50 miles)
350 (80)
445 (100)
275-HOT* (60-HOT*)
445-COLD** (100-CQLD**)
*H O T = Belt feels hot to the touch. Engine may have to be run 5 to 15 minutes
to warm the belt.
**C O LD = Belt feels only warm to the touch, or cooler.
-
NOTE -
The alternator/vacuum pump belt for 1984 G and P models is #14071081.
This is a cog type belt, 49" x 3/8".
6-39
7. Diagnosis
THIS DIAGNOSIS SECTION IS DIVIDED INTO THE FOLLOWING;
• General/Mechanical Diagnosis
Brake Diagnosis
• Smoke Diagnosis
Engine Oil Leak Diagnosis
• Idle and Performance Diagnosis
Checking For A ir Leaks
« MPG Diagnosis
Testing Fuel System Pressures
• Fuel and Air System Diagnosis
General/Mechanical Diagnosis
Diesel Engine Mechanical Diagnosis such as noisy lifters, rod bearings, main bearings, valves, rings and pistons is
the same as for a gasoline engine. This diagnosis covers only those conditions that are different for the diesel
engine.
G e n e r a l
D i a g n o s i s
CONDITION
Engine W ill Not Crank
Engine Cranks (Slowly)
But W ill Not Start or is
Hard to Start — Hot or
Cold (M inim um Crank­
ing Speed is 100 RPM
Cold, 180 RPM Hot.
7-1
C h a r t s
POSSIBLE CAUSE
CORRECTION
a. Loose or Corroded Battery
Cables
Check connection at batteries, engine
block and starter solenoid.
b. Discharged Batteries
Check generator output and generator
belt adjustment.
c. Starter Inoperative
Check voltage to starter and starter
solenoid. If OK, remove starter for
repair.
1. Low Cranking Speed
Due to:
a) Loose or Corroded
Battery Connections
Clean and/or tighten terminals.
b) Partially Discharged
Batteries
Charge batteries and check charging
system including belt tension and
battery terminals.
c) W rong Engine Oil
Use correct viscosity oil.
d) Defective Cranking
M otor
Repair or replace as necessary.
Figure 7-1, Summary of Major Diagnosis Conditions.
Ko
Diagnosis
~vj
7. Diagnosis
............. ......................
CONDITION
Engine Cranks Normally
— W ill Not Start
POSSIBLE CAUSE
CORRECTION
a. Incorrect Starting
Procedure
Use recommended starting procedure.
b. Glow Plugs Inoperative
Refer to Section 6.
c. Glow Plug Control System
Inoperative
Refer to Section 6.
d. No Fuel Into Cylinders
Remove any one glow plug. Depress
the throttle part way and crank the
engine for 5 seconds. If no fuel vapors
come out of the glow plug hole, go to
step e. If fuel vapors are noticed
remove the remainder of the glow
plugs and see if fuel vapors come out
of each hole when the engine is
cranked. If fuel comes out of one glow
plug hole only clean and test the
injection nozzle in that cylinder. Crank
the engine and check to see that fuel
vapors are coming out of all glow plug
holes. If fuel is com ing from each
cylinder, go to step k.
e. Plugged Fuel Return
System
Disconnect fuel return line at injection
pump and route hose to a metal
container. Connect a hose to the
injection pump connection, route it to
the metal container. Crank the engine.
If it starts and runs, correct restriction
in fuel return lines. If it does not start,
remove the top of the injection pump
and make sure that it is not plugged.
NOTE: If fitting is plugged and/or small
black particles are visible in the pump,
a governor weight retaier flex ring
may be needed (See Section 4B).
f. No Fuel to Injection
Pump
Loosen the line com ing out of the
filter. Crank the engine, the fuel should
spray out of the fitting, use care to
direct fuel away from sources of
ignition. If fuel sprays from the fitting
go to step j.
NOTE: Perform fuel supply system
checks at the end of this section.
g. Restricted Fuel Filter
7-3
Loosen the line going to the filter. If
fuel sprays from the fitting, the filter is
plugged and should be replaced. Use
care to direct the fuel away from
sources of ignition.
7. Diagnosis
CONDITION
Engine Cranks Normally
— W ill Not Start
(Cont’d)
POSSIBLE CAUSE
CORRECTION
h. Fuel Pump Inoperative
Remove inlet hose to fuel pump.
Connect a hose to the pump from a
separate container that contains fuel.
Loosen the line going to the filter. If
fuel does not spray from the fitting,
replace the pump. Use care to direct
the fuel away from source of ignition.
i. Restricted Fuel Tank
Filter
Remove fuel tank and check filter.
(Filter for diesel fuel is blue.)
j. No Voltage to Fuel
Solenoid
1. Connect a voltm eter to the wire at
the injection pump solenoid and
ground. The voltage should be a
m inim um of 9 volts. If there is
inadequate voltage, refer to the
ELECTRICAL DIAGNOSIS in Service
Manual for more information.
2. Disconnect pink lead from terminal
on top of injection pump. Turn key
to “ O N” position. Touch lead to and
remove — audible clicking sound
should be heard from w ithin pump.
If no sound is heard, turn key off
and remove governor cover. Check
solenoid arm and plunger for
freedom of movement. Repair or
replace solenoid as necessary.
NOTE: Occasionally, plunger
solenoid stickiness may be caused
by an accumulation of metallic
debris in the mechanism. Before
replacing inoperative solenoids, blow
off the debris with compressed air
and recheck for proper operation by
applying a minimum of 12 volts to
the terminal and grounding the
cover.
k. Incorrect or Contaminated
Fuel
Flush fuel system and install correct
fuel. Replace w ith correct fuel. To
verify suspected poor quality fuel,
connect a hose to the inlet of the fuel
supply pump and route to a container
of known good quality fuel. If engine
starts and runs, drain and flush poor
fuel from vehicle.
7-4
7. Diagnosis
CONDITION
Engine Cranks
Norm ally — W ill Not
Start (Cont’d)
Instrument Panel Oil
Warning Lamp “ O N ” at
Idle
POSSIBLE CAUSE
CORRECTION
1. Pump Tim ing Incorrect
Make certain that pump tim ing mark is
aligned with mark on adapter or front
cover. Check tim ing w ith tim ing meter
(if available or applicable)
m. Low Compression
Check compression to determine
cause. Repair as necessary. The 6.2L
Diesel should have com pression in
each cylinder of at least 380 psi, and
the lowest cylinder reading should not
be less than 80% of the highest
cylinder reading.
n. Bent Upper Compression
Ring
Replace rings.
o. Injection Pump
M alfunction
W ith pump on engine, check transfer
pressure during cranking. Housing
pressure should be a m inim um of 2 psi
less than transfer pressure which
should be at least 10 psi. Also check
the transfer pump pressure at idle,
should be approxim ately 30 psi. If
incorrect, remove pump from engine
and have the calibration checked by an
authorized repair agency. Particular
attention should be paid to cranking
delivery and transfer pressure at
cranking speed.
p. Nozzle M alfunction
Remove nozzles from engine and
check on nozzle tester according to
m anufacturers’ instructions.
q. Air In Fuel Supply Lines
Connect a known good hose to a
container of known good fuel, if engine
starts, locate source of air leak in
supply lines. See “ checking for air
leaks” , page 7-38).
a. Oil Cooler or Oil or Cooler
Line Restricted
Remove restrictions in cooler or cooler
line.
b. Oil Pump Pressure Low
See oil pump repair procedures in the
Service Manual.
_ ____________
7-5
_____________ J
7. Diagnosis
CONDITION
Engine W ill Not Shut
Off W ith Key
NOTE: With Engine at
Idle, Pinch the Fuel
Return Line at the
Flexible Hose to Shut
Off Engine.
POSSIBLE CAUSE
CORRECTION
a. Injection Pump Fuel
Solenoid Does Not Return
Metering Valve to “ O FF”
Position
Refer to ELECTRICAL DIAGNOSIS in
the Service Manual.
b. Disconnect Pink Wire at
Solenoid, if Engine Now
Shuts Off
Refer to ELECTRICAL DIAGNOSIS in
the Service Manual.
c. An Electrical Feedback
Signal From the
Generator.
1. 1983 G-Van w ithout gages use a
jum per wire pin 12038051. This wire
incorporates a diode which prevents
feedback.
2. Disconnect the negative battery
cable from both batteries.
3. Remove the engine harness
bulkhead connector.
4. Looking into the term inal end of the
bulkhead connector, locate the #25
circuit (brown wire) and remove it.
5. Insert the end of the jum per harness
into the bulkhead connector.
6. Using the supplied connector,
connect the other end of the #25
circuit (brown wire) to the jum per
harness.
7. Attach the bulkhead connector.
8. Reconnect both negative battery
cables.
Engine Starts But W ill
Not Continue to Run at
Idle and Stalls
d. If the Engine Still Does
Not Shut Off
Remove injection pump for repair.
a. Slow Idle Incorrectly
Adjusted
Adjust idle screw to specification.
b. Fast Idle Solenoid
Inoperative
W ith engine cold, start engine;
solenoid should move to hold injection
pump lever in “ fast idle position” . If
solenoid does not move, refer to
ELECTRICAL DIAGNOSIS in the
Service Manual.
7-6
7. Diagnosis
CONDITION
Engine Starts But W ill
Not Continue to Run at
Idle and Stalls (Cont’d)
POSSIBLE CAUSE
c. Restricted Fuel Return
System
CORRECTION
Disconnect fuel return line at injection
pump and route hose to a metal
container. Connect a hose to the
injection pump connection; route it to
the metal container. Crank the engine
and allow it to idle. If engine idles
normally, correct restriction in fuel
return lines. If engine does not idle
normally, remove the return line check
valve fitting from the top of the pump
and make sure it is not plugged.
NOTE: If the fitting is plugged and/or
small black particles are visible in the
pump, a governor weight retainer flex
may be at fault. See Section 4B
7-7
d. Glow Plugs Turn Off Too
Soon
Refer to Section 6.
e. Pump Tim ing Incorrect
Make certain that tim ing mark on
injection pump is aligned with mark on
adapter or front cover.
f. Limited Fuel to Injection
Pump (Fuel Supply)
Test the engine fuel pump; check fuel
lines. Replace or repair as necessary.
g. Incorrect or Contaminated
Fuel
Flush fuel system and install correct
fuel.
h. Low Compression
Check compression to determine
cause.
i. Fuel Solenoid Closes in
Run Position
Ignition switch out of adjustment. If
OK, refer to ELECTRONIC DIAGNOSIS
in Service Manual.
j. Injection Pump
M alfunction
Remove injection pump for repair.
k. Incorrect or Poor Quality
Fuel
Replace with correct fuel. To verify
suspected poor quality fuel, connect a
hose to the inlet of the fuel supply
pump and route to a container filled
with known good quality fuel. Start and
run engine. If performance of engine
improves, drain and flush system of
poor fuel and replace w ith correct fuel.
7. Diagnosis
CONDITION
POSSIBLE CAUSE
CORRECTION
Engine Starts But W ill
Not Continue to Run at
Idle and Stalls (Cont’d)
1. Air in Fuel
Check for presence of air by
disconnecting fuel return line from top
of pump and connecting a clear hose
to return fitting. Route hose to a metal
container. Start engine and allow to
idle. W atch return fuel for air bubbles.
If bubbles are present, locate source of
air leak in fuel supply system and
correct. If stalling occurs only on cold
engine start up, check for fuel leaking
backwards, or air leaking into the fuel
supply lines. See page 7-38 for
“ Checking for Air Leaks” . Pin hole in
tank sending unit.
Engine Stalls Under
Deceleration or Heavy
Braking
a. Idle Speed Too Low
Adjust to specification and also check
and adjust fast idle solenoid.
b. Governor W eight Retainer
Ring Fault.
Remove governor cover and check for
small black particles. If they are
present, a governor weight retainer flex
ring may be at fault.
c. Binding Condition
Between Min-Max Block
and Throttle Shaft
To check for binding between min-max
block and throttle shaft, remove
governor cover, place throttle in low
idle position and slide min-max
governor back and forth on guide stud.
Assem bly should move freely w ithout
binding.
d. Sticky Metering Valve or
Linkage in Injection Pump
Remove pump from engine, mount on
test bench and check calibration
paying particular attention to low idle
settings and action of governor around
low idle speed. Repair or replace
metering valve or other governor
com ponents as necessary (See
appendix 5).
a. Torque Converter Clutch
Engages Too Soon
See Section 7A, of the Service Manual
“ Torque Converter Clutch Diagnosis” .
b. Tim ing Retarded
Be sure tim ing mark on injection pump
is aligned w ith mark on adapter or
front cover.
Excessive Surge at
Light Throttle, Under
Load
NOTE: If Engine Has a
Rough Idle
7-8
7. Diagnosis
CONDITION
Excessive Surge at
Light Throttle, Under
Load (Cont’d)
Engine Starts, Idles
Rough, WITHOUT
Abnormal Noise or
Smoke (Fully Warmed
Up Engine)
POSSIBLE CAUSE
CORRECTION
c. Clogged Fuel Filter
Check fuel pump pressure on inlet and
outlet sides of filter, 5.5-6.5 psi.
d. Injection Pump Housing
Pressure Too High
1. Repair return line restriction.
2. Replace back leak connector.
e. Injection Line Volume Too
Low
Replace affected line(s).
f. Low Opening Pressure
Nozzle
Replace nozzle.
a. Slow Idle Incorrectly
Adjusted
Adjust slow idle screw to specification.
b. Injection Line Leaks
W ipe off injection lines and
connections. Run engine and check for
leaks. Correct leaks.
c. Restricted Fuel Return
Systems
Disconnect fuel return line at injection
pump and route hose to a metal
container. Connect a hose to the
injection pump connection; route it to
the metal container. Start the engine
and allow it to idle; if engine idles
normally, correct restriction to fuel
return lines. If engine does not idle
normally, remove the return line check
valve fitting from the top of the pump
and make sure it is not plugged.
d. Air in System
Install a section of clear plastic tubing
on the fuel return fitting from the
engine. Evidence of bubbles in fuel
when cranking or running indicates the
presence of an air leak in the suction
fuel line. Locate and correct. If foam or
bubbles are present, proceed as
follows:
1. Raise vehicle and disconnect both
fuel lines at the tank unit.
2. Plug the sm aller disconnected return
line.
3. Attach a low pressure (preferably
hand operated pump) air pressure
source to the larger 3/8 fuel hose
and apply 8-12 psi.
4. Observe the pressure pump reading
of 8-10 psi. A decrease in pressure
will push fuel out at the leak point
indicating the location of the leak.
7-9
7. Diagnosis
CONDITION
Fully Warmed Up
Engine Idles Rough in
Neutral and/or Drive
(Cont’d)
POSSIBLE CAUSE
CORRECTION
d. Air in System (Cont’d)
5. Repair as necessary. In checking for
air comments, the proper size
clam ps on all hoses should be
checked. Also, a burr on the edge of
a pipe could rip the inside of a line
and create air ingestion. Particular
attention should be given to
improper installation or defective
auxiliary filters or water separators.
e. Incorrect or Contaminated
Fuel
Flush fuel system and install correct
fuel.
f. Nozzle(s) M alfunction
Perform glow plug resistance test (in
this section), or crack open the nozzle
inlet fitting, to locate the missing
cylinder.
g. Incorrect Timing
1. Check housing pressure and supply
pressure. If housing pressure is
higher than 12 psi or supply
pressure is lower than 5 psi, the
injection pump advance mechanism
may be too far retarded. Replace
fuel filters, supply pump, or clear
return line restriction as necessary
to correct.
NOTE: Retarded timing will
cause white smoke. Advanced
timing will cause black smoke.
2. Check tim ing.
3. If pump is equipped with
mechanical light load advance,
check for sticky or stuck advance
mechanism (internal timing) by
depressing the rocker level on the
side of the injection pump while
the engine is idling. If the engine
sound does not change, the pump
should be removed and sent to an
authorized agency for repairs.
h. Governor W eight Retainer
Flex Ring Fault
Remove governor cover and check for
small black particles. If they are
present a governor w eight retainer flex
ring may be at fault. See Section 4B.
i. Low or Uneven Engine
Compression
Check compression according to
engine manual. GM diesel engines
should have compression in each
cylinder of at least 380 psi, and the
lowest cylinder reading should not be
less than 80% of the highest cylinder
reading.
7-10
7. Diagnosis
CONDITION
POSSIBLE CAUSE
CORRECTION
Fully Warmed Up
Engine Idles Rough in
Neutral and/or Drive
(Cont’d)
j. Internal Injection Pump
Fault
Remove pump from engine and have
calibration checked by an authorized
agency.
Cold Engine Idles
Rough A fter Start-up
But Sm ooths Out as it
W arms Up. (This
Problem is Often
Accom panied by W hite
Exhaust Smoke)
a. Incorrect Starting
Procedure
See section 1 or owners manual for
starting procedure.
b. Fast Idle Solenoid
Inoperative or Set
Incorrectly
Test and re-set according to engine
manual or vehicle em issions sticker.
c. Air in Fuel
See page 7-38 “ Checking For Air
Leaks” .
d. One or More Glow Plugs
Inoperative
Perform glow plug system diagnosis,
Section 6.
e. Injection pump tim ing to
engine.
Check alignm ent of tim ing mark on
pump with the engine front cover.
f. Insufficient engine breakin time.
Break-in engine 2,000 or more miles.
g. Incorrect Internal Timing
1. Autom atic Advance Fault
The pump is equipped with
mechanical light load advance,
check for stuck or sticky advance
mechanism by depressing the rocker
lever on the side of the pump while
the engine is idling. If the engine
sound doesn’t change, the pump
should be removed and sent to an
authorized agency for repairs.
2. Housing Pressure Cold Advance
M alfunction
Check pump housing pressure.
Pressure should be 0-1 psi when the
engine is cold and 8-12 psi when the
engine is fully warmed up.
h. Nozzle Valve(s) Sticking
Open (Usually
Accom panied by
Knocking Sound)
7-11
Remove nozzles from engine and repair
or replace as necessary.
7. Diagnosis
CONDITION
POSSIBLE CAUSE
Engine M isfires Above
idle or Runs Rough
W hile Driving But Idles
OK (“ C huggle” in
Vehicles Equipped with
a Transm ission
Converter Clutch (TCC).
a. Incorrect Pump to Engine
Timing
Check and adjust tim ing to
specifications.
b. Air in Fuel
Check for presence of air by
disconnecting fuel return line from top
of pump and connecting a clear hose
to return fitting. Route hose to a metal
container. Start engine and allow to
idle. W atch return fuel for air bubbles.
If bubbles are present, locate source of
air leak in fuel supply system and
correct.
c. Fuel Return System
Restricted
Measure pump housing pressure at
idle speed. Pressure should be 12 psi
maximum. If pressure is greater than
12 psi, correct restriction in fuel return
system.
d. Fuel Supply Restriction
Test fuel supply pump and check fuel
filter for plugged condition.
e. Incorrect or Contam inated
Fuel
Flush fuel system and install correct
fuel.
Poor Fuel Economy
a. See page 7-24
See page 7-24
Noticeable Loss of
Power
a. Restricted A ir Intake
Check air cleaner element.
b. Tim ing Set to
Specifications
Be sure tim ing mark on injection pump
is aligned with mark on adapter or
front cover.
c. EGR or EPR M alfunction
Refer to Emissions Diagnosis,
Section 5.
d. Restricted or Damaged
Exhaust System
Check system and replace as
necessary.
e. Plugged Fuel Filter
Replace filter.
f. Plugged Fuel Tank
Vacuum Vent in Fuel Cap
Remove fuel cap. If loud “ hissing”
noise is heard, vacuum vent in fuel cap
is plugged. Replace cap (Slight hissing
sound is normal).
CORRECTION
7-12
7. Diagnosis
CONDITION
Noticeable Loss of
Power (Cont’d)
CORRECTION
g. Restricted Fuel Supply
From Fuel Tank to
Injection Pump
Examine fuel supply system to
determine cause of restriction. Repair
as required.
h. Restricted Fuel Tank
Filter
Remove fuel tank and check filter.
(Filter for diesel fuel is blue.)
i. Pinched or Otherwise
Restricted Return System
Examine system for restriction and
correct as required.
j. Incorrect or Contaminated
Fuel
Flush fuel system and install correct
fuel.
k. External Compression
Leaks
Check for compression leaks at all
nozzles and glow plugs, using “ LeakTec” or equivalent. If leak is found,
tighten nozzle or glow plug.
I. Plugged Nozzle(s)
Remove nozzles. Have them checked
for plugging and repair, replace or
clean (where applicable) as necessary.
m .Low Compression
Check compression to determine
cause
n. Transm ission Fault
See Section 7A of the Sen/ice Manual.
Engine Stalls on
Deceleration or Stalls
at Idle
a. Sticking Metering Valve
Remove metering valve. Clean with 400
or 500 sandpaper. W et sandpaper with
diesel fuel and turn the metering valve
in the wet paper no more than 5-6
turns.
Engine W ill Not Return
to Idle
a. External Linkage Binding
or Mi sad justed
Free up linkage. Adjust or replace as
required.
b. Fast Idle M alfunction
Check fast idle adjustment.
c. Internal Injection Pump
M alfunction
Remove injection pump for repair.
a. Loose or Broken Fuel
Line or Connection
Examine com plete fuel system,
including tank, lines, and injection
lines. Determine source and cause of
leak and repair.
b. Injection Pump Internal
Seal Leak
Remove injection pump for repair.
Fuel Leaks on Ground
— No Engine
M alfunction
7-13
POSSIBLE CAUSE
7. Diagnosis
CONDITION
POSSIBLE CAUSE
CORRECTION
N oise— “ Rap” From
One or More Cylinders
(Sounds Like Rod
Bearing Knock)
a. Nozzle(s) Sticking Open or
W ith Very Low Nozzle
Opening Pressure
Remove nozzle for test and replace or
clean (where applicable) as necessary.
b. M echanical Problem
Refer to Mechanical Diagnosis.
c. Piston H itting Cylinder
Head
Replace m alfunctioning parts. Be sure
tim ing mark on injection pump is
aligned w ith mark on front housing.
Break in engine 2000 miles.
N oise— Objectionable
a. Tim ing Not Set to
Specification
Make certain that tim ing mark on
injection pump is aligned w ith mark on
front housing.
Noise Over Normal
Noise Level High
Excessive Black Smoke
a. EGR M alfunction
Refer to the Emission Section 5.
b. Injection Pump Housing
Pressure Out of
S pecifications
Check housing pressure as described
in this section.
c. Injection Pump Internal
Problem
Remove injection pump for repair.
Engine Noise Internal
or External
a. Engine Fuel Pump,
Generator, Water Pump,
Valve Train, Vacuum
Pump, Bearings, Etc.
Repair or replace as necessary. If noise
is internal, see Diagnosis For Noise —
Rap From One or More Cylinders and
Engine Starts and Idles Rough W ith
Excessive Noise and/or Smoke.
Engine Overheats
a. Coolant System Leak, Oil
Cooler System Leak or
Coolant Recovery System
Not Operating
Check for leaks and correct as
required. Check coolant recover jar,
hose and radiator cap.
b. Belt Slipping or Damaged
Replace or adjust as required.
c. Therm ostat Stuck Closed
Check and replace if required.
d. Head Gasket Leaking
Check and repair as required.
Poor Performance
Extended Hot Crank
Time No W.O.T. Upshift
a. King in the Fuel Supply
Hose Between the Fuel
Tank and Body
Shorten the fuel supply hose at the
kinked area.
Excessive Engine
Blowby
a. Bent Upper Compression
Ring
Check compression. If about 100 psi
low, change the piston rings.
...... ..............................
_... _
...... !
7-14
7. Diagnosis
General Diagnosis Conditions
DIESEL STARTING
It must be remembered that diesels need three ingredients to start — air, fuel, and heat. If the valves open, the
engine should have air. The best method to check for fuel is to pull a glow plug, crank the engine and look for fuel
vapors. Heat is furnished by the glow plugs and the heat of com pression by cranking.
DIESEL COMPRESSION LEAK
Some diesel engine equipped vehicles may exhibit an inadequate am ount of passenger com partm ent heat. If you
experience inadequate heat at idle, the cause may be a compression leak to the cooling system. Examine the
coolant recovery tank to see if bubbles are evident with the engine running. If bubbles are evident, the cause may
be a head gasket leak. To determine w hich head gasket is leaking, remove the water pump belts and the water
outlet and therm ostat. Run the engine and observe which side of the engine bubbles are com ing from.
DIESEL ENGINE KNOCK
Diesel engine knock may be caused by a piston. The piston knock sounds very sim ilar to com bustion knock.
To assist in the diagnosis, w ith the engine off, retard the injection pump tim ing as far as the slot in the pump
flange w ill allow. This w ill quiet down a com bustion knock. If the knocking is not substantially reduced, the noise is
most likely a mechanical problem. Crank the fuel injection lines one by one to identify the cylinder with the knock.
The knock tone w ill change when the line is cracked feeding the cylinder with the problem.
Smoke Diagnosis Principles
Three different types of smoke w ill be reviewed in this section. Black, white and blue.
BLACK SMOKE
Black smoke is the m ost com m on smoking com plaint. Diesels are usually rated according to the maximum
horsepower developed at the “ smoke lim it.” A t a certain speed, a definite amount of air enters the cylinder. This
am ount of air is sufficient to produce com plete com bustion of a given quantity of fuel. If more fuel is injected,
overloading the engine beyond the rated horsepower, there will not be sufficient air for com plete com bustion and
black sm oke w ill result. Under these conditions, the black smoke contains a large quantity of unburned carbon
(soot) formed by thermal decom position of the fuel in the over-rich mixture in the cylinder.
The injection pump is incapable of delivering rich or lean mixtures. Therefore any variable that increases fuel or
reduces the am ount of air taken into the cylinder w ill increase the tendency to produce black exhaust smoke.
Some sources of black smoke directly related to improper burning of fuel are:
• A ir into injection pump
• Fuel return restricted (both of the above w ill change autom atic advance; EPR 1981 only)
• Pump tim ing advanced (usually w ill be accompanied by excess com bustion noise)
• Wrong fuel
• Excess fuel delivery from nozzles due to low opening pressure or stuck nozzle
• Less than 5 1/2 lbs of fuel pump pressure
Although not directly fuel related some indirectly related sources of black smoke are:
• EGR stuck open (at w.o.t. only)
• Restricted exhaust
• Low com pression
• Clogged air inlet
• Missing prechamber (causes black smoke when hot and white smoke when cold)
7-15
7. Diagnosis
Presence of prechamber can be checked externally. To check, remove glow plug and insert a probe into the
prechamber. If more than 3%"-2%" of the probe can be inserted, prechamber is missing.
The fuel variables that can affect black smoke are gravity (an indirect measure of heating value); viscosity, and
cetane number. An engine may smoke when a fuel of lower gravity is used. This is an overfueling problem that
occurs because injectors meter fuel on a volume basis and low gravity fuels have more Btu’s per gallon, and
therefore, less fuel is required for equal power, equal air utilization, and equal smoke.
Increasing viscosity can also cause overfueling by reducing the leakage in the injection pump, thus allowing more
fuel to be injected into the cylinder.
In engines w hich are sensitive to cetane number, the tendency toward black smoke is greater as cetane number
increases. The short delay period of a high cetane number fuel assures that some raw fuel is sprayed into an
established flam e where the atmosphere is too lean for com plete com bustion.
W H IT E S M O K E
At light loads, the average tem perature in the com bustion chamber may drop 500 degrees due to the decreased
am ount of fuel being burned. As a result of the lower temperature, the fuel ignites so late that com bustion is
incom plete at the tim e the exhaust valve opens and fuel goes into the exhaust in an unburned or partially burned
condition producing the w hite smoke. Under these conditions, a higher cetane fuel or a more volatile fuel w ill tend
to promote better com bustion and reduce smoke. Any operating variable (jacket temperature, inlet air temperature,
etc.) that increases com pression temperature or reduces ignition delay w ill improve the white smoke problem.
W hite smoke is considered normal when the car is first started but should stop as the car warms up. A continuing
white sm oke condition could indicate a loss of compression. Retarded tim ing and plugged fuel return can cause
white smoke.
BLUE S M O K E
Blue smoke indicates that engine oil is burning in the cylinders and may be accom panied by excessive oil
consum ption.
Some m echanical conditions w hich should be considered are:
• Stuck piston rings
• Worn piston rings
• Failed valve seals
• Faulty crankcase vent valve
Some non-mechanical checks w ould include:
• Lube oil level too high
• Fuel oil in crankcase
• Wrong dipstick
7-16
7. Diagnosis
Black Smoke Diagnosis Chart
CONDITION
Excessive Black Smoke
.
7-17
POSSIBLE CAUSE
CORRECTION
a. Air Inlet Restriction
Replace air filter element.
b. EGR or EPR Valve
M alfunction
Refer to Section 5 for diagnosis.
c. Advanced Timing
Check tim ing marks and correct as
necessary.
d. Nozzle M alfunction
Check function of injection nozzles on
nozzle tester according to
m anufacturers’ instructions.
e. Engine Mechanical
Problem Resulting in Air
Inlet Restriction or Low
Compression
Check for carbon buildup in intake
m anifold or valve train wear which
would cause air inlet restriction. Check
engine compression. The 6.2L diesel
engine should have compression in
each cylinder of at least 380 psi, and
the lowest cylinder reading should not
be less than 80% of the highest
cylinder reading.
7. Diagnosis
White Smoke Diagnosis Chart
CONDITION
W hite Smoke During
Cold W eather Starting
POSSIBLE CAUSE
CORRECTION
a. Increased Operating
Noise and Light W hite
Smoke
This is normal.
b. Incorrect Starting
Procedure, Pumping the
Accelerator
Consult Owners Manual, for correct
starting procedure.
c. Glow Plugs Not On Long
Enough
Check Glow Plug Diagnosis in
Section 6.
d. H.P.C.A. Inoperative
1. Check for current at the H.P.C.A.
terminal on the right side of the
injection pump, when engine
temperature is less than 115°F
(1982) 95 °F on 1983’s and later. If
there is no current, determine the
cause and correct.
2. If current is available at the H.P.C.A.
terminal, remove the governor cover
and connect a feed wire to H.P.C.A.
terminal and ground governor cover,
the H.P.C.A. solenoid should
activate. If it does not, replace
H.P.C.A. solenoid.
W hite Smoke on Start
Up
e. Tim ing Incorrect
Time engine to specification, (see
Section 4).
a. Sticking Advance Piston
1. Hook up a dynam ic tim ing meter.
Push in on the bottom of the face
cam rocker lever on the right side of
the pump. This w ill retard the tim ing
and cause the engine to run rough,
if the advance piston is free.
2. If there is no change, the piston is
sticking, polish the piston to correct.
b. Low Compression
Check compression, repair as
necessary. The 6.2L diesel engine
should have compression in each
cylinder of at least 380 psi, and the
lowest cylinder reading should not be
less than 80% of the highest cylinder
reading.
c. Retarded Pump to Engine
Tim ing
Time engine to specifications, see
Section 4.
7-18
7. Diagnosis
Rough Idle Diagnosis
Rough idle is caused by variable power output between cylinders as they fire in sequence. The following can cause
variable fuel flow to each cylinder and, therefore, its relative power output.
• A ir in fuel system
• Nozzle opening pressure
• Nozzle tip leakage (seat tightness)
• Injection line volum e and internal diameter
• Line fitting leakage — norm ally this engine uses approximately .3 gal per hour at idle, and considering one wet
nozzle out of eight cylinders, the amount of fuel being consumed is so small that even a damp, not yet dripping
nozzle fitting can cause that cylinder not to fire
• Injection pump output
• Injection pump low speed governor sensitivity
1S82-83 6.2L DIESEL
A rough idle condition may be caused by a damaged injection pump drive shaft retaining ring.
If the ring is bent rearward, the governor arm can contact the ring. This affects governor control of fueling at idle,
causing a rough idle.
The retaining ring can be damaged during m anufacture or repair. It is used to retain the pump drive shaft.
If a vehicle is received w ith a rough, idle condition, use the following steps:
STEP 1 Request the date condition first appeared.
A. If since new, the retaining ring may be the cause.
B. If after pump removal or repair, the ring may be the cause.
C. If neither A nor B, then the ring is not likely the cause of rough idle.
STEP 2 If 1A or 1B does apply, and the condition is only a rough idle, with sm ooth operation above a 1,000 RPM,
proceed to Step 3.
STEP 3 Remove the injection pump governor cover.
STEP 4 Using a flashlight, look between the forward edge of the housing and the governor. The main shaft w ill be
visible below the governor. Where the main shaft enters the forward edge of the housing, a snap-ring
should be visible. The use of a mirror may help to get a better view. Refer to Figure 7-2.
STEP 5 If the snap ring appears to be bent out of the shaft groove rearwards towards the governor, the ring must
be replaced.
STEP 6 To replace the snap ring the injection pump must be removed and should be repaired at an authorized
pump repair facility.
STEP 7 If the ring is not bent, the rough idle is due to some other cause such as a fuel line air leak, tim ing, etc.
7-19
7. Diagnosis
VIEW
TOP VIEW OF PUMP WITH HOUSING COVER REMOVED
CROSS SECTION VIEW OF INJECTION PUMP
Figure 7-2, Diesel Injection Pump.
D IA G N O S IS PR O C ED U R E, R O U G H IDLE
See Figure 7-3.
7-20
7. Diagnosis
DIESEL ENGINE IDLE ROUGHNESS DIAGNOSIS PROCEDURE
CONDITION
CONDITION
IDLE ROUGHNESS
COAST DOWN ROUGHNESS
Idle roughness is defined as an uneven shaking of
the engine in com parison to others w ith the same
number of cylinders and in the same body style.
A condition may exist where a roughness is
observed on coast down at 50 mph or less w ith a
closed throttle.
A rough idle condition may be caused by a
difference in the output between cylinders on diesel
engines. By selection of parts it is possible to alter
the output between cylinders, and smooth out the
idle quality.
CORRECTION
Confirm that this condition is engine roughness
rather than a tire waddle or a bent wheel by
coasting down through the roughness period in
neutral with the engine at 1500 to 2000 RPM. If
roughness still exists, during the coast down, the
condition is not caused by engine roughness. If the
roughness condition is gone, follow the idle
roughness diagnosis procedure. If not corrected
prior to the glow plug resistance procedure, correct
the roughness using the glow plug resistance
procedures.
CORRECTION
Follow the diesel engine idle roughness diagnosis
procedure. Make all necessary adjustm ents and
corrections. The idle roughness procedure must be
followed step by step prior to performing the glow
plug resistance check. The glow plug resistance
check will only be successful after the idle
roughness procedure is performed and corrections
made.
Diesel engine roughness at idle
On new vehicles — vehicle should have V* tank fuel and it may
be necessary to run engine at high rpm to purge air from system
Remove air cleaner, install intake or crossover cover
Install Mag-Tach J-26925 — check idle speed (slow and fast)
Idle speeds OK
Idle speed incorrect
I
Set idle to specification
I
Make certain that timing mark on injection pump
is aligned with mark on front cover.
(if available or applicable)
Timing OK
Timing off
I
Reset timing
Continue on next page
*
Figure 7-3, Diesel Engine Idle Roughness Diagnosis Procedure.
7-21
7. Diagnosis
Disconnect vacuum hose from vacuum pump — check idle quality
Idle improves
No improvement
Reinstall vacuum hose to pump. Loosen vacuum pump hold down clamp. Rotate pump in engine.
If idle improves, clamp in that position. If idle does not improve, remove vacuum pump and
reinstall with drive gear in different relationship to camshaft.
Examine nozzles for leaks at nozzle body
or at fuel line connection (engine running)
Leaks
No leaks
I
Correct
Check for leak at injection pump to high pressure lines
I
Leaks
No leaks
I
Correct
Check for fuel pressure by cracking line at
fitting between fuel filter and injection pump
Pressure evident
No pressure evident
Determine cause of lack
of/or low pressure
Remove fuel return line from top of pump. Install short pieces of clear plastic tube between return
line and check for presence of bubbles or foam in tube
________________________________ I________________________________ _
No bubbles or foam
Bubbles evident
Find cause in fuel supply
"Loosen the line at the nozzles to bleed a small amount of fuel from the line. If solid fuel
appears, go on to the next nozzle. If foam appears, shut the engine off and disconnect the line
from the nozzle. Move the line so the inlet to the nozzle can be observed. Remove the pink wire
to the pump and crank the engine and observe the nozzle inlet for bubbles. If bubbles are
evident, replace the nozzle. Squirt some oil or fuel in the new nozzle inlet and recheck for
bubbles. If bubbles are not evident, reconnect the line and pink wire, and go on to the next
nozzle and repeat the process. Check the removed nozzle on a tester to determine if it is
inoperative or if it is incompatible with the cylinder head.
If an objectionable rough idle condition still exists, proceed using glow plug resistance
check to correct rough idle
Figure 7-3, (Cont’d.) Diesel Engine Roughness Diagnosis Procedure.
7-22
7. Diagnosis
Glow Plug Resistance Procedure
To determine glow plug resistance, use the follow ing steps:
STEP
1 Use the Kent-Moore High Impedence Digital M ultim eter (Essential Tool J-29125A, J-34520 or J-34029) for
measurements.
If another ohm m eter is used, different values will result. This does not mean that another ohm meter is not
accurate for measuring resistors or solenoids. Glow plugs can be individually probed, or a Cylinder
Balance Tester (J-34116) can be used w ith the Digital M ultim eter to select cylinders.
STEP
2 Select scales as follows: On K-M Tool J-29125A, LH Switch to “ OHMS,” RH Switch to full counter­
clockwise, “ 200 Ohm s,” Slide Center Switch to the left “ DC.LO.” On J-34520 or J-34029, select 200 “ OHS.”
STEP
3 Start engine, turn on heater and allow engine to warm up. REMOVE all the feed wires from the glow plugs.
STEP
4 Disconnect the generator tw o lead connector.
STEP
5 Using a tachometer, adjust engine speed by turning the idle speed screw on the side of the injection pump
to the w orst engine idle roughness, but do not exceed 900 rpm.
STEP
6 A llow engine to run at worse idle speed for at least one minute. The therm ostat m ust be open and the
upper radiator hose hot.
STEP
7 A ttach an alligator clip to the black test lead of the multimeter. THIS CLIP MUST BE GROUNDED TO THE
FAST IDLE SOLENOID. It must remain grounded to this point until all tests are complete.
STEP
8 On a separate sheet of plain w riting paper, write down the engine firing order. The 6.2L engine’s firing order
is 1-8-7-2-6-5-4-3.
STEP
9 W ith engine still idling, probe each glow plug terminal and record the resistance values on each cylinder in
firing sequence. Most readings w ill be between 1.9 and 3.9 Ohms. If these readings are not obtained, turn
engine “ OFF” for several m inutes and recheck the glow plugs. The resistance should be .5 to 1.6 Ohms.
(Ohm readings depend on method used to check glow plug resistance.) If this reading is not obtained,
check meter for correct settings, check for low or incorrect battery in meter, and check the meter ground
wire to the engine.
If the vehicle is equipped with an electric cooling fan, record the resistance values w ith the cooling fan not
running. Do not disconnect the cooling fan electrically.
The resistance values are dependent on the temperature in each cylinder, and therefore indicate the output
of each cylinder.
STEP 10 If an Ohm reading on any cylinder is between .5 and 1.6 Ohms (Ohm readings obtained depend on the
method used to check glow plug resistance), check to see if there is an engine mechanical problem. Make
a com pression check of the low reading cylinder and the cylinders which fire before and after the low
cylinder reading. Correct the cause of the low com pression before proceeding to the fuel system.
STEP 11 If the engine m isfires erratically, install the glow plug lum inosity probe that is included w ith the Diesel
Tim ing Meter (J33300-100, J33075, or equivalent) into the cylinder with the lowest resistance reading.
Observe the com bustion light flashes. They w ill be erratic in tim e with the misfire that is felt. If it is not,
move the probe to the next highest reading cylinder until the m alfunctioning cylinder is found.
STEP 12 Examine the results of all cylinder glow plug resistance readings, looking for differences between
cylinders. Normally, rough engines w ill have a difference of .4 Ohms or more between cylinders in firing
order. It w ill be necessary to raise or lower the reading on one or more of these cylinders by selection of
nozzles.
A nozzle w ith a tip leak can allow more fuel than normal into the cylinder, which w ill raise the glow plug
Ohm reading. This w ill rob fuel from the next nozzle in the firing sequence and w ill result in that glow plug
having a low Ohm reading. If this is encountered, it is advisable to remove and check the nozzle with a
high reading. If it is leaking, it could be causing the rough idle. Plugged nozzle(s) w ill be indicated by low
glow plug resistance readings.
Some glow plugs have been found w hich do not increase in resistance with heat. If you experience low
readings on a glow plug and it does not change with nozzle change, then switch glow plugs between a
good and bad cylinder. If the reading of each cylinder is not the same as before the switch, then the glow
plug cannot be used for rough idle diagnosis, although it w ill function for starting the vehicle.
7-23
7. Diagnosis
STEP 13 Remove the nozzles from the cylinders in w hich you wish to raise or lower the Ohm reading. Determine
the pop off pressure of the nozzles as well as checking the nozzle for leakage and chatter. (Refer to
Testing of Nozzles Section of Service Manual.)
• Install nozzles w ith a high pop off pressure to lower the Ohm reading, and nozzles with lower pop off
pressure to raise an Ohm reading. Normally, a change of about 30 psi in pressure will change the
reading by about .1 Ohm. Nozzles norm ally w ill drop off in pop off pressure w ith miles. Use nozzles from
parts stock or a new vehicle. Use broken-in nozzles on a vehicle with 1500 or more miles, if possible.
• Whenever a nozzle is cleaned or replaced, before installing the injection pipe, crank the engine and
watch for air bubbles at the nozzle inlet. If bubbles are present, clean or replace the nozzle.
• Install the injection pipe, restart engine, and check idle quality. If idle is still not acceptable, recheck
glow plug resistance of each cylinder in firing order sequence. Record readings.
• Examine all glow plug resistance readings looking for differences of .4 Ohm s or more between cylinders.
It w ill be necessary to raise or lower the reading on one or more of these cylinders as previously done.
• A fter making additional nozzle changes again check idle quality. Normally, after com pleting tw o series of
resistance checks and nozzle changes, idle quality can be restored to an acceptable level.
STEP 14 An injection pump change may be necessary if the follow ing occurs:
A. If the problem cylinder moves from cylinder to cylinder as changes in nozzles are made.
B. If cylinder Ohm readings do not change when nozzles are changed.
- NOTE —
It is important to always recheck the cylinders at the same RPM. Sometimes the cylinder
readings do not indicate that an improvement has been made although the engine
may in fact idle better.
Rough Idle/Performance Diagnosis Conditions
- note An intermittent miss at idle may not show up on the glow plug resistance test. To correct,
first find the cylinder that is not firing by moving the timing meter glow plug probe cylinder
to cylinder and observing the flash (wear safety glasses when watching the probe.) When
the miss is located, remove the nozzle in that cylinder and the prior cylinder in the firing
order. Use a lower opening pressure nozzle in the cylinder with the miss and/or a
higher opening nozzle in the other cylinder. This will increase the fuel flow to the
cylinder that has the miss.
M.P.G. Diagnosis Principles
The diesel, like any engine, is affected by driving habits. Speed is more critical on a diesel than a gas engine. On
the highway, in the 50-75 mph range, the fuel economy w ill go down about 3 mpg for each 10 mph increase in
speed. A gasoline engine will lose about 1V2 mpg for each 10 mph increase in speed. This condition is perhaps the
most significant factor in obtaining good fuel economy. Fuel economy may vary as much as 5 mpg in a given
vehicle w ith different drivers. M.RG. will increase with use of a steady foot, easy acceleration and light braking.
Most drivers are unaware of their “ jerky” driving habits. If the owner either traded in or still has a higher
performance vehicle, it may be a case of driving the diesel excessively hard trying to match this performance, but
at the same tim e reducing fuel economy.
The type and condition of a trade-in, if there was one, could be a clue to the owner’s driving habits. Another
indication which would be revealing would be a road test with the owner driving. Since most owners are unaware of
7-24
■" ■
7. Diagnosis
their habits, it may be valuable to observe if the accelerator pedal is “ pum ped” excessively. Stop and go driving
uses more fuel and hilly terrain will call for more accelerations, using more fuel.
Mechanical conditions of the vehicle, both engine related and non-engine related, also affect mpg. In diagnosing
poor fuel econom y com plaints, first determine if other conditions such as excessive smoke or poor performance or
unusual noises are also present.
N O N -E N G IN E RELATED C O N D IT IO N S
Some non-engine related items which play an important part in the fuel economy process are:
• Tires and inflation pressure — snow tires, radial types included, will drop fuel mileage by nearly two miles per
gallon. Standard inch size tires used in place of metric size tires can generate as high as a 6% error in
speedometer readings.
• Speedometer error
• Axle ratio
• Transmission m alfunctions
• Weather — cold weather and increased viscosity of all lubricants in the power train (especially wheel bearing
grease), stiffer tires, and driving through snow, slush, and ice require more power with a corresponding decrease
in mileage.
E N G IN E -R E L A T E D C O N D IT IO N S
Some engine related items which should be understood are:
• Check pump tim ing.
• Engine com pression — heat of compression is essential.
• Missing or improperly installed prechambers can result in poor combustion.
• Non-functioning glow plugs will result in poor com bustion during engine warm-up.
• A plugged air cleaner element or restrictions in the air intake system will cause a richer running condition.
• Plugged exhaust.
• Worn cam shaft or lifter will impair engine breathing.
• Therm ostatic fan — If the viscous drive in the therm ostatic fan fails or locks up, the fan will be forced to operate
at constant engine speed and will produce a very significant drop in mileage. M alfunction is easily recognized by
continuous roar from the engine cooling fan.
FUEL S Y STE M RELATED C O N D IT IO N S
Some fuel related items are:
• Fuel type and quality — The heating value of No. 1 Diesel fuel is about 5% less than No. 2 diesel fuel. Gasoline
mixed w ith diesel fuel w ill also reduce the heating value of the fuel and reduce fuel economy. Winterized blends
usually fall somewhere between No. 1 and No. 2, depending on the blend, and consum ption decreases
commensurately.
• Fuel line leaks.
• Restricted fuel return line retards advance mechanism.
• Restricted fuel filter.
• Pump tim ing — During factory calibration the pump dynamic tim ing mark is placed w ithin one quarter degree
electronically. Retarding the pump will result in quieter operation with less smoke. Advancing the pump will be
noisier with some increase in smoke. “ Right on” tim ing is best for maximum economy.
• Autom atic advance m alfunction usually dem onstrates poor idle or poor part load performance with smoke and
low power at higher speeds.
• Nozzle fault — (many possibilities here) opening pressure below spec., valve lift incorrect, excessive seat leakage,
sticking or stuck-open valve.
7-25
7. Diagnosis
PUMP CONDITION
Fuel System Diagnosis
&
V/f/ffa/d
<o
/o/b/Q).,
® 4 A a ?/ # v c
O / j£ r
SYMPTOM
Engine cranks but will not start - cold
•
•
•
Engine cranks but will not start - hot
•
•
•
Engine starts but then stalls
•
Rough operation at idle
•
•
•
•
•
•
Rough operation at all speeds
•
Low power and smoke
•
Low mileage
•
•
Engine speed fluctuates
•
Engine knock
•
•
Engine stalls
•
No fuel delivery
•
Engine stalls in panic stop
•
Smoke - black
•
•
•
Excess fuel no shutoff
•
Smoke - white
•
Low fuel delivery
•
Engine fails to shut off
•
•
•
Erratic fuel delivery
•
Incorrect timing
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Figure 7-4, General Diagnosis of Fuel System.
FUEL SYSTEM
'W /
, & /£ '
' a / co/
SYMPTOM
Engine cranks but does not start - cold
Engine cranks but does not start - hot
Engine starts but then stalls
•
•
Rough operation at idle
Rough operation at all speeds
•
Low power and smoke
•
•
•
Poor acceleration
•
•
•
•
•
Low mileage
•
Engine speed fluctuates
Engine knock
•
•
Engine stalls
•
•
•
•
•
•
Engine stalls in panic stop
Engine fails to shut off
Smoke - black
•
•
•
Figure 7-4A, Pump Diagnosis.
7-26
r------
7. Diagnosis
NOZZLE
CONDITION
SYMPTOM
SYMPTOM
Engine cranks but will not start - cold
Engine cranks but will not start - hot
Engine starts but then stalls
NOZZLE
CONDITION
Rough operation at idle
Rough operation at all speeds
No fuel delivery
Low power and smoke
Low fuel delivery
Low mileage
Excess fuel delivery
Smoke - black
Erratic fuel delivery
Figure 7-4B, Nozzle Diagnosis.
Diagnosis of Fuel System Conditions
DIESEL ENGINE INTERMITTENT START
An interm ittent no-start condition on some diesel engines could be due to an inoperative check valve in the engine
fuel delivery (lift) pump. This condition could occur after the engine has been running, then stopped for a short time.
Fuel could drain past the inoperative check valve back into the fuel tank. To correct this condition, replace the fuel
delivery (lift) pump.
PLUGGED DIESEL FUEL FILTERS - ALL DIESELS
Condition: Plugged fuel filters. Stanadyne checks a percentage of fuel filters with a light petroleum product before
leaving the factory. As a result, air w ill not pass through a wet filter element as easily as one that is dry. Therefore,
blowing through the filter element w ith your mouth cannot be used as a criteria to determine if the element is
plugged. Installation on the engine, or regulated air pressure of 2-3 PSI is the only way to determine if the filter is
plugged.
HARD START IN COLD WEATHER - ALL DIESELS
A condition of hard start in cold weather can be caused by SAE 30 weight oil in a diesel engine. Change the oil
using SAE 10W30 SF/CD.
-
NOTE -
Do not use 10W40 oil.
6.2L DIESEL -
HARD STARTING
Poor starting (good cranking speed but lim ited ignition) and excessive smoke after start up can be the result of a
restricted fuel supply. This can be m isdiagnosed as a glow plug system condition. This restriction m ost likely will
be from a plugged fuel filter but can also be caused by a pinched or kinked fuel line. After the engine warms up, it
generally w ill run satisfactorily. If the restriction gets progressively worse, top speed and performance w ill be
affected also.
Even though the filters may have relatively few miles, purchase of dirty fuel can plug the filters in a short time. A
check of the fuel lines for restrictions should also be made.
7-27
7. Diagnosis
6.2L DIESEL INJECTION NOZZLE RETURN HOSE — 1982 C/K/P AND 1983 C/K/P/G WITH 6.2L DIESEL
C onditions may arise where the fuel return hose or nipple is disconnected from the fuel injection nozzle.
The purpose of the fuel hose is to return the fuel w hich leaks past the pintle in the injector nozzle, back to the fuel
tank. This is a relatively small am ount of fuel. Starting w ith the end cylinders on each side of the engine, the fuel
passes through each succeeding nozzle. If a blockage occurs in this flow path, pressure w ill build up and result in
a small fuel leak or the cap or hose becoming disconnected.
One cause of blockage is the leak-off nipple on the nozzle being plugged on the bottom end. During assembly of
the nipple into the nozzle body, the epoxy sealant may have flowed over the hole in the nipple on the bottom end. If
this happens, the return flow of fuel is restricted (Figure No. 7-5).
To determ ine if the hose or nipple fall off was caused by a blocked nozzle passage:
1. Remove the hoses from all nozzle nipples on the side of the engine involved.
2. Using a vacuum source, attach it to one nipple on a nozzle. If the nozzle nipple end is plugged, a vacuum reading
w ill result. Check each nozzle.
3. Those nozzles that indicate a plugged or partially plugged opening w ill generate some reading on the vacuum
scale.
4. To unplug a suspected plugged nipple insert a sm all drill bit into the nozzle nipple and turn by hand to break the
epoxy covering.
5. Recheck w ith vacuum. If unable to break the epoxy barrier, the nozzle should be replaced.
6. Replace hoses and nipple.
7-28
7. Diagnosis
Brakes Diagnosis — Diesel Vehicles
NO POWER STEERING OR POWER BRAKES ON DIESEL ENGINE COLD STARTS
Diesel equipped trucks use the Hydro-Boost Brake System. In this system, the power steering pump provides the
hydraulic fluid pressure to operate both the power brake booster and power steering gear. If hard steering and a
lack of brake assist im m ediately after a cold start occur, make sure that the correct starting procedure is followed
by the owner (starting procedure on sun visor above driver.) The fast idle solenoid must be extended prior to starting
by depressing and releasing the accelerator pedal to obtain engine fast idle speed. This allow s the power steering
pump to build up the necessary fluid pressure to operate the power steering and brake system s im m ediately after
start up. If you verify that the solenoid has extended and is holding the throttle open and the condition persists,
check the fast idle speed as per the em ission label. If this is correct, and the power steering pump belt is tight and
not damaged, the cause may be in the power steering pump.
BRAKE ROUGHNESS FEEL -
DIESEL VEHICLES
On cars equipped w ith a diesel engine, a brake roughness feel may be experienced, just before the car comes to a
com plete stop. This condition could be caused by a rough engine idle transm itting a pulsation through the
transm ission. To determine whether the rough idle is the cause of the com plaint, shift the transm ission into neutral
w hile braking. If there is no brake roughness feel, refer to the Service Manual for procedures to correct the rough
engine idle.
Diesel Engine Oil Leak Diagnosis
This section tells how to locate an oil leak, how to repair the leak and what sealer should be used.
The removal and installation procedures w ill not be covered in detail. Refer to the Service Manual for these
procedures.
The only equipm ent needed to help locate any leaks is a spray can of foot powder.
The RTV sealer referred to in the book is room temperature vulcanizing sealer GE 1673 (22521437 or 1052915).
VENTILATION SYSTEM-CAUSED OIL LEAKS
The diesel engine is more subject to oil leaks than the gasoline engine because of no intake m anifold vacuum in
the diesel engine. W ith no vacuum, the crankcase pressure is higher in the diesel engine than in the gasoline
engine.
The CDR valve in the ventilation system helps to reduce some of the pressure. It is very im portant that the
ventilation system be free from any restriction.
OIL LEAKS FROM FRONT OF ENGINE
Wipe the front of the engine clean and spray foot powder over the entire area.
W ith the engine at operating temperature, let it idle for about 10 to 15 m inutes or until a leak is evident.
OIL PAN
If leak is com ing from the rear oil pan seal, remove the pan and install a new rear seal as shown in Figure 7-6.
• Examine the front cover for damage and correct as required.
• Apply GE1673 RTV sealer on top and bottom of seal and also to each end of seal where it contacts the cylinder
block.
« Examine the side rails for damage. File off any spot weld dim ples at the reinforcement at the end of the pan.
• Torque oil pan bolts, as follows:
6mm = 6-14 N-m
8mm = 18-27 N-m
7-29
7. Diagnosis
Figure 7-6, Oil Pan Assembly.
RTV Sealer And Gasket Eliminator
There are tw o (2) sealers used to seal the 6.2L engine. The first is RTV (Room Temperature Vulcanizing) w hich is
used where a non-rigid part is assembled to a cast or rigid part such as rocker covers, oil pans, etc. The second is
gasket eliminator, an anaerobic material (cures in the absence of air) w hich is used where tw o (2) rigid parts are
assembled together, such as the front covers. When tw o (2) rigid parts are disassembled and no gasket or sealer is
readily noticeable it is sealed w ith gasket eliminator.
When assem bling parts, use the preferred material. Don’t use RTV to seal together tw o rigid parts and don’t use
gasket elim inator on stamped parts such as rocker covers.
• DIRECTIONS FOR USE OF RTV:
1. When separating com ponents sealed w ith RTV, use a rubber mallet and “ bum p” the part sideways to shear the
RTV seal. “ Bum ping” should be done at bends or reinforced areas to prevent distortion of parts. RTV is weaker in
shear (lateral) strength than in tensile (vertical) strength.
Attem pting to pry or pull com ponents apart may result in damage to the part.
2. Surfaces to be resealed must be clean and dry. Remove all traces of oil and RTV. Clean w ith a chlorinated
solvent such as carburetor spray cleaner. Don’t use petroleum cleaners such as mineral spirits; they leave a film
onto w hich RTV w on’t stick.
3. Cut the tube opening to approxim ately 1/8" diameter.
4. Apply RTV to one of the clean surfaces. Circle all bolt holes. Use a 5mm bead.
5. Assemble w hile RTV is still wet (within 3 minutes). Don’t w ait for RTV to skin over.
6. Torque bolts to specs. Don’t over torque.
7. RTV w ill skin over in 15 m inutes sufficiently to allow for testing and lim ited operation of vehicle. Stop engine and
allow RTV to cure for approxim ately 1 hour before placing vehicle in service.
Don’t use RTV when extreme temperatures are expected, e.g. exhaust manifold, head gasket or where gasket
elim inator is specified.
7-30
7. Diagnosis
-
NOTE —
Higher temperature resistant compounds are visually red due to
the addition of iron oxide.
• DIRECTIONS FOR USE OF GASKET ELIMINATOR:
1. Clean surfaces to be resealed w ith a chlorinated solvent to remove all oil, grease and old material.
2. Apply a continuous bead of gasket elim inator to one flange.
3. Spread bead evenly w ith your finger to get a uniform coating on the com plete flange.
4. Assem ble parts in the normal manner and torque to specs.
5. Vehicle can be operated after com pletion of assembly. No need to wait for gasket elim inator to cure.
— NOTE —
The useful shelf life of most RTV and gasket eliminator products is one (1) year.
7-31
7. Diagnosis
Don’t use gasket elim inator where RTV is recommended. The key to satisfaction with RTV and gasket elim inators is
follow ing the directions and using where specified.Don’t cut the procedure short or a leak may result.
RTV’s differ in performance.
For best results, use GM RTV or gasket elim inator from the follow ing table:
GM RTV AND GASKET ELIMINATOR
W DDG M P/N
COLOR
SIZE AND
CONTAINER TYPE
RTV
1052734
Red
10 O unce C a rtrid g e
RTV
1052915
B lack
10 O unce C a rtrid g e
RTV
1052751
Red
3 O unce Tube
G asket
E lim in a to r
(A naerobic)
1052357
O range
6 ml. Tube
G aske t
E lim in a to r
(A naerobic)
1052756
Grape
6 ml. Tube
SEALANT TYPE
7-32
7. Diagnosis
Explanation of Abbreviations
A/T
EGR
EPR
VRV
TCC
H.P.C.A.
TV
Autom atic Transm ission
Exhaust Gas Recirculation (Valve)
Exhaust Pressure Regulation (Valve)
Vacuum Regulator Valve
Torque Converter Clutch
Housing Pressure Cold Advance
Throttle Valve
Procedure 1. Checking Cranking Speed
Cranking speed is extremely critical for a diesel to start, either hot or cold. Some tachometers are not accurate at
cranking speed. An alternate method of checking cranking speed or determining the accuracy of a tachom eter is to
perform the follow ing procedure:
1. Install a compression gauge into any cylinder. (One such gauge is Kent-Moore P/N J-26999-10.)
2. Disconnect the injection pump fuel shut off solenoid lead on the top of the injection pump or at the harness
connector.
3. Install the digital tachom eter to be checked.
4. Depress the pressure release valve on the compression gauge.
5. W ith the aid of an assistant, crank the engine for 2 or 3 seconds to allow the starter to reach full speed, then
w ithout stopping, count the number of “ puffs” at the compression gauge that occur in the next 10 seconds.
M ultiply the number of “ puffs” in the 10 second period by 12 and the resulting number will be the cranking speed
in revolutions per m inute (RPM).
Example: 10 seconds = 1/6 of a m inute
1 p u ff = 2 RPM
RPM = No. o f puffs x 2 x 6 or
RPM = No. o f p uffs x 12
M in im u m c ra n k in g speed on the 6.2L d ie sel engine is 100 RPM co ld and 180 RPM hot. The actu a l c ra n kin g
speed needed w ill vary d e p e n d in g on the c o n d itio n of the engine (com pression) and nozzles.
7-33
7. Diagnosis
Procedure 2.
Checking for Adequate Supply of Fuel to Injection Pump
• Open fold-out page, Figure 7-7, Gage Connections for Diagnosis Procedure.
STEP 1 CHECKING SUPPLY PRESSURE:
A. From fuel supply lift pump and fuel filter.
B. From fuel filter to injection pump.
A. Install a pressure, such as gage “ B” or equivalent, between the lift pump and the fuel filte r inlet. NOTE:
This would be the secondary filter for 1982-83 models.
1. The pressure should be 5.5 to 6.5 PSI, if less go to step #2.
B. Install pressure gage “ B” in series between the filter outlet and the fuel injection pump. NOTE: You will
be checking the lift pump pressure drop across the filter. This tells if there is a filter restriction.
1. The pressure at idle should be a 2 PSI m inim um and not drop below 1 PSI. If less go to step #2.
STEP 2 CHECK FOR RESTRICTION IN FUEL SUPPLY LINE (USING GAGE “C”):
A. Install pressure/vacuum gage in fuel supply line before supply pump as shown in using gage “ C” . On
1982-83 it can be installed at the primary filter outlet.
If engine is operable, start and check for a maxim um vacuum in fuel supply line of 3 inches Hg at idle
speed. If engine is not operable, disconnect fuel line from filter inlet, add an extension hose, and route to
a metal container. Crank engine and check for a maximum vacuum in supply line of 3 inches Hg. Vacuum
greater than 3 inches Hg. indicates a restriction such as a plugged fuel strainer in the fuel tank. If vacuum
is less than 3 inches Hg., replace fuel filter element(s) and recheck supply pressure after fuel filter (Step 1).
If pressure is still less than 2 PSI, go to Step #3.
STEP 3 PERFORM SUPPLY PUMP VOLUME CHECK:
Disconnect fuel line from filte r inlet, add an extension hose and route to a graduated container that can
hold at least one pint. Disconnect lead from electric shut off solenoid on top of pump and crank engine
(or turn key to “ O N” position if equipped w ith an electric supply pump) for 15 seconds. Fuel pump should
supply a m inim um of Vz pint. If less, replace supply pump and go back to Step #1.
7-34
7. Diagnosis
Procedure 3.
Measuring Housing Pressure and Transfer Pressure
STEP 1 CHECKING HOUSING PRESSURE:
Remove the return line connector from the top of the pump (both the blackened and brass fittings).
Examine the lower end of the regulator fitting where the glass ball seats for evidence of debris. If present,
blow through the fitting w ith compressed air to elim inate the debris or replace the fitting.
Before reinstalling the fittin gs to the cover, turn the ignition key to the “ O N” position and connect a
jum per wire between the electric shut off solenoid term inal and the H.P.C.A. terminal. Make and break the
connection to the H.RC.A. term inal and observe the H.P.C.A. solenoid plunger through the return fitting
opening. It should move up and down as the current is applied and removed. If it does not function, repair
or replace the solenoid as necessary.
STEP 2 MEASURE THE VOLTAGE AVAILABLE AT THE H.P.C.A. TERMINAL:
A. When the engine is cold < 9 5 °F, there should be 9 volts m inim um at the H.P.C.A. terminal. If voltage is
low check battery and charging system condition. If there is no voltage at terminal, check operation of
temperature sensor located on right rear head. (See chassis service manual).
B. Install housing pressure gage adapter as shown using gage “ D” or J34151. Reinstall return line
connector and fuel return line, then connect pressure gage.
C. Start the engine, the housing pressure should be 8-12 PSI, WHH no more than 2 PSI fluctuation. If
pressure is high check for restriction in fuel return system. If pressure is low or fluctuates excessively,
replace return line connector fitting.
STEP 3 CHECKING TRANSFER PRESSURE:
Connect adapter and pressure gage as shown above. At cranking speed, transfer pump pressure should
be 10 PSI m inim um and housing pressure should be at least 2 PSI less than transfer pressure. At idle
speed, transfer pressure should be 30 PSI minimum.
7-35
7. Diagnosis
1982-83 SECONDARY FILTER
(CK)
IN L E T M A N IF O L D
FROM
LIFT
PUMP
TO IN J E C T IO N
PUMP
OUT
1984 &
LATER
(C K S H O W N )
IN J E C T IO N
PUMP
M E A S U R IN G C R A N K C A S E
P R E S S U R E (S E E S E C T IO N 5)
A. M A G N E H E L IC G A G E
IN C R E M E N T S
.5 IN. W ATER
0.10 IN. W A T ER P R E S S U R E
PU RPO SE
M EA SU R E C R AN K C A SE PRESSU RE
B. P R E S S U R E G A G E
IN C R E M E N T S
RANGE
PU RPO SE
S T U D (6L2)
1 PSI
0-30 P S I
M E A S U R E S U P P L Y (LIFT)
PUM P P R E SSU R E
E N G IN E O IL P U M P P R E S S U R E
D. P R E S S U R E G A G E
IN C R E M E N T S
RANGE
PU RPO SE
PR ESSU R E GAGE
IN C R E M E N T S
RANGE
PU RPO SE
4 PSI
2-1 PSI
M E A S U R E H O U S IN G P R E S S U R E
1 P SI
0-160 P SI
M EA SU R E T R A N SF E R PUMP P R E S SU R E
C. C O M B IN A T IO N V A C U U M / P R E S S U R E G A G E
IN C R E M E N T S
1 PSI/1 IN HG.
RANGE
0-30 IN HG. V A C U U M
0-15 P S I P R E S S U R E
PU RPO SE
F U E L S U P P L Y V A C U U M R E S T R IC T IO N S
FUEL P R E S SU R E
Figure 7-7, Gage Connections for Diagnosis Procedure.
7-36
7-37
7. Diagnosis
Procedure 4. Checking for Air Leaks
If stalling or rough operation only occurs after cold startup, check for fuel leaking backwards or air leaking into the
fuel supply lines. Fuel leaking backwards may be caused by faulty check valves in supply pump. To check for this
condition, remove return line connector fitting (ball check) from the top of pump and install a plain fitting in its
place. C onnect a section of clear hose approximately 3 feet long to the fittin g and route to a container. Start engine
and allow to idle. Stop engine. Suspend clear hose from hood of vehicle and mark fuel level in hose.
— NOTE —
Allow sufficient room in hose for level of fuel to rise due to thermal expansion. If level
drops over a period of several hours (or sooner), a leak back condition is indicated.
O ccasionally a very sm all air leak w ill only let enough air into the system to cause a stalling problem or rough
running condition after the vehicle is shut down for many hours (such as overnight). Double check all fittings,
clam ps and fuel lines and do not overlook components after the supply pump such as the fuel filter elem ent or
base. There have been cases where tiny holes in the filter base casting or in the sealant used in the m anufacture of
the filte r elem ent have allowed air to enter but no external fuel leakage to occur.
Air Leak Diagnosis
AIR LEAK ON THE SUCTION SIDE
The housing vent wire may allow minute quantities of air to pass harm lessly out of the pump. However, at some
point there w ill be more air than can go out the vent and the air w ill go into the charging circuit. This air will
com press and upset fuel flow in the lines which w ill create a rough running engine. A plastic line placed on the
fuel return fittin g w ill show up this condition. To isolate the air leak, it may be necessary to feed the system out of
a container and hook it up at various places to bypass certain sections of the fuel system.
AIR LEAK ON SUCTION OR RETURN SIDE
An air leak in either the suction or return side can cause starting problems. Air entering the system w ill allow fuel
to drain back tow ards the tank. If an air leak occurring at some point like the filter, the fuel w ill drain back then the
fuel on the return side w ill be heavier and it w ill pull fuel out of the filte r through the pump and back towards the
tank. Because there is no fuel in the filter or pump, the engine w ill not start. When it finally does, surging will be
very evident.
7-38
7. Diagnosis
Procedure 5. Causes of
Underrun or Stalling
1. Sticky Metering Valve Or Linkage
a. Check metering valve for freedom of rotational
movement (Figure 7-8).
b. Check for twisted linkage hook spring.
c. Check for burrs on the metering valve arm in the
area where the linkage hook rides.
Figure 7-8
4 OUNCE WEIGHT
MIN-MAX
T
d. Check for excessive min-max gap on pumps
equipped with internal low idle springs. (See
Figure 7-9).
e. Check for binding condition between min-max
governor block and throttle shaft by placing
throttle lever in low idle position and moving
governor block back and forth on guide stud.
Governor assembly should move (jiggle) freely on
guide stud.
Figure 7-9
GOVERNOR WEIGHT
RETAINER
(SOCKET PORTION)
ROTATE IN
EACH DIRECTION
MIN-MAX
GOVERNOR BLOCK
Figure 7-10
7-39
f. Check for failed flex ring by attem pting to rotate
the socket portion of the retainer by hand or with
a screwdriver blade (Figure 7-10). If the retainer
can be rotated more than 1/16th of an inch in
either direction and doesn’t return when pressure
is released, then a failed flex ring is indicated. See
Oldsmobile Dealer Technical Bulletin 80-T16 for
instructions regarding flex ring replacement.
7. Diagnosis
Procedure 6.
Checking For Sticky or Stuck Advance Mechanism
(Pumps equipped with mechanical light load advance)
7-40
8. Glossary
ANALOG - Continuously variable electrical signal.
ATMOSPHERIC PRESSURE - The air pressure at sea
level 14.696 or 14.7 P.S.I.
ATOMIZATION - The breaking up of the fuel into fine
particles, so that it can be mixed with air.
BDC - Bottom Dead Center is the point of lowest piston
travel in a stroke.
CAFE - Abbreviation for Corporate Average Fuel Econ­
omy. Part of the Energy Policy and Conservation Act of
1975. This law mandates G M ’s fleet mileage at 22 mpg for
1981. By 1985, it will climb to 27.5 mpg.
CALIBRATION 1. B alancing - The setting of the delivery of several ele­
ments of an injection system or the setting of the rack
pointer on a single unit pump in relation to predeter­
mined positions of a quantity control member.
2. A d justm ent - Fixing fuel delivery and speed adjust­
ments to specified engine requirements.
CENTRIFUGAL FORCE - The inertia! reaction by which a
body tends to move away from the center about which it
revolved.
CENTRIPETAL FORCE - A constant force acting con­
tinuously at right angles to the motion of a particle (body)
which causes it to move in a circle at a constant speed.
CETON FILTER - A sock-type filter in the fuel tank cap­
able of wicking diesel fuel but not water. This keeps water
from the rest of the fuel system until the sock is 90%
submerged in water.
CLOUD P O IN T-T e m p eratu re at which paraffin crystals in
diesel fuel separate out of solution and solidify.
COMPRESSION IGNITION ENGINE - Internal combus­
tion engine where the heat of compression ignites the fuel
mixture. Diesels are, by definition, compression ignition
engines.
CRACKING - Oil refining technique where heavier frac­
tions of crude are subjected to heat and pressure and
transformed into lighter fractions.
DELAY PERIOD - Initial phase of diesel combustion. It
lasts from about 15° to about 5° before top dead center and
is where the injected fuel warms up and begins to burn.
Dl - Direct Injection diesel engine.
DIESEL - Engine that is powered by compressed fuel
injection.
DIFFUSION - The mixing by thermal agitation of the mole­
cules of two gases.
DISPERSANT - The act of dispersing or to scatter in
various directions. A state of matter in which finely divided
particles of one substance (the disperse phase) are sus­
pended in another (the dispersion medium) substance.
8-1
DRIBBLE - Insufficiently atomized fuel issuing from the
nozzle at or immediately following the end of main injec­
tion.
DURATION - The period of time during which anything
lasts.
EGR - Exhaust Gas Recirculation system. First used in
1980 diesels to control the output of nitrous oxides. The
1980 system was an external type with exhaust being
transmitted through hoses outside the engine. The 1981
system is an internal type with exhaust passages cast in
the cylinder head and an air crossover comparable to a gas
engine’s EGR system. In the external type, the system
operates at all times except during maximum speed. The
internal type is regulated by degrees from full-on at idle to
fully closed at maximum speed.
EMULSION 1. A liquid mixture in which a fatty or resinous substance is
suspended in minute globules.
2. The particles of one liquid finely dispersed in another.
FLAMMABILITY - The ability of a substance to catch fire
or be combustible.
FLASH POINT - Of a liquid fuel is the temperature at
which the fuel gives off sufficient flammable vapor to be
ignited in the presence of a flame.
FRACTIONS - Lighter and heavier elements in crude oil.
Lighter fractions, such as gas and liquefied gas, have
relatively few carbon atoms in each molecule. Heavier
fractions, such as wax and asphalt, have many carbon
atoms on each molecule.
FUEL ADVANCE SYSTEM - Standard in 1981, this sys­
tem advances fuel delivery during cold starts. It consists of
a thermal-sensitive solenoid on the intake manifold which
sends a signal to the HPCA terminal that opens a ballcheck valve on top of the injection pump housing. With
pump housing pressure reduced, the timing mechanism
has less resistance to overcome and so operates earlier to
advance fuel delivery 3°.
FUEL DISTRIBUTION - Section of injection pump that
feeds fuel to each cylinder at the proper time.
FUEL INJECTION PUMPS (COMPONENTS)
INJECTION PUMP - The device which meters the fuel
and delivers it under pressure to the nozzle and holder
assembly.
UNIT PUMP - An injection pump containing no actuat­
ing mechanism to operate the pumping element or
elements. It can be classified as “ in-line", “ distributor” ,
“ submerged” , etc.
CAMSHAFT PUMP - An injection pump containing a
camshaft to operate the pumping element or elements.
It can be classified as “ in-line” , “ distributor” , “ sub­
merged” , etc.
8. Glossary
IN-LINE PUMP - An injection pump with two or more
pumping elements arranged in line, each pumping ele­
ment serving one engine cylinder only.
NOTE: A pump which has the elements arranged in line
and in more than one bank, for instance, in two banks
forming a “ V ” , is a specific case of an in-line pump.
DISTRIBUTOR P U M P -An injection pump where each
metered delivery is directed to the appropriate engine
cylinder by a distributing device.
SUBMERGED PUMP - A pump with the mounting
flange raised to limit pump projection above the mount­
ing face.
CAMSHAFT PUMP MOUNTINGS 1. BASE M O U N T E D - A pump mounted on a surface of
the engine which is parallel to the axis of the pump
camshaft.
2. CRADLE MOUNTED - A special form of a “ base
mount” in which the base is contoured to permit
rotation of the pump around the axis of the pump
camshaft.
3. FLANGE MOUNTED - A pump mounted on a sur­
face of the engine which is at a right angle to the axis
of the pump camshaft.
INJECTION PUMP ASSEM BLY - A complete assem­
bly consisting of the fuel pump proper, together with
additional units such as governor, fuel supply pump,
and additional optional devices, when these are assem­
bled with the fuel injection pump to form a unit.
1. RIGHT-HAND MOUNTED - When the pump is
mounted on the right-hand side of the engine com­
monly viewed from the engine flywheel end.
2. LEFT-HAND MOUNTED - When the pump is
mounted on the left-hand side of the engine common­
ly viewed from the engine flywheel end.
PUMP ROTATION 1. C L O C K W IS E -T h e rotation of the pump camshaft or
driveshaft is clockwise when viewed from the pump
drive end.
2. COUNTERCLO CKW ISE- T h e rotation of the pump
camshaft or driveshaft is counterclockwise when
viewed from the pump drive end.
PUMPING ELEMENT - The combination of parts in an
injection pump by means of which the fuel is pressurized
for injection.
PLUNGER AND BARREL ASSEM BLY (OR PLUNG­
ER AND BUSHING ASSEM BLY) - The combination of
a pump plunger and its barrel constituting a pumping
element. The plunger and barrel assembly may also
perform the additional functions of timing and metering.
PORT AND HELIX METERING - A system of metering
fuel delivery by means of one or more helical cuts in the
plunger and one or more ports in the barrel. Axial rota­
tion of the plunger alters the effective portion of the
stroke by changing the points at which the helices close
and/or open the port or ports.
INLET METERING - A system of metering fuel delivery
by controlling the amount of fuel entering the pumping
chamber during the filling or charging portion of the
pump’s cycle.
SLEEVE METERING - A system of metering fuel deliv­
ery by incorporating a movable sleeve with which port
opening and/or port closing is controlled.
PORT CLOSING - A term referring to the fuel injection
pump of the port and helix or sleeve metering type in
which timing is determined by the point of the closing of
the port by the metering member, corresponding to the
nominal start of pump delivery.
PORT OPENING - A term referring to a fuel injection
pump of the port and helix or sleeve metering type in
which timing is determined by the point of the opening of
the port by the metering member, corresponding to the
nominal end of pump delivery.
HYDRAULIC HEAD ASSEM BLY - The assembly con­
taining the pumping, metering, and distributing ele­
ments (and may include the delivery valve) for distribu­
tor type pumps.
SPILL VALVE - A valve used to terminate injection at a
controllable point on the pumping stroke by allowing fuel
to escape from the pumping chamber.
INLET VALVE - A valve used to admit fuel to the pump
barrel.
DELIVERY VALVE ASSEM BLY - A valve installed in a
pump, interposed between the pumping chamber and
outlet, to control residual line pressures and which may
or may not have an unloading or retraction function.
DELIVERY VALVE HOLDER - A device which retains
the delivery valve assembly within the pump.
FUEL PUMP HOUSING - The main casing into or to
which are assembled all the components of the injection
pump and it may accommodate the camshaft in the
case of camshaft pumps; or the camshaft, or driveshaft
in the case of distributor type pumps.
CONTROL RACK (CONTROL ROD) - The rack or rod
by means of which the fuel delivery is regulated.
CONTROL PINION (CONTROL SLEEVE) - A collar
engaging the plunger and having a segment of gear
teeth, integral or attached, which mesh with the control
rack. By this means, linear motion of the control rack is
transformed into rotary movement of the plunger to
regulate the amount of fuel delivered by the pump.
8-2
8. Glossary
PLUNGER CONTROL ARM - A lever attached to a
collar or sleeve engaging the plunger, or attached
directly to the plunger, its other end engaging possibly
adjustable fittings on the control rod. This transforms
linear motion of the control rod to rotary motion of the
plunger to regulate the amount of fuel delivered by the
pump.
FUEL INJECTION TUBING - The tube connecting the
injection pump to the nozzle holder assembly.
FUEL INJECTORS
FUEL INJECTOR - An assembly which receives a
metered charge of fuel from another source at a rel­
atively low pressure, then is actuated by an engine
mechanism to inject the charge of fuel to the combustion
chamber at high pressure and at the proper time.
UNIT FUEL INJECTOR - An assembly which receives
fuel under supply pressure and is then actuated by an
engine mechanism to meter and inject the charge of fuel
to the combustion chamber at high pressure and at the
proper time.
DELIVERY VALVE - A spring loaded valve which
opens at some predetermined pressure to permit fuel
flow from the injector plunger and bushing to the spray
tip.
FUEL SOLENOID - Energizes the fuel metering valve
whenever the ignition is switched "on” .
GLOW PLUG - Used to heat pre-chamber before cold
weather starting.
GOVERNORS (TYPES AND COMPONENTS)
MECHANICAL GOVERNOR - A speed sensitive de­
vice of the centrifugal type, which controls the injection
pump delivery solely by mechanical means.
HYDRAULIC GOVERNOR - A mechanical governor
having a hydraulic servo-booster to increase output
force.
PNEUMATIC G O V E R N O R 1. VACUUM OR SUCTION GOVERNOR - One oper­
ated by a change in pressure created by the air
actually consumed by the engine.
2. AIR G O V E R N O R - One operated by air displaced by
a device provided for this particular purpose and
driven by the engine.
LOAD-SENSING G O V E R N O R -An engine speed con­
trol device for use on engine-generator sets to control
engine fuel settings as a function of electrical load to
anticipate resulting changes in engine speed. It may or
may not incorporate a mechanical speed-sensing de­
vice as well.
VARIABLE SPEED GOVERNOR - One of any of the
above varieties which controls injection pump delivery
throughout the speed range.
8-3
MAXIMUM-MINIMUM GOVERNOR - Any one of the
above varieties which exerts control only at the upper
and lower limits of the designed engine speed range,
intermediate speeds being controlled by the operator
setting the fuel delivery directly by throttle action.
OVERSPEED GOVERNOR - A mechanical speedsensitive device that through mechanical or electrical
action (operation of a switch) acts to shut down the
engine and limit the speed by cutting off fuel and/or air
supply should the engine speed exceed a preset
maximum.
TAILSHAFT GOVERNOR - A mechanical speedsensitive device commonly mounted on an engine
driven torque converter to monitor its tailshaft speed. It
is mechanically connected to the normal engine gov­
ernor such that engine output will be governed to main­
tain a constant tailshaft speed regardless of torque load.
FULL LOAD STOP - A device which limits the max­
imum amount of fuel injected into the engine cylinders at
the rated load and speed specified by the engine manu­
facturer.
TORQUE CONTROL - A device which modifies the
maximum amount of fuel injected into the engine cylin­
ders at speeds below rated speed to obtain the desired
torque output.
EXCESS FUEL DEVICE - Any device provided for
giving an increased fuel setting for starting only, gener­
ally designed to restore automatically action of the nor­
mal full load stop after starting.
ACCELERATION SMOKE LIMITER - A device which
limits the smoke of a diesel engine during acceleration
by temporarily limiting the amount of fuel injected into
the engine cylinders during speed and/or load tran­
sients below the steady-state limit.
TIMING DEVICE - A device responsive to engine
speed and/or load to control the timed relationship be­
tween injection cycle and engine cycle.
HELIX (SCROLL) - A term used to describe the control
edge of a spill groove provided on the plunger, usually of
helical form. The helices may be upper or lower or both and
may be the same hand or opposite. They can also be
duplicated on both sides of the plunger.
HELIX H A N D -T h e hand of the helix in plungers is desig­
nated right or left, the same as a thread.
HELIX LEAD - The axial advance of the helix edge in one
revolution.
HOMOGENEOUS - Having the same composition
throughout the substance (well mixed).
HYDRO B O O S T - Power brake system which operates on
fluid from power brake pump.
HYDROCARBON - A complex mixture of hydrogen and
carbon compounds.
8. Glossary
IDI - Indirect Injection diesel engine.
IGNITION INJECTION - A small charge of fuel used to
ignite the main gas charge in dual fuel engines.
IGNITION POINT (AUTO IGNITION) - This is a term ap­
plied to the event in which a combustible mixture under
certain conditions of density, pressure and temperature
ignites without a flame or spark.
PINTLE VALVE (IN A CLOSED NOZZLE) - A special
type of a “ needle valve” wherein an integral projection
from the lower end of the needle is so formed as to
influence the rate and/or shape of the fuel spray during
operation.
INERTIA - A resistance to any change in the state of
motion. It is Newton’s First Law of Motion.
NOZZLE BODY - That part of the nozzle which serves
as a guide for the valve and in which the actual spray
openings may be formed. These two parts, the body and
the valve, are considered as a unit for replacement
purposes.
INJECTION - Method of forcing fuel into chamber when air
is highly compressed by the piston.
NOZZLE TIP - The extreme end of the nozzle body
containing the spray holes (may be a separate part).
INJECTION L A G - T h e time interval (usually expressed in
degrees of crank angle) between the nominal start of injec­
tion pump delivery and the actual start of injection at the
nozzle.
POPPET VALVE - An outwardly opening valve used
with certain forms of closed nozzles.
INJECTION NOZZLE (COMPONENTS)
NOZZLE AND HOLDER ASSEMBLY - The complete
apparatus which injects the pressurized fuel into the
combustion chamber.
NOZZLE - The assembly of parts employed to atomize
and deliver fuel to the engine.
NOZZLE HOLDER ASSEMBLY - The assembly of all
parts of the nozzle and holder assembly other than
those comprised in the nozzle.
OPEN NOZZLE - A nozzle incorporating no valve.
CLOSED NOZZLE - A nozzle incorporating either a
poppet valve or a needle valve, loaded in order to open
at some predetermined pressure.
1. POPPET NOZZLE - A closed nozzle provided with
an outward opening, spring-loaded, poppet valve.
2. DIFFERENTIAL NOZZLE - A closed nozzle pro­
vided with a spring-loaded needle valve.
3. PINTLE NOZZLE - A closed nozzle provided with a
spring-loaded needle valve. The body of the nozzle
has a single large orifice into which enters a projec­
tion from the lower end of the needle, this projection
being so formed as to influence the rate and shape of
the fuel spray.
NOZZLE HOLDER CAP - A cap nut or other type of
closure which covers the outer end of the nozzle holder.
NOZZLE RETAINING NUT - The nozzle holder part
which secures the nozzle or nozzle tip to the other
nozzle holder parts.
S P IN D L E - A spindle transmits the load from the spring
to the valve.
PRESSURE ADJUSTING SCREW (SHIMS) - The
screw (shims) by means of which the spring load on the
nozzle valve is adjusted to obtain the prescribed open­
ing pressures.
SPRING R E T A IN E R -T h e spring retainer encloses the
spring and carries the adjusting screw or shims.
NOZZLE HOLDER SHANK LENGTH - The distance
from the top of the cylindrical shank to the seating face
of the nozzle holder.
SEATING FACE - The face upon which the nozzle and
holder assembly seats to make a gas tight seal with the
cylinder head. Commonly, this face is on the nozzle
retaining nut.
DIFFERENTIAL RATIO - The ratio between the guide
diameter of the needle valve and the effective diameter
of the needle valve seat.
SPRAY ORIFICE/ORIFICES - The opening or open­
ings in the end of the nozzle or tip through which the fuel
is sprayed into the cylinder.
4. HOLE TYPE NOZZLE - A closed nozzle provided
with one or more orifices through which the fuel
issues. Nozzles with more than one orifice are known
as multihole nozzles.
SPRAY DISPERSAL ANGLE - The included angle of
the cone of fuel leaving any single orifice in the nozzle or
tip including pintle type.
NEEDLE VALVE (IN A CLOSED NOZZLE) - A needle
valve has two diameters, the smaller at the valve seat.
The fuel injection pressure acting on a portion of the
total valve area lifts the valve at the predetermined
pressure, then acts on the total area. The end opposite
the valve seat is never subjected to injection pressure.
SPRAY ANGLE - The included angle of the cone
embracing the axes of the several spray holes of a
multihole nozzle. In the case of nozzles for large en­
gines, more than one spray angle may be needed to
embrace all the sprays, for example, an inner and an
outer spray angle.
SPRAY INCLINATION ANGLE - The angle which the
axis of a cone of spray holes makes with the axis of the
nozzle holder.
8-4
8. Glossary
SAC HOLE - The recess immediately within the nozzle
tip and acting as a feeder to the spray hole(s) of a hole
type nozzle.
DIFFERENTIAL ANGLE - The difference between the
angles of the seat face of the valve and that of the seat in
the body provided to insure its effective sealing.
LEAK-OFF - Fuel which escapes between the nozzle
valve and its guide. (This term is also used to describe
the leakage past the plunger of a fuel pump.)
NOZZLE OPENING PRESSURE - The pressure
needed to unseat the nozzle valve.
PEAK INJECTION PRESSURE - The maximum fuel
pressure attained during the injection period (not to be
confused with opening pressure).
INJECTION TIMING - The matching of the pump timing
mark, or the injector timing mechanism, to some index
mark on an engine component, such that injection will
occur at the proper time with reference to the engine cycle.
Injection advance or retard is respectively an earlier, or
later, injection pump delivery cycle in reference to the
injection cycle.
IN-LINE FUEL HEATER - A 100-watt heater which is
integral to the fuel line. This heat warms the fuel prior to the
filter to keep paraffin crystals from stopping fuel flow. The
heater warms the fuel by 20°.
INTERFACE - A surface forming the common boundary
between two close spaces or substances.
LAMINAR FLAME SPEED - This is the speed at which a
flame will burn through a quiet or still fuel-air mixture. A
laminar flame burns as a flat flame sheet, as it moves
through the mixture.
METERING - Method of controlling the amount of fuel
injected on each power stroke.
MIN/MAX GOVERNOR - Controls idle speed and pre­
vents overspeed.
MIN/MAX GOVERNOR KIT - A retro fit assembly that
desensitizes the governor to output variance between
cylinders at idle.
MODULE - Electronic control unit that controls the glow
plug system.
N O X E S - Oxides of nitrogen (NOx), a component of diesel
exhaust.
NUMBER ONE DIESEL FUEL - Diesel fuel used in cold
climates. Sometimes blended with # 2 diesel fuel to in­
crease # 1 s energy and # 2 ’s cold-weather performance.
NUMBER TWO DIESEL F U E L - Diesel fuel used in mod­
erate climates.
ORIFICE - Restriction to control flow in a line (tube).
OXIDATION - The process of adding oxygen to a sub­
stance.
8-5
PARAFFIN 1. A semi-transparent, waxy mixture of hydrocarbons, de­
rived principally from the distillation of petroleum.
2. Any hydrocarbon of the methane series.
PARAFFIN HYDROCARBON - Petroleum-base fuels
consist of hydrocarbons with varying molecular weights
and atomic structure. The hydrocarbons represented in
petroleum are, paraffins, olefins, diolefins, naphthene, and
aromatics.
PARAFFINIC - Pertaining to or containing Paraffin.
PCV - Positive crankcase ventilation.
PEAK PRESSURE PERIOD - The phase of diesel com­
bustion lasting from about 5° before top dead center to
about 10° after top dead center. During this phase, the
majority of diesel fuel burns.
PERPENDICULAR - A line which is at right angles to the
horizontal plane.
PILOT INJECTION-A small initial charge of fuel delivered
to the engine cylinder in advance of the main delivery of
fuel.
POUR POINT - The temperature at which the fuel be­
comes too thick to flow or be pumped.
POUR POINT DEPRESSANT - Pour point depressants
enable oil to flow or pour at low temperatures. Wax, pres­
ent in all oils, forms a honey-comblike structure at low
temperatures and restricts oil flow. Pour point depressants
lower or depress the temperature at which this occurs and
enable oil to pour more freely. They retard wax crystal
growth.
PRECHAMBER - A precombustion chamber built into the
cylinder head that creates turbulence in incoming air.
Sometimes called a swirl chamber.
PROPAGATE - To spread through a mixture.
PUMPING LOSSES - Energy used as the engine creates
a vacuum in the intake manifold.
RECIPROCATE - To move back and forth alternately, as
in an engine piston.
RESIDUAL - Pertaining to what is left or remaining in a
process, left over as a remainder.
RETRACTION VOLUME - The volume of fuel retracted
from the high-pressure delivery line by action of the deliv­
ery valve’s retraction piston in the process of the delivery
valve returning to its seat following the end of injection.
RISING VOLUME PERIOD - The final combustion phase
in diesels lasting from about 10° after top dead center to
about 60° before bottom dead center. During this period,
injection has stopped and the last few droplets of fuel burn.
ROTARY FUEL METERING VALVE - Regulates the flow
of pressurized fuel into the charging chamber. It is directly
controlled by the throttle linkage and is affected by the fuel
solenoid and governor.
SECONDARY INJECTION - The fuel discharged from the
nozzle as a result of a reopening of the nozzle valve after
the main discharge.
SOCK - The fuel pickup strainer in the tank. It is made of
saran, and water will not enter, until it becomes almost
totally engulfed by water.
SPECIFIC HEAT - The capacity of any substance for
absorbing heat.
SPONTANEOUS COMBUSTION - The oxidation of fuel
rapidly enough, to generate sufficient internal heat to ignite
it.
SPONTANEOUSLY - A self generated action resulting
from something’s own impulse.
STRATIFIED - To form or arrange in layers.
SUPPLY PUMP - A pump for transferring the fuel from the
tank and delivering it to the injection pump.
T.D.C. - Top Dead Center is the point of highest piston
travel in a stroke.
THERM AL EFFICIENCY - The thermal efficiency of a
heat engine is that portion of the heat supplied to the
engine which is turned into work.
THERM AL SWITCH - Bi-metal switch that contains four
switches that control the glow plug system.
THERMODYNAMIC - The branch of physics dealing with
heat, heat engines and other forms of energy.
TIMING ADVANCE CHAMBER - Part of the fuel injection
pump; the timing advance chamber provides the proper
timing of fuel injection for all operating conditions.
TRANSFER PUMP - Part of the fuel injection pump;
boosts fuel pressure from 20 PSI to 130 PSI, depending on
pump and engine speed.
VACUUM PUMP - Needed because vacuum can’t be
drawn from the unrestricted air manifold.
VISCOSITY - The viscosity of a liquid, is a measure of its
internal resistance to flow or movement. It is a result of the
molecular friction within the liquid. Thickness of oil; lower
viscosity indicates a thinner oil.
8-7
GM
Product
Service
Training
16015.05-1C
WE SUPPORT
VOLUNTARY TECHNICIAN
CERTIFICATION THROUGH
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National Institute for
A U T O M O T IV E
S ER VIC E
E X C E LLE N C E
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