Part 17 - - Offline - Repair and Maintenance of Stationary Diesel Engines

Part 17 - - Offline - Repair and Maintenance of Stationary Diesel Engines
4 project of Volunteers in Asia
al Mechanics Cuurse 3.. Reoair an&J&&@nance 42.f
Ey: John van Winden
Published by:
TOOL Found&an
Sarphr?tistraat 650
1018 AV Amsterdam
The Netherlands
Available from: TOOL Foundation
Sarphatistraat 650
101%AV Amsterdam
The Netherlands
Reproduced with permission.
Reproduction of this microfiche document in any form is subject to the same
restrictions as tnose of the original document.
John van Win&n
TOOL four&&on
1018 AY Am%-rdam
The NciMaii;
Bra. J van Windcn
Bm. J. vm ‘Winden. J. Hovingh :ind
R. Cirossen
and la::-out
bv. Soest
Jan van Arkel, titrecht
&ips Repro, Mcppel
@ Stichting &qmgatie
F.I.C.. Maa..tricht,
No part of this put4calicn may be repro&&
in any
form, by print, pho.!ognuhy , micro film. or any otiler
means without written permission from !he puolishcr.
Whiln every cam has bccu ticn 10 cnsurc t?le
of ‘dre information given in this publicadqn.
neither the publisher(s) nor the author(3 can bc held
responsible for any damage resulting from Ihr
apphcatiou of the dcscribti medmds. Any liability in
this rospcct is excluded.
John van
Rurul mcchanrcs court / [John van Windcn ; draw.
by tbc author .. . et al.]. - kmsierdam : Stichtiug TOOL
3: Muimcnancc and rep&r of stationary diesel engines
/ [%msl. by: Taalwerk Translation Bureau]. - Ill., r,ck.
lSBN 90-70857-16-7
‘SST, 650.2 UDC 62i.Ol(U75.3)
Trc.fw.: lccrmiddclcn : mechanischt technick.
We have decided to publish this edition of the
Rural Mechanics Course in response to the
many requests from peopie involved in
trxining for technicai vocations and in general
development work.
In many situations radical and urgent changes
are taking place in rural areas in order to
restore land to agricultur,, to bring about better
living conditions and secure health and
educationai facilities - the basis for 3 healthy
The main aim of this set of books is to provide
technical training information in
understandable language and with illustrziions
suited to the understanding of those involved.
The contents of these books reflect the rural
development taking place in the agricultural
sector in particular. where many urgent needs
have to be looked after and solved in order to
achieve sound development at all levels.
This Rural Mechanics Course has been
compiled for teaching in Technical Vocation
Centres in addition to a Rural Building Course,
which deals with skills such as carpentry and
We are pteful to the Stichting Brothers
F.I.C.. SI :hting TOOL for their technical
‘assistance, Stichting Cebemo for their flnwGal
support and the German Volunteer Service for
so many volunteer:, ivho have contributed in no
smP11way tr>the compilation of these books.
It is our sincere wish that the contents of these
books may be of assistance in stimulating the
use of appropriate techniques to aid agriculture
and grnPral development.
Brc ii;hn vun WindenF.I.C.
Needs arising from these changes are not
always dealt with because many technical
institutions do not provide appropriate
technical training geared to solving problems
which have gone unnoticed in the pasr.
lr can also be noted that small co-operative
workshops are being started these days in the
inicrests of agriculture and these too may
develop as they deal with the upkeep of small
mechanixd farm implements and diesel
engines used for water supply or with making
gloughs, handcarts, gardoaing tools, etc.
Integrated and relevarbrtech,lical training and
grouping young people together into
co-operative movements should lx emphasized
to ensure sound agricultural and seneral
development. That is why an attempt has been
made to achieve appropriate techmcal training
for rural mechanics. who will contribute in no
small way towards il~e necessary development.
Since the technical needs In rural c:eas are
many but do not on the :vhole need highly
specialised technicians to solve them. the rural
mechanic - because his training covers a broad
basis - will often be solving problems ansing
from the introduction of new implerr.ents or
The course lasts four years, almost two years
nf which are set aside fur so-tailed ‘on-the-job
training’. This is practical training provided in
various workshops under the guidance of
qualified technicians as well as a centre
insrvctor who visits the workshop at intervals
to see for himself how the trainees are
progressing. During ‘on-the-job training’ the
trainee is rewarded for his work which may
help him later to buy the set of tools he hzs
used during his training. so lie can start
working immediately after completing the
course successfully.
Rural mechanicscowse
A set of foul books has L~?e,cn
compiled to
accompany the four-yenr course for rural
1 - General metal work, sheetmetal work and
handpump maintenance
2 - Blacksmithing. welding tcT::dsoldering
3 - Maintenance and repair of stationary diesel
4 - Technical drawing
While e‘ach of these books covers the full
material of one course, a !ot of addiiional
information needed besides the contents of one
particular book will be found in another book.
So it is difficult to use just one lsf these books
without consulting the others. The text on the
properties of metal?, for example, is to ‘be
fcund in the general metal work book. Uut this
information is also needd when you are
dedi,lg with other subjects. such as diesel
engines, blacksmithing etc.
As mentioned above, this COUEXis made up in
such a way rhat most of the practic& can be
carried out with a limited set of tools. You wiii
however notice that p ‘_ c+.l,‘“~‘“‘. or tools
are needed sometimes and ;hese must btz
availatle in the Vocational Cenrre s workshop.
It ,s believed and hoped that with the
formation of co-operatives these additional
tools and equipment will be available in the
workshops &cause, though they anz qore
expensive, they can be owned by the group.
The main aim of this course is that the trainee,
&sides acquiring a good formative
background, will learn to master such skills as:
I_ working with and ma.i;uaining all the :cols
- blacksmithing to such a de,qreethat he will
be able to shape different metals to the
requbed implements, tools, etc.
- repairing, maintaining and installing hand
- dismantling, repairing and assembling
stationary diesel engines
- sketching or drawing simple items in
orthographic, oblique and isometric fol m;
reading engine or machine rnam&.
This set of books can be u:ed partly in the
classroom but must also bc used during
workshop practiz, where the reality of what
can be seen will add greatly ta the text and
i!lustraticns in the books. Practical exercises
recommended in the b\oks can be varied s;rrce
the practical nattua or th,rc course calls for
articles to be made which can be used directly
by people who may order them. But care
should be taken that, though production may
be necessary for one reason or another, all the
skills which must be mastered are iircorporzted
in each practical, so as to ensure sound training.
It is very imponant to study the proposed
timetable given in each book to ensure that all
skills are given the necessary attention. Apart
frotn the progress mluie by each trainee. the
time recommended fcr each skill ma,’ vary as
well. Some skills take more time to master
than others.
You v41 note the absence in this course of the
scien,:e which may be important in explaining
the diesel engine in particular, Providing this
background theory is however beyond the
scope of the course. But if the need arises, the
relevant science should be included during part
of the related subject time.
This Rural Mechanics Course Is the result of
many years’ observation z.ld exprimentation
with different techniques. fhe contents have
frequently been revG(d to serve all those
Interesic:: .‘; ;ug;.i ucvelopment. and it is hoped
this CO’USL‘
will be used in many technical
vocation ccz*es ‘andcommunities. It is also
the sincere wish of the founders of this course
that the trainees should feel on completion of
their training that they are able to contribute
personally to the development of the rural
areas, which is of such importance to any
general development.
Rural mechanics course lay-out
and timetable
Four year training course
a - Full Centre training: workshop practicals,
trade theory, technical drawing and related
Two years = 80 weeks
b - Partly Centre training: trade theory,
technical drawing, related subjects.
~racticals take place outside the
One year = 40 weeks
Vocational Centre.
c - On-the-job training: ptacticals take place
outside the Vocational Centre.
(Praeticals are however controlled by
Centre staff and marks are awarded for any
One year = 40 weeks
progress made.)
Three-year Centre timetable for trnde
General metal work
Welding and soldering
Sheetmetal work
Stationqry diesel engines
Waterpumps and supply
Total theory time:
240 hours
220 hours
20 hours
380 hours
Total vocational training time
Four years = 160 weeks
Weekly timetable for related subjects and
Trade theory
Technical drawing
Other related subjects
;,I2 ;;;
2l hours
2 hours
2’12 hours
‘Total related subjects
Total hours workshop practice :8
Total training time in centre
Four-year timetable, workshop practicals
One fuli year reserved for Centre workshop
a - General metal work
b - Blacksmithing
c - Weiri;Ag and Soldering
1120 hours
d - Sheetmetal work
One full year reserved for Centre workshop
a - Stationary diesel engines
1000 hours
b - Agricultural machinery
c - Water pumps and water supply
Two full ye:-rs reserved for on-the-job training:
1120 hours
a - One year partly practicals
b - One year full on-the-job
training outside the Centre.
(Care should be taken that
the time is evenly divided
for practical training in
ail skills.)
--- --
Stationmy diesel engilnes
With the introduction of mechanically driven
water pumps, small agricultural machinery and
electric plants for all kinds of purposes in
modem agriculture and general development,
an urgen! need ha? grown up for skilled people
able to look after diesel engines - the main
pot4 er source for these machines.
That is why a widely trained mechanic who
owns certain tools and equipment should be
eblt to carry out most of the common repairs
and maintain these engines used in rural areas.
This part of the Rural Mechanics Course
provides the necessary information for
technical training on water and air cooled 1,2,
3 and 4 cylinder stationary diesel engines,
- reading engine manuals,
- instal’ling stationary diesel engines,
- dismantling an engine,
- checking patts,
- repairing certain items,
- knowing how to order engine parts,
- assembly of the engine,
- ensuring sound running of the engine,
- keeping up the maintenance of the engine.
Diesel engine theory
This diesel engine theory book can be used in
the classroom as well as in the workshop,
where text and illustrations will help the
instrwtion on the operation of the diesel
engine and ensuring sound running of the
During workshop or classroom theory lessons,
making use of large technical aids is very
much encouraged. The aids may be real parts
cut in sections or self-made parts from all
kinds of material made and coloured, ta show
the trainee clearly the function(s) of that
particular part.
It is advisable to start instruction on diesel
engines only when the trainee has finished the
major part of the whole Rural Mechanics
Course, technical drawing and general metal
work, which can be seen as preparatory to this
part of the course.
Although some science is needed for the
inst,ruction on diesel engines, it is left to the
instructor to find the time and the suitable
materials to teach this science.
Going through this book you will rightly note
that no very detailed explanations are given on
the construction of the diesel engine. This is
because the course is only meant to teach the
trainee the princi$es behind the working of the
stationary diesel engine and not the
composition of special metals or materials
ased in these engines, or the repair of very
complicated parts.
During theory lessons in the classroom or
workshop, ampie time should be given the
trainee to make the necessary notes and any
question should be correctly formulated before
explanations are asked for.
Diesel engine workshop practice
During workshop practice where several
trainees are working on one engine, it is
advisable to appoint one trainee supervisor of
the group. He should be responsible for
org,anizing the work to be done, recording all
technical data, final checking of all parts, for
assembly and smooth running oi!he engine.
The engine may only run with permission from
the instructor and in his presence. Each trainee
should be appointed to the position of
supervisor by rota.
repairing all kinds of diesel engines which may
need repairs.
Instruction on cleaning and *ystematic working
is very important. During the practicals in the
workshop, parts should be handled with care,
recorded and stored in a box and locked in a
storeroom after the lessons.
The progress made by trainees in the workshop
and also during on-the-job training should be
recorded. In general. m&arksshould be given for
constructional skills and other marks for the
way in which the work is carried out. These
marks will differ in value when a final mark is
Enough time should be set aside for instruction
on how to install diese! engines and, if
required, to the attachment of equipment.
Special attention should be paid to vet rtilation
in an engine room, because high temperatures
reduce the life of diesel engines considerably.
The storage of fuel should be given the
necessary attention because in rural areas fuel
is mostly bought and stored in bulk, which
must be done under the correct conditions.
During workshop practice trainees should be
encouraged to carry out manv jobs on the
engine with a limited set of tools or equipment.
But, however the limited set of tools, the
trainee should learn to use the correct ones.
Too often spanners or tools are used which do
not fit correctly, resulting in damage to nuts
and bolts in parts of vital importance.
Correct teaching of this course makes it
necessary to have additional tools and
::quipment in the workshop and to instruct
trainees in how to work with them. This is
necessary, because the trainee himself may not
be able to buy this equipment but he may be
able to use them at a later stage when worktng
in a co-operative workshop where the group
owns these tools or equipment.
It is left to the discretion of the instructor to
use his creativity to teach trainees how to make
and construct additional equipment which they
can make by themselves during other
workshop practicals.
Working with limited equipment also means
that trainees must learn to judge when to go to
more specialized workshops where more
complicated engine parts, such as fuel pumps
and injectors, can be checked and repaired.
hs a lot of time in this course is set aside for
practical training, especially during on-the-job
training, not much time will be available for
Stationary diesel engines
Following the technicitl development in rural
areas you will nctice that, besides newly
developed tools and equipment, the diesel
engine has also been introduced to ensure extra
power supply where this is necessary.
Small electric plants used in hospitals, schools
and co-operative workshops, grinding mills for
flour, bore-hole water supply etc. demand
power that can LX supplied by diesel engines.
The need for more power supplied by diesel
engines is accompanied by the urgent question
of how to install and maintain these engines.
Since the power requirements are mostly
moderate, this book explains installation,
maintenance and smooth running of only
stationary diesel engines.
When you look at a s:ationary diesel engine.
you may be confused at first to see so many
exttirnal parts mounted on the engine and you
may also wonder about their purpose. But
basically there are only a few real differences,
such as the number of cylinders. the actual fuel
supply to the cylinders and the cooling which
can be either water or air cooling. Many other
parts are installed to ensure high engine
A typical air cooled stationary diesel engine is
shown on page 13 and all external parts are
named. This kind of engine is used widely and
is either air or water cooled, depending on
requirements. As you rightiy note, this engine
has one cylinder and one fuel pump which is
iocated behind the fuel pump cover. When
more power is needed, a similar eng!ne is
possible with a longer crankcase onto which
more cylinders are mounted. For each injector
a separate fuel pump may be installed or a
common fuel pump from which all injectors
are supplied with fuel.
Whatever the difference may be, you should
first understand that during performance,
maintenance and testing the engine should be
mounted ridgidly to a firm base.
Installation of stationary diesel
During maintenance in the workshop and
operation in the engine room a statiotiiary
diesel engine should be bolted to a firm base in
such a way that it cannot vibrate excessively
during operation. You must make sui‘e that all
points of the crankcase with holes for the bolts
are resting correctly on the base, to avoid stress
when the nuts are being frster,ed.
In dusty places, such as rooms where flour is
ground or woodwork is done, a water cooled
diesel engine is recommended, because dust in
the air may jam the fan blades and also block
the fins around the cylinders, reducing the
essential optimum flow of fresh air.
Especially in tropical areas, diesel engines
should be installed in such a way that a
generous supply of fresh air is ensured and
precautions arc taken against dust. It is very
important to keep in mind that c:enn air is very
irnpcrtarlt for correct performance by a diesel
When working on a diesel engine it is essential
to have the m,anufacturer’s manual in addition
to this book to ensure correct settings and
dimensions of pans.
Let us tilke a iook at the next page where you
will see figures of the external parts of a
typical air cooled one-cylinder diesel engine.
Typical air cooled diesel engine
F’ront vhw:
Fuel tank 1-A
Fuel pump cover 1-B
Stop/start hmdle 1-C
Crankcae cover 1-r)
Starting shaft 1-E
Flywheel 1-F
Fan cover 1-C
Cylinder head cover 1-H
Valve lifter 1-I
Fuel overflow 1-J
Eack view:
Fuel tank cover 2-A
Air filter 2-B
Exhaust 2-C
Fuel filter 2-D
Lubrication oil dip stick 2-E
Speed adjustment 2-F
Fuel pipe 2-G
Camshaft extension 2-H
Gear cover 2-I
Fuel tank cover 2-J
--.-- J
D --
Water cooled one-cylintier
diesel engine
Figure I shows a section ot a one-q tinder
- Rocker arms
- Exhnust valve
10 - Oi I scraper rings
17 -- Throw
27 It Piston rings
28 - Gudgeon pin
29 - Cylinder ulock
30 - Connecting rod
31 - Big end (connecring rod)
32 - Crankcase
33 - Flywheel
3J -- Sump
Figure 1 shows a cross-section of a
one-cylinder, wa;er cooled dtesel engine. The
most important parts connected to the
functioning of the diesel engine are shown.
- Valves
- Combustion chamber
- Top Dead Centre (T.D.C.)
- Full stroke
- Bottom Dead Centre (B.D.C.)
- Entrance coolant
- T.D.C. crankshaft
- Throw
- Jollmal
10 -Counterweight
11 - B.D.C. crankshaft
i2 - Sump
13 - Injector
14 - Cylinder head
15 - C> ,,;rder head gasket
16 - Cylinder bore
17 -Top, piston
18 - Piston rings
19 - Piston
20 - Gudgeon pin
21 - Engine block
22 - Cooling compartment
23 - Connecting rod
24 - Crank case
25 - Big end (connecting rod)
26 - Crankshaft
27 - Distance half stroke
28 - Distance full stroke
Water cooled one-cyiinder
diesel engine
j 13 /
i I, !
- 24
Internal combustion engine
An internal combustion eq.$nc is an engine
which burns fuel internally. This engine is
b;l+aliy a container, see Fig. 1, into which
fic4 and uir can be fed and made to bum.
!:; ::lre I-A shows just such a container, closed
w& a stopper, in which there is a mixture of
fuel and crir.The mixture of fuel and air is
highly flammable. If by any means the mixture
is ignited, the container explodes, throwing the
stopper out of the container with force, as
shown in Fig. 1-B.
Air has two properties which affect the engine:
- Air can be compressed.
- Air gets hot when it is compressed.
Fuel should mix readily with air and ignite
easily by vapori;rjng. Vapc~r-izinghelps each
particle of the fuel to contact enr;ugh hot air to
bum fully.
Cornhwion is the actual igniting and burning
of the fuel/air mixture. It is the oxygen in the
air which combines with fuel to cause
Fast burning fuel
If a container with diesel fuel is ignited in calm
outside air, ii bums rather lazily, because the
air contacts only the surface of the fuel. To
make it bum faster we have to:
- heat the fuel,
- vaporize the fuel.
But too powerful an explosion damages an
engine, so we have to control the rate of
burning. The rate of burning depends on:
- how much the air is compressed and thus
- how much fuel is used,
- how volatile the fuel is.
Figure 2 shows the fuel/air mixture 2-A
trapped in a strong cylinder which is closed at
one end. A piston 2-P is fitted into the cylinder
in such a way that it can move up and down
inside the cylinder, but while moving, it keeps
the gases tightly locked inside the cylinder.
When the piston is moved upwards the fuel/air
mixture is compressed in chamber 2-B.
When the compressed fuel/air mixture is
ignited it explodes, creating a high pressure in
the cylinder 2-C above the piston 2-P. The
pressure then pushes the piston down in the
cyiinder and this produces mechanical energy.
Reciprxating and rotary
The up-and-down motion occurrin;: in the
cylinder is cdled reciprocating motion, see
Fig. 1-R. In the engine the reciprocal motion of
the piston must be converted into rututy
motion, to be able :o drive any gears. Four
basic parts are needed to make the engine work
this way:
- cylinder
- piston
- connecting rod
- crankshaft
As explained before, the piston and the
cylinder are mated parts. They are fitted so
closely that no gases can escape, but with a
little clearance at the sides to ensure a smooth
reciprocating motion. See Fig. 2.
The link transmitting the reciprocating motion
of the piston to the crankshaft is called the
<onnecting rod, 2-A. The crankshaft 2-B has a
section off the centre line of the shaft so that it
‘cranks’ when the shaft is turned. This rotary
motion is basically the same as pedalling a
bicycle. Your leg is like t!!e connecting rod,
while the pedal crank and the sprocket are like
the crankshllft.
The whole combina;ion shown in Fig. 2 makes
it possible to convert the reciprocating motion
2-C into a rotary motion 2-D.
R j
T.D.C., B.D.C., stroke, bore,
volume throw and compression
Top dead ccntre
When the piston is at its highest position. the
piston is at rap dead cenrre (T.D.C.), see Fig. 1
Bottom dead centre
When the piston is at its lowest position. the
piston is at bottom cfeadcenrre(B.D.C.), see
Fig. 1.
The distance between T.D.C. and B.D.C. is
called strok (S), seeFig. 1. The stroke is
measured in mm.
The inside diameter of the cylinder is called
bore (B). see Fig. 1. The bore is measured in
The distance between the centres of the
crankshaft and connected rod journals is called
rhrow (T). The throw is half the distance of a
stroke, see Fig. 2.
Compression ratio
Com;lression ratio is the total volume of air in
a cylinder when the piston is at B.D.C.
compared to the volume in the combustion
chamber when the piston is at T.D.C. - for
example 16 to 1 in a diesel engine. Refer to
Fig. 3:
Compression ration =
in principle:
(Stroke (A) + Combustion Chamber(B)) /
Combustion chamber =
= Stroke volume = R/4 x D2 x Stroke length (A)
Comb volume = rc/4 x D” x Comb chamber
Compressian ratio = (A + B)/B
Described, for example, as 16: 1.
The four-stroke cycle engine
For the operation of this engine, a series ot
events must take place in sequence:
- Irduclion stroke 1-A
Clean air is drawn through an air filter in!
the cylinder. The air enters through the op~rl
inlet 1-I valve as the piston moves down on
the induction stroke.
- Compression stroke 1-B
The inlet vaive closes and, as the piston
rises, the trapped air is compressed to the
required prt=.ssure.Fig. 1-X shows the
moment the air is compressed and the fuel is
- Power stroke 1-C
At second the fuel is spral ‘l’ 1.particles
vaporise almost instam
sly and start to
burn. The heat needed th :ite the particles
comes from the very hl’ ;xessure of the
compressed air charg.
continues, the pres”
Ikecylinder rises
ib fmed d own to
very rapidly and ti?c
give the power st i ’
- Exhmststrob I-Y
Towards the t’~ rower stroke, the
exhaust vi&C*663iii 410~ the waste
products 04
tbustion to escape. With the
exhaust Y.
-E fully open, the cylinder is
~bptiedof the waste products as
the pistall I ises for the second time.
Figure 1-Y shows the moment the exhaust
valve closes and the inlet valve opens again.
Multiple cylinder engines
So far we have seen the operation of one
cylinder in an engine, but since this cylinder
gives only one power stroke every two
revolutions of the crankshaft, it produces
power only one quarter of the time.
For more continuous power, extra cylinders are
added to the engine and each one delivers one
power stroke during the two revolutions of the
The power strokes thus follow each other more
closely, resulting in a fairly continuous
delivery of power to the crankshaft. For
examp!e, in a typical fp.iar-st_T(_e&e engiqe
with three cylinders, the cranks are set 120
apart on the crankshaft, see Fig. 1.
The cylinders normally .fire and deliver their
power strokes in the following order: 1 - 3 -- 2.
The ~c wer strokes follow each other closely,
thus ensuring continuous and smooth delivery
of power to the crlcnkshaft.
The heavy flywheel I-A attached to the
crankshaft at the rear gives it momentum to
return the pistons to the stopsof the cylinders
after each power stroke. Counterweights on the
crankshaft are used to help balance the forces
created in the engine by the fast moving parts.
Different types of engines
Besides the in-line e.rgine shown in Fig. 2-A.
you may see some other types of engines, such
as an engine with the pistons lined up in a ‘V’.
So Fig. 2-O shows an engine called a V-engine.
Another arrangement of pistons is shown in the
engine in Fig. 2-C. This is called a boxer
engine. It has the pistons situated opposite to
each other on the side of the engine.
Components of the engine
Cylinderhead cover
Components of the engine
Cylinderhead: valve assembly
Engine block: flywheel and crankshaft
push rod
Engine block: camshaft
The cylindrt head is fitted at t’\e top end of the
cylinder block and secured with studs or bolts
passing through the head to the cylinder block,
Most cylinder heads are czst from an alloy of
iron and copper or aluminium. The intake and
exhaust passagesarc cast or bored into the
cylinder head as shown in Fig. 1:
- Cylinicr head 1-A
- floles for valves 1-B
- floles for pushrods 1-C
- Moles for air inlet 1-L)
- kiolel; for exhaust 1-E
- Floles for bolts or studs 1-F
Part c;l a typical cylinder head is shown in Fig.
2 with an exploded view of the stud with a nut.
Figure 3 shows an enlarged detail of a cylinder
head bolt 3-~ and nut 3-R.
Servicing the cylinder head
First r=‘move the rocker arm assembly before
taking off the cylinder head. Then carefully
loosen the cylinder head nuts and bolts. Leave
the injectors ire the cylinder head, because as
the crankshaft turned pressure built up in the
cylinders and this helps loosen the cylinder
head. Light tapping with a soft hammer may
make the cylinder heati come off more easily.
Never use a screwdriver or cold chisel between
the head and the cylinder block, since this wi!l
damage the edges of the cylinder &ad and the
enpir,e block. After ~<moval. check the surface
of the cylinder head for damage. Clean all
carbon deposits from the head by SCraping or
brushing with a wire brush. Also check the
water p3SSilgeS for lime deposits.
After a long period of service or overheating,
the heat may have caused the head to warp So
check the surface as follows, see Fig. 4.
- Use a heavy accurate straight edge and
feeler gauge to check for warp at each end
and between the cylinders.
.- Check too for end-to-end wq in at least six
- Decide whether the cylinder head must be
re-installed or rr-faced. Re-facing is done in
a specialty equipped shop.
- Also check the head for any cracks.
Cylinder head gasket
A typical cylinder head gasket is shown in
Fig. 1-A and an enlarged derail in Fig. 1-B.
This gtikct is placed between the cylinder
head and the cylinder block and is used to
make the connection between these two; it is
gas and water-tight.
Gaskets are made up from different materials.
For exlimple, the one shown is composed of
one layer of copper 1-C and three layers of soft
iron I-L). When inst,alling the cylinder head,
mind the top and front of the gasket.
Installing the cylinder head
After checking the valve seats, which will be
explained at a later stage, the cylinder head can
be installed agair,. First check the surface of
the cylinder blcc;i. Install ii new cylinder head
gasket, following the manufacturer’s
recommendatinns about application of a
sealing compound on one or two sides of the
head gasket. Carefully set the cylinder head on
the cylinder block, without disturbing the head
Make sure the ends of the bolts or studs are
clean and lightly oiled.
Press down the cylinder head gradually aid
evenly. This is very important to ensure a good
seal between the cylinder head ‘and the cylinder
Tighten the nuts or bolts fingertight. Use the
sequence shown in Fig. 2 for tightening the
head bolts or nuts. turning them one by one
about one-half turn until the torque specified
by the m‘anufacturer is reached. Sometimes
nuts or bolts are tightened in a way discribed
by the engine manufacturer.
Cylinder hcud mm or bolts shmld usually be
re-tightened IOthe specifiedwque ufter a
,_._ __ _, . .‘\.,,\
--. -----__---
Valve mechanism
As you know, an engine must take in fuel/air
and exhau. bzrned gases. Intake and rxhausi
must occur at precise intervals. Valves as
shown in Fig. 1-A are used to do this job. The
whole v&aliveoperating system is called the
valve truin:
- Valves (inlet small, exhaust large) 1-A
- Valve springs 1-B
- Valve rocker arm I-C
- Push rod 1-D
- Valve lifter 1-E
- Camshaft I-F
- Gear transmission 1-G
The position in which the valves operate here
is called overheudvalve mechanism.
Sequenceof valve operation
Figure 2 shows once again the sequence of the
valve operation in a typical four-cycle engine.
Each cylinder has one int;ake and one exhaust
valve in this case.
- Intuke
During the intake stroke, the inlet valve
opens as shown in Fig. 2-A. The fuel/air
mixture is drawn into the cylinder through
the open inlet valve while the piston moves
- Compression
Both valves are cioscd, see Fig. 2-B, when
compression takes place during the upward
movement of the piston.
- Power
Both valves remain closed while the
compressed fuel/air mixture is ignited and
expanded gases force the piston down, see
Fig. 2-C.
- Exttaust
The exhaust valve opens when the piston is
moving upwards and thus forces the burned
gasesthrough the open exhaust valve, see
Fig. 2-D.
Valve lifting system
A typical valve lifting system is shown in
Fig. 1. It consists of:
- Combustion chamber 1-A
- Valve seat 1-B
*..- ..-.- J
- Port 1-c
Valve guide 1-D
Valve stem 1-E
Valve springs 1-F
V&e spring retainer 1-G
Valve key 1-H
Rocker arm 1-I
V&e c!earance adjusting screw 1-J
Push rod 1-K
Valve lifter 1-L
- Cmhaf?
] k--- -- -.-- K
Valve detail
---.- F
Valve head 2-A
Margin 2-B
Face 2-C
Seat 2-D
Stem 2-E
Guide I-F
Poppet valve detail
- Inner valve spring 3-A
- Outer valve spring 3-B; nr,it: that the inner
and outer springs are wmded in opposite
- Valve spring retainer 3-C
- Valve stem 3-D
- Valve key (in two halves) 3-E
- Vdve cap 3-F allows the valves to rotate
during operation
Ccieling the valves
Valves have to be cooled while the engine is
hot due to operation. See Fig. 4. The valve heat
is transferred to the head 4-B and from there to
the water passages4-C which are cooled with
coolant (see arrows). At all times the heat of
the valve is transferred to the valve guide 4-A
and from there to the cylinder head.
The cylinder head is cooled with coolant. You
must ensure that all passagesin the cylinder
head are clean and wide open so the coolant
can pass freely during engine operation.
Removal of valves
Follow &is procedure when removing the
valves from the cylinder head:
- Using a valve spring compressor, compress
the valve springs, Fig. 1.
- Place the valve spring compressor
absolutely straight on the valve head and at
the other side on the valve spring ret&er,
see Fig. 2.
- When you turn the handle of the spring
compressor, the valve spring retainer 2-B
should move down and release the two
halves of valve key 2-A. Place the two
halves for easy replacement in their original
- Remove the valve spring retainer 2-B and
the two springs 2-C. Place them in order.
- Before pushing out the valve, check whether
the rotation of the valve has produced a burr
on the tip of the valve stem 2-D. If so,
remove the burr as it might otherwise
damage the valve guide bore 2-E.
- Push the valve out of the valve guide and
place it carefully in order.
Checking valves
Check all valves for:
- distortion and deposits on the valve face and
valve stem,
- burned and broken valve heads,
- erosion under the valve heads,
- fatigue and broken valves,
- worn valve guides,
- the thickness of the margin on the valve
head. If it is less than l mm, the valve must
be replaced, see Fig. 3.
Correct shape of valves
A correctly shaped valve is shown in Fig. 3-A.
The margin 3-X is the same on all sides and
the face is perfectly round. Fig. 3-B shows a
valve with a knife head. This valve cannot be
used any more. A warped and knife-edged
valve head is shown in Fig. 3-C.
Setting the valve clearance in a
four-stroke diesel engine
- Depending on the type of engine, the valves
should be set on a cold or a warm engine.
Consult the manufacturer’s manual.
- Remove the valve cover from the cylinder
on which the valve clearance is to be set.
Sometimes there is only one valve cover for
all the cylinders.
- Find (by looking at the manifolds, for
instance) the intake and exhaust valves of
the cylinder you are working on.
- Rotate the crankshaft in the correct direction
until the exhaust valve is comp!ctely opened
(seen from above it is pressed).
- Now rotate the crankshaft slowly until the
exhaust valve is almost closed and the
intake valve starts to open. At this moment
the cylinder concr med is between the
exhaust stroke and the inlet stroke, with the
piston in approximately TDC.
- Mmk the position of the crankshaft pulley
and make one complete revolution (360’).
- Now you can set both intake and exhaust
valves on this cylinder. You should always
use a feeler gauge of the correct size. To
ensure correct setting you also need the
feeler gauge of the next size up, which is
O.OSmm thicker. The correct feeler gauge
should just fit between the rocker and the
valve stem. The next larger feeler gauge
should not fit.
- Repeat this procedure for the other cylinder.
Reconditioning valves
The correct technical data on valves is
essential when they have to be ordered or
reconditioned. Take care that you know the
following measurements:
- Diameter, valve head 1-A
- Angle, valve face 1-B
- Width, valve seat 1-C
- Angle, valve face 1-D
- Diameter, valve stem 1-E
- Diameter, valve guide 1-F
- Length, valve guide 1-C
- Distance, guide from head 1-H
Note that inlet and exhaust valves are different.
intake valve seat inserts
If the engine has valve seat inserts fitted, the
maCmum amount that can be removed from
rhe valve seat insert during re-shaping is such
rhar a 45’ cutter makes contact with point 2-B.
To provide sufficient clearance between the
head and the piston crown, the intake valve
seats are machined approximately 1 mm blow
the cylinder head joint face.
Exhaust valve seat inserts
If a 45’ cutter .uakes contact with point 2-A,
the valve seat insert must be removed and
exchanged for a new one. The valve seat
should be 1.5 to 2 mm wide.
Intake valve seals
If an engine has halve seats cut directly into
the cylinder head casting, the maximum
amount that can be removed from the seat is
such that a step remains at 3-A. The width of
the valve seat should be about 1.5 to 2 mm.
Grinding precautions
Do not grind too long.
Do not use too much pressure.
Keep the work area clean.
Check the seat width and contact with
Grinding-in the valve seats
When removing valves from the cylinder head,
remember to place them in a numbered rack or
mark them, to ensure that all valves return to
their own valve guides. If ail valves, vn!ve
guides and valve seat5are in good condition,
each valve should be ground in.
It is important to know that the distance
between the valve head ‘and the cylinder head
joint face must not exceed 2.5 mm.
- Place the cylinder head on the work bench
with the cylinder head joint faced up.
- Coat one valve face lightly with grinding
paste. The grain size of the paste depends on
the condition of the valve scat.
- Insert the valve into its guide and rotate the
valve clockwise and counterclockwise using
a rubber suction type of grinding tool ;LS
shown in Fig. 1.
- While grinding in the valve seat, lift the
valve several times and press it down again.
allowing the paste to enter the gap.
- Examine the valve seat at intervals, until a
smooth dull ring is formed around the
seating face.
- Carefully remove all grinding paste from the
valve and the valve seat.
- Place the valve in its guide again and drop
diesel fuel onto the valve head. If the valve
seals through its own weight, the valve seat
is sufficiently ground in.
- Repeat this procedure for the remaining
+ -\
Valve guides
The valve guide ensures that the valve is
exactly centered, which in turn ensures a
proper valve seating. The wear of the valve
guide should also be checked when valve seats
are reconditioned.
To check the wear of the valve guide, raise t1e
valve with a piece of distance pipe to abol;. 13
mm above the cylinder head, see Figs. 2-A,
and 2-B. Place a piece of steel on top of the
cylinder head and against the margin of the
valve head. Move the valve left and right. If
the allowance is more than 1.5 mm the valve
guide must be renewed.
Camshaft and timing
The camshaft is fitted into the engine block on
the lefthand side, above the crankshaft, see
Fig. 1. In small and medium sized engines it is
generally made of a one-piece casting or
forging and is supported by three bearings.
Most camshafts are made of low-carbon alloy
steel. The cam and journal surfaces are
carburized before grinding them to their final
The intake and exhaust cams on the camshaft
‘rsefitted in pairs for each cylinder. The
arrangement of the cams ot.,the shaft
determines the firing order of the engine. The
contour of the cam, see Fig. 2, decides the time
and tie opening rate of each valve.
Camshafts may also drive oil pumps and fuel
pumps using extra lobs or a gear on the shaft.
The timing trnnmission
The camshaft, that is running at half the speed
of the crankshtit, can be driven by different
kinds of transmission, the mos: common are:
- Geurwheeltransmission
The gearwheel transmission uses a steel
gearwheel on the crankshaft, driving the
cLamshaft.See Fig. 3. To obtain a quiet
drive, this gear can also be made of other
material, sllch as pressed fibre or a light
alloy. Both gears have timing m;lrks. When
these are aligned, the crankshaft movement
and valve timing will always be in correct
relation to each other, see Fig. 3-A.
- Chain transmission
This transmission is used when the camshaft
is a long way from the crankshaft. See
Fig. 4. The timing sprockets on both
crankshaft 4-A and camshaft 4-B also have
timing marks 4-C. Both marks should be in
line with the centre line of the sprockets for
correct timing of the engine.
The timing chain is designed so that it H.III not
stretch during operation. But to improve
transmission efficiency and reduce noise. a
chain tensioner is placed on the non-puliing
side of the chain to maintain the proper tension
in the chain.
Valve timing
Valve timing is very important :hl obtaining the
best combination of:
- power - efficiency
- economy - long engine life
A key factor in achieving these objectives is
correct Wing of the cylinder with fuel/air
Valve timing diagram
Figure 1 shows a section of the inlet and outlet
pan. the inlet valve l-1, the exhaust valve 1-E.
the Diston, the connecting rod and a revolution
of the crankshaft, shown as a circle.
The inlet valve opens when the piston is just
about to reach the Top Dead Centre (TDC)
during its exhaust stroke. The valve remains
open during the inlet stroke and closes after ihe
piston has passed the Bottom Dead Centre
(BDC), see Fin 2.
This period when the valve is open (shown as a
dotted area) is given as degrees of the
revolution of the crankshaft in relation to the
position of the piston.
Valve timing degrees
Figure 3 shows a diagram with degrees, shown
3s A, B and C. In this case the inlet valve
opens when the position of the crankshaft is
20’ before the piston reaches TDC, see 3-A. It
closes when the position of the crankshaft is
60’ after ths piston has passed BDC. see 3-C.
The total time the valve remains open is
therefore 20 + 180 + 60 = 260’.
Valve timing degrees(exhaust)
Figure I shows the diagram with degrees for
the exhaust valve timing, where 1-A = 65’ and
1-B = 2V. The exhaust valve opens at 65’
before BDC (BBDC). The exhaust valve closes
at 20’ after TDC (ATDC).
The total time the valve remains open is
therefore 20 -t 180 + 65 - 265’.
Valve timing diagram
If we combine the inlet diagram and the
exhaust diagram in one drawing, we have a
valve timing diagram as shown in Fig 2. Valve
timing diagrams are supplied with each engine
according to the manufacturer’s
Typical engine valve timing
Sometimes a whole work cycle diagram is
supplied, as shown in Fig 3, where:
= 20
= 65’
= 60
D = 19”
The intake valve onens: 20 + 180 + 65 = 265”.
Both valves are closed during the compression
and power stroke:
180-65= 115’
180-60= 120
Total time 235’
The exhaust valve opens:
60 + 180 + 19 = 2.53”
This means the crankshaft rotates 265 + 235 +
259 = 759’ to complete the work circle.
Servicing the camshaft
A cam profile as shown in Fig. 1 includes the
ltO$e 1-A which holds the valve open, and the
buck 1-B which allows the valve to close.
If you look at the shape of the cam you will see
that it has curved faces. The right curved face
1-C causes the valve to open gradually until it
reaches the top of the nose. Face 1-D allows
the valve to close gradually.
Figure 2 shows how tappet 2-B res!s on a face
of the cam prior to being pushed open by the
nose of cam 2-A following the direction of the
Dismantling the camshaft
- Clamp the camshaft in a soft-jaw vice.
- Bend back the tab of the lock washer at the
front of the camshaft.
- Loosen the lock nut, remove the lock
washer, take off the drive gear and collect
the Woodruff key.
- Take off the front end of the camshaft
- Taks out the camshaft from the front of the
engine; be careful not to damage the cams
while removing the shaft.
- Clean the camshaft and the camshaft bores
with clean diesel fuel.
P .”
Checking the camshaft
A micrometer is needed to measure the cams
and journals of the camshaft and to check the
camshaft bores.
- First measure the camshaft journals for signs
of wear or out-of-round condition, see Fig.
3. This is done with an outside micrometer.
- Measure the camshaft bores with an inside
micrometer, see Fig. 4.
Compare the results with the technical data
provided with the engine.
- Check for wear ano scratches on the cam
lobes. Use the micrometer to check the
height and width of each cam lobe, see Fig 5.
- Compare the intake valve cam lobes with
each other. Compare the exhaust lralve cam
lobes with each other as well.
- Check the wear of the injection drive gear.
- Check whether the faces of the cams are
polished and examine the surface for
fatigue. The nose uf the cams should be
polished and flat.
- The end fioat, see Fig. 5. can be adjusted by
adding shims if it is too big or removing
material from the bearing bush if it is too
small. Carefully rub the bearing bush on
emery cloth until the correct end float is
obtained. Measrue with a feeler gauge.
The movement of Ihe cam is transferred by the
tappet first, see Fig. 1. When the tappet is
raised by the cam, some pressure is applied to
one side of it, see Fig. 2. To enable the lifter to
take this side pressure ir is designed with a
rather large diameter, see Figs. 1 and 2.
As you see in Fig. 3, the tappet is slightly
offset from the centre of the cam 3-C. This is
done so that the contact friction cl ites rotary
movement of the tappet. The resulr is that wear
is distributed evenly over the contact surface of
the tappet and lubrication is improved.
Figure 4 shows tappet 4-A which has been
turning satisfactorily and the wear is spread
evenly over the whole surface. Tappet 4-B has
not been turning and the wear is concentrated
in one place.
Chwk tappets
- Examine each tappet for wear and scratches
- Examine the tappets to see whether they
have been turning in their bores
- Check the seating of the push rods
Namesof tappet related parts
Tappet 3-B
Camshaft cam 3-C
Distance off-centre 3-D
Push rods
The push rod in Fig. 1-A transfers the motion
from the tappet to the rocker xm 1-B. It is
usually made of hollow steel pipe with solid
steel ends, see !*ig. 2. The upper end is
sometimes a:p-shaped to fit the ball-shaped
end of the adjusting screw. The other end is
slightly ball-shaped to fit the tappet. When
removing the pushrods, mark each rod so it can
be t-e-assembled with the same mating parts.
Check whether the push rods have become
bent. Place the rods on a flat steel plate and roll
them over. They must be replaced if they are
bznt more than the tolerance specified by the
Valve springs
The main function of the valve springs is to
close the valve and keep it closed until it is
forced open again by the camshaft. Cylindrical
springs as shown in Fig. 3 are installed in most
- Valve stem 3-A
- Spring cap 3-B
- Outer spring 3-C
- laner spring 3-D
Inspecting vnlve springs
- After taking off the springs, check the
casting on the cylinder block where the
springs rotate.
- Check that spring caps are of the correct
thickness. see Fig. 3-E.
- Check the end of the springs.
- Also check the springs by placing thern on a
flat surface, using the tee SCpliUtZ.
- Check the force of the springs with the
spring tester, see specifications.
- Do not worry if the springs are of different
lengths. Lengths may differ, yet the springs
will be the same length and have the same
force when they are,in the compressed
- Note that after valves and valve seats have
been re-ground there may be less spring
tension than before, because as the ground
valve seat is deeper the spring operating
height is longer. This can be remeuied with
a few washers.
.i _
Rocker arm
The rocker arm transmits the camsh,aft motion
to the valves. The rocker arms shown in Fig. 1
are mounted on a hollow shaft I-B which is
secured with brackets and bolted to the
cylinder head. LubnGating oil is pumped
through the hollow shaft to iubricate all rocker
arms. Springs are positioned between the
rocker arms to keep tt :m in place. A valve
adjusting screw is shown at 1-A.
A ---.---
Rocker arm tip
A rocker arm tip is shown in Figs. 2-A and
2-B. This tip 2-C, which comes into contact
with the valve cap 2-D. may exhibit concave
wear after some time and this will affect the
correct valve clearance. Sometimes a special
screw may be fixed in the rocker arm tip to
allow easy replacement of worn parts and extra
adjustment. When installing rocker arms, make
sure you install the arms and springs in the
same sequence as they were removed.
Valve ciearance
When valves arc properly adjusted, there is a
small clearance between the valve tip and the
valve cap- see 2-E. This clearance is called
valve lash or valve clearance. Valve clearance
is essential to allow for hea! expansion in all
the parts involved. Without clearance,
expansion of the heated parts means the valve
stays partly open during operation.
Accordirlg to the manufacturer’s
specifications, the valve clearance may depend
on whether the engine is hot or cold.
Too little valve clearance
Too little valve clearance affects the timing of
the engine. It may make the valve to open too
early and close too late. Additional it may
cause bending of the push rods, because they
expand in length due to the heat. Too little
valve clearance can also make the valves bum,
because hot combustion gases passir?ground
the valve can cause overheating. This is
because the valve has not been in contact with
the valve seat long enough and therefore
cannot cool down. See Fig. 3.
Too much valve clearance
Too much valve clearance may cause the
situation shown in Fig. 1. Contrary to the
situation shown in Fig. 3 on the previous page,
the combustion heat is transferred tlj the CGGkd
cyliider head, but the exhaust gases il~e sealed
into the cylinder and cannot escape because the
exhaust valve closes 100 early and the fuel/air
mixture is late entering the cylinder during the
intake stroke.
The valve itself may also be damaged, because
in a normal situation the shape of the cam
means the camshaft slows the speed of the
valve movement as it closes. with tOGmuch
valve clearance, tht: valves close with great
impact, cracking or breaking the valve and
damaging the cam and the tappets as well.
Refer to Fig. 2:
- Valve clearance 2-A
- Rocker arm 2-B
- Valve head 2-C
- Screw 2-D
- Valve 2-E
Follow the manufacturer’s \‘pecifcationswhen
adjusting the valve clea~anre!
- Make sure the engirie is at the recommended
- Check which are the inrake and which are
the exhaustvalves, because the clearance is
usually different for both.
- Most engines have trming marks on the
flywheel. Turn !)le fly wheel until the first
cylinder is at Top Dead Centre (TDC) of its
compression strokr*.
- ?5.method of finding GU& wherher the piston
is exactly at TDC is to remove the injector
and close the hole with your finger. On the
compression stroke, air is then forced out
through the hole against your finger until the
piston reaches exactly the TX point. Never
try to feel where t!!e piston is with your little
finger through the injector hole - this is very
- Check the valve clearance when the piston
is at TDC. If necessary, adjust the valve
clearance with a feeler gauge as shown in
Fig. 3, turning adjusting screw 2-D up or
down until the correct valve clearance
according to the specifications is obtained.
- hate the flywheel in its fling order and
adjust all valve clearances when each piston
reaches the TDC on its compression stroke.
- Check again after running in.
Cylinder blocks
Figure 1 shows a typical cylinder block. This
block is made of grey c*astiron as a one-piece
casting. Cylinder blocks are cast with centre
webs to suppon the crank and camshaft. They
have enlargements in their walls for coolant
and oil passages.
The cylinders in the cylinder block are
sometimes cast into the block or bored in the
block at a later stage to lodge replaceable
cylinder liners.
Cleaning cylinder blocks
After stripping, scrape all gasket material from
the surface of the block. Remove all oil gallery
and core hole plugs to facilitate cleaning inside.
Cleaning can be done with hot water or any
other recommended solution. A special
solution should be used in particular when the
water passagesare heavily scaled. Ir is very
important to clean the passages well to avoid
overheating of the cylinder block.
Inspecting the cylinder block
Cracks and leaks can be checked with water
and air pressure. Check the cylinder block top
surface as shown in Fig. 2. The surface is
checked in all directions with a straight edge
and a feeler gauge, see Fig. 3. This chc: king
must be very accurate. because the surface
must seal oft the ‘areato water, oil and
Inspect all studs, dowels, pins, pipe plugs etc.
for looseness, damage or wear and replace
parts as necessary. Inspect the cylinder bores
carefully. After cleaning and inspection, spray
the whole cylinder block with thin engine oil.
The cylinder
A cylinder is basically a hollow Nbe which
guides the piston and forms the combustion
chamber together with the cylinder head and
the piston. There are two basic types of
- Cast-in-block
- Individual castings
::...,..:, , ,I.....<
In a cast-in-block engine design, the cylinders
are cast and polished into the cylinder block,
thus forming a single unit.
Individual castings
In this type of casting the cylinder is made
together with the cooling fans and bolted
separately to a base. The main advantage of
such a system is that it is possible to build up
an engine with any number of cylinders.
Another advantage is that, if failure occurs in
one of the cyclinden. it can be replaced
. . . . . . .. . .. ... .:,
Dry and wet liners
Another type nf cylinder casting is one in
which the cylinder is made and shaped like a
hollow tube which fits into the cylinder block.
There are two types:
- Dry liners, see Fig. 1
- Wet liners, see Fig. 2
Dry liners
Dry liners are sleeves which fit inside an
already completed cylinder casting in the
cylinder block, see Fig. 1-C. The liner is in fact
a wearing surface for the piston, because the
imaterial the cylinder block is made of is not
able to withstand forces applied during
operation. As shown in Fig. 1 this liner is not
exposed to the engine coolant in 1-A and l-B,
so it is called a dry liner.
Wet liners
An engine with a wet liner is shown in Fig. 2.
You note that this liner 2-C has two functions:
it is the actual cylinder and it also forms the
inside of the water jacket 2-A and 2-B.
Two sections of wet liners are shown in Fig. 3.
As you see, both liners have flanges at the top
to seat in a mating counter-bore at the top of
the cylinder block. The bottom of the liner is
sealed with two rubber rings 3-A or with a
copper ring 3-B.
Servicing cylinders
A cylinder is removed with a cylinder puller as
shown in Fig. 1. After removing the cylinder
the rubber or copper seals can be taken off.
Then clean the counter-bores on top of the
cylinder block and remove the scale from the
water jackets with a wire brush. Also clean the
lower sealing surface in the cylinder block
where the rubber or copper seals are positioned.
When removing the cylinders, mark them and
place them in the same sequence as you take
them out of the cylinder block.
Checking cylinders
Measure the cylinders for taper shape and
out-of-roundness. This means measuring the
top and bottom parallel to the crankshaft.
Measure too the top and bottom parallel and at
right angles to the crankshaft. Then compare
the differences.
The tnlerances depend on the manufacturer’s
specitications for exact wear limits, which
should generally not exceed 0.127 mm. After
measuring decide what sho:t!d be done:
- replace the cylinder,
- re-bore the cylinder,
- hone the cylinder,
- de-glaze the cylinder.
Replace the cylinder when the wear is beyond
the tolerance. The piston is usually rep!aced as
Cylinder liners for larger engines are re-bored
when necessary to the smallest oversize
diameter. Oversized pistons should then be
fitted to provide the correct piston-to-liner
clearance. Re-boring is done with special
machinery complying with the manufacturer’s
Honing is done to smooth the cylinder and
produce a special finish which must be neither
too rough nor too smooth. A finish which is
too smooth can retard piston ring seatings nnd
a rough fmish may wear out the rings too
A typical honing tool is shown in Fig. 1. insert
the hone in the cylinder bore and adjust stones
X-A to the narrowest section. When it is
adjusted correctly, move the hone up and down
at low speed with a stroke overlapping by
about 2.5 mm. Concentrate first on the high
spots. When they are removed, the drag of the
hone becomes lighter. When honing, use a mix
of 50% diesel fuel md 50% engine oil to
ensure the honing stones are cooled and to
avoid excessive wear.
Remove the hone and measure the bore. It
shouM be clear that moving the hone from top
to bottom inside the cylinder will not take
away the out-of-round shape. Make sure that
you do not remain in one place too long while
honing, because the bore will become
irregular. Thoroughly clean the cylinder, and if
necessary the cylinder block, to temove all
particles caused by the honing.
De-glazing is done with a special de-gkazing
tool as shown in Fig. 1. This tool is brush-like
with coated tips. Move the tool at low speed
for at least 10 complete strokes. Move it at
such a speed that the result is a cross-hatch
pattern as shown in Fig. 1.
Installing dry cylinder liners
First read the manufacturer’s recommendations
on installing the dry liners. Clean all parts
correctly and insert the liner cnrefully. placing
each liner in the bore from which it came
Installing wet cylinder liners
Clean the cylinder flange and the lower sealing
surface. Also clean the cylinder block bore ‘and
the lower sealing surface inside the cylinder
Install the liner first without a seal and check
its height in relation to the top of the cylinder
block. See Fig. 2. Check whether the liner is
seated squarely. All cylinder liners should be
of the same height to avoid cylinder head
gasket leaks. Take out the liners and place the
new seals. If necessary, lubricate the seals and
the mating surfaces in the cylinder block. At
the same i me make sure the seals are not
twisted. F vss the liner as far into position as
possible Fy hand. Finish the job by placing a
hard woe :en block over the liner and tapping it
lightly w tb a hammer, moving it into position,
see 2-A. rhe liner may protrude above the
cylinder block 2-C, see 2-B. The cylinder head
2-D will finish the rest and press the bottom
seal together. The top of the liner is sealed off
with the cylinder head gasket 2-E.
The piston is basically a plunger which moves
up and down inside the cylinder. It seals off the
crank case from the combustion chamber. Its
main functions are:
- Sealing off the crank case from the
combustion chamber.
- Providing vacuum during the intake stroke.
- Receiving the force of the expanding gases
and passing it on to the connecting rod etc.
- Pushing out the exhaust gases.
- Compressing ‘air prior to ignition.
Pistons are made of:
-. cast iron,
- aluminium ahoy.
Parts of the piston are (see Fig. 1j:
- Pis:on head 1-A
- Reinforcement 1-R
- Head rib 1-C
- Lubrication holes 1-D
- Piston pin boss 1-E
- Top land 1-F
- 2nd land 1-G
- 3rd land 1-H
- Ring groove 1-I
- Skirt 1-J
~.- 21
Piston construction
Ribs inside the piston reinforce it and at the
same time transfer the heat from the head to
the piston rings. The skirt, see Fig. 2, keeps the
piston in alignment. It is usually tapered, so the
diameter of the skirt 2-A is slightly larger than
the diameter 2-B at the piston head. The
elliptical shape shown in Fig. 3 should be
slightly more across the thrust face in diameter
3-B than diameter 3-A.
Types of heads
- Flat head
- Irregular head
- Concave head
The different shapes of the piston faces are
shown in Fig. 4. They allow for more or less
compression and swirling. Remember that
diesel engines sometimes have swirling
chambers in the cylinder head, which will be
explained at a later stage.
Piston rings
Ring grooves are cut round the piston to
accommodate the piston rings. A typical piston
ring is shown in Fig. 1. Piston rings have three
- They form a gas-tight seal between the
piston and the cylinder.
- They transfer the heat from the combustion,
affecting the piston to the cylinder.
- They control the lubrication between the
piston and the cylinder wall.
Compression rings
Compression rings can have various shapes as
shown in Fig. 2, where you see:
- Rectangular type 2-A
- Taper-faced type 2-B
- Key-stone type 2-C
- Barrel-face type 2-D
- Other types are available
Compression rings can have different joints,
see Fig. 1. Three types are shown:
- Step joint 1-A
- Angle joint 1-B
- Straight joint 1-C
Oil rings can also have different shapes. The
ring shown in Fig. 3 has an expander spring
inside the ring. A detail of the function of the
oil ring is shown in Fig. 4. The oil control ring
is marked 4-A. The piston section is marked
4-C. The oil return holes are marked 3-A and
Oil consumption must be controlled to avoid
waste and a smokey exhaust. So the oil ring
must wipe any excess oil from the cylinder
wall and allow it to return through the oil
return holes in the oil rings and in the piston.
From there it returns to the crank case.
Pisim and piston sings
To obtain a good seal between cylinder wall
and piston, the piston rings should have the
correct shape and tension and be installed in
the specified sequence. If piston rings are
installed in the wrong sequence, are of the
wrong type or size or arc overstretched, oil and
gases may pass and cause overheating and
other problems.
Overheating, unburned fuel or an excess of
lubrication oil collected by the rings during
operation may cause them to stick or become
plugged into their grooves. Rings often break
when they are stuck or plugged.
If you look at the power stroke 1-A illustrated
in Figs. 1 *and2, you see that combustion
forces the ring dcwn against the lower side of
the groove 1-B. The gases which pass behind
the ring force it out against the cylinder wall,
resulting in a tight seal, see 1-C.
A new rectangular or tapered ring installed in
an old groove is shown in Figs. 3 and 4. The
worn sides of the old groove do not permit the
new ring to mate correctly, giving a bad seal
between both the face and the side of the ring.
The result will be broken rings and damaged
The top piston ring is very important &cause it
acts as a compression ring and at the same time
as the final oil control ring. The top ring and its
groove wear a lot because they are exposed to
most of the heat, pressure and dirt and get the
least lubrication. Rings must fit correctly in
their grooves and have the correct side
clearance. The grooves must be smooth and
Lubrication oil consumption
As explained before, tire function of tire piston
and the piston rings is to seal off the
combustion chamber from the rest of the
engine and prevent from:
- excessive lubrication oil consumption,
- gases passing to the crankcase.
Excessive oil consumption can occur due to
the pumping action of a piston with worn
piston rings. The more the cylinder and piston
rings are worn, the greater the oil consumption.
Piston rings must however let a small amount
of oil pass for correct lubrication, thus leaving
a film of oil on the cylinder wall to avoid
wearing out too fast.
Correct oil consumption is shown in the
illustrations, where you will see:
- Cylinder wall 1-A to 4-A
- Piston and rings 1-B to 4-B
- Lubrication oil (shaded areas) 1-C to 4-C
- Blow-by gases 4-D
As the piston moves down. oil is forced into
the ring grooves by the scraping action of the
rings on the cylinder wall, see shaded area 1-C.
This happens during the intake stroke.
During the corrgressionsrroke. seeFig. 2, the
piston rings are forced to the bottom of the ring
grooves, with the result that the oil is trapped
above the rings in the grooves Z-C.
The power stroke makes the piston move down
and the oil is rhen transferred to the cylinder
wall. The piston rings are held down against
the ring land by the force of expansion, see
Fig. 3.
During the exhausr stroke the oil is forced from
the cylinder wall into the combustion chamber,
where it is burned. See Fig. 4.
When cylinders or piston rings are worn, gases
can mass by between the cylinder wall and the
rings. This is called blow-by. A small amount
of gas alv’ays passesbetween the cylinder and
the rings. ‘ihe cr‘ank case must therefore be
well ventilated, see Fig. 4-D. Blow-by can
cause the pistons to overheat and expand, thus
scoring, both piston and cylinder wall. The
lubrif.ation oil is then contaminated and causes
wear. Compression is lost, leading to loss of
Wear of piston and piston rings
Wear of piston and piston rings may be caused
by dirty lubrication oil, wrong air intake and
dirty fuel. Another cause of wear Is scuffing.
what happens when two metal parts rub
together. Heat builds up to the melting point
due to the friction, after which some of the
melted metal is puUed out and deposited on the
cooler surface, as shown in Fig. 1. The coolest
part is of course the cylinder l-B, which is
cooled with water 1-C. If no coolant is present
the piston 1-A may be the hottest pan.
Scuffing is difficult to identify. If it develops
to the extent of becoming noticeable, it is
called scoring.
Another cause of piston and cylinder wear is
corrosion. Leaking coolant, the wrong
lubrication oils or cold engine operation can
cause this problem. Corrosion will leave a
mottled, grayish pitted surface on the pistons
and cylinder walls.
Burning the piston and breaking or sticking
rings may occur due to kno&ng. This is the
result of fuel in the cylinder combusting too
early, too fast or unevenly. Another cause of
knocking may be:
- wrong fue!,
- ignition timing advanced too much,
- over-fuelling,
- cooling system not working.
Piston damage
A piston may be damaged if:
- The piston is handled carelessly before
- The ring grooves are damaged while
cleaning out the carbon deposits.
- The gudgeon pin locks are faulty or wrongly
- The cylinder born is out of alignment.
- The crankshaft has too much float or the
journal has too much taper.
Cleaning the piston
Do not use a wire brush to clean the piston.
Avoid scratching the sides of the piston ring
Inspecting the piston
After taking the piston out of the cylinder. take
off the piston rings with a ring expander and
place the rings on the workbench in the correct
order, see Fig 1.
After cleaning, check the piston for cracks in
the head and skirt and for bent or broken lands.
Check the whole piston for score marks, signs
of overheating and fmally for damaged ring
Piston to cylinder clearance
To find the clearance between the cylinder and
the piston you must:
- measure the inside cylinder diameter with a
micrometer at rightangles to the crankshaft
in the lower area of the cylinder,
- measure the diameter of the piston with a
micrometer across the thrust face, see Fig. 2.
The difference between these measurements is
the clearance. Always compare the results with
the technical data in your engine manual.
Checking the ring grooves
A ring groove must be checked as shown in
Fig. 3. Place a corresponding ring 3-B into the
groove. Insert a feeler gauge 3-A between the
upper face of the new ring and the piston land.
The clearance is now found by reading the
result on the feeler gauge blade. Check the
groove at several points.
Grooves of different designs can be checked
with special wear gauges supplied by the
manufacturer, see Fig. 4. Donnot forget to
check at the same time whether the oil ring
holes are open.
Damaged pistons can be reconditioned in
special workshops. Always replace damaged
pistons to avoid further damage.
Checking piston rings
Piston rings can be checked by comparing the
old ring with a new one, *et Fig. 5. First
measure the radial wall 5-A of the new ring
with a micrometer. Compare the reading with
the radial wall dimensions of the old ring 5-B
and 5-C.
Ring gap measurement
The ring gap is measured as illustmled in
Fig. 1. Jnsen the ring into the cylinder and fiid
the clearance of the gap with a feeler gauge
Installing piston rings
.’ fter ensuring that the piston grooves and oil
retu.? holes are clean, the rings can be placed
acce,ding to the manufacturer’s specifications.
See Fig. 2. Rings are marked with a T, which
means Top side.
Use a ring expander to prevent the rings
twisting or stretching during installation. If you
twist or expand the rings too much, you diston
them permanently and thus reduce their
performance. Place the rings in such a way that
the ring ends are staggered round the piston.
Instailing the piston
Before installation, lubricate each piston
thoroughly with engine oil. This is necessary
because of engine cranking &luring the
installation until the oil [email protected] the
connecting rod journals is sufficient. Note that
several hundred revolutions are needed before
the engine lubrication system is working
Different types of ring compressors can be
used for installation. Sometimes a special
compressor is recommended by the
manufacturer. Press the rings, together with the
compressor, into their grooves. Place the piston
with the compressor in the cylinder, applying
gentle pressure on the piston as shown in
Fig. 3, where 3-A is the piston and 3-B the
compressor. The piston may be tapped lightly
on the edge - never tap the piston head,
because this will d‘amagethe head. The whole
piston assembly should move into place during
light tapping. If the piston sticks, compress the
rings again and check the cylinder for any
Prior to installation, the gudgeon pin md
connecting rod must be assembled.
Piston-connecting rod assembly
Figure 1 shows a piston-connecting rod
assembly, consisting of:
- Shank 1-A
- Shank 1-B
- Head 1-C
- Cap 1-D
- Bolt 1-E
- Gudgeon pin 1-F
- circlip 1-G
- Small end bush 1-H
- Piston 1-I
- Crankshaft 1-J
- Bearing 1-K
Before the piston assembly can be placed in
proper position, the connecting rod with the
gudgeon pin assembly must be checked and
Removing the gudeon pin
The gudeon pin may be removed from the
piston, see Fig. 2. with a tool 2-A or with the
help of a special shaped wooden block 2-B.
Before removing the gudeon pin, heat the
piston to 50 “C and then remove the pin in a
gentle way and with modcratc force.
The gudgeon pin connects the piston to the
connecting rod. The gudgeon pin can be
fastened in three ways:
- Most pistons arefu!!flcs!‘.q. This is s!?own
in Fig. 3. The gudgcon pin can turn in the
cylinder bore and the connecting rod small
end round the gudgeon pin. The pin must
t!.erefore be locked in the piston bore with
two circlips as shown.
- Aj3ed @eon pin is shown in Fig. 4. The
pin is fixed in the cylinder bore with screw
4-A. The gudgeon pin cannot move anymore
and the small end of the connecting rod
moves around the pin.
- Sometimes the gudgeon pin is fastened in
the small end of the connecting rod with a
bolt. This is shown in Fig. 5. The assembly
is called semi-floaiing because it turns only
in the piston. A bushing 5-A prevents swear
of the piston bore.
In high-speed engines, floating pins bear
directly on the piston material.
Checking the piston bore and
rod bearing
Befow the piston is assembled in the cylinder,
the gudgeon pin bearing in the piston and the
connecting rod must be checked for tapered or
misaligned holes.
To check for taper or misdignment between
the holes, check each bole in the piston
separately with the gudgeon pin. Both holes
must be straight and of equal size, The pin
must enter and be positioned square to the skirt
of the piston without any side play.
If the hole is not tapered, push the pin through
towards the second piston bore. The pin must
enter this bore without any force or binding
and also without a ‘click’. A good gudgeon pin
bearing should have equal drag (resistance)
through both holes, see Fig. 1.
Figure 2 shows a piston with tapered gudgeon
pin holes. The taper can he checked by
inserting the gudgeon pin in one side. If the pin
moves up and down, the hole is tapered.
Misaligned holes can be checked as shown in
Fig. 3. Insert the pin in one side. If the pin is
not ucsitioned square to the skirt of the piston,
the hole is misaligned. See 3-A.
A method of checking the gudgeon pin fit in
the small end bush of the connecting rod is
shown in Figs. 4 and 5. To check the bushing
for out-of-roundness or looseness, clamp the
pin carefully in the bench vice and move the
connecting rod a small end back and forth over
the gudgeon pin several times. After removing
the rod, examine the bushing for shiny contact
points. A good pin should show contact over
the entire surface of the bkshing in the small
While holding the guizeon pin in the vice,
move the connecting rod left and right and note
the allowance in the bushing.
Figure 4 shows a tapered hole in the small end
bushing. Figure 5 shows a bell-mouthed hole
in the small end bushing.
Check in the mam:al the exact clearance
between the gudgeon pin and the bearing to
sustain and support an adequate oil film.
Connecting rods
The function of a connecting rod is to transmit
the thrust of the piston to the crankshaft, see
Fig. 1. It is shaped in such a way that less
material is needed and a maximum of strength
is obtained. Parts are:
- Bearing 1-A
- Shank 1-B
- Cap 1-C
- Lock plate l-D
- Locking bolt I-F,
- Bushing 1-F
- Small end 1-C
- Big end 1-H
Most connecting rods are forged from one
piece of metal and the cap is cut off at a later
stage. Two split bearing h&es are inserted
into the head and the cap.
Connecting rods must be aligned with close
limits. If this is not so, the piston cannot work
squarely in the cylinder which causes oil
consumption and blow-by. Big loads are
imposed on rod bearings, pistons and cylinder
walls if the connecting rod is not correctly
Corrections can btt made to connecting rods.
But heavy rods may return to their distorted
shape and it is therefore better to replace them
with a new rod
Replacing a imsbimg
The old bushing can be removed from the
small end of the connecting rod with a
recessed pin. Be careful not to damage the
edges of the bore which have to receive the
new bushing. The new bushing must be
pressed into place exactly in line with the bore.
Tap the bushing i no place on all sides with
light taps. Never use force because you may
damage the bore and the bushing will be loose
in its bore.
Fix the cap back on the head with the old
bearings in place. Measure the inside diameter
as shown in Fig. 2. Measure at several points.
Measure the crankshaft connecting rod
journals as shown in Fig. 3. Measure at several
points and compare the result; to find rhe
bearing clearance.
The crankshaft
A one-piece drop-forged crankshaft is shown
in Figs. 1 and 2. This crankshaft is for a
four-piston engine and can be mounted in three
main bearing housings.
- Main bearing journals 1-A
- Connecting rod bearing journals 1-B
- Counterweights 1-C
- Cranks!& brows l-D
- Flywheel 1-E
- Lubrication oil passagt Z-F
An engine block with main bearing bores is
shown ira Fig. 3, where the bearing haif inserts
are also shown, see 3-A. Five main bearings
are located in this engine block. This is not the
case with all engines. Sometimes a four
cylinder engine may have three main bearings.
The cross-section in Fig. 4 shows how the
main bearing caps are secured with bolts to the
bearing bores.
- Crankshaft 4-A
- Engine block 4-B
- Top baring insert 4-C
- Bottom bearing insert 4-D
- Main bearing cap 4-E
Crankshaft throws
Crankshaft throws as shown in Fig. 1 are
placed in such a way that they counterbalance
each other when the crankshaft rotates at high
speed. They are designed to:
- balance the engine and reduce vibration
during performance,
- affect the loads on the main bearings.
To halance the force of the pistons and
connecting rods on the crankshaft,
counterweights are placed opposite the
connecting rod journals. This also helps to
control the vibration affecting the cranksh‘aft.
The weight of the flywheel also helps to
stabilix the rotating crankshaft.
A --- --------I
.J :
Inspecting the crankshaft
After the crankshaft has been removed it
shouid be washed with fuel oil. Special c’are
must be taken to ensure the oil passagesare
clean and open.
Figure 3.shows a crankshaft with a part section
of the oil passages:
- Main bearings 1-A
- Oil passages 1-B
Almost all engines have pressunr.ed oil
lubricating the crankshaft. See Fig. 2. Holes
leading in from the engine block via the main
bearings provide a path for the lubrication oil
2-A to reach the connectulg rod journals, see
2-B. As the oil is under pressure, the excess oil
will spray out via 2-C to help lubricate the
piston and the cylinders.
- Measure all the connecting rod bearing
journals. As instructed in previous lessons,
measure at several points and also round the
journal to find the smallest diameter.
- Then measure the main bearing journals in
the same way as the connecting rod journals.
- Install the main bearing caps again and
tighten the bolts to the correct torque. Use
an inside micrometer to measure the main
bearing inserts.
.- Compare all the readings and calculate the
difference between the two.
- Check in the mLanuaifor the correct
- Inspect the journals for tidges and the whole
crankshaft for crack.~due to fatigue.
A ridged journal is shown in Fig. 3. Ridge 3-A
is caused by the oil groove in the bearing shell
shown at 3-B.
Crankshaft float
A crankshaft must have a cenain amount of
float. Separate thrust washers on both sides of
the main bearing or bearing inserts with IWO
thrust flanges on it are used to keep the
crankshaft in place.
- Measure :he thrust and ( ompare the result
with the nuanufacturer’s specifications.
Bushings and bearings
Bushings and bearings are used on rotating
load bearing points in an engine to reduce
friction. Bearings are used in the engine for the
camshaft, connecting rod journals and main
bearing journals where heavy loads and high
speeds are imposed. See Fig. 1-A.
Bushings are used round the gudgeon pin,
rocker arms, oil pump and other places where
speed is not high and the load imposed is
rather light. See Fig. 2.
Bushings are pressed into place. This must be
done gently, with great care. They must be
inserted exactly straight, the pressure being
applied on all sides simultaneously.
Bearing inserts are placed in their housings and
bearing locks prevent rotation of the bearing.
One lug l-B on the insert prevents from
rotation of the insert in one direction and the
other lug 1-C prevents from rotation in the
opposite direction.
The connecting rod bearing is slightly larger
than the housing, to keep it tightly in place.
The difference in diameter is called the crusty
fif. Refer to Fig. 3. When tightening cap 3-A
over bearing 3-B. the crush height shown at
3-C makes the bearing fit tightly.
Bearing oil grooves
As you have already learned, lubrication oil for
the bearing is supplied from the engine block
via the crankshaft to the bearings. Inserts have
art oil groove as shown in Fig. 1-D to spread
oil over the bearing journals. Sometimes other
shapes of oil grooves are used, depending on
the function.
Thrust bearings
Thrust washers and thrust flanges on bearings
have already been mentioned in the
explanation of the crankshaft float. Figure 4
shows a section of a bearing with thrust
washers (4-A) and a bearing with thrust
flanges (4-B). These bearings are used near the
flywheel and must be on both halves of the
Bearing metal alloys
In general a bearing (see Fig. 1) has a body
made of steel i-A with some linings of
different material 1-B and 1-C. The hearing
material depends on the expected stresses.
Lining on hearings may be:
- copper or ah.m~inium alloys and silver
- copper or aluminium alloys,
- tin or lead-base babbitt,
- special alloys.
Bearing inspection
Before raking out the bearings, clean the top of
the workbench so that all bearings can be
placed in the same sequence as they are
removed, see Fig. 2. Use one line for the
gudgeon pin bushings 2-A, one line for the
connecting rod bearings 2-B and one line for
the main bearings 2-C.
- After cleaning the bearings, mark them with
a soft pencil to remember their position, see
Fig. 3.
- Check whether all the bearings fit correctly
into their housings.
- Fix the connecting rod and main bearings
back into their housings and measure with a
micrometer for wear.
Remember that a bent -‘onnecting rod can
damage hearings. So you rnlst pay special
attention to the connecting rod.
If the supply of lubrication oil is not adequate,
bearings show score marks. If fuel oil drips
into the crankcase, it dilutes :he lubrication oil
and causes the same problem.
A finely pitted surface exhibits corrosion due
to acid formation in the lubrication oil,
excessive blow-by or the oil temprature
exceeding 150 ‘C. It may also be due to
stop-and-go operation which causes
condensation in the crankcase.
Other damage can he caused by tapered
journals and dirt.
Do not just replace the bearings; fast fiid the
cause of the damage and repair it. Then replace
the bearings.
Measuring practice
Once you have worked through the chapters on
pistons, cylinders etc., it is good practice to
measure the diameters of;
- Cylinders
- Pistons
- Connecting rod bearings
- Crankshaft journals
- crankshafrbearings
To do this you need an inside and outside
micrometer, the use of which has already been
explained in volume 1 of the Rural Mechanics
Course: Cer&ral metal work, sheetmetal work
and ha&pump maintemince.
Copy the tables as shown on this and the next
two pages and fill in the correct diarntters you
measure. After each practical, consult your
Fiid the difference between the nominal size
and the actual size of the cylinder at positions
1-A and 1-B at levels I. II and III.
Enter the sizes in the table below.
Measuring practice
Check the diameter of the pistons in positions
1-A and 1-B at levels I, II and III.
Enter the sizes in the table below
-. I
Clean the bearings thoroughly and tighten
them again with the torque wrench. Use the
micrometer to meaSurethe bearings at the
positions t-Al, 2-AZ, 2-Bl, 2-132.
Enter the sizes in the table below.
Find the difference between the nominal size
and the actual size.
Nominal diameter of bearing:
Bearing no.:
Measuring practice
Check the crank journals at the points l-Al,
I-AZ, l-A3,1-Bl, l-B2 and l-83.
Enter the results in the following tables.
Clean the bearings thoroughly and tighten them
with the torque wrench.
Use the micrometer to measure the bearings at
positions 2-A& 2-A2,2-Bl and 2-B2.
Enter the sizes in the table. Fiid the difference
between the nominal size and the actual size.
The flywheel
A flywheel is heavy in weight and
construction. It is usually made of steel or cast
iron, see Fig. 1-A. The flywheel is mounted on
the crankshaft at the rear of the engine and its
purpose is to stabilize the engine. A flywheel is
used to:
- store energy for dead moments between the
power strokes,
- ensure a regular crankshaft rotation,
- transmit power via a clutch or pulley to any
machinery attached,
St&artthe engine, if fitted with a ring gear.
Parts of the flywheel
Figure 2 shows an illustration of a flywheel,
where you will see:
- Holes to balance the flywheel 2-A
- Possible bearing hole 2-B
- Holes for bolting the crankshaft to the
flywheel 2-C
- Dowel hole 2-D
- Flywheel body 2-E
- Starter ring gear 2-F
- Locking plates 2-G
- Bolts 2-H
Starter ring gear
The starter ring gear may be integrated in the
flywheel body or may be separated and shrunk
into place on the flywheel rim.
0 ‘.
If the teeth are damaged the ring must be
replaced. To make it easier to remove the ring,
it is best to drill an 8 mm hole (Fig. 3-A) as
near as possible to the inside edge of the ring
and then cut off the remaining part with a
hacksaw (3-B). Immersethe new ring in
boiiing water. Do not heat it more, because the
material may lose its hardness.
Place the flywheel on a solid base. With the
ring in place, fix clamps and with light turns
and taps drive it into place squarely against its
flange. Make sure the ring is correctly fixed
with the tapered edge of the teeth facing away
from the flywheel.
Fixing the flywheel
When re-fitting the flywheel, make sure it is
mounted in the same position as it was taken
off. The dowel pin must return in exactly the
same hole and the bolt and locking plates must
be fixed securely.
Timing transmission
Transmission from the crankshaft to the
camshaft is via gearwheels, as shown in Fig. 1
The crankshaft gear wheel 1-A has straight
teeth, square to the shaft. The camshaft gear
wheel 1-B runs with a reduction of only half
the speed ani in the opposite direction.
Wheels 1-C and 1-D have helical leeth, which
reduces the noise when the engine is running at
full speed.
The timing gear train
The timing gear vain is made up of two or
more gear wheels to drive the camshaft or
other engine parts, such as the lubrication oil
pump, fuel pump etc., see Fig. 2.
The power transmission can be realised by:
- a gearwheel transmission as shown in Fig. 3,
a chain transmission as shown iI, Fig. 4,
- a toothed belt transmission, used mostly in
car engines.
Timing the gear train
Many gears in the engine’s gear train must be
synchronized to ensure correct engine
operation. The camshaft operating the valves
must be synchronized with the pistons and the
To make it easier to set the gears correctly
after overhauling, mark the gearwheels with
either a short line or a ptinch dot. Figure 3
shows a short line made on the camshaft
gearwheel (3-A) and a punched dot (3-B) on
the crankshaft gearwheel. Figure 4-B shows a
punch dot made on both wheels.
In some cases the two marks must match each
other exactly, see Fig. 3. In other casesthe
punch dot on one of the teeth must match the
other punch dot between the gearwheel teeth of
the other wheel, see Fig. 4.
Other timing marks may be used. Check in the
engine operating manual on how to
synchronize the engine
Gear train backlash
Teeth of the gearwheels may be slightly worn.
The clearance between the teeth is called
backlash and the allowance for backlash is
given in the engine’s specifications. Chain
tension 4-A reduces the backlash.
Fuel and fuel storage
I-.----- - 7
_. _n
’ A
-. -
.- __-_
A.- ---C
--. _.
Fuel as received from the supplier is usually
stored in a bulk tank, which should be situated
outside the engine room. The main storage
tank is normally made of steel and it is
essential to make sure the steel is not
galvanised internally, because all fuels are to a
certain extent acid. Acid dissolves zinc platuing,
producing a gas that is highly explosive. It also
leaves a sludge deposit in the bottom of the
tank that could enter the fuel system, causing
much damage.
The storage tank should be installed with a
sloping bottom, see Fig. 1. The slope 1-X may
be between 100 to !50 mm and there must bc a
drain plug 1-A at the lowest point, so that
water and sludge can be drained at regular
intervals. A filler opening with a filter must be
positioned at the top of tank 1-B and a vent
pipe in the shade shown in 1-C should allow
air to enter. As mentioned before, the supply
outlet 1-D should be some 120 mm above the
Fuel is taken from the main supply tank to the
daily fuel tank. This tank must contain
sufficient fuel for the required operating hours.
Use a funnel with filter. If a drum is used as a
fuel tank, leave the drum for at least 12 hours
to ensure that dirt and water have been able to
Diesel fuel systems
No matter what diesel fuel equipment is fitted,
you must realize that the main function of the
system is to supply an exact amount of
atomircd and pressurized fuel to a cylinder at a
precise moment. As you have already le,amed,
combustion occurs in a diesel engine when a
charge of fuel is mixed with hot corn~~r~~sscd
As shown in Fig. 2, the main parts of a diesel
fuel system are:
- Fuel storage tank 2-A
- Daily fuel storage tank 2-B
- Sediment bowl 2-C
- Fuel transfer pump 2-D
- Fuel filter(s) 2-E
- Injection pump(s) 2-F
- Injection no&e(s) 2-G
- Spalway 2-N
Sediment bowl
A sediment bowl is used to let any din settle
down into a bowl made of glass. Through this
glass you can see how much din has settled
and when it must bc taken out. As shown in
Fig. 1, a fuel valve assembly I-A is Fixed to a
glass bowl l-b. A retainer I-C and a knurled
nut 1-D attach the sediment bowl to the valve
assembly. A rubber gasket 1-E and a filter
gauze 1-F are placed between the sediment
bowl and the valve assembly. A fuel valve 1-G
is located in the valve assembly.
When installing the bowl, fill it with fuel prior
to tightening, making sure no air is trapped in
the bowl.
Fuel feed pump
Fuel is pumped from the sediment bowl by a
mechanically operated diaphragm fue! supply
pump. see Fig. 2. This pump is mounted on the
side of the cylinder block and is cperated by
the engine’s camshaft 2-A and cam lob 2-B.
The fuel feed pump has a hnnd priming lever
2-C for bleeding the fuel system after it has
been drained or when air has entered the
system. The main parts of the pump are given
on the next page.
One of the most important parts of ihe fuel
supply pump is the diaphragm 2-D. This
diaphragm can be made of different materials
and carries out the pumping action in the
pump. After removing the diaphragm, check it
thoroughly for wear and cracks. Also check the
length of the pin 2-E and the strength of the
spring 2-F.
When checking the pump, pay special attentiun
to the operation of the valves 2-G and 2-H.
they arc of vital importance.
When assembling the diaphragm, tighten all
screws lightly at first, then gradually tighten
them further. If you tighten the screws too
much on one side at fist, it is difficult to
achieve a leak-proof connection.
Handle valves with the greatest care because
they are made of a very light material and
distort easily.
Cleaning the fuel filter 2-1 prior to assembly is
Typical fuel supply pump
- Filter cover screw
- Screw gasket
- Cover
- Cover gasket
- Filter gauze
- Upper housing
- Upper housing screw
- Gasket valve plate
- Valve retainer screw
- Valve retainer
- Valve assembly
- Diaphragm assembly
- Diaphragm spring
- Diaphragm spindle seal
- Retainer seal
- Body
- Hand primer assembly
- Hand primer parts set
- Hand primer
- Primer lever spring
- Rocker arm lever
- Rocker arm
- Rocker arm pin
- Rocker arm pin retainer
- Plain washer
- Rocker arm return spring
Assembling the pump
- Flush the valves in diesel fuel; this improves
the seal between the valves and the seats.
- Fit the outlet valve spring in the centre on
the four cast webs in the upper housamgand
place the outlet valve on the spring.
- Place the inlet valve on the valve seat in the
upper housing and the valve spring on the
centre of the inlet v,alve.
- Place the valve plate gasket and the valve
ret.ainer in pc.-ition and secure them with
three screws.
- Use a piece of wire to test whether the
valves are moving freely.
- Place the filter screen, cork gasket, cover
and fibre washer in position and fix them
with the retaining screw.
- Assemble the connecting rod link, the two
washers and the rocker arm spring inside the
lcwer housing, then spring the retaining
clips into their grooves.
- Insert the fabric washer first, then the metal
washer and position the diaphragm spring in
the lower housing.
- Fix the upper and lower housings together
with screws.
Fuel filters
Fuel filters can be installed singly or in pairs to
prevent harmful dirt and abrasive substances
finding their way into the delicate parts of the
injection pump and injectors.
Dual filters connected in cascade are shown in
Fig 1. Fuel enters the first filter through inlet
1-A. After the large particles are filtered. the
fuel moves to filter l-B, from where it runs to
the fuel pump through 1-C. Excess of fuel is
returned via 1-D.
Typical fuel filter parts
- Filter bowl 2-A
- Drain plug 2-B
Drain plug washer 2-C
Dished plate 2-D
Dished plate steel 2-E
Centre bolt 2-F
Circlip 2-G
Plain washer 2-I
Washer, centre bolt sealing 2-J
Plate 2-K
Sealing ring 2-L
Filter element 2-M
Sealing ring 2-N
Sealing head to bowl 2-O
Filter head 2-P
Bleeding plug 2-Q
Bleeding plug washer 2-R
Assembling the fuel filter
- Replace filter head assembly
Replace all fuel pipes, m&e all unions
finger tight and check whether the
connections are centred correctly. Tighten
the connections correctly, do not
over-tighten them.
- Refit the filter bowl with the new filter
element and O-ring. Engage the head
assembly with the cerrire stud and screw
firmly. Again. do not over-tighten.
- Close the drain plug.
- Open the fuel supply valve at the tank and
bleed the fuel system.
- Check all connections for leaks.
---- R
M .~
Note: some fuel filters can not be washed.
E -.
Injection and combustion
Spontaneous combustion through high
compression in a diesel engine may be difficult
to understand, since it is by no means an
uncontrolled explosion. Though the charge of
fuel may be injected into the cylinder in a
hundredth of a second, the resultant
comhstion is a general process which occurs
in stages. These stages can be controlled to
ensure optimum performance.
First stage of combustion
The first stage of combustion is a warming up
stage during which the fuel, as it is sprayed
into the combustion chamber under high
pressure, is raised from its normal temperature
almost to that of the compressed air in the
combustion chamber.
The compression temperature is higher than
the ignition temperature of the fuel. So
obviously. after a certain delay, the fuel must
actually bum.
The delay between injection and the beginning
of combustion is known as the Ignition Delay
Period and sometimes takes as much &sone
third of the total injection time. It is important
to reduce this delay period as much as
possible, especially in diesel engines which run
at high speed.
The Ignition Delay Period is influenced by
severii factors:
- the ignition quality of the fuel,
- the fineness of the fuel atomization.
- the difference between the air and fuel
For these reasons it is important to use the best
quality fuel available, because the fineness of
the atomized fuel during injection detemlines
the time taken for the fuel 10 mix with the air
charge. The temperature difference between
the injected fuel and the compressed air in the
combustion chamber is directly related to the
temperature of compression and hence to the
compression ratio of the engine.
causes a very high cylinder temperature and
along with it a high cylinder pressure.
Third stage of combustion
The final stage of the combustion process is a
direct burning phrasewhen the fuel already in
the combustion chamber continues to bum and
the fuel still being injected ignites almost
instantaneously on entry. The pressure attained
during this period depends almost entirely on
the rate of fuel injection. That is why
combustion can be partly ccntrolled by the
design of the camshaft-fuel cam profile.
When fuel injection is completed, combustion
continues until the fuel charge has expanded,
which is accompanied by expansion of the
gases being produced as a direct result of
combustion and displacement of the piston on
its power stroke.
Combustion conditions
Two essential conditions for complete
combustion a:
- The fuel must be injected into the cylinder
in a highly atomiTzd condition.
- An adequate supply of air must be available
so the fuel can mix with it intimately.
To make sure the fuel is in a highly atomized
condition, various fuel pumps and injectors are
used which are explained in detail in the
following lessons.
An adequate supply of clean fresh air is also
explained at a later stage.
Second stageof combustion
After combustion has taken place, the
temperature inside the cylinder rises very
gradually since heat is still absorbed by most
of the fuel particles created by atomization.
The delay period is thus prolonged until the
heat caused by the burning fuel is more than
sufficient to offset the heat required to prepare
for further fuel combustion. Following the
delay period there is a stage of uncontrolled
combustion as the flame spreads to the entire
charge of fuel which has been injected
throughout the delay period. This naturally
Fuel injection pumps
Each cylinder in a diesel eng:;le has its own
injector and each injector has its own fuel
supply through a fuel pump.
Only a single-element fuel pump is installed in
a one-cylinder diesel engine. This file1 pump is
powered by the engine’s camshaft. See Fig. 1.
Single-element pumps are sometimes installed
in a multi-cylinder diesel engine. These pumps
are powered by the camshaft. They arc joined
together with a fuel control bar, so that all
pumps work correctly at the same time.
In-line pump
The in-line pump provides for each cylinder a
different fuel pump. Basically the in-line pump
is similar to the single-element pump. The
difference is that this pump is not powered by
the engine’s camshaft, but by the timing gear
via a small camshaft located inside the in-line
pump housing. from where each injector is
supplied via a built-in pump. See Fig. 2.
Distributor fuel pump
Multi-cylinder engines may also have a
disttibutor type of fuel pump. See Fig. 3. This
pump is also connected to the timing gear 3-A
but the fuel supply to the different injectors is
different from that of the in-line pump, 8 we
will see at a later stage.
Single-element fuel injection
- Washer3-H
- Locating pin 3-I
Figure 1 shows a cross-section of a
single-element fuel injection pump. A pump
element consists of a highly ground steel
plunger operating in a barrel which is also
precision ground. The fitting clearance for
these components is so precise that the plunger
and barrel are matched as pairs by the
manufacturer. It is important to note that, if a
new element must be fitted, both the barrel and
the plunger must be replaced.
If for any reason the elements of several pumps
are removed at the same time, care must be
taken to snsure that plungers are reassembled
in their correct barrels. The delivery valve
fitted at the upper end of each barrel is
mitre-fitted and has a cylinder body with an
3igular groove cut into it. The lower part of
the valve has four longitudinal grooves
communicating with the annular groove. The
upper part forms a small piston, which fits very
accurntely in the valve guide. In Fig. 1 you will
see the following parts:
- Opening to fuel pipe 1-A
- Pipe connection 1-B
- Delivery valve spring 1-C
- Delivery valve 1-D
- Element locking screw I-E
- Pump barrel 1-F
- Pump plunger 1-G
- Control sleeve 1-H
- Plunger part 1-I
- Plunger return spring 1-J
- Fuel control bar 1-K
- Fuel supply inlet 1-L
- Bleed screw 1-M
Pump action
The fuel injection pump plunger is moved with
power from the camshaft. If you study Fig. 2,
you will see how the plunger in the fuel
injection pumps is moved via a roller in a
tappet from the fuel cam cn the camshaft:
- Single fuel pump element 2-A
- Shim 2-B
- Tappet 2-C
- Camshaft 2-D
- Pushrod tappet 2-E
- Fuel cam on camshaft 2-F
- Guide. fuel pump element 3-A
- Cap3-B
- Tappet 3-C
- Roller pin 3-D
- Retaining pin 3-E
- Bushing>F
- Roller 3-G
B --_.
F _---
- ---
Operation of the fuel pump
plunger stroke. The result is a total absence of
pressure build-up and the fuel simply
ci; :tllates from the delivery side to the suction
side of the pump in a continious cycle.
When the plunger is at its lowest point as
shown in Fig. 1, the fuel is free to flow into the
barrel through the fuel port. The injection
pump is constantly flooded by a supply of fuel
from a fuel booster pump or by gravity feed.
The different parts are called:
- Delivery valve spring 1-A
- Delivery valve 1-B
- Futl inlet port 1-C
- Vertical slot in plunger 1-D
- Helical land in plunger 1-E
- Fuel spill port 1-F
As the p!unger rises to the position shown in
Fig. 2, the top of the plunger closes the inlet
and spill ports to the barrel. Further movement
of the plunger cuws the pressure to rise on the
fuel trapped in the pump barrel. The only
outlet for the fuel is through the delivery valve
into rhe pipe leading to the injector.
Make sure the delivery pipe is flooded during
operation, then the pressure rise is transmitted
to the fuel injector valve, causing it to open
and the nozzle to spray fuel into the cylinder
combustion chamber.
injection continues in this way until the pump
plunger has risen to the position shown in
Fig. 3, where the helical land on the bottom of
the plunger has uncovered the ports in the
pump barrel, thus allowing the pressurised fuel
to flow back to the suction side of the pump
via the vertical slot in the plunger. This causes
an immediate pressure drop in the delivery
line. so the delivery valve at the top of the
pump closes under the action of its spring. The
pressure drop also causes the injector nozzle
valve to snap-shut on its seat.
To vary the fuel supply the control rod 4-A on
the pump element can rotate the plunger 4-B as
shown in Figs. 4..5.6 and 7. The plunger
stroke is always constant, but that part of it
which is actually effective can be varied by
rotating the plunger in its barrel. This rotation
alters the position of the bottom of the plunger
helix in ret tion to the ports in the barrel, so
the point of cut-off can be made to occur
earlier or later in the stroke.
The effective stroke shown in figs. 4 and 5 is
long and corresponds to almost maximum
load, where - as in Fig. 6 - the plunger has
been rotated in such a way that thi: helix opens
the barrel ports earlier in the stroke,
corresponding to a very light load. In the stop
position, Fig. 7. the vertical slot actually
registers with the suction port over the entire
Typical fuel injection pump
and fuel under injection pressure passesup the
central bore of the rotor through the aligned
ports to one of the injectors.
In Fig. 1 you will see the parts of a typical fuel
injection pump:
- Gavemor weights 1-A
- Drive hub screw 1-B
- Drive shaft 1-C
- Drive hub 1-D
- Back leak ccnnection 1-E
- Shut-off lever 1-F
- Governor spring 1-C
- Idling stop 1-H
- Control lever 1-I
- Maximum speed stop 1-J
- Metering valve 1-K
- Fuel inlet 1-L
- Pressure regulating valve 1-M
- Hydraulic head 1-N
- Rotor 1-O
- Fuel filter I.-P
- Regulating piston 1-R
- Priming spring 1-S
- Transfer pump 1-T
- To injector 1-U
- Advance device 1-V
The rotor normally has as many inlet ports as
the engine has cylinders and a simular number
of outlet ports in the hydraulic head of the
- Plungers 1-X
Typical rotary (D.P.A.) Fuel pump
The distributor type of fuel pump, an example
of which is shown in Fig. 1, is very compact. It
is flange-mounted to the side of the crnkcnse.
The pump IS driver. by a shaft through a gr,lr
attached to the camshaft and is self-lubricated
by fuel.
Fuel entering the pump through the main inlet
connection I-L is pressurised by B sliding vane
transfer pump 1-Y carried on the rotor inside
the hydraulic hciati 1-N. The pressure rise is
control14 by a regulating valve assembly 1-M
located in the pump end plates. The fuel then
passes frcm the regulating valve to the
pumping elements 1-X.
The internal cam ring, mounted in the pump
housing, normally has as many lobes as there
are engine cylinders, see I-W, and operates the
opposed pump plungers 1-X via cam rollers.
The plungers are forced inwards
simultaneously as the rollers contact the
diametrically opposed cam lobes. This IS the
injection stroke. The plungers are returned by
pressure of the in-flowing fuel. This is the
charging stroke.
Figures 2 and 3 show that, as the rotor turns,
the i.rlet port 2-A is cut off and the single
disributor port in the rotor registers with an
ol~Jet port 3-A in the hydraulic head. At the
sme time the plungers 3-B are forced inwards
A --
Governor systems
To understand the working principle of the
governor, study carefully Figs. 1 and 2. Two
pieces of rope with weights at the end are
attached to the disk in Fig. 1. If you rotate the
disk at a certain speed as m Fig. 2. the weight
swings outwards due to centrifugd force. If
you decrease the speed, the weight moves
inwards again. Both weights must be exactly
the same to avoid vibration during rotation.
The governor
The governor is a method of regulating the
amount of fuel delivered by the fuel pump so
that a specific engine speed can be maintained
during operation.
Jn the multi-cylinder pump the governor is
inside the housing of the fuel pump and is an
integral part of the pump.
Single element pumps have a common
governor, a typical lay-out of which is shown
in Figs. 3.4 and 5.
Figure 3 shows at 3-D the last part of the fuel
pump rack. This rxk is moved by a governor
sleeve 3-C. which in turn is moved up and
down by forces produced by the governor’s
weights 3-A and 3-B. ‘Wiien the speed
increases, the weights of the governor move
outwards and the fuel pump rack is then
moved in such a way that it closes off the fuel
supply and so reduces the speed.
When the speed decreases,the weights move
inwards and the fuel pump rack is then moved
in such a way that engine speed increases
again. See Fig. 4.
The type of governor shown is called a
v‘ariable speed governor. The speed is finally
controlled with a lever or cable, operating
between set limits.
Figure 5 shows c constant speed governor. The
special spring 5-A allows the governor weight
to return to a position as required. You must
understand that not just any spring may be
used - this spring is made precisely for that
particular governor and that particular speed.
Always check the manufacturer’s technical
data when working on the governor.
Fuel and governor setting
Since the fuel pump pumps with the action of
the camshaft, make sure that the mark 01’ the
pin coincides with the gearwheel mark, SIe
Fig. 1.
Typical governor setting for a one-cylinder
diesel engine
Figure 2 shows a typical fuel pump setting
assembly. Study this lay-out carefully and
name all the parts. To set the fuel pump and
governor for a single fuel injection pump you
have to set the conno! on the rrz position 2-R.
Then adjust the linkage 2-A in such a way that
the calibration mark 2-B coincides with the
side of the fuel pump, see Fig. 2.
Adjust the linkage with the nut 2-C in such a
way that the calibration mark 2-B coincides
with the side of the fuel pump within a
tolerance given by the manufacturer. However.
the fuel pump rack must move freely after this
Adjust the governor lever fulcrum 2-D so that,
when the calibration mark 2-B is against the
outside of the fuel pump, the distance between
the inside of the governor s!ccvc and the
outside of the governor weight carrier
complies with the nnanufacturer’s technical
Set the clearance 2-E to the correct figure for
the application and speed of the engine; check
these in the technical data. Maintain the correct
clearance and rotate the locating plate 2-F until
the calibration mark 2-B coincides with the
side of the fuel pump. The full width of the
calibration mark must be visible. Fn/henthe
marks coincide and the clearance is correct,
secure the locating plate with the screw.
After making adjustments, check that the fuel
pump rack and the linkage move freely.
Firhg point
r’ ‘\
For an engine to operate efficiently the: fuel
must be injected into the cylinder com’bustion
chamber at the correct time. This is known as
thefiring poinl and it occurs at a very precise
time marked in degrees before TDC on the
flywheel, see Fig. 1.
The firing point for each cylinder is usually
marked as FP on the flywheel. The letters FP
occur when this mark coincides with a fixed
mark or pointer attached tu the engine.
Thing the fiat4 i$xtIen
There are several methods of checking fuel
pump timing, such as Spill Timing, Air Timing
and Pump Drive Shaft Timing. Each
manufacturer has developed his own fuel
system and it is therefore essential to study the
manufacturer’s instructions and follow them
The timing is said to be advortc~~dif the fuel is
injected too e;lrly, see Fig. 2. The timing is
said to be retarded if injection takes place after
the flywhee! has passed the fixed mark.
On single element pumps the firing point
position can be adjusted by changing the
vertical distance between the fuel pump and
the camshaft, either by adding or removing
thin metal shims under the pump body or by
moving the pump vertically by a fixed
adjuster. See Fig. 3-A.
In multi-cylinder pumps the fuel pump drive
shaft is rotated after spill timing in line pumps.
For rotary pumps a specially designed tool is
used to show the angular degrees.
Fuel injection
The way the fuel is injected into the air charge
is very important, as you have seen before.
There are two main methods of injection:
- Direct injection
- Indirect injection
Dim3 injection
When the piston rises during its compression
stroke, a swirling motion of air is produced at
the top of the stroke. This swirling motion
takes the form of a ring of air revolving at high
speed, like a ring of smoke blown from a pipe.
It is into this rotating ring of air that the fuel
charge is sprayed from many fme holes at the
tip of the injector nozzle, see Fig. 1.
Direct injection by means of multi-hole
injectors is widely used because, with this
method of injection, the fuel is highly
atomizd before it mixes with the swirling air.
But one disadvantage of direct injection is that,
to produce a very fine spray, the fuel is
injected through several very fine holes which
may become blocked by carbon.
Indirect injection
!Q tmfid!i-hn-&
_._-___ _.
injection nozzles have large holes through
which the fuel is sprayed into the combustion
chamber. Indirect injection nozzles are usually
of the single or twin hole type with larger
ho:es. So atomizing is not as satisfactory
unless additional means are provided to ensure
good mixing of the fuel and air, see Fig. 2.
One way of improving this situation is to force
the compression stroke air through a small
orifice into a separate cell or combustion
space, improving the swirling motion of the air.
indirect combustion ensures good combustion
over a wide range of load and speed
conditions. In general the engine will be able
to operate using poorer quality fuels with less
risk of carbon formation.
Combustion chamber
In the previous lessons you have learned that
the injection nozzle and its atomizing helps to
mix the fuel and the air. The piston crown and
the design of the cylinder head play an
important roie in improving the air and fuel
Turbulence chamber
Figure 1 shows a so-called open combustion
chamber. In this chamber all fuel and air are
confined to one area due to the concave shape
of the piston crown, see Fig. 2. The piston
comes close to the cylinder head and makes it
easier for the fuel to be sprayed evenly into the
ch&amber.The concave in the piston crown also
sets up a turbulence of the compressed air.
This speeds up the air and makes it easier to
mix with the fuel.
A turbulence chamber in the cylinder head is
shown in Fig. 3. As you see, the fuel is injected
into a small chamber in the cylinder head and
shaped in such a way that it produces a highly
turbulent condition.
As the piston starts the compression stroke, the
air is forced into the chamber and sets up the
rotary motion. Near the top of the piston stroke
the fuel is injected into the swirling air, which
results in a good mixture of air and fuel.
Pre-combustion chamber
This chamber is shown in Fig. 4-A and is
similar to the turbulence chamber except that
only part of the air charge is forced into it. If
the fuel starts to bum with an insufficient
amount of air. it ignites, forcing the burning
fuel into the cylinder 4-B. where the fuel
readily mixes with the remaining air during
Glow plug
Diesel engines are sometimes equipped with B
glow plug to speed up the starting procedure
by pre-heating the chamber. See Fig. 4-C.
Injectors spray the fuel into the swirl chamber
the moment the air in the swirl chamber has
- the nozzle holder.
A typical injector holder with nozzle is shown
in Fig. 1, where you will see:
- Copper washer 1-A
- Nozzle body 1-B
_- - ..-
Fuel inlet connection 1-C
Leak-off connection 1-D
Protective cap 1-E
Compression screw I-F
Spring cap nut I-G
Valve spring I-H
Valve spindle 1-I
- Nozzle valve 1-J
- Nozzle cap nut 1-K
When fixing the injector, you must make sure
the nolxle cap nut is seated correctly &and:he
copper washer 1-A is of good quality, because
there must be no pressure leaks.
Injection nozzles
Two typical inward-operming nozzles are
shown in Figs. 2 and 3. Both are of the pi&
The multiple hole type nozzle in Fig. 2 uses a
tapered valve 2-A which seats in a single
orifice 2-B in the valve body. When fuel is
pressed through the fuel inlet 2-C, it pushes the
valve upwards and allows fuel to pass towards
the spray tip 2-D ‘and be sprayed through the
nozzle holes 2-E.
As soon as the fuel pressure drops, the valve
resistance declines and the valve spring pushes
the valve spindle and the nozzle v‘alve down,
thus closing off the fuel supply.
A closed pintle type nozzle is shown in Fig. 3.
This type of nozzle has auxiliary spray holes
3-A to assist easy starting under cold
-- A
Faulty injectors
If you see excessive black or grey smoke
coming from the exhaust of the engine, it is
likely ihat one or more injectors are faulty. If
the exhaust gives distinct puffs, probably one
of the injectors must be serviced. White smoke
shows that one or more cylinders have cut out.
Uneven running or stalling under load are also
symptoms of faulty injectors.
A good method of locating a faulty injector is
to stat the engine and let it warm up and then
note the r.p.m. (revolutions per minute).
Loosen one of the fuel lines. As the nut is
loosened, the full pressure drops and injection
stops at that particular injector. While doing
this, keep your face and hands out of the way,
because the fuel is under extreme pressure and
may penetrate your skin. If the injector is good
and working correctly, the engine slows down
more than before and the sound of the engine
changes. You understand that when the
injector fuel inlet is loosened on a faulty
injector, there will be no change in either
sound or r.p.m.
Continue this test until all injectors have been
checked. When you have identified the faulty
injector remove it, service it or replace it with
a new injector or nozzle.
-. A
Injector parts
- Valve cone 1-A
- Valve stem 1-B
- Valve seat 1-C
- Pintle 1-D
- Fuel inlet 1-F
Pressure face 1-E
Nozzle shoulder 1-C
Nozzle trunk 1-H
Fuel gallery 1-I
- Valve seating 1-J
- Pintle orifice 1-K
- Nozzle retaining shoulder 1-L
Servicing the nozzle
- If the nozzle is faulty, take it out of the
nozzle body, examine it for carbon and
check whether it lifts out freely.
- Examine the polished surfaces for scratches
or dull patches.
- Examine the nozzle valve and the nozzle
body for damage and blue parts, which are
results from over-heating.
- Immerse the nozzle body and nozzle valve
in clean diesel fuel to soak and soften the
- Brush all carbon from the outside of the
nozde body with a brass wire brush. Never
use a sreelbrwh!
- Clean the small fuel feed bore with a
corresponding fine drill, set Fig. 1.
- insert a special groove scraper until the nose
latches into the fuel gallery. Press hard
against the side of the cavity and rotate the
groove scraper to clear all carbon deposits
from this area, see Fig. 2.
- Clean all carbon from the valve seating with
the correct valve seat scraper. Press the tool
onto the seating and rotate it as shown in
Fig. 3.
- Select the right pintle orifice cleaning tool
and insert it into the nozzle body until it
passesthrough the pintle orifice. Then rotate
the tool to clear off all carbon as shown in
Fig. 4.
- If there is an auxiliary spray hole, clean it
with the relevant cleaning wire. It must be
fixed into the tool chuck so that it protrudes
about 2 to 3 mm, thus offering maximum
resistance to bending. Extreme care must be
taken to prevent the wire from breaking
inside the hole, because such particles &are
almost impossible to remove.
- Put the wire into the hole and push and
rotate it gently until the hole is clean, see
Fig. 5.
- Flush the nozzle body and the nozzle valve
with clean diesel fuel. All remaining carbon
particles can be removed carefully with a
piece of hardwood soaked in diesel fuel.
Then flush again.
- After cleaning, do not dry the nozzle valve,
just put it in the nozzle body. Check its
gliding capacity by pulling it half out of the
body; it should sink slowly by its own
- Pressure faces must be very clean.
Nozzle test bench
A nozzle test bench consists of the following
components, see Fig. 1:
- Fuel container/filtering unit 1-A
- Check valve 1-B
- Air vent screw 1-C
- Injection pump 1-D
- Hand pump lever 1-E
- Pressuregauge1-F
- Pressure feed pipe 1-G
- Pressure adjusting screw 1-H
- Locking nut (adjusting screw) 1-I
- Protective shield (container) 1-J
- Crank the engine until all air is expelled
from the fuel system.
- Crank the engine again and note the
atomizing of the fuel spray. Also compare
the atomizing of all injectors at the same
time; they must be the same.
It cannot be said too often that great care must
be taken during these tests. On no account
should your hands come into contact with the
fuel spray. It has a very great penetration force
and the spray easily passes through the skin.
Testing the injectors and nozzles
An injector and a nozzle can be tested on a
nozzle test bench as shown in Fig. 1.
- Fill the tank with clean diesel fuel.
- Bleed the system for a few seconds, using
the air vent screw. Operate the pump several
times until the fuel flows from the pressure
- Then connect the injector to the fuel feed
- Close the check valve so the pressure gauge
is out of circuit. Operate the hand lever
several times to expel all air from the test
bench and injector.
- Open the check valve to bring the pressure
gauge into circuit.
- Set the opening pressure of the nozzle on the
required bar, see the handbook.
- Wipe the face of the nozzle dry and pump
up to the required bar. Hold this pressure for
ten seconds. First wipe your finger across
the face of the nozzle and inspect for
- With the check valve still open, pump again
to just below the opening pressure, release
the hand lever and let it fall on its own
- Time the drop of the gauge needle from . . .
bar to . . . bar: see handbook.
Nofe: Carry out this test only when the valve
seat is in good condition and if there is no
leakage at the valve tip. During this test, make
sure the protective shield is in the correct
Injector/nozzle teskan engine
If no bench tester is available, a simple
injector/nozzle test can be carried out on the
engine itself.
- Take out the injectors and mark them
- Re-fit them upside down on the fuel pipes
and tighten them correctly.
Injector testing
The primary function of a fuel injector nozzle
is to atom& the liquid fuel so rhat it can be
burned rapidly and efficiently in the cylinder
of a diesel engine.
Atomizing the fuel is a purely mechanical
process in which the fuel is forced through
small orifices under high pressure and the
multi-hole nozzle shown in Fig. 1 is used to
help spread the fuel charge over the entire
combustion chamber area.
Under high pressure the nozzle should spray
from all the holes evenly, as shown in Fig. 1-B.
If one of the holes is blocked, the spray is not
even, as shown in Fig. 1-A.
For satisfactory operation of the injector
nozzle, it is essential that the nozzle valve
snap-shuts in the shortest possible time to
avoid dribble, shown in Fig. 1-C. which would
rapidly cause excess carbon formation al Ihe
nozzle with blocking of the jets. For the valve
lo snap-shut, shown m Fig. I-D, rhe pressure in
the fuel tine must have some positive means of
being reduced to 30 bar almost
insranraneously, when the strong spring on the
delivery valve itself wilt ensure that the valve
closes as desired.
This pressure reduction is achieved by the
construction of the mitre-faced delivery valve,
see Fig. 2-A, fitted at the top of the pump body
and by the flutes 2-B at the tower end of the
valve. Just below the Y ve face there is a
small plunger 2-C whbi has a very accurate
fit in the bon: of the vatv. guide. While the
pump is actually delivering fuel to dre
cyiinder, this plunger is raised clear of the
valve body and fuel flows round it into the
delivery pipeline, see Fig. 3.
~ ~~A
~-.- I3
On a slight pressure drop in the pump. the
delivery valve starts to return to its scJL
through the action of valve spring 4-A in Fig.
4, resulting immediately in location of the
plunger in the bore of the valve guides. This
forms a hydraulic seat so, at the moment under
consideration, the pipe from the delivery valve
to the injectsr nozzle can b: regarded as being
a separate system in which the fuel is still
under considerable hydraulic pressure.
As the delivery valve moves fractionatty
towards its seat, the plunger displacement
causes a small increase in volume of the fuel
still under pressure, and the pressure:is thus
reduced immediately to zero, enabling the
no~de vaive io snap-shut withour sputtering or
Fuel pipe fittings
Fuel fitters, injectors, pumps and other units
are connected by means of couplings or
fittings. There are several types, such as:
- S.A.E. 45’ flared
- Inverted flared
- Compression couplings
- Compression sleeve couplings
Each of these types consists of a mate fining, a
seat and a female nut. To prevent damage to
the seat when tightening or loosening a
coupling. hold the fitting with one spanner
while turning the nut with another. One of the
most important rules for tightening tube
fittings is:
Only tighten by hand !ightly at,rir,Pt.Do .~a!
If a fitting starts to break and seems to be
loose. re-tighten it only up to the point where
the leak stops.
FAE. 45” flared fitting
Figure 1 shows this type of coupling. The seat
is achieved by compressing the flared tube
between the tapered faces of the mate and
female connectors. One advantage of this
connector is the locking action of the sleeve
and the fact that the flared tube is net rotated
during assembly.
Inverted flared fitting
This coupling is shown in Fig. 2. The seat
produced by compressing the flared tube is the
same way as the S.A.E. 45’ finings. In our
opinion this connector gives the best seat.
Compression fitting
This coupling shown in Fig. 3 requires no
flared tubing or sleeves. The seat results from
the tubing being crimped by the mate fining
when forced against the female nut. A
disadvantage is that during tightening it tends
to bind on the tubing, which may cause
unequal seating. The friction can also twist the
tubing slightly.
Compression sleevefitting
This type of fining, see Fig. 4, uses a sleeve
instead of flared tubing. The sleeve is placed
on the tubing between the nut and the fitting. It
crimps the end of the tube to seat it.
Bleeding air from the fuel
When the diesel fuel system has run dry or has
been dismantled, a lot of air has entered the
system. If this air is left in the system it may
form an air lock which will prevent the fuel
from reaching or passing through the injection
pump and then to the injectors. The result may
be that the engine does not statt, misfues or
loses power.
Bleeding the air from the diesel fuel system
must be carried out in the correct sequence,
otherwise the air lock remains inside the
system. A correct method of bleeding the fuel
system is explained below:
- Fill the fuel tank with clean fuel.
- Open the shut-off valve at the tank.
- Loosen the bleeding plug on the fuel filters
and pump with the primer lever of the fuel
pump until a continuous flow of :?lel, free
‘and air bubbles, flows from the <i,;ning in
the bleed plugs.
- Tighten the plug. If there is more than one
filter, bleed the next one. When bleeding is
completed, make sure you leave the primer
lever on the fuel pump at its lowest point of
- Loosen the injection line nuts one Sy one
and crank the engine until fuel flows
without foam around the couplings. Foam is
mixed air and fuel.
- Tighten the pipe connections carefully and
check for leaks.
- Make sure you loosen the conne&rls by
only one turn to avoid excessive spray,
which may be harmful.
Engine trouble-shooting
Every diesel engine is accompanied by a
handbook in which you will find a
trouble-shooting guide to the engine and its
fuel injection system. If the engine fails to
start, is difficult to start or misfues. the main
problems may be:
- No fuel in the fuel tank. Clogged fuel supply
or water in the fuel.
- Fuel transfer pump not operating.
- Air lock in injection pump.
- Governor linkage to pump is loose or
- Fuel pump(s) or distribution pump not
working correctly.
- Delivery valves are not seated correctly
which may be due to broken springs or dirt.
- Pump(s) out of time.
- Nozzles not operating because the valves
are stuck or the orifices plugged.
Manufacturer’s handbook
It must be understood that it is essential to x:ad
the manufacturer’s instructions on the
particular engine you service All adjustments
must be made according to the techni: al data
Wrong idling speed
If the engine does not idle smoothly it may be
due to:
- Dirty fuel filters.
- Governor idling speed adjustment is not set
correctly or the trottle linkage is worn.
- Pump rack or control may be stuck or is
- Fuel pump plunger sticks.
- Node opening pressure may be wrong.
- Stuck nozzle vaIves.
- Fuel pump(s) are not correct - loose control
sleeves, pump timing incorrect or leaky
delivery valves.
Engine smokesand knocks
Fuel pump out of time.
Dirty or wrong nozzles.
Valve stuck open.
Opening pressure too low.
Fuel stop setting incorrect.
Excessive fuel delivery.
Causes such as: broken valves, scored
pistons or dirty air cleaner.
Engine lacks power
Some:imes the engine lacks power, which may
be due to:
- Retarded pump timing.
- Worn pump plungers.
- Worn distributor.
- Faulty nozzles.
- Governor out of adjustment.
- Dirty or plugged air or fuel filters.
Fault-finding guide for
injection system
i3lginc is diflCUl~ !I) start
lncorrea fuel pump timing
Defective fuel injection pump
Defective or incorrect injectors
Check fuel pump timing
Renew fuel injection pump
Check the fuel pump
Engine will not start
Broken fuel injection pump drive
Check Ihe fuel pump
Engine misffues
Incorxcct fuel pump timing
Defective or incorrect type of
fuel injection pump
Defective or incorrect injectors
Check the fuel pump timing
Check the fuel injx tion pump
Check the injeclors
Lack of power
Incorrect fuel pump timing
Defective or incarte
tw of
fuel injection pump
Defective or incorrect injectors
Check Ihe fuel pump liming
Check the fuel injection pump
Check the injectors
Excessive fuel pump
Incorrect fuel pump timing
Defective or incorrecl type of
fuel injcclion pump
Defective or in correct injectors
Cheek the fuel pump timing
Check the fuel injection pump
Check the injectors
Black exhaust
Incorrea fuel pump timing
Defective or incorrect injeaors
Cheek the fuel pump
Check the injectors
Blue exhaust
Oil consumption by the
fuel injection pump
Renew leaking gaskets
Engine knocking
bcorrcct fuel pump timing
Defective or incorrecl injectors
Check the fuel pulnp timing
Cheek the injcclors
Erratic running
Incorrect fuel pump timing
Defecdvc injectors
Check the fuel pump timing
Service lhe injectors
Excessive oil consumption
Consumption by Ihe fuel injectionpump
Check the fuel injdon
Engine ovcrheaing
Engine stats and stops
Sticking injams
or incorrect injectors
Check ll~c injcclors
Service the injeclors
Cooling systems
The operating temperatum of a diesei engine is
very critical to ensure maximum efficiency and
to reduce wear on moving engine parts. If
cooling is not adequate, the engine becomes
over-heated causing possible:
- piston seizure,
- low engine performance,
- wear of movable parts,
- breakdown of lubricating parts,
- formation of carbon deposits.
Eirgine room design
Figure 1 shows an tllustration of an engine
room design. One of the cooling air intake
holes must be near the bottom of the engine
room to bring cool air in and also to strike
along the engine sump to assist cooling of the
lubrication oil, see 1-A. Another air intake hole
1-B must be opposite the air filter to ensure a
good supply of cool combustion air. One or
two cooling air holes must be near the top of
the engine room to prevent an accumulation of
hot air above the engine. Holes I-C and 1-n
allow hot air to leave the engine room. The
exhaust leaves through the opening 1-E.
Two systemsof engine cooling
We will explain two coolirg systems:
- Air cooling
- Watercooling
Air cooling system
Air cooling is used widely on sm uler engines
used for water pumps, small electric plants,
compressors etc. See Fig. 2. II is a simple but
reliable principle using a fan 2-A secured to a
flywheel which forces air through a system of
deflector plates 2-B over the fined cylinder
barrel and sometimes over a finned section of a
sump for oil cooling.
Air cooled diesel engines require
approximately 35% less air than water cooled
It must be understood that in tropical ch..lates
special attention must be paid to the supply of
fresh air. Clean the finned section 2-A
regularly. The shroud or deflector plates must
be taken off at regular intervals to make it
possible to clean the fins of the cylinder barrel
and thus ensure adequate cooling.
Water cooling systems
There are several systems to cool down an
engine with cooling water. One such system is
the thermo-siphonsystem, shown in Fig. 1. A
gravity feed is taken from a tank 1-A located
outside the engine room. This tank must be
very well protected against the sun to ensure
that the water used for cooling is not too hot.
Water circulates through the engine cooling
system 1-B and is returned to the tank by the
thermo-siphon action alone. The water
circulates due to expansion of the heated water
in the engine jacket, thus becoming less dense
and rising as a result to the highest point of the
system. Its return from the tqp of the engine
system to the top of the coolmg tank is ensured
by a sloping pipe 1-C which rises gradually to
avoid possible air locks.
Since this system cools the water slowly. a
huge tank is necessary. Some 250 liters of
water are needed per brake horse-power
(b.h.p.) for 22 hours running. In tropical
countries it is advisable to double this amount
to 500 liters per b.h.p.
To aid the thermo-siphon action a circulation
pump is sometimes mounted on the engine,
increasing the flow of water through the
system. If such a pump is provided, the total
amount of water needed for cooling may be
20% less than recommended above.
Another water cooling system is the rudiator
cooling system,as shown in Fig. 2. Water
flows from 2-A through the radiator 2-B via a
flexible rubber hose to the waterpump 2-C ,
where it is forced through ttre water jackets of
the engine 2-D. The heated water returns to the
radiator via a rubber hose 2-E. A cooling fan
2-F is driven from a suitable extension shaft on
the engine with one or more V-belts to draw
cool air through the radiator and over the
engine. This type of radiator is illustrated in
Fig. 3.
Water cooling system
A lay-out of a typical water cooling system is
shown in Fig. 1.
The water pump 1-A draws hot coolant from
#.heengine block and forces it through the
d.qdiator 1-C for cooling. The thermostat 1-B
x~ntrols the flow of coolant to the radiator to
-,xtintain the comxt operating temperature of
the engine.
The radiator 1-C allows tht coolant to cool
xfore it reenters the engine block. It also
provides a reservoir for sufficient coolant for
operation. The radiator cup 1-D is also used to
fill the reservoir of the radiator with coolant. In
addition it allows operation of the engine at a
higher temperature without boiling or loss of
the coolant by evaporation.
Rubber /loses 1-E make the connections
between the rigid generator and the vibrating
engine block.
The blow or suctionfan 1-F makes cool air
flow through the radiator tubes or water
passages.The fan may also suck cool air
through the radiator tubes.
A typical diesel engine radiator is shown in
Fig. 2. The different parts are:
- Radiator cap 2-A
- Top reservoir radiator 2-B
- Radiator water passagesand fins 2-C
-. Bottom water reservoir 2-D
- Drain plug for coolant 2-E
- Bottom connection to engine block 2-I;
- Top inlet for coolant from engine block 2-G
- Shroud to guide air flow 2-H
Note how the rubber hoses are connected wirh
hose clips between the radiator and the engine
Core type radiators
A section of a tube-fin type core radiator is
showrl in Fig. 3. This type of radiator is
common in all types of engines. Water from
the engine block enters the radiator via the top
tank :1r.5:!x!, pasxs dawn through the tubes
3-P. The fii 3-E ensures maximum air flow
fc: xoling.
Radiator cap
The radiator cap shown in Fig. 1 is of the
pressure system type. It Jlows the engine to
operate at a higher temperature without boiling
or loss of the coolant by evaporation.
Figure 2 shows the radiator cap with its valve
2-A closed completely. No coolant can escape
via the overflow pipe 2-B.
Figure 3 shows the same radiator cap with the
pressure valve 3-A completely opened. When
in this position, thi valve idlOWS the coolant to
escape under pressure and leave the radiator
via the overflow pipe 3-B.
The vacuum valve shown in Fig. 4 opens as
relevant to prevent a vacuum in the cooling
system. Valve 4-A passesair via route 4-B.
As there may be pressure in the mdiator, you
must be careful to remove the radiator cap
slowly. so that any pressure cIuI escape first.
Figure 5 shows a part of the cooling system
with the thermostat at 5-A in a closed position.
If &hethermostat is open, the water can
circulate through the radiator marked 5-B. If
the thermostat is ciosed, the coolant continues
circulating through the pump in the engine
block, see dotted area.
Figure 6 shows a typical bellows thermostat.
The action of the thermostat valve 6-A is
corrtrolled by the bellows, to which valve 6-B
is linked. In cold conditions Lhe ‘Wlows are
fully contacted and hold the valve tightly on
the seat. so the coolanf continues circulating
from the cylinder head through the water pump
and not through the radiator. This ensures a
rapid rise in the coolant temperature. The
thermostat in Fig. 6 is fully open, as you can
see, so the coolant can circulate through the
radiator, pump and engine block.
If the thermostat is not functioning correctly
the engine may run too hot or loo Lold.
Over-heating can damage the thermost? As a
resuh the valve does not function conrctly and
damages the engine. Rust caused by water in
the system can also interfere with sound
operation of the thermostat. Make sure you use
a thermostat design recommended by the
Water pump
The water pump shown in an exploded view,
Fig. 1, is bolted at I-A to the engine block. The
main part of the pump consists of an impeller
1-B in the form of a disc with tapered blades
on one side. The impeller is force fitted to one
end of the drive shaft I-C. The hub 1-D is
fitted at the front of the shaft ard the pulley
and fan blade are bolted to it, see Fig. 2.
Two greased ball bearings 1-E are fitted on the
drive shaft. Between the impeller and the
pump housing, a seal 1-F is fitted to prevent
leakage of the coolant. Between the pump
housing and the engine block, a gasket 1-G
prevents the leakiig of coolant. Between the
pump housing and the engine block a gasket
prevents leakage of the coolant, mwhi!ea holr in
the plate l-11 .diows the coolant to pass from
the engine l ’ the pump and then to the radiate,;.
Coolant enters through l-11and ieaves the
pumps to the engine at 1-J. see cross-section in
Fig. 1.
Cleaning the ccoling system
During engine operation, clogging materials
such as rust, lime. scale and grease may
prevent maximum cooling of the engine. Rust
accounts for some 90% of clogging which
forms on the walls of the engine jacket, see
Fig. 3-A, and other metal parts. The coolant
circulation may loosen the rust particles and
carry them to the radiator, blockmg the tubes.
It is advisable to use clean rain water as a
coolant to prevent lime deposits, due to
so-called hard water forming a layer and thus
blocking the circulation of the coo!ant. Lime
may settle anywhere, while dirt settles at the
bottom of the jacket 3-B and the radiator tank.
Flushing the cooling system
Before flushing the cooling system, tilk! out
the thermostat to make sure the water can run
freely through the system. Then fill the system
with clean water. Run the engine for some
time. Stop the engine and open all drain piugs
and drain the system completely. Also clean
the radiator tubes and remove all insezts from
the fins.
Check the thermostat, radiator pressure cap
and the cap-seat for dirt and corrosion.
V-Belt construction
As already shown, a V-belt drives the water
pump 1-C in Fig. 1 and sometimes also the
alternator 1-B from a pulley attached to the
crankshaft 1-A. Sometimes a separate V-belt is
used for large alternators. The advantage of
using a V-Mt instead of a gear or chain drive
is that the V-belt is a simple construction,
cheap and noise-less.
A cross-section of a V-belt is shown in Fig. 2.
V-belts are usually made of rubber
incorporating steel wire and with cloth on the
outside, see Fig. 3.
Shape of pulley and V-bell
A section oi a pulley is shown in Fig. 4. The
groove is shaped in such a way that it
corresponds tr the shape of the belt.
Tne force of the V-belt is tmnsferred by
friction between the V-belt shoulders and the
pulley. see Fig. 4-A. That, as you will
understand, is why the V-belt must fit correctly
to be able to transfer the force. A V-belt of the
wrong six fails to meet its purpose.
Length of the V-belt
If you have to measure the length of a V-belt,
mark the belt with a pencil. see Fig. S-A. Place
the mark 5-A at 0 on a ruler and roll the belt
along the ruler until the mark indicates the
coour4G SYfiTEM!s
Checking the V-belt conditiun
The demands made on the V-beit in connection
with cooling the engine make it necessary to
check the V-belt at regular intervals for signs
of wear. The V-belt must be replaced if fibres
along the sides become loose, spe Fig. 1.
Also roll the belt over tU inspect the bottom
and sides If the belt is glazed, many small
cracks appear and you must &tail a new belt.
Also change the belt if signs of oil soaking or
any other damage is visible.
Check too whether the belt still runs correctly
in its groove.
Figure 2-A shows the correct position of the
belt. Figure 2-B shcws a V-belt which is too
wide, so grooves will soon appear at its sides.
Such belts must not be used. Sections of worn
belts are shown in Fig. 2-C. These b&s must
be replaced to avoid over-heating through a
slipping belt.
V-belt tension
Figure 3 shows a quick and good method of
checking the tension of the V-b&. Place a
straight edge over the pulleys and press the belt
inwards in the centre between the two pulleys,
using moderate pressure. Measure the
deflection with a ruler. Deflection varies
according to the length and size of the belt.
The following can be taken as a general rule:
- Distance between the centres of the two
pulleys is i5W mm. The deflection may be
15 mm.
- Distance between the centres of the two
pulleys is 2000 mm. The deflection may be
20 mm.
Friction between metals
To understand the working of the lubrication
system in an engine you must be aware of the
effects of friction. You ale already familiar
with the properties of friction from your
childhood. When you watched a woman
grinding grain to make flour, you perhaps
noticed at some stage that the small stone she
used to grind the gram became hot after a
while. if she had used the smdl stone without
adding the grain, the stone would have become
even hotter due to the friction between the
huge and the small stone. She reduced the
friction by adding the grain, which acted as a
lubricant, see Fig. 1.
For these lessons it is good to remember that
two metal surfaces are made up of hills and
valleys when they are seen under a
microscope, see Fig. 2. These hills and valleys
tend to interlock and grab each other when
pushed in motion. Even highly polished
surfaces are still made up of these valleys and
hills. though to a lesser degree.
A stabie oil film prevents this interlocking if
the hills and valleys are not too big, see Fig. 3.
Sliding friction
To experiment with sliding friction, take a
square polished steel bar and hook it onto a
spring balance, see Fig. 4. Drag the bar over a
polished steel surface and, while doing so,
record on a piece of paper the reac!;ng on the
spring balance.
After finishing the fit experiment, cover the
steel surface with a film of engine oil. Drag the
square bar over the surface again and record
the reading, see Fig. 5.
You will discover that dragging the bar over
the oil-coated surface takes far less force. Even
if water or any other kind of liquid is used, the
friction is less, so less power is needed.
Rolling friction
Repeat ihe experiment described above but this
time use two round penciii. Position the
pencils between the flat plate and the square
bar. Pull the bar as above and record the
reading on the spring balance.
Less force is needed to overcome rolling
friction, see Fig. 6.
Fluid friction
On the previous page you saw how a film of
lubricar,t prevents comact between two solid
materials. The same thing happens when a
shaft rotates ir, a bushiug or a bearing, see
Fig. I-A.A film of oil under pressurrt ensures
that the two metal surfaces slide over one
‘another. see Fig. 1-B. The only friction that
occurs is in fact between the oil particles
Mixed friction
Mixed frictiorl is friction between two metals
with agood film of lubricant between them.
hut this film is not thick enough to completely
avoid any contact between the two metal
Friction between cylinders and cy!inder wails
is an exaqte of mixed friction. The metal of
both parts touches for a short time, but just
long enough to produce a lot of heat.
It must be noted that roller and ball bearings
are also exposed to mixed friction, see Fig. 2.
Boundary friction
Boundaq friction occurs between two
materials with a little lubricant. Gear joints,
hinges, linkage joints etc. are all subject to
boundary friction, see Fig. 3. A regular check
must be made for lubrication in the form of oil
or grease.
Dry friclion
Examples of dry friction without any lubricmt
are between brake lining and brake drum
(Fig. 4-A). the clutch plate and flywheel (Fig.
4-B) etc. A lot of heat is generated, so this
friction must no; be applied for too long at one
Classification of oils
in order to specify the different classes of
engine oil, the American Petroleum Institute
(API) has introduced a system of classification
which is accepted all over the world.
The classification for petro! engine oil is made
up of five classes, all staning with the letter S
and followed by the letter A, B, C, D, or E.
The letter S comes from Service, meaning that
this type of oil is normally available from
service centres. The letters A, B, C, D and E
indicate the actual quality of the engine oil. For
example: nn oil with the letters SE indicates art
oil of very high quality.
Oils used for diesel engines are marked with
the letter C followed by the letter A, B. C or D.
Diesel engine cil marked with the letters CA is
of a low quality, while oil marked with the
letters CD is of a high quality.
Sometimes oils are sold of a quality which can
be used for both petrol and diesel engines. If
this is the case, you will find both marks on the
oil container - for exnnlple the letters SE-CC,
see Fig. 1.
reco,i?mended because the high quality oil has
a high cleaning ability and after tla: first
chang: combustion particles are washed out
quickly, making the first oil dirty.
Always follow the manufactuar’s
recommendations regarding the quality and the
grade of the engine oil to be used for that
particular engine.
diiia oii t$igiW OiiS
Oil for petrol engities is marked with the
following letters:
SA = Is not used in modem engines.
SB = Used in engines running under very
favourablc conditions.
SC = This oil can ‘beused in older typos of
petrol engines
SD = Is the lowest quality oil which can be
used in modem engines.
SE = This type of oil is tar quality and can
be used in all modem engines even
under severe conditions.
Oil for diesel r+$nes is marked with the letters:
CA = This oil can be used in engines running
under favourable conditions.
CB = Suitable for diesel engines running
under fairly difficult conditions using a
low grade fuel.
CDC= This oil can be used in engines running
under fairly difficu2 conditions using a
good type of fuel.
CD = This oil is suitable for diesel engines
with a high output. It is a ton quality
oil used in engines running under
severe conditions.
Note: If an engine has been running on low
quality engine oil and a change is to be made
to a high quality oil, an extra oil change is
Engine oils
Crude oil found in several parts of the world is
the raw material from which different products
are made, such as petrol, kernsine. diesel fuels,
gas and lubrication oils etc.
Engine oil is a high quality oil designed
especially for the lubrication of particular
engines under specific conditions. The basic
function of engine oil is to ensure that all the
moving parts in the engine function efficiently
with a minimum of wear and friction. As noted
above, engine oil has to provide a durable and
protective fdm between the. moving parts from
the fust to the last moment under both hot
conditions and full In-d.
Oxidation occurs very farit at high
temperatures and a good oil should also clean
the internal parts of the engine, removing
carbon and other deposits c,rused by
combustion. Cylinder walls. bearings and other
engine components must be protected against
corrosion due to moisture and acids. This can
tre done with a good grade of engine oil.
A good grade of lubrication oil must form a
correct sealing film between the pistons and
cylinder walls so the high pressure needed for
combustion is not lost due to leakage. A good
engine oil should not form air bubbles when it
is being splashed about, because this could
prevent good lubrication.
Another function of engine oil is heat
conduct&~, even when it becomes hot.
As you have now seen, engine oil has several
functions to perform und the straight mineral
oil is modified by various additives, such as:
- Oxidaationinhibitors which reduce the
tendency of the oii to absorb oxygen and so
cause oxidation.
- f?bst inhibirors which assist the oil in
preventing corrosion of the engine pill%.
- Pressureagentswhich reduce friction.
- Detergents which increase the cleaning
efficiency of the oil.
Engine oil quality and viscosity
engines or in badly worn engines with high oil
To guarantee all the requirements Listed ahove
it has been necessary to develop standards for
the quality and viscosity of oils which are
uniform and acceptable all over the world.
When selecting oil for an engine it is imponant
to choose the correct one. Two important
factors which determine the choice of oil are:
- The oil must have the right thickness, which
is called viscosify.
-- The oil must meet the quality required by
the manufacturer of the e.tgine.
Multigrade oil
For practical reasons it is not possible to use a
low viscosity oil for cold starring and then
change to an oil with a higher viscosity when
the engine is mnning and hot. That is why a
multigrade oil has been developed which
overcomes these difficulties.
The term viscosity refers to the relative
thickness of an engine oil. A thin free-flowing
oi 1has low viscosity and a thick slow-flowing
oil has high viscosity. The viscosity of oil
changes as the temperature changes. At high
temperatures the oil becomes thinner and ar
low temperatures it becomes thicker. That is
why correct viscosity of the is essential to
efficient running of the engine. If the oil is IOO
thick it causes resistance and much more
power is needed to turn the engine, which also
makes it dGcult to start the engine when it is
cold. Thick oii does not circulate freely enough
during the starting period, causing insufficient
lubrication of the engine parts.
On the other hand, if oil is too thin the
combination of high tempera:ure and heavy
load presents the risk of oil being pressed out
from between the working surfaces of bearings
of other engine parts. This causes the oil film
to break down. Oil which is too thin does not
provide an efficient seal between the cylinder
wall and the piston rings.
Grades of engine oil
Engine oils are graded by the Society of
Automotive Engineers (SAE) and numbered
according to thickness.
The viscosity of oil grades SAE 5W. lOW,
15W and 20W is measured at a temperature of
18 l C. Oil grades SAE 20.30.40 and 50 are
measured at an oil temperature of 100 ‘C,
which is the normal oil temperature when the
engine is running. Note that the lower the
numbers, the thinner the oil.
The correct oil viscosity
Oils with a viscosity of SAE 5 W to 20W are
suitable for climates with a low temperature.
Oils with a viscosity of SAE 20 and 30 are
suitable for moderate to hot climates. Oils with
a viscosity of SAE 40 and 50 are used in old
Technical data on engine oils
A general technical specification for engine
oils has &en accepted;
- Single grade oil which covers one SAE
grade, such as SAE 40.
- Double grade oil which covers two
consecutive SAE grades, such as SAE
- Multigrade oil which covers three SAE
grades, such as SAE 20/4OW.
- Super multigrades which cover more than
three SAE grades, such as 15/5OW.
Lubrication system
A typica! one cylinder diesel enginc may have
a lubrication system as shown in Figs. I and 2.
The lubricarion oil flows through:
- Sump 1-A
- Strainer 1-B
- Oil supply pump 1-C
- Pressure valve 1-D
- Main bearing 1-E
- Drilling main bearing 1-F
- Rocker arms 1-G
- Dip stick 1-H
- Lubrication oil level mark 1-J
- Lubrication oil level 1-K
Lubrication system
A typical 4-cylinder diesel engine may be
equipped with a pressl: z feed lubrication
system, see Fig. 1. A pump forces rhe oil to the
various engine parts requiring lubrication. The
oil is sucked from the sump through a primary
gauze filter (strainer) and then pumped under
pressure to the full now oil filter. An
adjustable pressure relief valve is fLxed in the
filter head. The pressurized oil then passesto
the main oil gallery where the pressure gauge
is fixed. Front, centre and rear main bearings
are connected directly to the oil gallery, where
a pressure gauge is fured. Front, centre and rear
main bearings are directly connected to the oil
gallery by oil feed drillings. The big end
bearings and camshaft bearings are !ubricated
from the cramshaft main bearings. The
cylinder walls and the Fmall end bearings are
splash lubricated. The rear pedestal of the
rocker arm shaft is supplied with oil from the
rear crankshaft main bearing via thr: rear
camshaft bearing. From there, oil passes
through the hollow rocker shaft IO each rocker
and push rod. It then flows back to the suz~p.
Lubrication oil is supplied by the front
crankshaft bearing to the chain tensioner, the
timing chain and, via the front camshaft
bellring, to the fuel injection pump drive. See
Fig. 2.
Pressurized lubrication oil
The pressurized oil in the sump is pumped
through a strainer and the oil pump to the oil
filter and from there to the main oil gallery and
oil passages which lead to the crankshaft and
camshaft bearings, the rocker shaft and the
rocker arms. Oil splashed from the crankshaft
lubricates the piston and other internal moving
parts of the engine.
After lubricating the moving parts the oil drips
back into the sump.
In Fig. 1 the following components can be
- Oil pan/sump 1-A
- Strainer 1-B
- Oil pump 1-C
- Relief valve I-D
- Main oil gallery 1-E
- Oil pressure indicator 1-F
- Oil filter 1-G
- Dip stick 1-H
- Filler cap 1-I
The working of lubrication oil
In the previous chapter we learned about the
working of lubrication oil. Remember that,
even when they appear to be smooth and
polished, surfaces are in reality uneven, as
shown in Fig. 2.
Oil enters the bearing under pressure and a
very small clearance is needed to allow the oil
to form a film between the bearing and the
shaft. The clearance data ran be found in the
manufacturer’s manual.
What actually happens with the shaf: ad the
oil film is shown in Fig. 3.
- When the shaft is not rotating it rests on the
bearing and only a very thin film of oil
separates the surfaces. This thin oil film is
imponant because it is the only lubrication
during the fast revolutions of the shaft when
the engine stafs. See Fig. 3-A.
- As soon as the engine starts and the
revolutions increase, the oil pump starts to
deliver oil and press it into the bearings, It
forms a kind of wedge on which the shaft is
raised from the bearing. See Fig. 3-B.
- At full speed and with the right kind of oil
and oil pressure, the shaft rotates freely in
its bearing on the oil film. See Fig. 3-C.
You realize it is very important that khe
bearings of an engine have the correct
clearance. Too much clearance allows the oil
to escape from the bearing without being able
to create the required oii wedge. Too little
clearance nxtricts the entry of the oil into the
space between bearing and shaft, thus causing
met&to-metal contact. In both cases wear
Figure 1 shows how the oil is pressed out from
the bearings and splashed around, forming an
oil mist which lulxicates the inside cylinder
wall and the piston.
Figure 2 shows that in some cases the
connecting rod has a hole drilled from the side
of the connecting rod into the bearing shell to
spray oil onto the cylinder wall.
Oil pan
When you fill the engine with engine oil 3-D,
see Fig. 3, it sinks through the engine 3-A to
the bottom where it is held in a reservoir 3-C.
This reservoir is either integral with the engine
or sometimes it is attached to the engine block
by bolts, in which case it is called the oil pan.
One end of the oil pan shown in Fig. 5 is lower
and forms a reservoir called the sump. A drain
;Lg 3-E is located at the bottom of the sump
so that dirty oil can be drained off.
The oil level in the oil pan in Fig. 3 can be
checked with a SO-cal!eddip stick 3-B on
which the minimum and maximum oil levels
are marked, see Fig. 4.
Typical oil pump
The oil pump in a diesel engine creates the
pressure required to force the oil from the
sump to the various lubrication points.
Different pumps are used in different engines,
such as a piston pump shown in Fig. 1. This
kind of oil pump is used in small diesel
engines and the push rod is moved by a cam on
the camshaft. Parts of this pump are:
- Push rod 1-A
- Spring 1-B
- Plunger 1-C
- Valve spring 1-D
- Ball valve X-E
- Valve holder 1-F
- Pump housing 1-G
- Valve holder 1-H
- Plug l-l
- Strainer 1-J
The oil pump pushes oil into the main gallery
and from there to other parts of the engine. A
relief valve is attached to the main oil ripe, see
Fig. 2.
When the engine speed increases the oil pump
produces a higher oil pressure than required.
This pressure can damage the oil pump. So a
relief valve is used to take away some of the
extra pressure and maintain it at a suitable
level for the bearings.
The relief valve is connected either to the
pump or to the main gallery and can be of any
shape. All pumps consist mainly of a plunger,
as shown in Fig. 3. or a ball held in position by
a spring.
When the oil pressure rises above the setting
specified by the manufacturer the plunger 3-C
is pushed back against the spriig 3-D and
opens the outlet to the sump via the oil pipe
3-B. When the plunger is pushed back the
pressure decreases and the rest of the oil 3-A is
forced under the correct pressure to the
bearings via.
Figure 3 also shows the relief valve in a closed
position; no oil returns through the oil pipe 3-B
to the sump.
Figure 4 shows a typical oil bal! relief valve in
the closed position. It works in the same way
as the plunger relief valve.
Typical gear pump
Gear pumps as shown ip Figs. 1 and 2 are
commonly used in diesel engines. They are
either attached to the engine block as in the
case of the pump in Fig. 1, or they are closed
with a cover as shown in Fig. 2.
This pump consists of two gears as shown in
Fig. 3, one of which is driven by a helical gear
3-C from the camshaft or an auxili:ary shaft,
depending on the type of engine and its
manufacturer. Oil is sucked in at 3-A and
pressed into the system at 3-B. The gears mesh
with a minimum amount of clearance and they
also only just clear the sides of the housing.
It is clear that the housing must be connected
very tightly against the engine block or the
cover must close very tig+t!:s.
Oil gear pump operation
The oil gear pump operates as follows;
- When the driven gear rotates, it turns the
other gear as well. See Fig. 4. When both
gears are rotating, the oil enters through
inlet port 4-A into the space at the bottom of
the pump.
- While rotating, the teeth of each:gear catch
the oil ‘andcarry it alung the casing towards
the other end of the pump housing, see
Fig. 5.
- The oil leaves the pump under pressure
through outlet port, see Fig. 6 and enters the
tnain oil gallery.
The rotary oil pump
Figure 1 shows a rotary pump consisting of the
following components:
- Inner rotor 1-A
- Outer rotor 1-B
- Oil pump housing 1-C
The inner rotor is driven from a gear 1-D on
the camshaft 1-E.
Rotary pumps may differ in design but the
principle is always the same.
Rotary pump design
Rotary pumps are designed in the form of a
shaft 2-D with four lobes 2-A. see Fig. 2. It is
fitted off-centre inside the outer rotor 2-B with
five recesses corresponding to the lobes. When
the inner rotor turns, its lobes slide over the
corresponding recessesin the outer rotor and
turn it round in the pump housing 2-C.
The working of the rotary oil pump
Figure 3 illustrates the working of the oil
pump. Oil enters at 3-D and leaves the pump at
3-E thmrrgh the inlet *andoutlet ports in the oil
putnp housing 3-C.
As the inner rotor 3-A turns (see arrow), the
lobe 3-G sliding inside the recess of the outer
rotor 3-B creates a space which, as it becomes
larger or smaller. produces an alternating
suction and pumping action.
When the space between the lohe 3-G and the
recess 3-F increases, the oil is sucked into the
pump through the inlet 3-D. As the rotor turns
further, the following lobe of the inner rotor
closes the inlet pon and the space reaches its
With further rotation of the rotor, the outlet
port 3-E opens, the space decreases and the oil
is pushed out.
Servicing the oil gear pumps
The oil pump must be checked for wear or
damage during a general engine overhaul or
when the oil pressure indicator shows the
pressure is too low.
While loosening and handling the oil pump, be
very careful not to damage the mounting
surfaces, the housing or the cover.
Some pumps do not hxve a gzket, only the
machined surfaces act as a seal.
In a gear pump, Fig. 1, most wear develops
between !he teeth of the gears. In a rotary
pump, Fig. 2, wear develops mostly between
the lobes on the rotor ring.
Measuring the clearance
Xefer to Fig. 3. With the gears mounted in the
pump housing, place a straight edge 3-A across
the top of the pump housing to act as the cover
and measure the clearance between the gears
and the straight edge with a feeler gauge 3-B.
The number on the feeler gauge blade should
comply with the manufacturer’s
Clearance between the teeth of the gears and
the housing can be measured as shown in
Fig. 4. Place the correct feeler bhadebetween
ti.e side of the housing 4-A on top of the teeth
4-B and measure the clearance while moving it
backwards and forwards.
Almost all the pumps have a screen over the
inlet to strain out dirt and foreign material. If
possible, remove the screen and clean it. Also
inspect all the bushings in the housing and
replace them if necessary.
Engine oil flltratiorn
When oil passesthrough the engine during
operation it becomes contamined with metal
particles, carbon, dust etc. As you realiie, all
these impurities cause en&e parts to wear if
they are left in the oil and that is why the oil
system must be equipped with an oil filtering
Full flow filtration system
Nowadays all engines are equipped with a
filtering system that filters alL the engine oil
before it reaches the lubrication system.
In this system of oil fitration, see Fig. 1. all
the oil is pumped from the sump 1-A through
the oil pump 1-B to the oil filter 1-C. Lrl the
filter the oil is pressed through a cleaning
material and leaves the filter to pass to the
main oil gallery and the engine parts. A relief
valve 1-D regulates the pressure in the system
and the oil pressure gauge L-E indicates the
actual pressure of the oil during operation.
Bypass filtration system
Sometimes a bypass filtration system is futed
on the engine, so only a portion of the oil
passesthrough the filter. Figure 2 shows how
the oil is pumped from the sump straight into
the lubrication system But some of the oil
passesthrough a filter 2-A and returns to the
sump after filtration.
The volume of oil bypassed through this filter
is coatroLled by a restriction in the filter outlet.
If the filter is dirty or clogged, the volume of
oil passing through the cylinder is reduced.
Due to the two separate oil flows, oil pressure
at the bearings is constant regardless of ldre
condition of the filter, which is an Ldvarttage,
but only checking can tell you whether the
filter is dirty or clogged. That is why both filter
and oil must be changed regularly IO prevent
loss of filtering.
Full flow/bypass filtration system
Some modem engines have both the full flow
and the bypass filtration systems to ensure
maximum cleaning of the oil during operation.
Oil pressure regulating valves
As you have already learned, the oil pressure
built up by the oil pump may exceed the valve
setting. That is why the oil pressure regulating
valves are designed in suLh a way that, in the
event of over-pressure. the valve opens by
itself and the excess oil returns to the oil sump.
Regulating valves are usuaIly connected to the
main oil gallery through passages in the engine
block, may be parr of the oil pump and may be
installed ai bypass oil filters.
Figure 1 shows a typical oil pressure regulating
valve installed in a bypass oil filter. It consists
of a body 1-A which is part of the oil filter
assembly. A ball valve 1-B. held in position by
a spring 1-C. closes off oil passage 1-D by
normal pressure. The pressure put on the ball
by the spring can be increased by adding shims
at 1-E.
--- c
Another oil regulating valve is shown in Fig. 2.
At normal oil pressure the ball valve remains
closed due to the pressure from the spring 2-A.
If the oil pressure builds up, the ball is pressed
upwards, the oil passes the ball and returns to
the sump, see Fig. 3.
In this type of oil pressure regulating valve the
pressure can be changed by loosening nut 2-B
and turning screw 2-C in or outwards,
depending on whether you wan; to increase or
decrease the pressure. After adjusting the
screw, tighten the nut properly to ensure the
cofrect setting.
Oil filters
In different engines you mq find different oil
cleaning systems and filters. A good 6 rilter
must be capable of btopping the flow of very
small particles of dirt, carbon and metal
without restrictin- the oi! flow. Resin
impregnated pap& is the most commonly used
material nowadays. This paper is folded and
enclosed in perforated cy! Jers, one inner
cylinder and one outer cyknder, as shown in
Figs. 1 sr.d 2.
When the oil passes through the paper the dirty
particles accumulate on the surface of the
paper. As shown in Fig. 2. the oil enters
through the @orations at the outside of the
cylinder, passes through the filter element and
leaves the filter through the inner cylinder.
Cartridge filter
Some filter elements are enclosed in metal
.. . _ see Fig. 3. forming one unit. When
the or1is changed, the whole cartridge has to
be replaced.
Cartridges are removed with the special too:
shown in Fig. 4. Do not use pliers to fasten the
new cartridge because you will damage the
metal container. Once the container is
loosened. the element is simply changed out.
Other types of filter
Other filter elements are used sometimes, such
as the depth filter made from cotton waste. In
this filter the oil moves in many directions
before it finally enters the top of the lubrication
Manufacturers recommend the kind of filter to
be used. It is advisable to follow their
Typical oil filter parts
A typical sil filter assembly is shown in Fig. 1,
in which the parts are:
- Relief valve seal 1-A
- Relief valve washer 1-B
- Valve body 1-C
- Ball valve 1-D
- Spring P-E
- Adjusting screw I-F
- Lead washer 1-C
- Lock nut 1-H
- Top guide element 1-I
- Centre tube 1-J
- Filter element 1-K
- circlip 1-L
- Bottom guide element 1-M
- Seal 1-N
- Washer 1-O
- spring 1-P
- Sump seal 1-Q
- Reinforcing washer 1-R
- Centre bolt 1-S
- Sump assembly 1-T
- Head seal 1-U
- Head 1-V
- Relief valve 1-W
- Relief valve spring I-X
- Relief valve washer I-Y
- Relief valve circlip 1-Z
Intake system
The air needed for combustion enters the
engine through an air filter. as shown in Fig. 1.
The air filter 1-A-B-C is attached to the intake
manifold 1-D. It may be a straight connection
or via a rubber hose. The manifold is
connected rigidly with bolts to the cylinder
head of the diesel engine 1-H. Figure 1 shows
the inlet manifold near the exhaust manifo!d.
But since diesel engines do not require heat,
they may also be located on the other side of
Intake system parts are:
- Air filter cover P-A
- Filter housing 1-B
- Sump or oil pan 1-C
- Rubber hose 1-D
- Clamp 1-E
- Inlet manifold 1-F
- Exhaust manifold 1-G
- Cylinder head, inlet valve 1-H
Exhaust system
Figure 2 shows the exhaust system. It consists
of the exhaust valve in the cylinder head, the
exhaust manifold and the muffler. The exhaust
valve seals the burning gases in the cylinder
until Ihe energy is spent, then opens so the
burned gases CNI escape via the manifold,
which brings them to the exhaust pipe. The
muffler 2-B reduces the engine noise during
Exhaust system parts are:
- Exhaust pipe 2-A
- Muffler 2-B
- Clamp 2-c
.- Drain plug 2-D
- Plug 2-E
- Exhaust manifold 2-F
- Inlet manifold 2-C
- Cylinderhead, exhaust side 2-H
Air cleaners
When air is sucked into the cylinder dming its
inlet stroke, dust or other material may enter as
well. Dry wind during the harmattan or dust
blown by stom:s are a potential danger because
they can cause severe wear on cylinders and
pistons, leading to loss of power, higher oil
consumption and possible clogging of the lube
oil system.
To prevent these particles entering the
cylinder, air is passed through a filter. Types of
air filters are:
- Dryfilters, where air passes through a
porous paper element.
- Oil bathjilters. where air passes over an oil
surface and &rough a filter of meshed wire.
.' I
.- #
Figuz 1 shows a cross-section of a
pre-cleaner, in which air passes through a
gauze-prorected contziner and then through a
glass bowl where, through whirling action, the
dust settles at the bottom of the g!ass bowl.
Dry filter
Figure 2 shows a cross-section of a typical dry
filter assembly. Air enterS the fi!ter at 2-A and
passes round the filter element. The air is then
filtered through the element and leaves at 2-B.
Figure 3 shows a paper filter.
Dry element air cleaners
Dry element air cleaners m used in engines
with a high demand for more air. Figure 4
shows a cross-section of iin air cleaner
assembly in which air is directed into the
cleaner at a high speed so that it sets up a
centrifugal rotation, see 4-A. assisted by tilted
fins attached to the end of the dry flrter
element. The air ieaves the filter ti 4-B to the
manifold. The centrifuga! action continues
until the air reaches the far end of the cleaner
housing, where the dust collects in a dust cap
4-C at the bottom of the housing.
Instead of a dust cap, a dust bowl can he
installed as shown in Fig. 5. The bowl can be
removed to take away the dust.
Light duty air cleaner
Fjs*tre 1 shows a cross-sectio,r of a lig!lt ;.rty
011bath air cleaner. It consists of:
- Oil pan 1-A
- Air outlet to engine 1-B
- Oil bath 1-C
- Air inlet 1-D
- Meshed wire filter element 1-E
- Air filter assembly COVET1-F
The air cleaner may be loosened frcm the
engine, after which the cover can be taken off
and the filter element taken out. The oil sump
has a level mark to which engine oil is filled.
Air entering at 1-D first passes over the oil
before it is sucked through the actual filter.
The filter element in this kind of filter can be
cleaned in kerosine and dried, after which it is
soaked in clean engine oil and lowered so the
excess oil drips out. Before assembling, fill the
oil sump with clean engine oil to the level
mark 1-X.
Heavy duty air cleaner
Figure 2 shows a partly opened heavy duty oil
bath air cleaner. Air enters the filter through
the tube T-A and passes over the oil surface
:I- B, from where it is sucked through a filter
element 2-D at the top of the sump 2-F. From
the filter element, the air is then sucked
through a second fi!ter in the top housing 2-C
and leaves the air cleaner through the tube 2-E.
This filter is not directly connected to the inlet
manifold but connected with a rubber hose, so
that it is not affected by vibration from the
engine itself.
General safety precautions
- Keep a clean and well ventilated workshop.
- Keep ail the rools in locked cupboards.
- Before working on an engine, check on all
technical data in the workshop manual.
- Before dismantling an engine, make a clean
space available in which all parts can be
p!aced in correct sequence.
- Make the necessary notes about faults found
in parts etc.
- Question the engine attendant before you
attempt to work on the engine.
- After questioning, study the fault-finding
chart for possible solutions.
- Ensure the engine is mounted securely.
- Ensure a general supply of air is available
for the engine.
- Keep all safety guards in good condition.
- Keep hands and loose clothing away from
air filters, shafts, belts, manifolds, fans and
all other moving and hot parts.
- Do not smoke near starting batteries.
- Disconnect the battery before starting
maintenance work (if installed).
- Do not allow the starting handle to rotate on
the shaft.
- Keep all fuel and oil pipes free from
- Do not allow rubber hoses to come into
contact with the exhaust system.
- Never allow unprotected skin to come into
contact with high pressure fuel oil - for
example, when testing fuel injection
- Thoroughly remove any diesel fuel and
lubricating oil from your skin as soon as
practicable after contact.
- Rectify all fuel oil and water leaks as soon
as practicable.
- Ensure the engine and surrounding area are
kept clean.
- The lifting plates and eyes supplied on the
engine are designed for carrying the engine
and fitted accessories. They must not be
used to lift complete assemblies such as a
complete power unit.
- Check all fuel, oil and coolant levels before
- When using a starting handle, hold the
handle firmly with the thumb on top of the
grip, not around it.
- When using a rope, do not wind the rope
round your hand or wrist. Do not use a
twisted or frayed rope or one that is
contaminated with fuel or oil.
Guide to starting and running
4. Dark blue smoke
- Piston rings worn
- Cylindei bore WON
Faint blue smoke
l., Dif?icult starting
- Light load
White smoke
- Water in the fuel supply
- Water in the cylinder combustion area
Overload trip/excess fuel device not operated
Incorrect grade of fuel
Choked fuel filter
Air lock in fuel system
Injector nozzle valve stuck open
Fuel pump delivery valve scored
Sticking fuel pump rack
Stop/start lever in wrong position
Retarded injection
Injector loose on seat
Leaking valves
Sticking piston rings
Exhaust valve sticking
Worn cylinder
Choked air lifter
Incorrect decompressor clearance
Black smoke
Choked air filter
Inlet air temperature too high
Defective injector spraying
Unsuitable fuel oil or water in fuel
5. Engine stops
- Lackoffuel
- Choked air filter
- Inlet air temperature too high
- Defective injector spraying
- Excessive overload
- Over-heating
- Loss of compression
- Loss ofoil
6. Lass of power
- Unsuitable lube oil (too heavy)
- Load not disconnected
- Turning the crankshaft the wrong way
2. Knocking
- Valve, probably exhaust, sticking in guide
and touching piston
- Worn connecting rod bush or bearing
- Worn gudgeon pin or small end haring
- Insufficient clearance between piston and
cylinder head
- Injection too early
- Flywheel coupling or pullpy loose
- Too much crankshaft end float
- Excessive carbon deposit on piston
- Excessive clearance between piston and
- Engine loose on its mountings
- Wrong type of fide1
3. Excessive arbon deposits
- Choked air filter
- Choked exhaust system
- Unsuitable fuel oil
- Unsuitable lube oil
- Continuous idling
- Defective injector spraying
- Late injection of fuel
- Too much side clearance on valve rockers
- Low load running
- Low temperature running
Loss of compression
Incorrect tappet clearance
Choked a3 filter
Choked exhaust filter
Defective fuel pump or injector
Choked fuel filter
7. Failure to attain normal speed
- Engine started at overload
- Fuel system not properly primed
- Insufficient fuel
- Injection retarded
- Governor out of adjustment
- Wrong type of governor weights etc. for
speed expected
Lass of oil pressure
Low oil level
Strainer choked
Fractured pipe or leaking joint
Badly worn bearings
Relief valve not seating
Oil pump worn or drive failed
Oil cooler choked
Oil diiuted with fuel
Unsuisable lube oil (too thin)
Guide to starting and running
problems (continued)
9. Overheating
Air cooled engines
- Cooling air being recirculated
- Fins of cylinder head or cylinder blocked
with dirt
- Cooling air inlet obstructed
- Cooling air outlet obstructed
- Engine cooling tj used to cool driven unit
as weIl
- Overload
- Lube oil level too low
- Lnjection timing faulty
Wafer cooled engines
- Thermostat faulty
- Injection timing faulty
- Overload
- Cooling water level too low
- Lube oil level too low
- Water pump belt slipping
- Blockage in water cooling system
10. Low compression
- Injector loose on its seat
- Injector washer scored
- Piston ring caps in line
- Inlet or exhaust valve noi seating
- Cylinder head gasket leaking
11. Hunting
- Tight spots on governor linkage
- Fuel pump rack not free
- Air in fuel system
- Faulty injector
12. High oil consumptiuu
- Valve guides worn
- Piston rings worn
- Cylinder bore worn
13. Loss of crankcase vacuum
- Worn piston rings
- Worn cylinder barrel bore
- Worn oil seals
- Too much oil in the sump
- Oil ftiter cap not seating
14. Leaking oil seals
- Too much oil in the sump
- Loss of crankcase vacuum
Only a few engine tnanufacturers give a
specific number of running hours after which
decarbonizing should be carried out. The
number of running hours depends on such
factors as the type of fuel used, ambient
temperature, period of low load running and
others. Perhaps the best indication that
carbonizing is due, is when the engine shows
loss of compression or blow-by past the
pistons. To decarbonize an engine thoroughly
clean and examine for wear the following
components, replacing any defective parts as
- Piston, piston rings and grooves and
gudgeon pin
- The combustion chamber or ceil
- Valves, valve springs, puns and seats
- Exhaust manifold, piping and silencer
- Inlet manifold and trunking
- C&inder barrel, head and crankcase cooling
- Injector
Conversion factors
1 metre =
1 inch=
1 foot=
1 yard=
us pint
US gallon
UK pint
: : K gallon
1 UK pint =
1 UK gallon =
1 US pint =
1 US gallon =
i!. 1041
cubic mctre
cubic decimetre
cubic inch
cubic foot
1 UK pint = 0.5683 litre
1 litrc = 1.7598 UK pint
1 in’=
1.6387x 1O-5
1 ft3 =
5.7870 x 10 4
Linear velocity
1 ftjs =
1 fi/m=
1 in/s=
metrc per second
foot per second
foot per minute
0.005 1
1 lb/s =
1 lb/h=
1 kS/s=
per second
Rate of flow - mass
1 kg/X=
inch per second
2.7777 x lo4
1.2599 x lo4
per hour
per second
6.1239 x 10.4
2 7777 x 10-l
per hour
Conversion factors
Rata of flow - volume
cubic metrc
per second
1 m3/s =
1 us=
I fl’/S =
1 g&=
4.5460 x IO3
per second
cubic foo[
per second
35.3 147
UK gatlon
per second
6 3288
1 N/mm2 =
1 kgf/cm2 =
1 Ibf/in2 =
1 lbf/fe =
per square
per square
per square
9.8066 x 10 *
6.8947 x IO-’
4.788 x 10.’
4.8824 x 10 4
6.9444 x N3
per square
I bar=
1 kgf/cm2 =
1 Ibf/in* =
per square
per square
I bf/in2
I .0197
I .0332
inch of
foot of
millimcvc of
inch of
1 fIH20 =
I mmHg=
1 inHg
t’ 8827
Conversion factors
Torque (moment of force)
1 kgfm=
1 Ibfft=
1 Ibfin=
kilogramforce melrc
kgf m
poundforce foot
lbf fi
I .3558
kgf m
fl Ibf
hp h
2.7240 x 10 ’
3.7661 x W7
3.6709 x 16
2.7375 x ld
2.6552 x IO6
1.98 x IO’l
3.6530 x 1W6
British thermal
unir per hour
3.9846 x 10 ’
3.9301 x lo4
poundforce inch
Ibf in
1 fr tbf =
1 hpp=
1 bhp=
1 Btu/?r=
Metric prefixes
Tine unit of temperature most commonly used
in practice in many countries is the degree
Celsius (‘C), though the terms Centigrade (“C)
and Fahrenheit (‘F) are still in use. The
Fahrenheit scale is not formally defined, but it
is generally recognized that the tempxnwe
difference of 1 “F is equal to five ninths of the
temperature difference of 1 ‘C.
“C = ‘/g (OF- 32)
Factor by which
the unit iy multiplied
1 rxH!M-!-oNKl
0.001 001
0400 ooo M!l
Tightening torques for nuts
and bolts
The t&le gives the torque in Nm and lbf ft for
unified and IS0 metric nuts and bolts. The
unified ones are to BS 1768: 19C3Grade S for
bolts and Grade 3 for nuts, whilst the IS0
metric are to BS3692: 1967 Grade 8.8 for bolts
and Grade 10 for nuts.
of rhrsad
I ”
(fine and course)
18/l 1
3 I)
1 *
Threuds per inch
or mm pi&h
-10.7 pitch
Standard bolt and nut torque
Thread size
2mu boll torque
'I* 'i.i ‘J,6 'h‘Js 'J, l/,6 ‘Jib 'Jz ‘J2 giM gJ,6‘J* 'JR'Li ‘Jd ‘/a ‘Jn -
I - 14
Thread size
'14 - 20
‘J, - 28
'JM- 18
'JM- 24
'/I - 16
'13 - 24
7J~t,- 14
‘J,e - 20
72 - 13
‘Jz - 20
‘/I6 -12
‘/,,I - 18
‘J, - 1I
'Jg - 18
7/:‘/I l1-
8- 11
14- 18
15- 19
31- 35
35- 40
47- 5!
58- 62
72- 76
84- 95
171 - 181
417 -427
697 -705
18- 23
20- 26
41- 47
47- 53
62- ii8
77- 83
96- 102
23- 26
26- 29
35- 38
43- 46
S3- 56
62- 70
68- 75
so- 88
126- 134
180 - 188
218 - 225
or belier torque
8- IO
13- 17
lS- 19
30- 35
3s- 39
46- SO
57- 61
71- 75
R3- 93
137 -- 147
168 - 178
Useful terminology
Abrasion: The wearing or rubbing away of a
metal surface.
Air cleaner: Various types of device for
removing particles of dust from air before it
enters the engine.
Ambient temperature: Ihe mean temperature
of the combustion and cooling air entering the
AP: The American Petroleum Institute.
Atmospheric pressure: The weight of air at
sea tevel. this is usually taken as being 1 Bar
or 14.7 lbshn’.
Backlash: The clearance 3r movement
between the teeth of meshed gears.
Back pressure: A resistance to Freeflow, such
as the restriction in an exhaust line.
Balancing fuel pumps: In multi-cylinder
engines with single-element pumps the pump
racks are adjusted to ennbte all pumps to
deliver a similar amount of fuel.
Bearing: A precision fiiished surface that
allows another part to turn or move against it.
B.h.p.: Brake horse-power is the measurement
of the total power of the engine available at
the flywheel.
Blow-by (past): The loss of compression past
the piston rings.
Bore: The internal diameter of the cylinder
BS (I): British Standard (Institution).
Bypass: \Jsuaily used as an alternative route
for oil when the Filter is blocked.
Calibration marks: Marks on the fuel pump
or pump rack to show when the pump is
delivering optimum fuel.
Camshaft: The camshaft is timed to the
rranksh<aFtand cams operate the inlet and
exhaust valves.
Celsius: Celsius has generally replaced
centigrade, though the two are identical.
Cetane: The term used to show the pressure
and temperature at which fuel ignites and
Combustion: The process of burning.
Combustion chamber: The space between the
underside of rhe cylinder head and the top of
the piston when it is at the top of its stroke.
Compression: The reduction in volume of a
gas by squeezing.
Compression ratio: The total volume of air in
the cylinder compared to the volume in the
combustion chamber, for exampie 16: 1.
Connecting rod: The part which connects the
piston to the crankshaft.
Constant speed: An engL7e with its governor
adjusted to give one speed only.
Crankcase: The lower casting of the engine
which contains the camshaft, bearings,
crankshaft, oil etc.
Crankcase breather: A method used to
maintain a crankcase vacuum.
Crankcase (sump) dilution: Wher: fu4 finds
its way into the oil and dilures it.
Crankcase pressure: Usually caused by
combustion gases finding their way into the
Crankcase vacuum: A slight vacuum in the
sump is required to prevent oil s?ais and
joints leaking oil. A vacuum is sometimes
called negative pressure.
Crankshaft: The main drive shaft of the
engine which transforms reciprocating
motion into rotary motion.
Crankshaft counterweights: Either an
integtal part of or bolted onto the crrtnkshaft
to offset the weights of the piston and
connecting rod.
CV: Cheval Vapeur (Metric Horse Power).
Also known % CH in some countries.
Cyclic irregularity: Indicates the degree by
which the flywheel varies from uniftirm
rotary motioil.
Cylinder: The component the piston is Fitted
into. Often called the barrel in zir cooled
engines and the block in water cooled engines.
Cylinder bore: The internal diameter of ?he
Cylinder head: Fits onto the rop of the
cylinder and contains the valves, injector
ansd manifold ports.
Decarbonize: Removal of the build-up of
carbon from the piston and heads.
DEMA: American equivalent of BS.
De-rating: AI certain site levels and
temperatures the oxygen content of th.: air is
less and the load must th?reFore be reduced to
Detergent: An additive used in lubricating oil!;
to hold deposits of carbon in suspension and
to help prevent frothing. The oil is usually
referred to as having a mild or heavy duty
DIN: German equivalent of BS.
Diesel engine: ahis type of engine is called a
compression ignition engine as the fuel is
ignited by the heat of compression without
the need of a spark.
Direction of rotation: Looking onto the
flywheel, this is the way the engine is turning.
Dynamometer: Test equipment used to
measure energy expended from an engine or
mechanical force.
Exhaust: The waste producs of combustion.
Exhaust manifold: The component used to
col!ect the exhaust gases to pass them to the
Exhaust valve: A spring-loaded valve
operated from the camshaft to allow the
exhaust gases in the cy!inder to pass out at the
correct time.
Excess fuel device: An automatic or manual
method of moving the fuel pump rack to
allow extra file1 to pass through the fuel
pumps for starting.
Filter (oil, water, fuel): A device for
removing particles of din from the fluids to
protect the engine components concerned.
Flash point: The temperature at which a liquid
or vapour will ignite when heated.
Flywheel: The flywheel is used mainly to
provide the rotary motion for the driven unit;
it also helps to reduce the variation in the
speed of the crankshaft which is caused by
the reciprocating motion of the cylinders.
Four-stroke cycle: The crankshaft turns twice
but the cylinder fires only once.
Induction stroke
Compression stroke
Power stroke
Exhaust stroke
FP: Firing point, when fuel is sprayed into the
combustion chamber.
Fuel consumption: The amount of fuel used
by the engine to give a certain output rating.
Glazed bore (see also Polished bore): Used to
describe the surface of a cylinder barrel bore
when it has become extremely smooth and
polished. Usually asssociated with using the
wrong type of oil.
Governor: A device to control the speed of the
engine by regulating the amount of fuel
passing through the fuel pumps.
Gudgeon pin: Used to connect the piston to
the connecting rod and held in position by
two r&lips.
Heat exchanger: Only used on water cooled
engines to cool the water after it has
circulated round the system. Works in a
similar way to a radiator but uses colder
water instzad of the fan and air flows.
Hertz (Hz): Unit of frequency. The number of
repetitions of a regular occurrence in one
Humidity: The measure of the percentage of
water vapour held in suspension in the air.
Hunting: Often cause by a fuel pump rack or
governor with tight spots resulting in the
speed of the engine increasing and decreasing
over a wide range.
Idling speed: The lowest speed setting on a
variable speed engine.
Injection pump: A s;dgle-element or
multi-cylinder pump used to meter and
deliver fuel under pressure to the injector.
Injector: Used to inject atomized fuel into the
combustion chamber at a very precise
Iujector leak off: A small diameter pipe
allowing excess fuel from the injector to be
fed back IO the engine fuel tank.
Injector set pressure: The pressure at which
the injector valve opens. This is adjustable
and is controlled by an internal spring.
Inlet manifold: The casting which carries the
combustion air fmm the air cleaner to the
cylinder head.
InYet valve: A spring-loaded valve operated
from the camshaft to allow the combustion
air to enter the cylinder barn3 at the correct
Intercooler: A method of cooling the
combustion air charge in some turbo-charged
Internal combustion: The process of burning
the air/fuel mixture in an enclosed chamber.
158: International Organization for
Journal: The part of the crankshaft which runs
in the main and connecting rod bearings.
Lapping. The process of rubbing two surfaces
with an aSrasive material until a seal is
formed. as is performed with a valve and
valve scar.
Lbf ft: Pounds-force feet.
Manometer: An open ended U-shaped tube
partly filled with a liquid used to measure a
Mechanical efRciency: The ratio between the
indicated and the brake horse power of an
Micrometer: An itistmment to measure
external or internal dimensions.
MIL.: American military standards as applied
to lubricating oils.
Nm: Newton metres.
Overload: The amount of load given by the
engine above its rated load.
Piston ring: A ring fitted into a piston ring
groove to prevent gases or oil passing.
Polished bore (see &I Glazed bole): A term
used to describe the cylinder barrel bore when
it has become smooth and polished, usually
after the engine has run for a high number of
Psi.: Pounds per square inch.
Pumping oil: A term describing the condition
when an engine is using an excessive amount
of lube oil.
Push rod: A metal rod operating from the
camshaft to open and close the inlet and
exhaust valves.
Rated load: The amount of power the engine
is designed to deliver at a given speed.
Radiator A series of enclosed pipes through
which the ergine water passesto enable air,
which is fan driven across the pipes, to
dissipate the heat.
Rotary motion: A circular movement such as
the rotation of the crankshaft.
R.p.m., rev/mitt, r/min: Revolutions per
SAE: SKiety of Automotive Engineers.
St: System International.
Sludge: A composition of oxidised petroleum
products and contaminants usually found in
the crankcase oil sump or fuel tank.
Stroke: The distance the pistor, moves from its
highest to lowest points.
Tachometer: An instmment for measuring the
speed of an engine.
Tappet: The component which operates the
fuel pump from the camshaft.
Tappet clearance: The clearance between the
valve stem and the valve rocker arm.
TDC: Top Dead Centre.
Thermostat: A device used to regulate the
flow of water from a cylinder block to the
radiator or heat exchanger.
Throw: The distance between the centres of
the crankshaft and connecting rod journals,
Thrust washer: A flat bearing surface fitted
between a shaft and its housing to absorb any
Timing marks: Marks used to show the
crankshaft and other driven gears are
correctly aligned to ensure the valves and fuel
pumps operating at the correct time. Marks
on the flywheel show when the piston is at
TM: or PP.
Torque: The effort of turning.
Torque wrench: An adjustable spanner or
wrench to measure the applied turning force
being put onto a bolt head or nut.
Turbo-charger: An engine-mounted device
using the engine exhaust to drive a rotor and
turbine to enable a larger combustion air
charge to be delivered to the combustion
chamber, resulting in a higher b.h.p. being
Vacuum: A term used to describe a pressure
less than atmospheric pressure. Also known
as negative pressure or, in case of an engine,
crankcase depression.
Valve bounce: Occurs when the valve does
not seat correctly and opens and closes
Valve clearance: The distance between the
valve stem and valve rocker when the engine
is at TDC on the compression stroke.
Valve grinding: See lapping.
Valve guide: A bush through the cylinder head
into which the valve fits.
Valve seat: The matched surface in the
cy!inder head ontn which the valve seat mates.
Valve seat cutting. A process used to cut the
untrue surface of the valve seat until it is
correct to the profile of the valve head.
Variable speed engine: An engine designed to
run at various speeds throughout a
predetermined range.
Viscosity: The resistance to flow of a liquid.
The viscosity of oil is denoted by numbers,
for exampie IOW, 2OW, 30W etc.
Viscous damper: A device usually fitted to
larger multi-cylinder engines to reduce the
twisting or torsional vibration of the
Wrist pin: See ydgeon pin.
Rural Meeharaics Course
Rural Mechanics Course
Lay out and timetable
Stationary diesel engines
Diesel engine theory
Diesel engine workshop practice
Stationary diesel engines
Installation of stationary die& engines
Typical air cooled diesel engine
Water cooled one-cylinder diesel engine
Water cooled one-cylinder diesel engine
How the diesel engine operates
Internal combustion engine
Reciprocating and rotary motion
T.D.C., B.D.C., stroke, bore, volume throw
and compression ratio
The four-stroke cycle engine
Multiple cylinder engines
Components of the engine
Components of the engine
Cylinder head and valves
Cylinder head
Cylinder head gasket
Valve mechanism
Valve lifting system
Removal of valves
Setting the valve clearance in a four-stroke
diesel engine
Reconditioning valves
Grinding precautions
Camshaft and timing mechanism
Valve timing
Valve timing degrees (exhaust)
Servicing the camshaft
Push rods
Rocker arm
Too much valve clearance
Cylinder block and cylinders
Cylinder blocks
The cylinder
Servicing cylinders
Pistons and piston rings
Piston rings
Piston and piston rings
Lubrication oil consumption
Wear of piston and piston rings
Inspecting the piston
Ring gap measurement
Connecting rod and crankshaft
Connecting rods
The c.rankshalt
Inspecting the crankshaft
Bushings and bearings
Bearing metal alloys
Measuring practice
The flywheel
Timing transmission
Fuel systems
Fuel and fuel storage
Sediment bowl
Typical fuel supply pump assembly
I‘uel filters
Injection and combustion
Fuel injection pumps
Single-element fuel injection pump
Operation of the fuel pump element
Typical fuel injection pump
Governor systems
Fuel and governor setting
Fig point
Fuel injection
Combustion chamber
Faulty injectors
Servicing the nozzle
N,zzle test bench
Injector testing
Fuel pipe fittings
Bleeding air from the fuel system
Engine trouble-shooting
Engine trouble-shooting
Fault-finding guide for injection system
Intake and exhaust
Intake system
Air cleaners
Light duty air cleaner
Ger, :ral safety precautions
Guide to starting and running problems
Guide to starting and running problems
Conversion factors
Metric prefixes
Tightening torques for nuts and bolts.
Standard bolt and nut torque specifications
UseM terminology
Cooling systems
Cooling systems
Water cooling systems
Radiator cap
Water pump
V-Belt construction
Checking the V-belt condition
Lubrication system
Friction between metals
Fluid friction
Classification of oils
Engine oils
Engine oil qualiLy and viscosity
Lubrication system
Pressurized lubrication oil system
Typical oil pump
Typical gear pump
The rotary oil pump
Servicing the oil gear pumps
Engine oil filtration
Oil pressure regulating valves
oil filters
Typical oil filter parts
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