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AUTOMOTIVE
SERVICING

DIESEL ENGINE
FUNDAMENTALS and
SERVICING
DON BOSCO TECHNICAL INSTITUTE OF MAKATI, INC.
Technical Vocational Education and Training Center
A. Arnaiz Ave. Cor. Chino Roces Avenue, Makati City
FORMING GOOD CHRISTIANS and UPRIGHT CITIZENS
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DIESEL ENGINE FUEL SERVICING

Course Description
The Diesel Engine is one of the first major subjects of the Automobile Mechanics Program. The
course provides comprehensive training to develop the theoretical and practical skills of trainees in
the Diesel engine, engine systems, and fundamentals of operation through experiments and
hands-on activities on preventive maintenance, diagnosis, minor repair and basic troubleshooting.

Brief History of Diesel Engine

In 1892, Dr. Rudolf Diesel, a young German engineer, patented a compression ignition engine that
attempted to use coal dust as a fuel. Coal dust proved be a workable fuel, presenting many
problems that caused diesel to search for another fuel. Lamp petroleum selected to replace coal
dust. After much trial and error, Dr. Diesel’s third engine was considered a success. It used the
compression ignition principle with air-fuel injection. Within two years, the diesel engine had been
adopted as a power source for many applications in Germany.

 Advantages of Diesel Engines

 Low fuel consumption
 Low fuel cost
 Low fire hazard
 High reliability in operation
 Less pollution
 High power per pound of engine
 High sustained torque

 Disadvantages of Diesel Engine

 Cost
 Weight
 Attendance
 Fuel cost
 Space
 Hard starting in cold weather

 Uses of Diesel Engines

 Construction machinery
 Power generation
 Transportation
 Farm machinery
 Aerospace and National defence
 Marine uses

 What is a Diesel Engine?

An internal combustion engines which produces power by burning fuel oil in a body
of compressed air.

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 General Types of Engine

1. External Combustion Engine
2. Internal Combustion Engine

Kinds of Internal Combustion Engine

1. Rotary Engine
2. Piston engine
Two Kinds of Piston Engines
1. Spark-ignition engine
2. Compression-ignition (Diesel) engine

The differences between them are:

The type of fuel used
The way the fuel gets into the cylinders
The way the fuel is ignited

 The Basics of Diesel

In the diesel or compression-ignition engine, the fuel mixes with air after it enters the engine
cylinders. The piston compresses the air to as little as 1/22 of its original volume. Compressing the
air this much raises its temperature to 10000F (5380C) or higher. Light oil called diesel fuel is then
sprayed or injected into the hot air. The hot air or heat of compression ignites the fuel. The
methods of ignition-by heat of compression-gives the diesel engine the name compression-ignition
engine.

 Basic Construction of Diesel Engine

Spark-ignition and diesel engines are similar in construction. Both have cylinder blocks, cylinder
heads, crankshafts, bearings, pistons, connecting rods, and valve trains. The main difference
between spark-ignition parts and diesel engine parts is that diesel parts are usually heavier and
stronger. This is because the internal pressure is higher in diesel engines.

 DEFINITION OF TERMS
1. Cycle ------------------------------ a series of events repeated in the same regular order.
2. Stroke ----------------------------- refers to the distance travelled by the piston from top to
bottom or vice versa.
3. Top Dead Center (TDC) ------ refers to the topmost part reached by the piston during its
upward motion.
4. Bottom Dead Center (BDC)-- refers to the lowermost part reached by the piston during its
downward motion.
5. Combustion ---------------------- refers to burning of the air-fuel mixture in the combustion
chamber.
6. Injection timing ------------------ the injection of fuel from the nozzle at the proper time for the
combustion stroke relative to the piston position, usually
expressed in crankshaft degrees before or after top dead
center (TDC) at the end of the compression stroke.
7. Revolution------------------------- refers to one complete rotation of the crankshaft.

8. Suction----------------------------- drawing of air into the engine cylinder due to the downward
movement of the piston.
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9. Scavenging----------------------- refers to the process of removing burned gases inside the

cylinder by means of air that enters the engine during intake
stroke.
10. Running mate-------------------- refers to two piston moving at the same time in the same
direction but performing different strokes or events.
11. Firing order----------------------- refers to the order in which the cylinders must be fired.

 Basic Elements of an Engine

♦ Air, fuel, and combustion
♦ Reciprocating and Rotary motion
♦ Compression of air and fuel
♦ Engine cycles

 Three basic elements needed to produce heat energy in the engine

1. Air ---- needed to combine with fuel and give it oxygen for fast burning. Air heats
when compressed.
2. Fuel -- must mix readily with air and ignites easily.
3. Combustion ---- burning or actual igniting of the air-fuel mixture.

 Two forms of motion to transmit energy

1. Reciprocating motion ----- motion in a straight line back and forth or up and down.
2. Rotating motion ----------- circular motion around a point.
 Compression of the Air and Fuel
Compression ratios tell us how much the fuel-air mixture is compressed by volume.
8:1 compression ratio for gasoline
16:1 compression ratio for diesel engine
In other words, air in this engine is compressed to one-eight or one sixteenth of its former
volume by the moving piston.

 Engine Cycles
For an engine to operate, a definite series of events must occur in sequence they are:
Intake -------------- fill the cylinder with a combustible mixture.
Compression ---- compress this mixture into a smaller space.
Combustion ------ ignites the mixture and causes it to expand, producing power.
Exhaust ----------- remove the burned gases from the cylinder.

To produce sustained power, the engine must repeat this sequence over and over again. One
complete series of these events in an engine is called cycle.

 Principle of Operation of Four Stroke Cycle Engine

In four-stroke cycle engine, there are four strokes of the piston, two up and two down, during each
cycle. This cycle occurs during two revolutions of the crankshaft. As a result, the crankshaft will
rotate two complete turns before one cycle is completed (720 degrees).

 Principle of Operation of Two Stroke-Cycle Engine

In two-stroke cycle engine, there are two strokes of the piston, up and down, during each cycle.
This whole cycle occurs during one revolution of the crankshaft. The complete cycle of events –
intake, compression, power and exhaust takes place during two piston strokes.
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Comparison of the Gasoline and Diesel engine during each stroke

Engine Stroke Gasoline Engine Diesel Engine

Intake Air-fuel mixture is draw into Air only is drawn into the cylinder.
combustion chamber by vacuum.

Compression Piston compress the air-fuel Piston compresses air to increase

mixture both pressure and temperature.

Power / Combustion Spark plug ignites compressed Fuel is ignited into heated highly
mixture. compressed air where it ignites
due to heat of pressurized air.

Exhaust Piston forces exhaust gases out Piston forces exhaust gases out of
of cylinder. cylinder.

Method used to Controlled by controlling air-fuel Controlled by controlling amount of

regulate power mixture supplied to cylinders fuel injected (amount of air
using throttle valve. entering cylinder is not regulated.)

 Summary

1. Has no throttle valve to restrict air flow into the engine (except for some modified
engine).

2. Compress only air on the compression stroke.

3. Has much higher compression ratio.

4. Does not have an electric ignition system, instead heat of compression ignites the
fuel sprayed into the cylinder.

5. Engine power and speed are controlled only by the amount of fuel sprayed into the
cylinders. For more power, more fuel is injected. For less power, less fuel is injected.

6. Have glow plugs, which make it easier to start a cold engine.

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Valve Timing
The valve timing is the opening and closing of the valves in relation to the piston position.

Valve Overlap
The number of degrees of crankshaft rotation during which the intake and exhaust
valves are open together. Overlap helps scavenge or expel the remaining gases from the
cylinders.
It helps cool and clean the combustion chamber.

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DIESEL ENGINE FUEL SYSTEM SERVICING

Summary of Fuel System Operation
1. A vane type feed pump draws fuel from the fuel tank
through the water sedimenter and fuel filter, and sends it
to the inner pump housing.
2. A pressure regulating valve controls the fuel pressure
inside the injection pump.
3. Excess fuel is returned to the fuel tank through the
overflow tube via overflow screw. This helps to cool the
moving parts of the injection pump.
4. The cam plate is driven by the pump drive shaft. The
pump plunger fits into the cam plate and fuel is delivered
by rotating and reciprocating motion of this plunger.
5. Injection volume is controlled by the mechanical governor
assembly.
6. Injection timing is controlled by the timer piston, which is
operated by fuel pressure.
7. A fuel cut off solenoid shuts off the fuel passage to the
pump plunger when the engine starter switch is turned off.
8. The delivery valve performs the dual function of
preventing the fuels in the injection pipe from flowing
backward to the plunger and removing from the nozzle (by
suction) the remaining in it after injection.

Fuel System operation with Distributor type Injection pump

The injection pump generates the pressure required for fuel injection. The fuel under pressure is forced
through the high pressure fuel injection tubing to the injection nozzle which then injects it into the
combustion chamber. To keep pace with the ever increasing demands placed upon the diesel fuel injection
system, it has been necessary to continually improve and develop the fuel injection pump.

PREHEATING CIRCUITRY
Preheating Circuitry Components
The glow plug controller type preheating system consist of the glow plugs, a glow plug controller, a glow
plug relay, etc. The glow plug controller on the instrument panel indicates when the glow plugs are heating.

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1. Glow Plugs (Heater Plugs)

Device used to heat up the air inside the combustion chamber. Use as a cold starting aid. There are
several types of glow plug. The three types have been used most commonly up to the present are:

1. Conventional type
2. Self-temperature-controlling type
3. Low-voltage type

2. Glow Plug Controller

The glow plug controller, located on the instrument panel, monitors the heating of the glow plugs.

3. Glow Plug Relay

The glow plug relay prevents a large flow of current through the starter switch, and ensures that the
voltage drop caused by the glow plug controller does not affect the glow plugs.

4. Glow Plug Resistor

This resistor reduces the voltage applied to the glow plugs. When the no.1 glow plug relay is off (i.e.
glow plug raised to approximately 800C or 1,472 F), current flows to the glow plugs through this
resistor.

5. Glow Plug Current Sensor

This sensor maintains an almost constant resistance even during changes in temperature. Since the
resistance value of the glow plugs greatly changes with variations in temperature, the preheating
timer detects the voltage differences at each end of this sensor to maintain glow plug temperature
between 750 and 900C for most engines.

6. Water Temperature Sensor

This is the same type of sensor as that used in the variable delay type preheating system.

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GLOW PLUG SERVICING

1. Remove the 4 nuts holding the glow plug connector to the glow plugs.
2. Remove the nut holding the glow plug connector to the intake manifold.
3. Remove the two insulators and glow plug connector
4. Using an ohmmeter, check that there is continuity between the glow plug terminal and ground. If
there is no Continuity the glow plug is defective or burnt out.

REPLACING GLOW PLUGS (if necessary);

1. Using a 12 mm deep socket wrench, remove the four glow plugs
2. Install new glow plugs using a 12 mm deep socket wrench. Torque 130kg-cm /9ft-lb.
3. Install the glow plug connector.

CAUTION:
1. Be careful not to damage the glow plug pipes as this could cause an open circuit or shorten the life of
glow plugs
2. Avoid getting oil and gasoline on the glow plugs when cleaning them.
3. During inspection be sure to wipe any oil off the glow plug terminal and Bakelite washer with a dry
cloth.
4. Stop applying battery voltage when the glow plug begins to glow red. Applying battery voltage for a
long period could cause burn out.

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NOZZLE
Device in the diesel fuel system that is responsible for delivering atomized fuel inside the combustion
chamber.

Nozzles can broadly classified into the hole type and the pin type.
1. Hole Type Nozzles ----- Single hole and Multiple holes
2. Pin Type Nozzles ------- Throttle type and Pintle type

HOLE TYPE INJECTOR PINTLE TYPE INJECTOR

A. SERVICE INJECTION NOZZLES

REMOVAL :
1. Remove glow plug connector
2. Remove injection pipes
3. Remove nozzle leakage pipe (overflow)
4. Remove injection nozzles. Arrange the
injection nozzles in the correct order to ensure
correct installation.

TESTING INJECTION NOZZLES:

I. Injection pressure test

1. Pump the nozzle tester several times to flush
out the nozzle fittings, then tighten the fittings.

2. Install the injection nozzle to nozzle tester and

bleed the air from the union nut.

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3. Pump the tester handle a few times as fast as

possible to discharge the carbon from the
injection hole.

4. Pump the tester handle slowly while observing

the pressure gauge.

5. Read the pressure gauge just as the injection

nozzle pressure begins to drop. If the opening
pressure is not as specified, disassemble the

II. Leakage Test

While maintaining pressure at about 10 – 20

kg/cm2 (142-284psi; 981 – 1,961kPa) below the
opening pressure, check that there is no dripping
for 10 seconds from the injection hole or around
the retaining nut.

If the nozzle drips within 10 seconds, replace,

or clean and overhaul the nozzle assembly.

III. Spray Pattern Test:

1. Pump the nozzle tester 15 to 60 times (for old

nozzle) or 30 to 60 times (for new nozzle) per
minute.

2. Check the spray pattern,

If the spray pattern is not correct the nozzle
must be replaced or cleaned.

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IV. Chatter Test

1. Pump the nozzle tester and listen to a

hesitating swishing sound means it is properly
operating. You hear a continues squeaking sound
the nozzle must be cleaned and adjusted to
specifications.

DISASSEMBLY; CLEANING; INSPECTION

1. DISASSEMBLE INJECTION NOZZLES

a. Using SST, remove the nozzle holder retaining
nut.
b. Remove the pressure spring

CAUTION:
When disassembling the nozzle, be careful not to
drop the inner parts.

2. NOZZLE CLEANING

a. To wash the nozzles, use a wooden stick and

wire brush. Wash in clean diesel fuel.

HINT: Do not touch the nozzle mating surfaces

with your fingers.

b. Using a wooden stick, remove the carbon adhering

to the nozzle needle tip.
c. Using a brass wire brush, remove the carbon from
the exterior of the nozzle body (except for the
lapped surfaces.)
d. Check the seat of the nozzle body for burns or
corrosion
e. Check the nozzle needle tip for damage or
corrosion. If any of these conditions are present,
replace the nozzle assembly.

3. INSPECT NOZZLE ASSEMBLY

a. Wash the nozzle in clean diesel fuel.

b. Tilt the nozzle body about 60º and pull the needle
out about one third (1/3) of its length.
c. When released, the needle should sink down into
the body vent smoothly by its weight.
d. Repeat this test, rotating the needle slightly each
time. If the needle does not sink freely, replace the
nozzle assembly.
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4. ASSEMBLY

1. ASSEMBLE INJECTION NOZZLE HOLDERS

a. Assemble the nozzle holder retaining nut, the nozzle
assembly, the distance piece, the pressure pin, the
pressure spring, the adjusting shim and the nozzle
holder body, and finger tighten the retaining nut.

b. Tighten the retaining nut using SST. Torque 375 kg-

cm / 27ft-lb / 37 N-m

2. PERFORM PRESSURE AND SPRAY PATTERN

TEST

5. INSTALLATION

1. INSTALL INJECTION NOZZLE

a. Place four new gaskets and the four nozzle seats
into the injection nozzles holes of the cylinder head.
b. Using SST, install the four injection nozzles. 650kg-
cm /47ft-lb /64 N-m

2. INSTALL NOZZLE LEAKAGE PIPE

a. Install four new gaskets and leakage pipe with the
nuts
b. Connect the fuel hose to the return pipe Torque:
300kg-cm/22ft-lb/29N-m

3. INSTALL INJECTION PIPES

a. Place the two lower clamps on the intake
manifold.
b. Install the four injection pipes
c. Secure the injection pipes with the two upper
clamps and bolts

4. INSTALL GLOW PLUG CONNECTOR

5. START ENGINE AND CHECK FOR FUEL LEAKS.

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FUEL FILTER

SERVICING DIESEL FUEL FILTERS

There are very small clearances in the injection pump and injectors and so the diesel fuel must be
kept clean. All care must be taken to ensure fuel does not become contaminated. Dirty fuel will not
only cause engine performance issues but may cause damage to the injection components and
end in expensive repairs.

Below are some General notes in relation to Servicing Fuel Filters:

1. Before servicing a filter, clean all external oil and dirt from around the filter.
2. Maintain clean conditions
3. If fitted with a drain plug, drain the filter before removing the filter bowl
4. After removing the bowl clean inside the filter head with a clean cloth using diesel
fuel. Clean the bowl as well.
5. Replace the sealing ring.
6. Tighten the filter canister
7. Once the filter has been installed correctly, prime and bleed the system and check for
fuel Leaks

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CANISTER FUEL FILTERS

Canister filters (throw away filters) are threaded on to the filter housing. When servicing the filter
the complete canister is removed and replaced. The filter can be removed with an oil filter tool but
when the new filter is installed it should be tightened by hand. Before installing the filter seal should
be coated with diesel fuel. The filter should be hand tightened until the filter makes contact with the
seal and then it is tightened an additional half turn (approximately).

FILTERS WITH DISPOSABLE ELEMENTS

Some filters have a disposable element. The bowl is attached to the top cover by a center bolt. A
plug in the bottom of the centre bolt allows the filter to be drained before the bowl is removed.
Once removed, the bowl is washed in clean fuel and a new filter element is installed.

STRAINERS
Strainers of fine mesh are fitted to some systems. They can be used at the fuel tank, the supply
pump or at a banjo connection. Strainers are serviced by washing in fuel and blowing clean.

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TWO WAY FUEL FILTER

INJECTION PUMP

I. INLINE INJECTION PUMP

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II. ROTARY INJECTION PUMP (VE = Distribution Injection)

IN-LINE AND DISTRIBUTOR TYPE INJECTION PUMP FUEL SYSTEM

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TROUBLESHOOTING
Troubleshooting means solving a problem by considering each possible cause of a problem in turn
and eliminating those that are found to be not applicable. The remaining possible cause(s) can
then be considered to be probable cause(s). This method is much faster and more accurate than
simply guessing or making random adjustment or repairs.

INJECTION NOZZLE TROUBLESHOOTING

Never remove an injection nozzle from the engine except for service or replacement. The following
indicate injection nozzle troubles:

1. One or more cylinders knocking.

2. Loss of power.
3. Smoky black smoke
4. Engine overheating.
5. Excessive fuel consumption.

One way to check injection nozzle, is to run the engine at fast idle. Loosen the connector at each
nozzle in turn, one at a time. Wrap a cloth around the connection before you loosen it to keep fuel
from spurting out. If loosening the connector causes speed to drop, the nozzle is probably working
normally. If the engine speed remains the same, the nozzle is not working properly. Clogged holes
are preventing fuel delivery or causing an improper spray pattern.

If the engine misses at all speeds and produces a puff of exhaust smoke each time it misfires, an
injection nozzle is probably sticking open. The nozzle can be disassembled and cleaned. Some
manufacturers recommend replacing a faulty nozzle. If you disassemble a nozzle, do not damage
the tip or enlarge the holes. This can cause leakage and other troubles.

Diesel Fuel System Troubleshooting Chart

COMPLAINT POSSIBLE CAUSE REMEDY

1. Engine Cranks a. Incorrect or dirty fuel a. Flush fuel system – use correct
Normally but will b. No fuel to nozzle or Injection fuel
not start pump b. Check for fuel to nozzle
c. Clogged fuel-return line c. Check return line
d. Pump timing off d. Retime
e. Defective glow plugs e. Replace

2. Engine starts a. Fuel low in tank a. Fill tank

but stalls on idle b. Incorrect or dirty fuel b. Flush system-use correct fuel
c. Limited fuel to nozzle or c. Check fuel to nozzle or pump
injection pump d. Check return line
d. Restricted fuel-line/return line e. Reset idle
e. Idle incorrectly set f. Retime
f. Pump timing off g. Calibrate or replace
g. Defective injection pump h. Check engine

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H. Internal engine problem

3. Rough idle, no a. Low idle a. Adjust

abnormal noises b. Injection line leaks b. Fix leaks
or knock c. Restricted return-line c. Check return-line
d. Defective nozzle d. Check and repair
e. Defective fuel supply pump e. Check and service
f. Uneven fuel distribution to f. Check nozzles and service
nozzles g. Clean and use correct fuel
g. Incorrect or dirty fuel

4. Rough idle with a. Injection timing off a. Retime

abnormal noises b. Defective nozzle b. Check cylinders in sequence
and smoke and check defective nozzle

5. Idle okay but a. Plugged fuel filter a. Replace filter

misfires as b. Injection-pump timing off b. Retime
throttle opens c. Incorrect or dirty fuel c. Flash system-use correct fuel

6. Loss of power a. Incorrect or dirty fuel a. Flush system-use correct fuel

b. Restricted fuel-return line b. Check and clean
c. Plugged fuel-tank vent c. Check and clean
d. Restricted fuel supply d. Check fuel lines, fuel supply
e. Plugged fuel filter and injection pump
f. Plugged nozzles e. Replace filter
g. Internal engine problems, loss f. Selectively test nozzles and
compression service
g. Perform compression testing

7. Noise – “Rap” a. Air in fuel system a. Correct and bleed

from one or b. Gasoline in fuel system b. Replace fuel
more cylinders c. Air in high-pressure line c. Bleed system
d. Nozzle sticking open or with d. Check and replace nozzle
low opening pressure e. Check engine
e. Engine problems

8. Combustion a. Timing off a. Reset timing

noise with b. Injection-pump trouble b. Check or replace pump
excessive c. Nozzle sticking open c. Check and service
black smoke d. Internal engine problems d. Check engine

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9. With White a. Timing off a. Reset timing

Smoke b. Preheating and after-glow b. Check and replace defective parts
problems c. Check and correct
c. Engine burning oil d. Perform compression testing
d. Compression pressure too low e. Flush system-use clean fuel
e. Water mixed in with fuel

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COMPRESSION TESTING
For Diesel Engine

Compression Tester
An instrument for testing the amount of pressure, or compression developed in an engine cylinder
during cranking.

Testing Procedures
1. Be sure the battery is fully charged.
2. Run the engine to normal temperature.
3. Turn of the engine and remove all the glow plugs.
4. Do not allow the glow p[lug wires to contact to ground, tape if necessary.
off apply – disconnect the wire on injection pump with electric solenoid, tape if
necessary.
On injection pump with manual linkage, secure the linkage in the “no fuel position”.
5. Cover the air inlet (intake manifold) with suitable wire screen.
6. Screw the compression tester fitting into the glow – plug hole of the cylinder to be
checked.
7. Crank the engine noting the number of compression strokes (puffs) by listening to the
adjacent
cylinder and watching the gauge pointer for pressure build up. The gauge will reach
its highest reading in approximately 6-10 puffs.
8. Check all the cylinders the same way. Record your findings.

Data and Results:

Compression Cylinder Cylinder Cylinder Cylinder Findings Assessment /

testing #1 #2 #3 #4 Recommendation

Dry Test

Wet test

Carefully note the “gauge rate” or build-up of pressure. Normal compressions build up quickly and
evenly to the manufacturer’s specified compression on each cylinder. It is important to compare the
difference between cylinders.

Interpretation: _______________________________________________________

Causes of Problem:
____________________________________________
____________________________________________
____________________________________________
____________________________________________
Recommendation: ___________________________________________________
Good If the lowest reading is within 90% of the highest reading.
Acceptable If the lowest reading is within 80-90% of the highest reading.
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Marginal If the lowest reading is within 70-80% of the highest reading.

Unacceptable If the lowest reading is below 70% of the highest reading.

Example:
If the highest reading is 450 Psi (.90 X 450 = 405) good reading could range from 405 – 450
Psi

Compression Testing
Process of checking the actual compression pressure of an engine to determine whether the
engine is for tune-up or overhaul.

Compression Tester
An instrument for testing the amount of pressure, or compression developed in an engine cylinder
during cranking.

Causes of Poor Compression

1. Too little valve clearance
2. Loose cylinder head bolts
3. Loose glow plugs / spark plugs
4. Loose injection nozzles
5. Warped cylinder head
6. Blown-out cylinder head gasket
7. Cracked cylinder head
8. Broken/weak valve spring
9. Sticking valve
10. Worn out valve seat
11. Worn out valve
12. Loose valve retaining lock
13. Worn out valve guide
14. Cracked cylinder block
15. Worn out piston
16. Worn out piston rings
17. Worn out cylinder walls
18. Broken connecting rod

Dry Test Compression testing

Process of checking the actual compression pressure after warming-up the engine.

Wet Test Compression Testing

Putting small amount of oil inside the cylinder before checking the compression pressure of an
engine. The purpose of this testing is to double check and pinpoint the causes of the problem.

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COMPRESSION
TESTER

DIESEL ENGINE TROUBLESHOOTING

NOTE: This is GENERAL information. This article is not intended to be specific to any unique
situation or individual vehicle configuration. The purpose of this Troubleshooting information
is to provide a list of common causes to problem symptoms. For model-specific
Troubleshooting, refer to SUBJECT, DIAGNOSTIC, or TESTING articles available in the
section(s) you are accessing.

NOTE: Diesel engines mechanical diagnosis is the same as gasoline engines for items such as
noisy valves, bearings, pistons, etc. The following trouble shooting covers only items
pertaining to diesel engines.

BASIC DIESEL ENGINE TROUBLESHOOTING CHART

CONDITION & POSSIBLE CAUSE CORRECTION

I. Engine Won't Crank
1. Bad battery connections or dead batteries Check connections and/or replace batteries
2. Bad starter connections or bad starter Check connections and/or replace starter
II. Engine Cranks Slowly, Won't Start
1. Bad battery connections or dead batteries Check connections and/or replace batteries
2. Engine oil too heavy Replace engine oil
III. Engine Cranks Normally, But Will Not Start
1. Glow plugs not functioning Check glow plug system, see FUEL SYSTEMS
2. Glow plug control not functioning Check controller, see FUEL SYSTEMS
3. Fuel not injected into cylinders Check fuel injectors, see FUEL SYSTEMS
4. No fuel to injection pump Check fuel delivery system
5. Fuel filter blocked Replace fuel filter
6. Fuel tank filter blocked Replace fuel tank filter

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CONDITION & POSSIBLE CAUSE CORRECTION

7. Fuel pump not operating Check pump operation and/or replace pump
8. Fuel return system blocked Inspect system and remove restriction
9. No voltage to fuel solenoid Check solenoid and connections
10. Incorrect or contaminated fuel Replace fuel
11. Incorrect injection pump timing Re-adjust pump timing, see FUEL SYSTEMS
12. Low compression Check valves, pistons, rings, see ENGINES
13. Injection pump malfunction Inspect and/or replace injection pump
IV. Engine Starts, Won't Idle
1. Incorrect slow idle adjustment Reset idle adjustment, see TUNE-UP
2. Fast idle solenoid malfunctioning Check solenoid and connections
3. Fuel return system blocked Check system and remove restrictions
4. Glow plugs go off too soon See glow plug diagnosis in FUEL SYSTEMS
5. Injection pump timing incorrect Reset pump timing, see FUEL SYSTEMS
6.No fuel to injection pump Check fuel delivery system
7. Incorrect or contaminated fuel Replace fuel
8. Low compression Check valves, piston, rings, see ENGINES
9. Injection pump malfunction Replace injection pump, see FUEL SYSTEMS
10. Fuel solenoid closes in RUN position Check solenoid and connections

V. Engines Starts/Idles Rough W/out Smoke or Noise

1. Incorrect slow idle adjustment Reset slow idle, see TUNE-UP
2. Injection line fuel leaks Check lines and connections
3. Fuel return system blocked Check lines and connections
4. Air in fuel system Bleed air from system
5. Incorrect or contaminated fuel Replace fuel
6. Injector nozzle malfunction Check nozzles, see FUEL SYSTEMS
VI. Engines Starts and Idles Rough W/out Smoke or Noise, But Clears After Warm-Up
1. Injection pump timing incorrect Reset pump timing, see FUEL SYSTEMS
2. Engine not fully broken in Put more miles on engine
3. Air in system Bleed air from system
4. Injector nozzle malfunction Check nozzles, see FUEL SYSTEMS
VII. Engine Idles Correctly, Misfires Above Idle
1. Blocked fuel filter Replace fuel filter
2. Injection pump timing incorrect Reset pump timing, see FUEL SYSTEMS
3. Incorrect or contaminated fuel Replace fuel
VIII. Engine Won't Return To Idle
1. Fast idle adjustment incorrect Reset fast idle, see TUNE-UP
2. Internal injection pump malfunction Replace injection pump, see FUEL SYSTEMS
3. External linkage binding Check linkage and remove binding
IX. Fuel Leaks On Ground
1. Loose or broken fuel line Check lines and connections
2. Internal injection pump seal leak Replace injection pump, see FUEL SYSTEMS
X. Cylinder Knocking Noise

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CONDITION & POSSIBLE CAUSE CORRECTION

1. Injector nozzles sticking open Test injectors, see FUEL SYSTEMS
2. Very low nozzle opening pressure Test injectors and/or replace
XI. Loss of Engine Power
1. Restricted air intake Remove restriction
2. EGR valve malfunction Replace EGR valve
3. Blocked or damaged exhaust system Remove restriction and/or replace components
4. Blocked fuel tank filter Replace filter
5. Restricted fuel filter Remove restriction and/or replace filter
6. Block vent in gas cap Remove restriction and/or replace cap
7. Tank-to-injection pump fuel supply blocked Check fuel lines and connections
8. Blocked fuel return system Remove restriction
9. Incorrect or contaminated fuel Replace fuel
10. Blocked injector nozzles Check nozzle for blockage, see FUEL SYSTEMS
11. Low compression Check valves, rings, pistons, see ENGINES
XII. Loud Engine Noise With Black Smoke
1. Basic timing incorrect Reset timing, see FUEL SYSTEMS
2. EGR valve malfunction Replace EGR valve
3. Internal injection pump malfunction Replace injection pump, see FUEL SYSTEMS
4. Incorrect injector pump housing pressure Check pressure, see FUEL SYSTEMS
XIII. Engine Overheating
1. Cooling system leaks Check cooling system and repair leaks
2. Belt slipping or damaged Check tension and/or replace belt
3. Thermostat stuck closed Remove and replace thermostat, see ENGINE
COOLING
4. Head gasket leaking Replace head gasket
XIV. Oil Light on at Idle
1. Low oil pump pressure Check oil pump operation, see ENGINES
2. Oil cooler or line restricted Remove restriction and/or replace cooler
XV. Engine Won't Shut Off
1. Injector pump fuel solenoid does not return Remove and check solenoid and replace if needed
fuel valve to OFF position

VACUUM PUMP DIAGNOSIS

CONDITION & POSSIBLE CAUSE CORRECTION
I. Excessive Noise
1. Loose pump-to-drive assembly screws Tighten screws
2. Loose tube on pump assembly Tighten tube
3. Valves not functioning properly Replace valves
II. Oil Leakage
1. Loose end plug Tighten end plug
2. Bad seal crimp Remove and re-crimp seal

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Diesel Preventative Maintenance

According to recent studies, 5 percent of all motor vehicle fatalities are clearly caused by
automobile maintenance neglect. The following simple and inexpensive preventive checks will
greatly extend the life of your diesel vehicle, ensure safer operation and even benefit the
environment.

Always consult your owner's manual for individual diesel service schedules. Maintenance
requirements vary by manufacturer.

 Always consult your owner's manual, but a good rule of thumb is to have the oil and filter
changed regularly - every 3,000 to 4,000 miles. Diesel oil changes are even more important.

 Have all fluids checked, including brake, power steering, transmission/transaxle, windshield
washer solvent and antifreeze. These fluids play a large role in the safety and performance
of the vehicle.

 Regularly changing diesel fuel filters can extend diesel fuel pump and diesel injector life and
ensure optimum engine performance.

 Air filters have a great impact on fuel mileage and should be inspected frequently. The air
filter should be checked every other oil change for clogging or damage. This ensures that
your vehicle is performing at its peak condition.

 Check tire inflation. Under-inflated tires can result in a loss of diesel fuel efficiency. This is
the least expensive form of preventive and safety maintenance. Tires should be checked
once a month.

 Keep your engine tuned. A worn or defective fuel injector can reduce fuel efficiency by as
much as 30 percent.

 Have the chassis lubricated frequently. This step extends the life of the moving components
of the vehicle's suspension system.

 Check battery cables and posts for corrosion and clean them as needed. The battery fluid
also should be checked and filled if it is low, unless it is a maintenance-free battery.

 Have the lighting system checked frequently, including headlights, turn signals, and brake
and taillights.

 Check windshield washer blades for cracks, tears and windshield contact. Replace them at
least once a year, or sooner if streaking begins.

 Inspect engine accessory drive belts regularly. Worn belts will affect the electrical charging
system and engine performance. Look for cracks and missing sections or segments.

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