Isuzu 4JB1, 4JB1T, 4JB1TC, 4JG2 Service Information

SERVICE INFORM

ATION 00 – 3

1.

HARD STARTING

1. STARTER INOPERATIVE
Checkpoint Possible cause Correction

Loos

e battery cable terminal poor

connections due to rusting

Clean and/or retighten the battery
cable terminal

Batter

y discharged or weak Recharge or replace the battery

Battery

F

an belt loose or broken Adjust or replace the fan belt

F

usible link Fusible link shorted Replace the fusible link

Star

ter switch Defective starter switch or starter relay Replace the starter switch or the

Starter relay

Def

ective magnetic switch or starter relay Repair or replace the magnetic switch

Starter m

otor

Defective starter motor Repair or replace the starter motor

2. STARTER MOTOR OPERATES BUT ENGINE DOES NOT TURN OVER

Loos

e battery cable terminal Clean and/or retighten the battery

cable terminal

Poor

connections due to rusting Recharge or replace the battery

Batter

y discharged or weak Recharge or replace the battery

Battery

F

an belt loose or broken Adjust or replace the fan belt

Def

ective pinion gear Replace the pinion gear

Def

ective magnetic switch Repair or replace the magnetic switch

Star

ter

Brush wear, Weak brush spring Replace the brush and/or the brush

spring

Engine

Piston, crank bearing seizure, or other
damage

Repair or replace the related parts

00 – 4 SERVICE INF

ORMATION

3. ENGINE TURNS OVER BUT DOES NOT START
Checkpoint Possible cause Correction

Engine s

top

mechanism

Defective fuel cut solenoid valve Replace the fuel cut solenoid valve

FUEL IS NOT BEING DELIVERED TO THE INJECTION PUMP

F

uel Fuel tank is empty Fill the fuel tank

F

uel piping Clogged or damaged fuel lines. Loose fuel

line connection

Repair or replace the fuel lines
Retighten the fuel line connection

F

uel filter overflow valve does not close Repair or replace the fuel filter

overflow valve

F

uel filter

Clogged fuel filter element Replace the fuel filter element or the

filter cartridge

F

uel system Air in the fuel system Bleed the air from the fuel system

F

uel feed pump Defective feed pump Repair or replace the feed pump

FUEL IS BEING DELIVERED TO THE INJECTION PUMP

Us

e of the wrong fuel Use the correct fuel

W

ater particles in the fuel Change the fuel

F

uel

Fuel system

Air in the injection pump Bleed the air from the fuel system
Inj

ection nozzle sticking

Inj

ection nozzle

Injection nozzle injection starting pressure
too low
Improper spray condition

Adjust or replace the injection nozzle

Def

ective fuel injection nozzle resulting in the

fuel drippage after fuel injection

Replace the delivery valve

Def

ective injection pump control rack

operation

Repair or replace the injection pump
control rack

Inj

ection pump plunger worn or stuck Replace the injection pump plunger

assembly

Inj

ection pump drive shaft seizure or other

damage

Replace the injection drive shaft

Inj

ection pump

Injection pump governor spring seizure Replace the injection pump governor

spring

SERVICE INFORM

ATION 00 – 5

4. QUICK-ON START SYSTEM

PREPARAT

ION

1 Disconnect the thermoswitch connector.

2. Determine whether or not the glow plugs are receiving power.
a) Make sure that the starter switch is “OFF”.
b) Connect a voltmeter between one of the glow plugs and the cylinder wall.
c) Move the starter switch to the “ON” position.

The voltmeter needle will show the souse voltage (12V) if the glow plugs are receiving power.
If the voltmeter needle does not move, the glow plugs are not receiving power.

3. Perform the troubleshooting procedure.

GLOW PLUGS ARE RECEIVING POWER

Checkpoint Possible cause Correction

G

low plug indicator

light does not turn on

Defective indicator light bulb Replace the indicator light bulb

Q

uick-on start timer Defective quick-on start timer Replace the quick-on start timer

G

low plug indicator
light turns on the 0.3
seconds

Defective quick-on start timer Replace the quick-on start timer

Return the s

tarter switch to the “ON” position
from the “START” position after the engine
starts if the glow plug relay remains on less
than 14 seconds, the quick-on start timer is
defective

Replace the quick-on start timer

G

low plug indicator
light turns on for 3.5
seconds

Move the starter switch from the “OFF”
position to the “ON” position if the glow plug
relay remains on less than 14 seconds, the
quick-on start timer is defective

Replace the quick-on start timer

T

hermoswitch Defective thermoswitch Replace the thermoswitch

G

low plug continuity No glow plug continuity Replace the glow plugs

GLOW PLUGS ARE NOT RECEIVING POWER

G

low plug indicator
light does not turn on

Broken indicator light fuse Replace the fuse

Q

uick-on start timer Defective quick-on start timer Replace the quick-on start timer

00 – 6 SERVICE INF

ORMATION

GLOW PLUGS ARE NOT RECEIVING POWER (Cont’d)

Checkpoint Possible cause Correction

Def

ective glow plug relay
The glow plug relay does not turn on after the
starter switch is moved from the “OFF”
position to the “ON” position

Replace the glow plug relay

Defective quick-on start timer Replace the quick-on start timer
Defective glow plug relay wiring harness Repair or replace the wiring harness

G

low plug indicator
light turns on for 3.5
seconds

Defective fusible link or wiring harness
The glow plug relay turns on when the starter
switch is moved from the “OFF” position to
the “ON” position

Replace the fusible link or the wiring
harness

2.

UNSTABLE IDLING

Checkpoint Possible cause Correction

Idling s

ystem Idling improperly adjusted Adjust the idling

F

ast idling speed Defective fast idling speed control device Repair or replace the fast idling speed

control device

A

ccelerator control

system

Accelerator control system improperly
adjusted

Adjust the accelerator control system

F

uel system leakage or blockage Repair or replace the fuel system

Air

in the fuel system Bleed the air from the fuel system

F

uel system

Water particles in the fuel system Change the fuel

F

uel filter Clogged fuel filter element Replace the fuel filter element or the

fuel filter cartridge

F

uel feed pump Defective fuel feed pump Repair or replace the fuel feed pump

Inj

ection nozzle sticking Replace the injection nozzle

Inj

ection nozzle

Injection nozzle injection starting pressure
too low
Improper spray condition

Adjust or replace the injection nozzle

Inj

ection pump Defective delivery valve resulting in fuel

drippage after fuel injection

Replace the delivery valve

SERVICE INFORM

ATION 00 – 7

Checkpoint Possible cause Correction

Inj

ection timing improperly adjusted Adjust the injection timing

Ins

ufficient injection volume Adjust the injection volume

Def

ective idle spring Replace the idle spring

Def

ective governor lever operation Repair or replace the governor lever

Regulator

valve improperly adjustment Adjust or replace the regulator valve

Br

oken plunger spring Replace the plunger spring

W

orn plunger Replace the plunger assembly

Inj

ection pump

(Cont’d)

Worn cam disc Replace the cam disc

Valve c

learance Valve clearance improperly adjusted Adjust the valve clearance

Com

pression pressure Blown out cylinder head gasket. Worn

cylinder liner.
Piston ring sticking

Replace the related parts

3. INSUFFICIENT POWER

Checkpoint Possible cause Correction

Air

cleaner Clogged air cleaner element Clean or replace the air cleaner

element

F

uel Water particle in the fuel Replace fuel

F

uel filter Clogged fuel filter element Replace the fuel filter element or the

fuel filter cartridge

F

uel feed pump Defective fuel feed pump Repair or replace the fuel feed pump

Inj

ection nozzle sticking Replace the injection nozzle

Inj

ection nozzle

Injection nozzle injection starting pressure
too low
Improper spray condition

Adjust or replace the injection nozzle

F

uel injection pipes Fuel injection pipes damaged or obstructed Replace the fuel injection pipes

00 – 8 SERVICE INF

ORMATION

Checkpoint Possible cause Correction

Def

ective regulating valve Repair or replace the regulating valve

Def

ective delivery valve Replace the delivery valve

Def

ective timer Repair or replace the timer

W

orn cam disc Replace the cam disc

Im

proper control lever operation Adjust or replace the control lever

Def

ective injection timing Adjust the injection timing

Repair or replace the injection pump
timer

W

eak governor spring Replace the governor spring

Inj

ection pump

Worn plunger Replace the plunger assembly

Com

pression pressure Blown out cylinder head gasket. Worn

cylinder liner.
Piston ring sticking

Replace the related parts

Valve c

learance Valve clearance improperly adjusted Adjust the valve clearance

Valve s

pring Valve spring weak or broken Replace the valve spring

Ex

haust system Exhaust pipe clogged Clean the exhaust pipe

F

ull load adjusting

screw seal

Open and improperly set adjusting screw
seal

Adjust and reseal the adjusting screw

SERVICE INFORM

ATION 00 – 9

4. EXCESSIVE FUEL CONSUM

PTION

Checkpoint Possible cause Correction

F

uel system Fuel leakage Repair or replace the fuel system

related parts

Air

cleaner Clogged air cleaner element Clean or replace the air cleaner

element

Idling s

peed Poorly adjusted idling speed Adjust the idling speed

Inj

ection nozzle Injection nozzle injection starting pressure

too low
Improper spray condition

Adjust or replace the injection nozzle

F

uel injection timing Fuel injection timing improperly Adjust the fuel injection timing

Inj

ection pump Defective Delivery valve resulting is fuel

drippage after fuel injection

Replace the delivery valve

Valve c

learance Valve clearance improperly adjusted Adjust the valve clearance

Com

pression pressure Blown out cylinder head gasket. Worn

cylinder liner.
Piston ring sticking

Replace the related parts

Valve s

pring Valve spring weak or broken Replace the valve spring

5. EXCESSIVE OIL CONSUM

PTION

Checkpoint Possible cause Correction

Engine oil

Engine oil unsuitable
Too much engine oil

Replace the engine oil
Correct the engine oil level

O

il seal and gasket Oil leakage from the oil seal and/or the

gasket

Replace the oil seal and/or the gasket

Air

breather Clogged air breather Clean the air breather

Intak

e and exhaust

valve

Worn valve stems and valve guides Replace the intake and exhaust

valves and the valve guides

00 – 10 SERVICE INF

ORMATION

6.

OVERHEATING

Checkpoint Possible cause Correction

Cooling w

ater Insufficient cooling water Replenish the cooling water

F

an clutch Oil leakage from the fan clutch Replace the fan clutch

F

an belt Fan belt loose or cracked causing slippage Replace the fan belt

Radiator

Defective radiator cap or clogged radiator
core

Replace the radiator cap or clean the
radiator core

W

ater pump Defective water pump Repair or replace the water pump

Cy

linder head and
cylinder body sealing
cap

Defective sealing cap resulting in water
leakage

Replace the sealing cap

T

hermostat Defective thermostat Replace the thermostat

Cooling s

ystem Cooling system clogged by foreign material Clean the foreign material from the

cooling system

F

uel injection timing Fuel injection timing improperly adjusted Adjust the fuel injection timing

7. WHITE EXHA

UST SMOKE

Checkpoint Possible cause Correction

Cooling w

ater Insufficient cooling water Replace the cooling water

F

uel Water particles in the fuel Replace the fuel

F

uel injection timing Delayed fuel injection timing Adjust the fuel injection timing

Com

pression pressure Blown out cylinder head gasket. Worn

cylinder liner.
Piston ring sticking

Replace the related parts

Inlet and ex

haust valve

Valves seals

Defective valve seals.
Worn valves stems and valve guides

Replace the valve seals, the valves,
and the valve guides

SERVICE INF

ORMATION 00 – 11

8. DA

RK EXHAUST SMOKE

Checkpoint Possible cause Correction

Air

cleaner Clogged air cleaner element Clean or replace the air cleaner

element

Inj

ection nozzle Injection nozzle injection starting pressure

too low
Improper spray condition

Adjust or replace the injection nozzle

F

uel injection timing Fuel injection timing improperly adjusted Adjust the fuel injection timing

Def

ective delivery valve resulting in fuel

drippage after fuel injection

Replace the delivery valve

Inj

ection pump

Excessive injection volume Adjust the injection volume

9. OIL PRESSURE DOES NOT RISE

Checkpoint Possible cause Correction

Engine oil

Improper viscosity engine oil.
Insufficient engine oil

Replace the engine oil
Correct the engine oil volume

O

il pressure gauge or
unit
Oil pressure indicator
light

Defective oil pressure gauge or unit
Defective indicator light

Repair or replace the oil pressure
gauge or unit
Replace the indicator light

O

il filter Clogged oil filter element Replace the oil filter element or the oil

filter cartridge

Relief

valve and by-

pass valve

Relief valve sticking and/or weak by-pass
valve spring

Replace the relief valve and/or the by­pass valve spring

Clogged oil pum

p strainer Clean the oil pump strainer

O

il pump

Worn oil pump related parts Replace the oil pump related parts

Roc

ker arm shaft Worn rocker arm bushing Replace the rocker arm bushing

Cam

shaft Worn camshaft and camshaft bearing Replace the camshaft and the

camshaft bearing

Cr

ankshaft and

bearings

Worn crankshaft and bearings Replace the crankshaft and/or the

bearings

00 – 12 SERVICE INF

ORMATION

10.

ABNORMAL ENGINE NOISE

1. ENGINE KNOCKING

Chec

k to see that the engine has been thoroughly warmed up before beginning the troubleshooting procedure.

Checkpoint Possible cause Correction

F

uel Fuel unsuitable Replace the fuel

F

uel injection timing Fuel injection timing improperly adjusted Adjust the fuel injection timing

Inj

ection nozzle Improper injection nozzle starting pressure

and spray condition

Adjust or replace the injection nozzle

Com

pression pressure Blown out head gasket

Broken piston ring

Replace the head gasket or the piston
ring

2. GAS LEAKAGE NOISE

Ex

haust pipes Loosely connected exhaust pipes. Broken

exhaust pipes

Tighten the exhaust pipe connections
Replace the exhaust pipes

Inj

ection nozzles

and/or glow plugs

Loose injection nozzles and/or glow plugs Replace the washers

Tighten the injection nozzles and/or
the glow plugs

Ex

haust manifold Loosely connected exhaust manifold and/or

glow plugs

Tighten the exhaust manifold
connections

Cy

linder head gasket Damaged cylinder head gasket Replace the cylinder head gasket

3. CONTINUOUS NOISE

F

an belt Loose fan belt Readjust the fan belt tension

Cooling f

an Loose cooling fan Retighten the cooling fan

W

ater pump bearing Worn or damaged water pump bearing Replace the water pump bearing

G

enerator or vacuum
pump

Defective generator or vacuum pump Repair or replace the generator or the

vacuum pump

Valve c

learance Clearance improperly adjust Adjust the valve clearances

SERVICE INF

ORMATION 00 – 13

4. SLAPPING NOISE
Checkpoint Possible cause Correction

Valve c

learance Valve clearance improperly adjusted Adjust the valve clearance

Roc

ker arm Damaged rocker arm Replace the rocker arm

F

lywheel Loose flywheel bolts Retighten the flywheel bolts

Cr

ankshaft and thrust

bearings

Worn or damaged crankshaft and/or thrust
bearings

Replace the crankshaft and/or the
thrust bearings

Cr

ankshaft and
connecting rod
bearings

Worn or damaged crankshaft and/or
connecting rod bearings

Replace the crankshaft and/or the
connecting rod bearings

Connec

ting rod

bushing and piston pin

Worn or damaged connecting rod bushing
and piston pin

Replace the connecting rod bushing
and/or the piston pin

Pis

ton and cylinder

liner

Worn or damaged piston and cylinder liner. Replace the piston and the cylinder

liner.

00 – 14 SERVICE INF

ORMATION

11. ENGINE COOLING TROUBLE

Checkpoint Possible cause Correction

Low

coolant level Replenish

T

hermo unit faulty Replace

F

aulty thermostat Replace

F

aulty coolant unit Repair or replace

Clogged r

adiator Clean or replace

F

aulty radiator cap Replace

Low

engine oil level or use of improper

engine oil

Replenish or change oil
Replenish

Dam

aged cylinder head gasket Replace

Clogged ex

haust system Clean exhaust system or replace

faulty parts

Loos

e fan belt Adjust

E

xcessive fuel injected Adjust

Engine over

heating

Improper injection timing Adjust

Engine over

cooling Faulty thermostat Replace

F

aulty thermostat Replace

T

oo long engine

warm-up time

Thermo unit faulty Replace

SERVICE INF

ORMATION 00 – 15

12. ENGINE ELECTRICA

L PART TROUBLE

STAR

TER DOES NOT RUN

C

HECK BATTERY

CHA

RGING FAILURE OR LIFE

C

HECK BATTERY

CONNE

CTION FAILURE

CLE

AN BATTERY TERMINALS, AND RECONNECT

T

URN ON HEAD LAMP AND STARTER S WITCH

HE

AD LAMP DOES NOT COME ON

OR IT IS EXTREMELY DARK

a)

LACK OF BATTERY CHARGI NG
b) SHORT-CIRCUIT IN STARTER OIL
c) FAULTY STARTER PARTS

a)

DISCONNECT STARTER CI RCUIT
b) DISCONNECT STARTER COIL
c) FAULTY STARTER SWITCH

B

ATTERY IS NORMAL

CHE

CK TERMINAL CONNECTION

CHECK STARTER OR STARTER SWITCH

T

ERMINAL CONNECTION IS NORMAL

F

AILURE

R

EPAIR OR REPLACE

HE

AD LAMP ILLUMINATES

00 – 16 SERVICE INF

ORMATION

F

AULTY MESHING OF PINION AND RING GEAR

C

HECK IF BATTERY VOLTAGE IS PRESENT AT
MAGNETIC SWITCH TERMINAL “S” WHEN
STARTER SWITCH IS TURNED TO “START (ST)”

YES

EX

TREME WEAR OF
PINION AND RING
GEAR

R

EPAIR OR REPLACE
STARTER, REPLACE
RING GEAR

OR

NO

UNDE

R THIS CONDITION, CHECK IF VOLTAGE
OF CONNECTOR 3BW ON MAGNET IC SWITCH
OF RESTART RELAY IS NORMAL

YES NO

DI

SCONNECTION OR
FAULTY CONNECTION
BETWEEN STARTER
SWITCH AND MAGNETIC
SWITCH

C

HECK IF VOLTAGE IS
PRESENT AT WIRING
CONNECTOR 3BW ON
STARTER SWITCH OF
RESTART RELAY

STAR

TER SLIDING
RESISTANCE IS
LARGE

R

EPAIR OR REPLACE

STARTER

FAU

LTY CONNECTION OF

STARTER SWITCH

DI

SCONNECTION OR
FAULTY CONNECTION
BETWEEN STARTER
SWITCH AND BATTERY

R

EPLACE STARTER

SWITCH

R

EPAIR

YES NO

RE

PAIR

SERVICE INF

ORMATION 00 – 17

M

AGNETIC SWITCH DOES NOT OPERATE THOUGH

STARTER SWITCH IS TURNED TO “START (ST)”

C

HECK IF VOLTAGE IS PRESENT AT MAGNETIC
SWITCH TERMINAL “S” WHEN STARTER SWITCH IS
TURNED TO “START (ST)”

YE

S

NO

CHE

CK GROUND CABLE

YE

S

YES

YES NO

R

EPAIR

OR

PIN

ION
SLIDING
PART DOES
NOT MOVE

M

AGNETIC SWITCH
OR COIL IS
DISCONNECTED OR
BURNED OUT

R

EPAIR OR REPLACE STARTER

CHE

CK IF INDICATOR LAMP ON

METER COMES ON NORMALLY

YES NO

DI

SCONNECTION OR
FAULTY CONNECTION
BETWEEN BATTERY
AND STARTER SWITCH

CHE

CK CONTINUITY
STARTER SWITCH AND
MAGNETIC SWITCH
TERMINAL “S”

C

HECK STARTER

RELAY

F

AULTY CONNECTION

OR STARTER SWITCH

R

EPAIR

CHE

CK CLUTCH
START

R

EPLACE STARTER

SWITCH

00 – 18 SERVICE INF

ORMATION

PIN

ION MESHES WITH RING GEAR BUT

ENGINE DOES NOT RUN

CHE

CK GROUND CABLE

YES

NO

R

EPAIR OR REPLACE

GROUND CABLE

F

AULTY CONNECTION
OF BRUSH AND
COMMUTATOR

B

URNED-OUT
MAGNETIC
STARTER SWITCH

R

EPAIR OR REPLACE STARTER

DI

SCONNECTION
OR DAMAGE OF
FIELD COIL

DI

SCONNECTION
OR DAMAGED OF
ARMATURE COIL

SL

IP OF
PINION
CLUTCH

SERVICE INF

ORMATION 00 – 19

M

AGNETIC SWITCH CONTACTS ARE
FUSED AND NOT MOVED, OR A
RETURN SPRING IS BROKEN OR
DETERIORATED

NO

STAR

TER DOES NOT STOP THOUGH STARTER

SWITCH IS RETURNED TO “ON” FROM “START”

R

EPLACE STARTER SWITCH

D

ISCONNECTED STARTER SWITCH WIRING CONNECTOR, AND CHECK STARTER SWITCH OPERATION.

KEY
POSITION

BATTERY

B1

IGNITION

IG1

BATTERYB2ACCESSORIES

ACC

IGNITION

IG2

STARTER

ST
LOCK
OFF
AC

C
ON
STAR

T

TH

ERE MUST BE NO CONTINUITY EXCEPT ABOVE LINES.

YES

R

EPLACE MAGNETIC SWITCH

00 – 20 SERVICE INF

ORMATION

13.

TURBOCHARGER

1) ENGINE HAS LESS THAN NORMAL POWER

Checkpoi

nt Trouble Cause Countermeasure

Air

cleaner

R

estricted

Clean or

replace

Intak

e pipe and hose

R

estricted

Clean or

replace

Com

pressor/Intake manifold

Loos

e (Leaking)

Repair

Ex

haust manifold/turbine inlet

Loos

e (Leaking)

Repair

Ex

haust piping and silencers

R

estricted

Clean or

replace

Air

breather

R

estricted

Clean or

replace

Boos

t compensator

(Injection pump)

Def

ective

Repair

or replace

Continued on the nex

t page

OKOK

OK

OK

OK

OK

OK

NG

NG

NG

NG

NG

NG

NG