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
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