Isuzu engine 4j series. Instruction - page 1

SERVICE INFORMATION 00 – 3

1. HARD STARTING

1. STARTER INOPERATIVE

Checkpoint

Possible cause

Correction

Loose battery cable terminal poor
connections due to rusting

Clean and/or retighten the battery
cable terminal

Battery discharged or weak

Recharge or replace the battery

Battery

Fan belt loose or broken

Adjust or replace the fan belt

Fusible link

Fusible link shorted

Replace the fusible link

Starter switch

Defective starter switch or starter relay

Replace the starter switch or the
Starter relay

Defective magnetic switch or starter relay

Repair or replace the magnetic switch

Starter motor

Defective starter motor

Repair or replace the starter motor

2. STARTER MOTOR OPERATES BUT ENGINE DOES NOT TURN OVER

Loose battery cable terminal

Clean and/or retighten the battery
cable terminal

Poor connections due to rusting

Recharge or replace the battery

Battery discharged or weak

Recharge or replace the battery

Battery

Fan belt loose or broken

Adjust or replace the fan belt

Defective pinion gear

Replace the pinion gear

Defective magnetic switch

Repair or replace the magnetic switch

Starter

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 INFORMATION

3. ENGINE TURNS OVER BUT DOES NOT START

Checkpoint

Possible cause

Correction

Engine stop
mechanism

Defective fuel cut solenoid valve

Replace the fuel cut solenoid valve

FUEL IS NOT BEING DELIVERED TO THE INJECTION PUMP

Fuel

Fuel tank is empty

Fill the fuel tank

Fuel piping

Clogged or damaged fuel lines. Loose fuel
line connection

Repair or replace the fuel lines
Retighten the fuel line connection

Fuel filter overflow valve does not close

Repair or replace the fuel filter
overflow valve

Fuel filter

Clogged fuel filter element

Replace the fuel filter element or the
filter cartridge

Fuel system

Air in the fuel system

Bleed the air from the fuel system

Fuel feed pump

Defective feed pump

Repair or replace the feed pump

FUEL IS BEING DELIVERED TO THE INJECTION PUMP

Use of the wrong fuel

Use the correct fuel

Water particles in the fuel

Change the fuel

Fuel

Fuel system

Air in the injection pump

Bleed the air from the fuel system

Injection nozzle sticking

Injection nozzle

Injection nozzle injection starting pressure
too low
Improper spray condition

Adjust or replace the injection nozzle

Defective fuel injection nozzle resulting in the
fuel drippage after fuel injection

Replace the delivery valve

Defective injection pump control rack
operation

Repair or replace the injection pump
control rack

Injection pump plunger worn or stuck

Replace the injection pump plunger
assembly

Injection pump drive shaft seizure or other
damage

Replace the injection drive shaft

Injection pump

Injection pump governor spring seizure

Replace the injection pump governor
spring

SERVICE INFORMATION 00 – 5

4. QUICK-ON START SYSTEM

PREPARATION
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

Glow plug indicator
light does not turn on

Defective indicator light bulb

Replace the indicator light bulb

Quick-on start timer

Defective quick-on start timer

Replace the quick-on start timer

Glow plug indicator
light turns on the 0.3
seconds

Defective quick-on start timer

Replace the quick-on start timer

Return the starter 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

Glow 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

Thermoswitch

Defective thermoswitch

Replace the thermoswitch

Glow plug continuity

No glow plug continuity

Replace the glow plugs

GLOW PLUGS ARE NOT RECEIVING POWER

Glow plug indicator
light does not turn on

Broken indicator light fuse

Replace the fuse

Quick-on start timer

Defective quick-on start timer

Replace the quick-on start timer

00 – 6

SERVICE INFORMATION

GLOW PLUGS ARE NOT RECEIVING POWER (Cont’d)

Checkpoint

Possible cause

Correction

Defective 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

Glow 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 system

Idling improperly adjusted

Adjust the idling

Fast idling speed

Defective fast idling speed control device

Repair or replace the fast idling speed
control device

Accelerator control
system

Accelerator control system improperly
adjusted

Adjust the accelerator control system

Fuel system leakage or blockage

Repair or replace the fuel system

Air in the fuel system

Bleed the air from the fuel system

Fuel system

Water particles in the fuel system

Change the fuel

Fuel filter

Clogged fuel filter element

Replace the fuel filter element or the
fuel filter cartridge

Fuel feed pump

Defective fuel feed pump

Repair or replace the fuel feed pump

Injection nozzle sticking

Replace the injection nozzle

Injection nozzle

Injection nozzle injection starting pressure
too low
Improper spray condition

Adjust or replace the injection nozzle

Injection pump

Defective delivery valve resulting in fuel
drippage after fuel injection

Replace the delivery valve