Isuzu N-Series. Manual - part 547

 

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Isuzu N-Series. Manual - part 547

 

 

SERVICE INFORMATION 00-3

3. Engine Turns Over But Does Not Start

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.

Checkpoint

Possible cause

Correction

Engine stop mecha-
nism

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

Fuel filter overflow valve does not close

Repair or replace the fuel filter overflow 
valve

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

Fuel

Use of the wrong fuel

Use the correct fuel

Water particles in the fuel

Change the fuel

Fuel system

Air in the injection pump

Bleed the air from the fuel system

Injection nozzle

Injection nozzle sticking

Injection nozzle injection starting pressure
too low
Improper spray condition

Adjust or replace the injection nozzle

Injection pump

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

Replace the delivery valve

Defective injection pump control rack oper-
ation

Repair or replace the injection pump con-
trol 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 governor spring seizure

Replace the injection pump governor 
spring

00-4 SERVICE INFORMATION

* When being normal temperature, the indicator lamp of 4JH1TC is not turn on.

Checkpoint

Possible cause

Correction

Glow Plugs are Receiving Power

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

Glow plug indicator 
light turns on for 3.5 
seconds

Return the starter switch to the “ON” posi-
tion 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

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

Replace the quick-on start timer

Thermo switch

Defective thermo switch

Replace the thermo switch

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

Glow plug indicator 
light turns on for 3.5 
seconds

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

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 har-
ness

SERVICE INFORMATION 00-5

Unstable Idling

*The adjustment of the position which is related to the injection pump is unnecessary for 4JH1TC by the adoption of
the electronic control injection pump.

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

Fuel system leakage or blockage

Repair or replace the fuel system

Air in the fuel system

Bleed the air from the 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

Injection nozzle sticking

Replace the 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

Injection timing improperly adjusted

Adjust the injection timing

Insufficient injection volume

Adjust the injection volume

Defective idle spring

Replace the idle spring

Defective governor lever operation

Repair or replace the governor lever

Regulator valve improperly adjustment

Adjust or replace the regulator valve

Broken plunger spring

Replace the plunger spring

Worn plunger

Replace the plunger assembly

Worn cam disc

Replace the cam disc

Valve clearance

Valve clearance improperly adjusted

Adjust the valve clearance

Compression pressure

Blown out cylinder head gasket. Worn cyl-
inder liner.
Piston ring sticking

Replace the related parts

00-6 SERVICE INFORMATION

Insufficient Power

Checkpoint

Possible cause

Correction

Air cleaner

Clogged air cleaner element

Clean or replace the air cleaner element

Fuel

Water particle in the fuel

Replace 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

Injection nozzle sticking

Replace the injection nozzle 

Injection nozzle injection starting pressure
too low
Improper spray condition

Adjust or replace the injection nozzle

Fuel injection pipes

Fuel injection pipes damaged or 
obstructed

Replace the fuel injection pipes

Injection pump

Defective regulating valve

Repair or replace the regulating valve

Defective delivery valve

Replace the delivery valve

Defective timer

Repair or replace the timer

Worn cam disc

Replace the cam disc

Improper control lever operation

Adjust or replace the control lever

Defective injection timing

Adjust the injection timing
Repair or replace the injection pump timer

Weak governor spring

Replace the governor spring

Worn plunger

Replace the plunger assembly

Compression pressure

Blown out cylinder head gasket. Worn cyl-
inder liner.
Piston ring sticking

Replace the related parts

Valve clearance

Valve clearance improperly adjusted

Adjust the valve clearance

Valve spring

Valve spring weak or broken

Replace the valve spring

Exhaust system

Exhaust pipe clogged

Clean the exhaust pipe

Full load adjusting 
screw seal

Open and improperly set adjusting screw 
seal

Adjust and reseal the adjusting screw

 

 

 

 

 

 

 

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