Unstable Idling - Isuzu NHR 4J Series Workshop Manual

00 – 6 SERVICE INFORMATION
GLOW PLUGS ARE NOT RECEIVING POWER (Cont'd)
Checkpoint
Glow plug indicator
light turns on for 3.5
seconds
Checkpoint
Idling system
Fast idling speed
Accelerator control
system
Fuel system
Fuel filter
Fuel feed pump
Injection nozzle
Injection pump
Possible cause
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
Defective quick-on start timer
Defective glow plug relay 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

2. UNSTABLE IDLING

Possible cause
Idling improperly adjusted
Defective fast idling speed control device
Accelerator control system improperly
adjusted
Fuel system leakage or blockage
Air in the fuel system
Water particles in the fuel system
Clogged fuel filter element
Defective fuel feed pump
Injection nozzle sticking
Injection nozzle injection starting pressure
too low
Improper spray condition
Defective delivery valve resulting in fuel
drippage after fuel injection
Correction
Replace the glow plug relay
Replace the quick-on start timer
Repair or replace the wiring harness
Replace the fusible link or the wiring
harness
Correction
Adjust the idling
Repair or replace the fast idling speed
control device
Adjust the accelerator control system
Repair or replace the fuel system
Bleed the air from the fuel system
Change the fuel
Replace the fuel filter element or the
fuel filter cartridge
Repair or replace the fuel feed pump
Replace the injection nozzle
Adjust or replace the injection nozzle
Replace the delivery valve