Isuzu 4LC1 - Unstable Engine Rotation Diagnosis

106 TROUBLESHOOTING
Unstable engine rotation
Unstable engine
idling
Idling speed
too high
Defective control
lever adjustment
Defective
(Repair or
replace)
Defective injection
pump (Bring it to a
specialty shop for
repair)
Defective idling
adjustment
Unstable rotation at
medium speed
(Hunting)
Governor spring
deteriorated
Check fuel pipe for
crash
Crash
(Replace)
Defective
valve return
(Adjust)
Check high pressure
pipe for cracking,
clogging or bending
Cracked,
clogged or
bent
(Replace)
Check nozzle
Defective
(Repair or
replace)
Check cylinder for
uneven compression
pressure
Uneven
compression
pressure
(Adjust)
Defective injection
pump (Bring it to a
specialty shop for
repair)
Unstable rotation at
high speed
Check fuel for air
mixing
Air mixed
(Bleed
air)mixing
Check fuel filter for
clogging
Clogged
(Clean or
replace)
Check uneven fuel
injection
Uneven
(Adjust)
Check valve clearance
adjustment
Poor
adjustment
(Adjust)
Defective injection
pump (Bring it to a
specialty shop for
repair)
Engine does not
change from high to
low rotation
Check accelerator
pedal
Pedal
sticking or
hitching
(Clean or
replace)
Defective injection
pump (Bring it to a
specialty shop for
repair)
OK OKOK
OK
OK
OK
OK
OK
OK
OK
OK