Isuzu KB P190. Manual - part 342

6A-8  ENGINE MECHANICAL (4JK1/4JJ1) 

Trouble Shooting 

Engine does not turn over 

Condition Possible 

Cause Correction 

Dead or weak battery 

Charge battery 

Replace battery 

Incomplete circuit 

Connect 

Repair 

Starter motor brushes stuck, worn, 
or broken 

Replace brushes 

Starter motor does not rotate 

Starter motor internal damage 

Repair motor 

Ring gear abrasion 

Replace ring gear 

Starter motor not meshed with 
flywheel 

Magnetic switch (starter motor) not 
properly adjusted 

Adjust 

Dead or weak battery 

Charge battery 

Replace battery 

Insufficient contact pressure 
between starter motor brushes and 
commutator 

Adjust pressure 

Armature (starter motor) stuck 

Repair armature 

Starter motor pinion meshed with 
ring gear but does not rotate 

Engine internal damage (Seizure) 

Repair engine 

 
Engine turns over but does not start 

Condition Possible 

Cause Correction 

Air in fuel system 

Bleed air from fuel system 

Air entering fuel pipe 

Replace pipe and bleed air from 
fuel system 

Empty fuel tank 

Replenish fuel 

Clogged strainer (fuel suction) 

Clean or replace strainer 

Clogged fuel pipe 

Clean or replace pipe 

Feed pump malfunction 

Replace pump 

Use of wrong fuel for prevailing 
temperatures 

Drain existing fuel and replace with 
appropriate fuel 

Fuel is not delivered to fuel supply 
pump 

Clogged fuel filter 

Replace filter 

Loose injection pipe connections 

Tighten connections 

Loose or broken electrical 
connectors 

Tighten and/or replace connectors 

Bad rotational sensor 

Replace sensor 

Fuel is delivered to fuel supply 
pump 

Engine control system malfunction 

System diagnosis 

Air in fuel system 

Bleed air from fuel system 

Feed pump malfunction 

Repair pump 

Loose or broken electrical 
connectors 

Tighten and/or replace connectors 

Clogged fuel filter 

Replace filter 

Insufficient or unstable fuel delivery 
volume 

Engine control system malfunction 

System diagnosis 

ENGINE MECHANICAL (4JK1/4JJ1)  6A-9 

 
Excessive black exhaust smoke 

Condition Possible 

Cause Correction 

Bad injection timing 

Engine control system malfunction 

System diagnosis 

Carbon deposit at nozzle tip 

Clean fuel injector assembly 

Sticking nozzle 

Replace fuel injector assembly 

Bad fuel injector condition 

Engine control system malfunction 

System diagnosis 

Excessive valve clearance 

Adjust clearance 

Sticking valve stem (valve open) 

Repair or replace valve 

Damaged valve spring 

Replace spring 

Valve seat abrasion 

Repair valve seat 

Compression leakage due to 
damaged piston ring 

Replace piston ring 

Damaged gasket 

Replace gasket 

Insufficient compression pressure 

Piston scoring 

Replace piston 

Water in fuel 

Drain existing fuel and replace with 
new fuel 

Fuel condition 

Poor fuel quality 

Drain existing fuel and replace with 
new fuel 

Clogged intake pipes 

Clean or replace pipes 

Poor engine aspiration 

Clogged air cleaner element 

Clean or replace element 

Defective sensor 

Replace sensor 

Malfunction detected by engine 
control system 

Engine control system malfunction 

System diagnosis 

Intake throttle valve sticking 

Repair or replace valve 

EGR valve sticking 

Repair or replace valve 

EGR valve and/or intake throttle 
valve malfunction 

Engine control system malfunction 

System diagnosis 

Damaged turbocharger blade 

Replace turbocharger 

Rough turbocharger shaft rotation 

Replace turbocharger 

Oil leakage from oil seal 

Replace turbocharger 

Turbocharger malfunction 

Broken actuator 

Replace turbocharger 

 

6A-10  ENGINE MECHANICAL (4JK1/4JJ1) 

Excessive white exhaust smoke 

Condition Possible 

Cause Correction 

Bad injection timing 

Engine control system malfunction 

System diagnosis 

Defective sensor 

Replace sensor 

Control unit malfunction 

Replace unit 

Malfunction detected by engine 
control system 

Engine control system malfunction 

System diagnosis 

Excessive valve clearance 

Adjust clearance 

Sticking valve stem (valve open) 

Repair or replace valve 

Damaged valve spring 

Replace spring 

Valve seat abrasion 

Repair valve seat 

Compression leakage due to 
damaged piston ring 

Replace piston ring 

Damaged gasket 

Replace gasket 

Insufficient compression pressure 

Piston scoring 

Replace piston 

Fuel condition 

Water in fuel 

Drain existing fuel and replace with 
new fuel 

Worn or damaged piston ring(s) 

Replace ring(s)  

Defective valve stem oil seal 

Replace oil seal 

Defective turbocharger oil seal 

Replace turbocharger 

Excessive oil consumption 

Clogged turbocharger oil return 
pipe 

Repair pipe 

 
Engine knocking 

Condition Possible 

Cause Correction 

Bad timing 

Engine control system malfunction 

System diagnosis 

Defective sensor 

Replace sensor 

Control unit malfunction 

Replace unit 

Malfunction detected by engine 
control system 

Engine control system malfunction 

System diagnosis 

Fuel condition 

Poor quality fuel 

Drain existing fuel and replace with 
new fuel 

Clogged air cleaner element 

Clean or replace element 

Clogged intake pipes 

Clean or replace pipes 

Poor engine aspiration 

Engine control system malfunction 

System diagnosis 

Foreign material in cylinders 

Engine overhaul 

Engine break-down 

Scored pistons and/or bearings 

Replace pistons and/or bearings 

 

ENGINE MECHANICAL (4JK1/4JJ1)  6A-11 

Abnormal engine rotation 

Condition Possible 

Cause Correction 

Defective control unit 

Replace unit 

Engine speed cannot be increased 

Engine control system malfunction 

System diagnosis 

Defective control unit 

Replace unit 

Engine control system malfunction 

System diagnosis 

Clogged fuel filter element 

Replace element 

Defective fuel injector(s) 

Replace fuel injector assembly 

Water in fuel 

Drain existing fuel and replace with 
new fuel 

Engine speed unstable 

Air in fuel system 

Bleed air from fuel system 

Damaged turbocharger fan 

Replace turbocharger 

Rough turbocharger shaft rotation 

Replace turbocharger 

Turbocharger malfunction 

Broken actuator 

Replace turbocharger 

 
Abnormal battery charging 

Condition Possible 

Cause Correction 

Open or shorted wiring and/or 
connectors 

Repair or replace wiring and/or 
connectors 

Defective generator 

Repair or replace generator 

No charging 

Defective battery 

Replace battery 

Open or shorted wiring and/or 
connectors 

Repair or replace wiring and/or 
connectors 

Defective generator 

Repair or replace generator 

Loose generator drive belt 

Adjust belt tension or replace belt 

Insufficient charging 

Defective battery 

Replace battery 

Shorted wiring 

Repair or replace wiring 

Defective generator 

Repair or replace generator 

Excessive charging 

Defective battery 

Replace battery