Isuzu N-Series. Manual - part 476

Engine Mechanical (4HK1-TC)   6A-9

Trouble Shooting

Engine does not turn over

Engine turns over but does not start

Condition

Possible Cause

Correction

Starter motor does not rotate

Dead or weak battery

Charge or
Replace battery

Incomplete circuit

Connect
Repair

Starter relay

Replace starter relay

Starter motor brushes stuck, worn,
or broken

Replace brushes

Starter motor internal damage

Repair motor

Starter motor not meshed with
flywheel

Ring gear abrasion

Replace ring gear

Pinion gear abrasion

Replace pinion gear

Magnetic switch (starter motor) not
properly adjusted

Adjust

Starter motor pinion meshed with
ring gear but does not rotate

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

Engine internal damage (Seizure)

Repair engine

Condition

Possible Cause

Correction

Fuel is not delivered to fuel supply
pump

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

Use of wrong fuel for prevailing
temperatures

Drain existing fuel and replace with
appropriate fuel

Clogged fuel filter

Replace filter

Fuel is delivered to fuel supply
pump

Loose injection pipe connections

Tighten connections

Loose or broken electrical
connectors

Tighten and/or replace connectors

Bad rotational sensor

Replace sensor

Engine control system malfunction

System diagnosis

Insufficient or unstable fuel delivery
volume

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

Engine control system malfunction

System diagnosis

6A-10   Engine Mechanical (4HK1-TC)

Excessive black exhaust smoke

Excessive white exhaust smoke

Condition

Possible Cause

Correction

Bad injection timing

Engine control system malfunction

System diagnosis

Bad injection nozzle condition

Carbon deposit at nozzle tip

Clean nozzle tip

Sticking nozzle

Replace fuel injector assembly

Engine control system malfunction

System diagnosis

Insufficient compression pressure

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

Piston scoring

Replace piston

Fuel condition

Water in fuel

Drain existing fuel and replace with
new fuel

Poor fuel quality

Drain existing fuel and replace with
new fuel

Poor engine aspiration

Clogged intake pipes

Clean or replace pipes

Clogged air cleaner element

Clean or replace element

Malfunction detected by engine
control system

Defective sensor

Replace sensor

Engine control system malfunction

System diagnosis

EGR valve and/or intake throttle
valve malfunction

Intake throttle valve sticking

Repair or replace valve

EGR valve sticking

Repair or replace valve

Exhaust brake valve sticking

Repair or replace valve

Engine control system malfunction

System diagnosis

Turbocharger malfunction

Damaged turbocharger fan

Replace turbocharger

Rough turbocharger shaft rotation

Replace turbocharger

Oil leakage from oil seal

Replace turbocharger

Defective booster sensor

Replace sensor

Condition

Possible Cause

Correction

Bad injection timing

Engine control system malfunction

System diagnosis

Malfunction detected by engine
control system

Engine control system malfunction

System diagnosis

Control unit malfunction

Replace unit

Defective sensor

Replace sensor

Insufficient compression pressure

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

Piston scoring

Replace piston

Engine Mechanical (4HK1-TC)   6A-11

Engine knocking

Abnormal engine rotation

Abnormal battery charging

Fuel condition

Water in fuel

Drain existing fuel and replace with
new fuel

Excessive oil consumption

Worn or damaged piston ring(s)

Replace ring(s) 

Defective valve stem oil seal

Replace oil seal

Defective turbocharger oil seal

Replace turbocharger

Clogged turbocharger oil return
pipe

Repair pipe

Condition

Possible Cause

Correction

Bad timing

Engine control system malfunction

System diagnosis

Malfunction detected by engine
control system

Defective sensor

Replace sensor

Control unit malfunction

Replace unit

Engine control system malfunction

System diagnosis

Fuel condition

Poor quality fuel

Drain existing fuel and replace with
new fuel

Poor engine aspiration

Clogged intake pipes

Clean or replace pipes

Engine control system malfunction

System diagnosis

Engine break-down

Foreign material in cylinders

Engine overhaul

Scored pistons and/or bearings

Replace pistons and/or bearings

Condition

Possible Cause

Correction

Engine speed cannot be increased

Engine control system malfunction

System diagnosis

Defective control unit

Replace unit

Engine speed unstable

Defective control unit

Replace unit

Engine control system malfunction

System diagnosis

Clogged fuel filter element

Replace element

Defective fuel injector nozzle(s)

Replace fuel injector assembly

Water in fuel

Drain existing fuel and replace with
new fuel

Air in fuel system

Bleed air from fuel system

Exhaust brake valve sticking

Repair or replace valve

Turbocharger malfunction

Damaged turbocharger fan

Replace turbocharger

Rough turbocharger shaft rotation

Replace turbocharger

Defective booster sensor

Replace sensor

Condition

Possible Cause

Correction

No 

charging

Open or shorted wiring and/or
connectors

Repair or replace wiring and/or
connectors

Defective generator

Repair or replace generator

Defective battery

Replace battery

Condition

Possible Cause

Correction

6A-12   Engine Mechanical (4HK1-TC)

Turbocharger Troubleshooting

Insufficient 

charging

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

Defective battery

Replace battery

Excessive charging

Shorted wiring

Repair or replace wiring

Defective generator

Repair or replace generator

Defective battery

Replace battery

Condition

Possible Cause

Correction

Engine has less than normal power

Air leakage from intake pipe rubber
hose

Repair

Air leakage from inlet cover

Repair

Clogged intercooler cooling section

Clean

Clogged air cleaner element

Clean or replace

Exhaust brake valve stuck

Repair or replace

Turbine and housing contact
(Interference)

Replace

Excessive carbon deposit near
turbine exhaust port that interferes
with turbine

Clean or repair

Rough turbine shaft rotation

Repair or replace

Damaged turbine fan

Repair or replace

Blue exhaust smoke

Oil leakage from turbocharger oil
seal

Repair or replace

Clogged turbocharger oil return
pipe

Repair

Clogged center housing oil
passages

Repair or replace

Engine oil deterioration

Change engine oil

Noisy turbocharger operation

Gas leakage from intake or exhaust
system

Repair

Turbine and housing contact
(Interference)

Repair or replace

Damaged turbine fan

Replace

Turbine shaft bearing abrasion or
scoring

Repair or replace

Excessive rotating part wear

Engine oil deterioration

Change engine oil

Clogged turbocharger oil feed pipe

Repair

Low engine oil pressure

Repair

Condition

Possible Cause

Correction