Isuzu KB P190. Manual - part 502

6-8 ENGINE DIAGNOSIS (C24SE) 

Condition Possible 

cause Correction 

Engine overheating 

Level of Engine Coolant too low 

Replenish 

 

Thermo switch or fan motor 
defective 

Replace 

 Thermostat 

defective 

Replace 

 

Engine Coolant pump defective 

Correct or replace 

 

Radiator clogged 

Clean or replace 

 

Radiator filter cap defective 

Replace 

 

Level of oil in engine crankcase 
too low or wrong oil in engine 

Change or replenish 

 

Resistance in exhaust system 
increased 

Clean exhaust system or replace 
defective parts 

 

Throttle Position Sensor 
adjustment incorrect 

Adjust Wide Open Throttle switch 
setting 

 

Throttle Position Sensor circuit 
open or shorted 

Correct or replace 

 

Cylinder head gasket damaged 

Replace 

 

Cooling Fan clutch defective 

Replace 

 

Fan belt slipping 

Adjust tension of V-belt or replace 
V-belt 

Engine overcooling 

Thermostat defective 

Replace (Use a thermostat set to 
open at 92

°C (197.6°F)) 

Engine lacks compression 

- 

Refer to Hard Start 

Others 

Tire inflation pressure abnormal 

Adjust to recommend pressures 

 Brake 

drag 

Adjust 

 

Clutch slipping 

Adjust or replace 

 

Level of oil in engine crankcase 
too high 

Correct level of engine oil 

 

Engine Noisy  

Abnormal engine noise often consists of various 

noises originating in rotating parts, sliding parts and 

other moving parts of the engine. It is, therefore, 

advisable to locate the source of noise systematically.

 

 

 

Condition Possible 

cause Correction 

Noise from crank journals or from 
crank bearings 
(Faulty crank journals and crank 
bearings usually make dull noise 
that becomes more evident when 
accelerating) 

Oil clearance increased due to 
worn crank journals or crank 
bearings  

Replace crank bearings and 
crankshaft or regrind crankshaft 
and install the over size bearing 

 

Crankshaft out of round 

Replace crank bearings and 
crankshaft or regrind crankshaft 
and install the over size bearing 

 

Crank bearing seized 

Replace crank bearings and 
crankshaft or regrind crankshaft 
and install the over size bearing 

 

ENGINE DIAGNOSIS (C24SE) 6-9 

Abnormal Noise Due to Hydraulic Lash Adjuster 

Should abnormal noise due to the hydraulic lash 
adjuster trouble be heard immediately after the engine 
is started, inspect as follows: 

 

 

 

Condition Possible 

cause Correction 

Abnormal noise is heard 

Air contaminated 

Bleed 

HLA is spongy 

Check ball valve broken 

Repair 

 

Safety valve in cylinder head 
broken 

Replace 

Valve clearance is not zero 

HLA inside stick 

Replace HLA assembly 

 

Troubleshooting Procedure 

Short out each spark plug in sequence using insulated 
spark plug wire removers. Locate cylinder with 
defective bearing by listening for abnormal noise that 
stops when spark plug is shorted out. 

 

 

 

Condition Possible 

cause Correction 

Noise from connecting rods or 
from connecting rod bearings  
(Faulty connecting rods or 
connecting rod bearings usually 
make an abnormal noise slightly 
higher than the crank bearing 
noise, which becomes more 
evident when engine is 
accelerated) 

Bearing or crankshaft pin worn 

Replace connecting rod bearings 
and crankshaft or regrind 
crankshaft and install the under 
size bearing 

 

Crankpin out of round 

Replace connecting rod bearings 
and crankshaft or regrind 
crankshaft and install the under 
size bearing 

 

Connecting rod bent 

Correct or replace 

 

Connecting rod bearing seized 

Replace connecting rod bearings 
and crankshaft or regrind 
crankshaft and install the under 
size bearing 

 

Troubleshooting Procedure 

Abnormal noise stops when the spark plug on the 

cylinder with defective parts is shorted out. 

 

 

 

Condition Possible 

cause Correction 

Piston and cylinder  
(Faulty piston or cylinder usually 
makes a combined mechanical 
thumping noise which increases 
when engine is suddenly 
accelerated but diminishes 
gradually as the engine warms up) 

Piston clearance increased due to 
cylinder wear 

Replace piston and cylinder body 

 

Piston seized 

Replace piston and cylinder body 

 

Piston ring broken 

Replace piston and cylinder body 

 

Piston defective 

Replace pistons and others 

 

6-10 ENGINE DIAGNOSIS (C24SE) 

Troubleshooting Procedure 

 

 

 

Condition Possible 

cause Correction 

Piston pin noise  
(Piston makes noise each time it 
goes up and down) 

Piston pin or piston pin hole worn 

Replace piston, piston pin and 
connecting rod assy 

 

Troubleshooting Procedure 

The slapping sound stops when spark plug on bad 

cylinder is shorted out. 

 

 

 

Condition Possible 

cause Correction 

Timing belt noise 

Timing belt tension is incorrect 

Replace pusher or adjust the 
tension pulley or replace timing 
belt 

 

Tensioner bearing defective 

Replace 

 

Timing belt defective 

Replace 

 

Timing wheels defective 

Replace 

 

Timing belt comes in contact with 
timing cover 

Replace timing belt and timing 
cover 

Valve noise 

Valve and valve guide seized 

Replace valve and valve guide 

 

Valve spring broken 

Replace 

 

Valve seat off-positioned 

Correct 

Crankshaft noise 

Crankshaft end play excessive  
(noise occurs when clutch is 
engaged) 

Replace thrust bearing 

Engine knocking 

Preignition due to use of spark 
plugs of inadequate heat range 

Install Spark Plugs of adequate 
heat range 

 

Fuel too low in octane rating 

Replace fuel 

 

Wide Open Throttle enrichment 
system failure 

Refer to Section 6E 

 

Selection of transmission gear 
incorrect 

Caution operator or incorrect gear 
selection 

 

Engine overheating 

Refer to "Engine Lacks Power" 

Others 

Water pump defective 

Replace 

 

V-belt slipping 

Adjust tension of V-belt or replace 
V-belt 

 

ENGINE DIAGNOSIS (C24SE) 6-11 

Abnormal Combustion 

Condition Possible 

cause Correction 

Trouble in fuel injection system 

Fuel pressure control valve 
defective 

Replace 

 

Fuel filter clogged 

Replace 

 

Fuel pump clogged 

Clean or replace 

 

Fuel tank or fuel pipe clogged 

Clean or replace 

 

Fuel injector clogged 

Clean or replace 

 

Fuel pump relay defective 

Replace 

 

Power supply cable for fuel pump 
loosely connected or defective 

Reconnect, correct or replace 

 

Manifold Absolute Pressure 
Sensor circuit open or shorted 

Correct or replace 

 

Manifold Absolute Pressure 
Sensor defective 

Replace 

 

Engine Coolant Temperature 
(ECT) Sensor circuit open or 
shorted 

Correct or replace 

 

ECT Sensor defective 

Replace 

 

Throttle Position Sensor 
adjustment incorrect 

Reconnect 

 

Throttle Position Sensor defective 

Replace 

 

Throttle Position Sensor 
connector loosely connected 

Reconnect 

 

Vehicle Speed Sensor cable 
loosely connected or defective 

Correct or replace 

 

Vehicle Speed Sensor loosely 
fixed 

Fix tightly 

 

Vehicle Speed Sensor in wrong 
contact or defective 

Replace 

 

Engine Control Module cable 
loosely connected or defective 

Correct or replace 

Trouble in emission control 
system 

Heated Oxygen Sensor circuit 
open (If applicable) 

Correct or replace 

 

Heated Oxygen Sensor defective 
(If applicable) 

Replace 

 

Signal vacuum hose loosely fitted 
or defective 

Correct or replace 

 

ECT Sensor circuit open or 
shorted 

Correct or replace 

 

ECT Sensor defective 

Replace 

 

Evaporative Emission Control 
system (If applicable) 

Refer to Section 6E 

Trouble in ignition system 

- 

Refer to "Engine Lacks Power" 

Trouble in cylinder head parts 

Carbon deposits in combustion 
chamber 

Remove carbon 

 

Carbon deposit on valve, valve 
seat and valve guide 

Remove carbon