Excessive Fuel Consumption; Excessive Oil Consumption - Isuzu NHR 4J Series Workshop Manual

Checkpoint
Fuel system
Air cleaner
Idling speed
Injection nozzle
Fuel injection timing
Injection pump
Valve clearance
Compression pressure
Valve spring
Checkpoint
Engine oil
Oil seal and gasket
Air breather
Intake and exhaust
valve

4. EXCESSIVE FUEL CONSUMPTION

Possible cause
Fuel leakage
Clogged air cleaner element
Poorly adjusted idling speed
Injection nozzle injection starting pressure
too low
Improper spray condition
Fuel injection timing improperly
Defective Delivery valve resulting is fuel
drippage after fuel injection
Valve clearance improperly adjusted
Blown out cylinder head gasket. Worn
cylinder liner.
Piston ring sticking
Valve spring weak or broken

5. EXCESSIVE OIL CONSUMPTION

Possible cause
Engine oil unsuitable
Too much engine oil
Oil leakage from the oil seal and/or the
gasket
Clogged air breather
Worn valve stems and valve guides
SERVICE INFORMATION 00 – 9
Correction
Repair or replace the fuel system
related parts
Clean or replace the air cleaner
element
Adjust the idling speed
Adjust or replace the injection nozzle
Adjust the fuel injection timing
Replace the delivery valve
Adjust the valve clearance
Replace the related parts
Replace the valve spring
Correction
Replace the engine oil
Correct the engine oil level
Replace the oil seal and/or the gasket
Clean the air breather
Replace the intake and exhaust
valves and the valve guides