Isuzu 4LC1 - Oil Pressure and Consumption Issues; Engine Knocking Diagnosis

TROUBLESHOOTING 109
Oil pressure too low Oil consumption too much Oil consumption too much
Check oil level Check for oil leakage Check for oil leakage
Leaking (Retighten,
replace packing seal)
Poor quality
(Change to specified oil)
Check oil quality
Leaking (Retighten,
replace packing seal)
Defective
(Repair or replace)
Check nozzle
Check injection timing Check bleeder for clogging
Abnormal (Adjust) Clogged (Clean)
Low
Defective injection pump
(Bring it to a specialty
shop for repair)
Excessive
blow-by gas
Gas leak from
valve and gasket
(Repair or
replace)
Check compression ratio Check up and down movement of oil
1. Oil pump malfunction
2. Loosened or cracked pipe
3. Wear of sliding part
4. Oil pump clogged
5. Defective valve stem seal
(Overhaul)
(*) Worn bore,and worn or broken
ring (Measure compression
pressure, and check entrance of
dust)
Low (Replenish)
Check cooling water temperature
Check oil in crankcase
Water or fuel mixed. Check fuel
system and cooling system
High
(See “Overheat”)
Improper
viscosity
Check relief valve
Defective
(Repair or replace)
1. Oil pump malfunction
2. Loosened or cracked pipe
3. Wear of sliding part
4. Oil pump clogged
(Overhaul)
OK
OK
OK
OK
OK OK
OKOK
OK OK
OK
Engine knocking
Mechanical system
Check up movement of oil Check injection timing
Oil stained (Overhaul) Abnormal (Adjust)
Check compression pressure Check nozzle
Low
Defective
(Repair or replace)
Note: Fuel used is of poor quality.
Excessive
blow-by gas
(Overhaul)
Gas leak from
valve and gasket
(Repair or
replace)
Fuel system
OK OK
OK OK
To fuel system