Oil circuit fault diagnosis

Fault	Cause	Remedy
Warning lamp does not illuminate for oil pressure after switching on the ignition.	Oil pressure switch defective. Power supply to switch interrupted; check electrical wiring and connections.

Contacts corroded.

Warning lamp defective.

• Switch on ignition, disconnect wire from oil pressure switch and hold it to ground. If the warning lamp illuminates, replace the switch.
• Check electrical wiring and connections.
• Replace warning lamp.

Warning lamp does not go out after engine starts. Oil very hot. Harmless if the warning lamp goes out when accelerating. Warning lamp does not go out when accelerating, or illuminates while driving. Oil pressure too low.

Electrical wire to oil pressure switch has short circuit to ground.

Oil pressure switch defective.

• Check oil level, top up if necessary; check oil pressure as specified.
• Disconnect cable from switch and place it insulated (do not ground), switch on ignition. If the warning lamp illuminates, check wiring.
• Replace switch.

Oil pressure too low in the

entire speed range.

Insufficient oil in engine.

Intake screen in the suction bell dirty, suction pipe broken.

Oil pump worn.

Bearing damage.

• Top up the engine oil.
• Remove oil pan, clean intake screen, replace suction pipe if necessary.
• Remove and check oil pump, replace if necessary (workshop job).
• Remove engine.

Oil pressure too low in the lower speed range. Oil pressure regulator valve jammed in open position due to dirt.

• Remove and check oil pressure regulator valve.

Oil pressure too high at engine speeds above 2,000 rpm. Oil pressure regulator valve does not open due to contamination.

• Remove and check oil pressure regulator valve.