Cummins/Onan 4-cyl. Engine

How to read your Cummins/Onan engine serial & model number →

• The O/U VOLTAGE lamp lights. Engine shuts down.
  Fix: Contact an authorized service center for service.
• SWITCH OFF lamp flashes.
  Fix: Indicates Run/Stop/Remote switch is in the Stop position which will prevent automatic starting if an automatic transfer switch is used. Move the Run/Stop/Remote switch to the Remote position for automatic starting.
• PRE HET/LOP lamp lights. Engine continues to operate.
  Cause: Indicates engine has begun to overheat and engine temperature has risen to approximately 205°F (97°C) or coolant level is low.
  Fix: A. Reduce load if possible by turning off non-critical loads. b. Check air inlets and outlets and remove any obstructions to airflow.
• OVERCRANK lamp lights and engine stops cranking.
  Cause: Indicates possible fuel system problem.
  Fix: A. Check for empty fuel tank (LPG Vapor), fuel leaks, or plugged fuel lines and correct as required. b. Check for dirty fuel filter and replace if necessary (see Maintenance section). c. Check for dirty or plugged air filter and replace if necessary (see Maintenance section). d. Reset the control and restart after correcting the problem. Contact an authorized service center for service if none of the above.
• No AC output voltage.
  Fix: Field breaker is tripped. Reset breaker. Contact an authorized service center if voltage buildup causes breaker to trip.
• LO OIL PRES lamp lights. Engine shuts down.
  Cause: Indicates engine oil pressure has dropped to 30 psi (207 kPa).
  Fix: NOTE: See also step 5.
• HI ENG TEMP lamp lights. Engine shuts down.
  Cause: Indicates engine has overheated (engine temperature has risen above 215°F/102°C) or coolant level is low.
  Fix: A. Check coolant level and replenish if low. Look for possible coolant leakage points and repair if necessary. b. Check for obstructions to cooling airflow and correct as necessary. c. Check for a slipping fan belt and tighten if loose. d. Reset control and restart after locating and correcting problem. Contact an authorized service center if none of the above.
• Green RUN lamp does not light following engine startup.
  Fix: Indicates possible Start/Disconnect relay failure. Test light with LAMP TEST position on switch. Contact an authorized service center for assistance.
• Fault lamp lights but no fault exists. Engine gauges show oil pressure, engine temperature, and frequency (speed) are within normal limits.
  Fix: The monitor board or a sensor may be at fault. Contact an authorized service center for service.
• Engine will not crank.
  Fix: Indicates possible fault with control or starting system. Check for the following conditions: a. Fault lamp on. Correct fault and reset control. b. Poor battery cable connections. Clean the battery cable terminals and tighten all connections. c. Discharged or defective battery. Recharge or replace the battery. d. Emergency stop button pushed in. To reset, pull switch out and move Run/Stop/Remote switch to Stop position. Then push test switch to Reset/Lamp position. e. Contact an authorized service center if none of the above.
• Engine runs and then shuts down, OVERSPEED lamp lights.
  Fix: Contact an authorized service center for service.
• The OVERLOAD lamp lights. Engine shuts down.
  Cause: If load exceeds generator current rating, the breaker will trip preventing the generator from being overloaded.
  Fix: Locate the source of overload and correct as necessary. Manually reset breaker to reconnect the load to the generator.
• Pre-Low Oil Pressure
  Fix: A pre-low oil pressure sensor and lamp provides an alarm that oil pressure is marginally low, 20 psi (137 kPA) or less. The cause should be found and corrected as soon as possible.
• Pre-High Engine Temperature
  Fix: A pre-high engine temperature sensor and lamp provides an alarm that engine temperature is marginally high, 215° F (102° C). The cause should be found and corrected as soon as possible.
• Low Oil Pressure
  Fix: Shuts down the engine immediately if oil pressure drops below 14 psi (97 KPA) and lights a fault lamp. The fault is time-delayed about 10 seconds following starter disconnect and inhibited during cranking.

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan 4-cyl..

Pooled from every document that names this exact engine — confirm the interval and part number against your unit's serial number.