Cummins/Onan 6CT8.3G Engine Engine

• The FAULT 1 or FAULT 2 fault lamp lights. Engine shuts down immediately, engine runs for several seconds and then shuts down, or engine continues to run.
  Fix: The standard undesignated fault functions are programmed to shut down the set when a fault is sensed. Fault 1 is time delayed while Fault 2 is immediate. The nature of the fault is an optional selection that is determined when the set installation is designed. The undesignated fault functions may also be programmed for non-shutdown or non-time delay.
• 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 LO OIL PRES lamp lights. Engine continues to operate.
  Cause: Indicates engine has overheated (engine temperature has risen above 222°F/106°C) or coolant level is low (sets with coolant level sensor).
• PRE HI ENGINE TEMP lamp lights. Engine continues to operate.
  Cause: Indicates engine has begun to overheat and engine temperature has risen to approximately 215°F (102°C).
  Fix: If generator is powering non-critical and critical loads and cannot be shut down, use the following: 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.
  Fix: A. Check for empty fuel tank, 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.
  Fix: Check oil level, lines and filters. If oil system is OK but oil level is low, replenish. Reset control and restart. Contact an authorized service center if oil pressure is not in the range of 25 to 40 psi (172 to 275 kPa).
• LO FUEL LAMP lights. Engine shuts down and LO OIL PRES lamp lights.
  Fix: Indicates engine has run out of fuel. Check fuel level and replenish as required.
• LO FUEL lamp lights. Engine continues to run.
  Fix: Indicates diesel fuel supply is running low. Check fuel supply and replenish as required.
• LO ENG TEMP lamp lights. Set is in standby mode but is not operating.
  Fix: A. Coolant heater not connected to power supply. Check for blown fuse or disconnected heater cord and correct as required. b. Check for low coolant level and replenish if required. Look for possible coolant leakage points and repair as required. c. Contact an authorized service center for service if none of the above.
• Green RUN lamp does not light following engine startup.
  Fix: Indicates possible Start/Disconnect relay failure. 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: 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 (if equipped) 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 starts from generator control panel but will not start automatically or from a remote panel.
  Fix: Remote circuit breaker is tripped. Reset breaker and restart. Contact an authorized service center if breaker trips after resetting.
• Engine runs and then shuts down, OVERSPEED lamp lights.
  Fix: Indicates engine has exceeded normal operating speed. Contact an authorized service center for service.

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan 6CT8.3G.

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