Cummins/Onan DFN Engine Engine

• Voltage regulation poor
  Fix: Check continuity from the junction of Control Rectifiers 3 and 4 to the junction of Control Rectifiers 1 and 2
• 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.
  Cause: Engine standard undesignated fault functions are programmed to shut down the set when a fault is sensed. Fault 1 is timed 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.
• The external alarm is activated
  Fix: Check the conditions that may have caused the fault
• The engine does not start.
  Cause: The starter will disengage after a specified period of time and the control will indicate an overcrank fault.
  Fix: Place the Run-Stop-Remote switch in the STOP position and momentarily depress the Reset switch. Wait two minutes for the starter motor to cool and then repeat the starting procedure.
• The engine does not run after a second attempt at starting.
  Fix: Refer to the Troubleshooting section.
• SWITCH OFF lamp flashes. 8
  Fix: 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. 4
  Fix: 4. Indicates engine oil pressure has dropped to 20 psi (138 kPa). If generator is powering critical loads and cannot be shut down, wait until next shutdown period and then follow step 5 procedure. If engine can be stopped, follow procedures in step 5.
• PRE HI ENGINE TEMP lamp lights. Engine continues to operate. 2
  Fix: 2. Indicates engine has begun to overheat and engine temperature has risen to approximately 205°F (97°C). If generator is powering non-critical and critical loads and cannot be shutdown, 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. c. Open doors or windows in generator area to increase ventilation. If engine can be stopped, follow procedure in step 3.
• Partial loss of residual in Rotor from E2 to heat sink of field rectifier No. 1 until voltage begins to build-up.
  Fix: None; Then remove.
• Overspeed shutdown. Overspeed
  Fix: Check governor and throttle linkages for freedom of movement.
• Overspeed light on, no shutdown.
  Fix: 6. Disconnect wire at TB11-29. Light ON after reset; replace engine monitor board.
• OVERCRANK lamp lights and engine stops cranking. 6
  Fix: 6. Indicates possible fuel system problem. 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. Refer to Step 5. e. Reset the control and restart after correcting the problem. Contact an Onan Dealer or Distributor for service if none of the above.
• Overcrank fault lamp lights and engine stops cranking after approximately 75-seconds.
  Fix: Check for empty fuel tank, fuel system leaks, or plugged fuel supply lines. Correct as required.
• Output voltage slow to build up
  Cause: Open in one or both Field Rectifiers 1 and 2 if defective
  Fix: Test rectifiers and replace if defective
• Output voltage builds up normally with slightly less than rated voltage at no load and low voltage and low voltage and high voltage after build up
  Cause: Shorted winding in Control Reactor and Gate windings G1-G2 of Reactor A or B if defective
  Fix: Test rectifiers and replace if defective

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

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