Cummins/Onan 4A2.3 Engine

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

• Voltage is unstable, high or low
  Fix: Push to reset breaker. Does generator AC output voltage build up? If no, flash exciter field per TEST [D]. Does generator output voltage build up?
• 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.
• Residual voltage across terminals 2 and 3 of VR21 is less than 5 to 10 VAC
  Fix: Disconnect stator leads from leads 1 and 2 from AC across the leads. Is residual voltage 4 and 5,5 VDC or more now? Check reactor CMR21 and transformer T21 per TESTS (B) and (E). For shorts per TEST [MI.
• PRE LO OIL PRES lamp lights. Engine continues to operate.
  Fix: 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.
  Fix: Indicates engine has begun to overheat and engine temperature has risen to approximately 202°F (94°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.
• OVERCRANK lamp lights and engine stops cranking.
  Fix: 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 a Cummins Dealer for service if none of the above.
• No AC output voltage.
  Cause: Field breaker is tripped.
  Fix: Reset breaker. Contact a Cummins Dealer or Distributor if voltage build up causes breaker to trip.
• NO AC OUTPUT VOLTAGE AT RATED ENGINE RPM
  Fix: Check lead continuity between AC terminals on A1 and terminals 2 and 3 on VR21 per TEST [Ml. Replace defective field breaker. Remove one lead from breaker and check continuity with ohmmeter. Is breaker open? Is control panel field breaker CB21 on?
• LO OIL PRES lamp lights. Engine shuts down.
  Fix: Indicates engine oil pressure has dropped to 14 psi (97 kPa). Check oil level, lines and filters. If oil system is okay but oil level is low, replenish. Reset control and restart. Contact a Cummins Dealer or Distributor if oil pressure is not in the range of 35 to 55 psi (241 to 379 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.
• HI ENG TEMP lamp lights. Engine shuts down.
  Fix: Indicates engine has overheated (engine temperature has risen above 222°F/106°C) or coolant level is low (sets with coolant level sensor). Allow engine to cool down completely before proceeding with the following checks: 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 a Cummins Dealer or Distributor if none of the above.
• Engine will not crank.
  Cause: Possible fault with control or starting system.
  Fix: Check for the following conditions: - Fault lamp on. Correct fault and reset control. - Poor battery cable connections. Clean the battery cable terminals and tighten all connections. - Discharged or defective battery. Recharge or replace the battery. - Contact a Cummins Dealer or Distributor for assistance if none of the above.
• Engine starts from generator control panel but will not start automatically or from a remote panel.
  Cause: Remote circuit breaker is tripped.
  Fix: Reset breaker and restart. Contact a Cummins Dealer if breaker trips after resetting.
• Engine starts but stops after running several seconds.
  Cause: A fault condition indicated by fault breaker CB12 on control panel or DC control breaker trips when the generator set is started.
  Fix: Check for a possible fault condition. If none, check fault monitors S1 through S5 and fault breaker CB12 for improper wiring. Check all B+ wiring for shorts to ground.

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan 4A2.3.

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