Cummins/Onan B3.3 Engine

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

• No output voltage
  Cause: The line circuit breaker is OFF.
  Fix: Find out why the circuit breaker was turned OFF, make sure it is safe to reconnect power, and then throw the circuit breaker ON.
• The engine does not crank in Run mode
  Cause: The Emergency Stop switch has been used. (The switch button is lit.)
  Fix: Pull the Emergency Switch button. To reset the engine control, push the Run-Stop-Remote switch to Stop and the Reset switch to Reset. Then push the Run-Stop-Remote switch to Run.
• The engine lacks power or is unstable
  Cause: Fuel delivery to the genset is inadequate.
  Fix: Check for clogged fuel lines and filters; Check for air in the fuel lines and repair all air leaks; Check fuel inlet and outlet restriction. Refer to Cummins B3.3 Series Engines Operation and Maintenance Manual Specifications section.
• An amber warning lamp is on
  Cause: The PRE LO OIL PRES lamp comes on while the engine is running.
  Fix: Shut down the set if possible or disconnect non-critical loads. (Oil pressure will be less than 20 psi [138 kPa] but greater than 14 psi [97 kPa].) Service the engine lubricating system according to the engine service manual.
• The field circuit breaker keeps tripping
  Cause: The rotating rectifier assembly (diodes CR1 through CR6) is faulty.
  Fix: Shut down the set and check each diode according to Section 5. Service as necessary.
• The engine does not crank in Remote mode
  Cause: The Run-Stop-Remote switch is at Stop. (The Switch-Off light will be flashing, if provided.)
  Fix: Push the Run-Stop-Remote switch to Remote.
• The engine cranks but does not start
  Cause: The engine is not getting fuel.
  Fix: Open any closed fuel shutoff valve; Fill the main fuel supply tank; Restore fuel pump prime according to the engine service manual.
• The phase currents are unbalanced
  Cause: The connected loads are distributed unevenly among the phases.
  Fix: Shut down the set and redistribute the loads as evenly as possible.
• The engine runs until fault shutdown
  Cause: The OVERSPEED lamp comes on and the engine shuts down.
  Fix: Reset the ECM by pushing the Run-Stop-Remote switch to Stop and the Reset switch to Reset and restart the set, monitoring engine speed. Readjust the cutout speed if it is lower than specified. Replace the overspeed module (PMG equipped sets) or the overspeed switch if it cannot be readjusted (see Section 3); Adjust the governor (see Section 6); If the governor cannot be adjusted to prevent shutdown due to overspeed, check for binding in the linkage. Repair and adjust the linkage as necessary. (A spring inside the actuator will resist movement, which is normal.); If the set still shuts down due to overspeed, re-install the magnetic speed pick-up unit to make sure the clearance with the flywheel gear teeth is correct. Replace the speed-pickup unit if output voltage at cranking speed is less than 2.5 VDC as measured at terminals 10 (–) and 11 (+) on the governor controller; Disconnect the actuator leads at governor controller terminals 4 and 5. Jumper the lead for terminal 4 to the BAT terminal on the starter solenoid and touch the lead for terminal 5 to a good ground on the block. Replace the actuator unit if it does not drive the linkage through its full travel when power is connected or return it when power is disconnected; Replace the governor controller if the set still shuts down due to overspeed.
• Output voltage is too high or too low
  Cause: Engine speed is unstable.
  Fix: Troubleshoot according to the chart, The Engine Lacks Power or is Unstable.
• The green RUN lamp stays off but the set runs normally
  Cause: The set mounted RUN lamp does not light, although the starter has disconnected normally and the engine is running. The remote RUN lamp does light (AC start disconnect is okay).
  Fix: Press the panel Lamp Test switch and replace the run lamp bulb if it does not light; If the RUN lamp, wiring connections and battery charging alternator are all good and the RUN lamp does not light, replace the ECM.
• 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. FAULT 1
  Cause: 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.
• RUN or fault lamp(s) does not light when Lamp Test switch is engaged.
  Fix: Contact an authorized service center for assistance.
• Output voltage is unstable
  Cause: The voltage has been adjusted improperly.
  Fix: Adjust output voltage according to Section 2, AC Control.
• No AC output voltage.
  Cause: Field breaker is tripped
  Fix: Reset breaker. Contact an authorized service center if voltage buildup causes breaker to trip.

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan B3.3.

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

Parts cataloged across all variants of this engine family — verify the exact part fits your specific variant and serial number before ordering.