Cummins/Onan 4.0BGEFA261 OOL Engine Engine

• There is no electrical power even though the genset runs.
  Fix: A. Reset tripped circuit breakers. See Powering Equipment. b. Unless there is an automatic power transfer switch, plug the boat power cord into the genset power output receptacle (if so equipped) or turn the pontoon boat power selector switch to its genset position (if so equipped).
• The remote battery condition meter indicates low voltage.
  Fix: A. Clean and tighten the positive (+) and negative (-) battery cable connections at the battery and the genset. b. Recharge the battery. Refer to the battery manufacturer's recommendations.
• The genset keeps stalling or the circuit breaker keeps tripping.
  Fix: Try running with fewer appliances connected. See Powering Equipment.
• The engine runs and then stops or surges.
  Fix: A. Check the fuel tank and fill if necessary. b. Check the engine oil level and add oil as necessary. Drain excess oil if the level is above the dipstick Full mark. c. Check and reset the carburetor preheater lever and altitude adjust knob. See Varying Weather and Altitude. d. Secure the spark plug leads on the spark plugs. e. Replace the spark plugs.
• The engine fails to crank.
  Fix: A. Try starting at the genset rather than at the remote control. b. Replace fuse F1 on the control panel if it has blown. c. Clean and tighten the positive (+) and negative (-) battery cable connections at the battery and the genset. d. Recharge the battery. Refer to the battery manufacturer's recommendations.
• The engine cranks slowly.
  Fix: A. Disconnect the air conditioner and other large loads. b. Clean and tighten the positive (+) and negative (-) battery cable connections at the battery and the genset. c. Recharge the battery. Refer to the battery manufacturer's recommendations. d. Change the engine oil to oil having the proper viscosity for the ambient temperature. See Table 1.
• The engine cranks but fails to start.
  Fix: A. Check the fuel tank and fill if necessary. b. Open any closed fuel shut off valve. c. Check engine oil level and add oil as necessary. d. Replace fuse F2 (side of control panel) if it has blown. e. Service the air cleaner. f. Secure the spark plug leads on the spark plugs. g. Replace the spark plugs.
• Black smoke exits the tailpipe.
  Fix: Service the air cleaner.
• UNIT RUNS THEN SURGES
  Cause: 1. Loose or worn spark plug leads. 2. Ignition coil, wiring, or control components defective. 3. Faulty spark plugs. 4. Governor defective. 5. Incorrect fuel mixture.
  Fix: 1. Check security of spark plug leads at spark plug and ignition coil. 2. Contact an Onan service center. 3. Remove and clean or replace faulty spark plugs. 4. Contact an Onan service center. 5. Contact an Onan service center.
• UNIT RUNS THEN STOPS
  Cause: 1. Out of fuel. 2. Low oil level. 3. Excess oil.
  Fix: 1. Refill fuel tank. 2. Add oil if necessary. 3. Reduce engine oil level.
• UNIT RUNS BUT SURGES
  Cause: 1. Loose or worn spark plug leads at spark plugs and ignition coil. 2. Ignition coil, wiring, or control components defective. 3. Faulty spark plugs. 4. Governor out of adjustment.
  Fix: 1. Check security of spark plug leads at spark plugs and ignition coil. Replace leads if worn. 2. Contact an Onan representative. 3. Remove and clean or replace faulty spark plugs. 4. Contact an Onan service center.
• Smoke and rough operation
  Cause: Oil in the cylinders has not been burned off yet.
  Fix: Continue running the generator set until the oil in the cylinders is burned.
• High/Low AC Output (Genset)
  Fix: -01 Check: - Broken or loose wires - Voltage regulator - Transformer regulator - Engine speed - Voltage ad
• Generator set runs louder than usual, compartment has holes to the interior, or exhaust system has leaks
  Fix: Do not operate the generator set and have the exhaust system repaired as soon as possible. See your Onan service center.
• FAILS TO CRANK
  Cause: 1. Low battery. 2. Bad battery connection. 3. Blown fuse.
  Fix: 1. Check battery electrolyte level. 2. Clean and tighten all battery and cable connections. 3. Replace fuse on control box. See specifications for proper fuse rating.

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan 4.0BGEFA261 OOL.

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