Cummins/Onan AK Engine Engine

• VOLTAGE UNSTEADY BUT ENGINE NOT MISFIRING
  Cause: Speed too low. Loose connections. Fluctuating load.
  Fix: Adjust governor to correct speed. Tighten connections. Correct any abnormal load condition causing trouble.
• VOLTAGE LOW AT FAR END OF LINE BUT NORMAL NEAR POWER PLANT
  Cause: Too small line wire for load and distance.
  Fix: Install larger or extra wires or reduce load.
• VOLTAGE DROPS UNDER HEAVY LOAD
  Cause: Engine lacks power. Poor compression. Faulty carburetion.
  Fix: See remedies for engine misfires under heavy load. Tighten cylinder head & spark plugs. Clean the fuel system.
• SHARP METALLIC THUD, ESPECIALLY WHEN COLD ENGINE FIRST STARTED
  Cause: Low oil supply. Oil badly diluted.
  Fix: Add oil. Change oil.
• Restricted exhaust line.
  Fix: Clean or increase the size.
• PINGING SOUND WHEN ENGINE IS SUDDENLY OR HEAVILY LOADED
  Cause: Wrong spark plug. Spark plug burned out/carboned. Fuel stale or low octane. Lean fuel mixture.
  Fix: Install correct spark plug. Install new plug. Use good, fresh fuel. Clean & adjust carburetor.
• LIGHT POUNDING KNOCK
  Cause: Low oil supply. Oil badly diluted.
  Fix: Add oil. Change oil.
• GENERATOR OVERHEATING (Approximately 160°F higher than ambient)
  Cause: Overloaded.
  Fix: Reduce load.
• Excessive oil consumption, light blue smoky exhaust
  Cause: Oil leaks from unl base ot connections. Oil too light or diluted. Engine misfiting. Faulty ignition. Too much
  Fix: Replace gaskets. Tighten screws and connection.
• Engine will not start when cranked
  Cause: Lack of fuel or faulty catburetion. Clogged fuel screen. Cylinders flooded. Poor fuel.
  Fix: Refill tank. Check fuel system. Clean, adjust, as necessary. Clean. Crank few times with spark plug removed. Drain, fill with fresh fuel.
• Engine will not crank
  Cause: Battery discharged. Loose connections, Defective starting circuit. Defective switch.
  Fix: Recharge. Tighten connections. Repair or replace as necessary. Replace.
• ENGINE STOPS UNEXPECTEDLY
  Cause: Fuel tank empty. Defective ignition.
  Fix: Fill with fresh fuel. Check ignition system.
• ENGINE RACES
  Cause: Governor not controlling carburetor. performance & linkage condition.
  Fix: Check governor performance & linkage condition.
• ENGINE OVERHEATING
  Cause: Poor air circulation. Improper lubrication. Fuel mixture too lean.
  Fix: Clean cooling fins. See Low Oil Pressure. Adjust carburetor.
• ENGINE MISFIRES AT LIGHT LOAD
  Cause: Spark plug gap too narrow. Intake air leak. Faulty ignition. Low compression.
  Fix: Adjust to correct gap. Tighten or replace manifold and carburetor gaskets. Clean, adjust or replace spark plugs. Tighten cylinder head and spark plug.

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

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

• Recoil Starter Installation
• Recoil Starter Cord Replacement
• Recoil Starter Re-wind Spring Replacement

Step-by-step procedures compiled from the Cummins/Onan service manual for this engine.