Cummins/Onan NHB Engine Engine

• White or Blue Exhaust Smoke
  Cause: Rich fuel mixture due to: a. incorrect float level b. faulty carburetor float.
  Fix: 1a. Adjust carburetor float level. 1b. Replace faulty carburetor float.
• Weakness and Sleepiness
  Fix: IF YOU OR ANYONE ELSE EXPERIENCE ANY OF THESE SYMPTOMS, GET OUT INTO THE FRESH AIR IMMEDIATELY. If symptoms persist, seek medical attention. Shut down the unit and do not operate until it has been inspected and repaired.
• Vomiting
  Fix: IF YOU OR ANYONE ELSE EXPERIENCE ANY OF THESE SYMPTOMS, GET OUT INTO THE FRESH AIR IMMEDIATELY. If symptoms persist, seek medical attention. Shut down the unit and do not operate until it has been inspected and repaired.
• 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.
• 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 vehicle power cord into the genset power output receptacle (if so equipped) or turn the vehicle power selector switch to its genset position (if so equipped).
• There is no electrical power even though the genset runs and Gen AC (Fig. 3) lights.
  Fix: A. Reset tripped circuit breakers. See Powering Equipment. b. Unless there is an automatic power transfer switch, plug the vehicle power cord into the genset power output receptacle (if so equipped) or turn the vehicle 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: A. Try running with fewer appliances connected. See Powering Equipment. b. Check the fuel tank (LPG, vapor-withdrawal models) and fill as necessary. On cold days the LPG container may have to be kept at least half full to provide the rate of vaporization necessary to keep up with the genset fuel demand.
• 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 (gasoline models only). 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 fails to crank at the remote START switch.
  Fix: A. Turn the enable switch (if so equipped) to the enable position. b. Try starting at the genset rather than at the remote control. c. Push the genset control panel switch to RESET and then to START.
• The engine fails to crank at the genset START switch but Start Sol (Fig. 3) does light.
  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 engine fails to crank at the genset START switch and Start Sol (Fig. 3) does not light.
  Fix: A. Turn the enable switch (if so equipped) to the enable position. b. Push the genset control panel switch to RESET and then to START. c. Replace fuse F1 on the side of the control box if it has blown. d. Clean and tighten the positive (+) and negative (- ) battery cable connections at the battery and the genset. e. Recharge the battery. Refer to the battery manufacturer’s recommendations.
• The engine cranks slowly.
  Fix: A. Disconnect large electrical and mechanical 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 on Page 3.

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

• Remove Blower Wheel

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