Common Causes for Onan Generator Failure to Crank
An Onan generator may refuse to start or crank due to a variety of issues such as overheating, low voltage supply, defective starter motor, faulty spark plugs, worn wiring, or a clogged carburetor. Understanding these potential problems can help diagnose and resolve the issue efficiently.
1. Overheating Problems
Overheating is a prevalent reason why an Onan generator might fail to crank. When the system detects excessive heat, it may trigger a warning light or flash a specific error code, such as code 33. This overheating can result from a number of factors, including:
- Accumulation of debris blocking air intake or exhaust passages
- Poor ventilation around the generator, with insufficient clearance on sides or above
- Low coolant levels or coolant leaks
- Clogged filters impeding airflow
- Damaged or blocked exhaust components
- Generator overload during operation
- High ambient temperatures exceeding recommended operating conditions
- Low oil pressure leading to inadequate lubrication
- Neglected routine maintenance and servicing
How to Address Overheating
Overheating poses significant risk to your generator’s longevity. It’s essential to address the root causes promptly. Follow these steps:
- Reduce load if the generator is overloaded to prevent excessive heat buildup.
- Disconnect all loads to allow the generator to cool down and prevent damage to the inverter or other components.
- Perform regular oil changes and ensure the oil level is within specifications.
- Clean or replace air and coolant filters regularly to maintain proper airflow and cooling.
- Add coolant as needed, checking for leaks and repairing any found.
- Replace damaged hoses and clear any obstructions in the exhaust system.
- Maintain proper clearance around the unit; a minimum of 18 inches from walls as recommended by Norwall Power Systems.
- If the generator has already overheated and started, seek professional inspection to assess potential damages to rotors, bearings, or the alternator.
2. Low Voltage Caused by Battery Issues
When attempting to start, if you hear a clicking sound or the engine cranks slowly, the problem may stem from insufficient voltage, often due to a faulty or discharged battery. Use a voltmeter to measure the voltage before and during startup to diagnose the issue.
Low voltage can also result from:
- Corroded battery terminals
- Loose or damaged wiring connections
- Worn-out or aged batteries that can no longer hold a charge
How to Fix Battery-Related Problems
- Test the battery with a multimeter; replace it if it fails to hold proper voltage.
- Clean corrosion from terminals using a mixture of baking soda and water, then scrub with a wire brush.
- Ensure all terminal connections are tight and secure.
- Replace damaged or frayed cables.
- Use an external charger or jump-start with a reliable power source to recharge or replace the battery.
3. Faulty Starter Motor
The starter motor plays a crucial role in initiating engine rotation. If it is defective, you might experience symptoms such as a clicking noise, grinding sounds, or a slow engine turn. Since the starter motor is composed of complex parts such as field coils, a solenoid, pinion gear, brushes, and armature, diagnosing issues may require technical expertise.
Indicators of a Bad Starter Motor
- Persistent clicking when attempting to start
- Unusual grinding or burning smells during startup
- Slow or unresponsive engine rotation
Repair or Replacement Procedures
- Ensure the battery is fully charged; a weak battery can mimic starter issues.
- Check contact points between brushes and the commutator; replace worn or burnt parts.
- Clean or replace the commutator if it shows signs of damage.
- Replace the entire starter motor if necessary, after confirming the fault.
4. Bad Spark Plugs
Spark plugs are vital for igniting the fuel-air mixture within the engine cylinders. Faulty or fouled plugs can prevent proper combustion, leading to failure to start. Symptoms include engine misfires, difficulty starting, and poor performance.
Steps to Address Spark Plug Issues
- Replace spark plugs approximately every 100 hours of operation, as recommended by Briggs and Stratton.
- Inspect and clean spark plugs if they show carbon buildup or fouling.
- Use high-quality, fresh fuel and consider fuel stabilizers if storing for long periods.
- Regularly replace air filters and clean the carburetor to ensure optimal combustion.
- Make sure the spark plugs are firmly seated and properly gapped.
- Verify oil levels meet the manufacturer’s specifications to ensure engine health.
5. Worn or Damaged Wiring
The extensive wiring network within an Onan generator transmits power and signals between components. Damage caused by mishandling, corrosion, overheating, vibrations, or electrical surges can lead to starting problems or complete failure.
How to Repair Wiring Issues
Due to the complexity and risk, it’s advisable to have a trained technician inspect and repair the wiring. Attempting to fix wiring yourself may void warranties or cause further damage. A professional will identify loose connections, broken wires, or damaged insulation and replace or repair as needed.
6. Clogged Carburetor
A clogged carburetor impairs the fuel delivery, preventing the engine from starting or running smoothly. Stale fuel residues cause blockages, especially if the generator has been inactive for an extended period.
Cleaning and Restoring the Carburetor
- Disassemble and thoroughly clean the carburetor to remove deposits and blockages.
- Use fresh, high-quality gasoline; consider draining old fuel before storage.
- Flush the fuel system if stale or contaminated fuel has accumulated.
- Replace any damaged gaskets, seals, or components during reassembly.
- Ensure proper adjustment of the carburetor for optimal fuel mixture.