7 Reasons Onan Generator Keeps Shutting Off (Explained)

onan generator keeps shutting off

An Onan generator shouldn’t shut itself off. This behavior is not normal. If yours runs for a few minutes or hours before shutting down, inspect the unit. You will probably identify one of the following variables as the culprit:

1). Insufficient Fuel

Generators need fuel to run. If you installed yours in an RV, a line will pull fuel from the RV’s tank to the generator. The fuel line can’t perform its duties when the RV’s fuel is less than a quarter full.

If the RV has plenty of fuel, but the generator keeps turning off, the fuel line is pinched or broken. Keep an eye on the weather. Extreme temperatures can lead to a vapor lock.

2). Generator Overloaded

An Onan generator is no different from your home’s electrical circuit. It is designed to carry a specific load. Exceeding the generator’s capacity will compel the unit to shut down. This is a good thing because it protects the generator.

The Onan generator won’t survive if you force it to carry a bigger load than it can tolerate. You can test this theory by disconnecting some of the loads. If the generator’s symptoms fade, overloading is the problem. If the generator continues to shut down every few minutes, the fault lies elsewhere.

3). Oil Not Enough

The Onan generator will turn off if the oil is low. Sophisticated units have a low-oil shutoff sensor that stops the engine when oil levels fall below a specific threshold. This protects the generator’s moving parts from wear and tear.

If the dipstick reveals sufficient oil levels, inspect the oil. A generator can shut down because of dirty oil. What if you’ve added clean oil to the tank, but the generator continues to turn off? The low-oil shutoff sensor is probably defective.

4). Clogged Onan Generator

Dust and debris can create obstructions in the pipes, preventing oil and gasoline from circulating. Additionally, the pipes and hoses can develop tears and breaks, causing leaks. The generator will continuously lose oil and fuel until you plug the leaks.

5). Clogged Carburetor

Dirty or poor-quality fuel can clog the carburetor. The fuel in a generator can become stale because you’ve kept the unit in storage for a long time.

6). Spark Plugs Defective

When was the last time you replaced the spark plugs? Spark plugs can accumulate carbon deposits that disrupt their work. They are among the first components a technician checks when you service the generator.

7). Failed Battery

A generator with a dead battery won’t start. However, if the battery is on its last legs, the unit will start, run for a few minutes or hours, and then stop.

Onan Generator Turns Off After 5 Minutes

  • The carburetor is dirty.
  • The tank is empty.
  • The fuel is depleted.
  • The fuel pump is defective.
  • The oil levels are low.
  • The controller board is faulty.
  • A chip probably blew.
  • The filter is clogged.
  • The generator has a crimped fuel line.
  • The battery is low.
  • The fuel line is broken.
  • The engine is overheating. This can occur because of low coolant levels.
  • Either the generator has low oil levels, or the oil pressure switch has failed.
  • Loose connections.
  • Loose plug wires and bad contacts.

Onan Generator Turns Off After 15 Minutes

  • The carburetor is dirty.
  • The onboard timer clock settings are wrong.
  • The generator keeps tripping the overfill sensor. This can happen when you add too much oil.
  • You’ve overloaded the generator.
  • You have a bad fuel pump. Test it when it’s hot. A cold pump will mislead you. A pump that doesn’t pump while hot has gone bad.
  • The oil pressure is low.
  • Loose or damaged wiring.

Onan Generator Turns Off After 20 Minutes

  • The gas cap has failed.
  • Oil levels are low.
  • The oil sensor has failed.
  • The tank, lines, and carburetor have too much sediment.
  • Overheating
  • Low oil pressure.
  • The gas cap has a plugged vent hole.
  • The carburetor has gone bad.
  • The fuel filter is clogged or damaged.
  • The fuel line is leaking.

Onan Generator Turns Off After 30 Minutes

  • The oil level sensor is dead.
  • The oil level is low.
  • The fuel pump keeps overheating.
  • This can happen because of hot weather.
  • Low oil pressure.
  • Either you don’t have enough fuel, or the fuel is not fresh. The fuel shutoff valve is closed. The carburetor is dirty.

Onan Generator Turns Off After 2 Hours

  • The oil level sensor is dead.
  • The oil level is low.
  • The fuel pump keeps overheating.
  • This can happen because of hot weather.
  • Low oil pressure.
  • Either you don’t have enough fuel, or the fuel is not fresh.
  • The fuel shutoff valve is closed.
  • The carburetor is dirty.

How To Fix Onan Generator That Keeps Shutting Off?

  • If the Onan generator keeps overheating, ask a technician to add a heat shield (Between the engine and exhaust).
  • You can also add an air diverter to separate the air intake and exhaust. A skilled welder can perform this task for you.
  • Test the fuel pump. If it’s dead or too weak, replace it.
  • If the generator is programmed to shut down once the fuel falls below a specific threshold, keep the fuel above that threshold.
  • If the generator is overloaded, disconnect some of the loads. You can also buy a bigger generator. Ensure the unit’s wattage exceeds the total wattage of all the tools and appliances you want to run.
  • Consumers usually close the shutoff valve before placing the generator in storage. This prevents the fuel from becoming stale. Unfortunately, they forget to open the valve after removing the generator from storage. The fuel won’t flow when the shutoff valve is closed. Fortunately, you can solve this problem by simply opening the valve. If you don’t know what it looks like, the experts at electric problems have published pictures showing the shutoff valve on a generator.
  • Replace a defective oil pressure sensor.
  • If the oil is insufficient, add more. Use the dipstick to track the oil level. Modern generators have a low-oil sensor that comes on when the unit needs more oil. Pay attention to this indicator.
  • If the oil on the dipstick is dirty, change the oil in the generator.
  • If the temperature keeps climbing to unhealthy levels because of insufficient water, add water to the radiator.
  • Don’t over-chock the generator. You can maintain a full chock while starting the generator. Once the unit starts, shift to a half-chock after a few minutes before finally settling on ‘RUN.’ Maintaining a full chock will shut the generator down.
  • Fuel gums up if you keep the generator in storage for a long time without running it. This clogs the carburetor. You can clean or replace the carburetor depending on the severity of the problem.
  • Use Seafoam to treat a sticking fuel gauge.
  • Identify and replace leaking hoses and pipes.
  • Tighten loose plug wires.
  • Clean dirty spark plugs. According to Woodstock Power, you should replace the spark plugs after 100 hours.
  • Clean any corrosion you find on the battery. Make sure the battery’s connections are firm.
  • Replace a bad generator battery.
  • Clean or replace dirty and damaged filters.
  • Place traps around the generator to defend against rodents. Otherwise, they will chew through the wires.
  • Replace a defective fuel cap.
  • Replace coolant sensors with bent terminals. Power Continuity has pictures showing a damaged coolant sensor.

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