Onan Fuel Vapor Leakage / Venting Issue

Strong fuel odor around generator during or after operation, no visible leak

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Loose fuel fittings allowing vapor escape, Faulty fuel tank vent, Carburetor or injector leakage after shutdown, Overfilled fuel tank

How to Fix / Troubleshooting

Safety first: Shut down the generator, disable auto-start, and ventilate the area. Do not smoke or create sparks nearby.

  • Inspect fittings: Check all fuel line connections for slight dampness or staining that may indicate seepage. Tighten as needed.
  • Check tank vent: Ensure the fuel tank vent is not blocked. A blocked vent can force vapors out of seals.
  • Carburetor/injector leak-down: On gas units, inspect carburetor for dripping fuel after shutdown. On diesel, check injector return lines. Repair or replace leaking components.
  • Fuel level: Avoid overfilling the tank, especially in hot weather, to reduce vapor expansion.
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Repair Difficulty

Medium 3/5

Required Part

Fuel Tank Vent
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