Skip to main content


To determine if aerated fuel is causing the cylinder to misfire, perform the following steps: ‪

  1. Disconnect the fuel line return hose from the fitting located at the fuel tank.
  2. Place the opened end of fuel line into a suitable container.
  3. Start the engine.
  4. Run the engine at 1000 r/min.
  5. Visually check to see if air bubbles are rising to the surface of the fuel within the container.
    1. If air bubbles are present, refer to section .
    2. If air bubbles are not present, check for improper calibration setting; refer to section . Shut down the engine.

Aerated Fuel Repair

Perform the following steps for air in fuel repair: ‪

  1. Shut down engine.
  2. Tighten all fuel line connections between fuel tank and fuel pump; refer to OEM guidelines.
  3. Visually inspect all fuel lines between fuel tank and fuel pump for leaks.
  4. Replace any damaged components; refer to section .
  5. Verify repair of fuel lines:
    1. If no air in the fuel return, refer to section .
    2. If air in the ruel return, locate and repair. Then refer to section .
Test the Engine with Repair for Aerated Fuel

Perform the following steps to determine if the aerated fuel repair resolved the misfiring cylinder condition: ‪

  1. Refer to section for exhaust caution before preceeding. Start engine.
  2. Run engine at 1000 r/min.
  3. Listen for misfiring cylinder.
    1. If the engine is not misfiring, no further troubleshooting is required. Shut down the engine.
    2. If the engine is misfiring, check for improper injector setting. Shut down the engine; refer to section .