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 rpm.
5. Visually check to see if air bubbles are rising to the surface of the fuel within the container.
[a] If air bubbles are present, refer to section 3.2.1.
[b] If air bubbles are not present, check for improper calibration setting. 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 appropriate service manual, fuel system chapter.
5. Verify repair of fuel lines:
[a] If no air in the fuel return, refer to section
[b] If air in the rule 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 section3.2 for exhaust caution before preceding. Start engine.
2. Run engine at 1000 rpm.
3. Listen for misfiring cylinder.
[a] If the engine is not misfiring, no further troubleshooting is required. Shut down
the engine.
[b] If the engine is misfiring,, shut down the engine and check for improper injector

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