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Cabin Fuel Smell

The fuel smell is strong with cowl flaps open and no fuel smell with cowl flaps closed. Any ideas?

Model: Bonanza F33
Posted 4/8/2023 - 10 months ago
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Cowl flaps (obviously) change airflow. The engine driven fuel pump has a cavity drain coming from the bottom near the crankcase, follow that down, most F33A they are just outboard of the keel through the cheek skin about 10" forward of the left cowl flap; check that for any fuel staining at the end of the tube.

Mike
ABS Tech Advisor

Posted 4/8/2023 - 10 months ago
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Thank you Mike, I’ll have a look. I changed the electric aux fuel pump due to some seepage. That didn’t fix the problem but that pump has been there since new. At least we have the S/B complied with the new pump.

Posted 4/8/2023 - 10 months ago
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Does the engine driven fuel pump drain line come out of the back of the engine? I checked that drain line and it did not have any blue die of streaking. Should we run it and check for fuel dripping out of the drain?

Steve

Posted 4/11/2023 - 10 months ago
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The fuel pump is on the back of the engine, just inboard of the oil filter, the drain line comes out of the pump just aft of the mounting flange at the engine. Boost pump on with mix and throttle forward generally is enough pressure to reveal a leaking seal. Also check your flow divider, they have a drain line out the bottom also (unless it is really old, then it just has a 'weep hole' to equalize pressure), check that line or the weep hole for blue staining. Another thought might be the fuel selector leaking out the top; often, full rich / low fuel consumption settings coincide with cowl faps open position, so the cowl flaps may be a red herring.

Posted 4/11/2023 - 10 months ago
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Cabin Fuel Smell