Fuel intermittent leak

Hi John,

To be sure its coming from the mechanical pump; put a temporary catch can on the drain tube. I use a plastic kids drink bottle, from the supermarket (nothing stopping you from drinking the contents).

Drill a hole in the cap, so that the drain tube fits tightly, drill a few vent holes in the bottle neck, secure bottle to any convenient structure using zip/cable ties - go fly.

Check bottle contents.

Thanks Sean, Actually I tried that the only difference is I put Vent Tied to the lower end of my cowling, I didn’t have any results with that but that pump is the only thing at the front right side of my engine compartment where the leak is coming from.??

In theory (?) the pump can only leak fuel through the vent line.

You may need to double check all your fuel connections.

As for the petrol stain - remember, due to unpredictable air flow/turbulence, within the cowling, leaks/stains can show up at a distant point from the source.

Thanks ,

I guess the next test will be to do a  run up with the fuel boost on , I’ll use a go pro so I don’t have to get close to the prop 

Although you said that you have checked the fuel system, I suggest that you pressurize the fuel system with the auxiliary fuel pump ON (I.e., electric pump if so equipped) with the aircraft on the ground and the engine not running.  Look for any fuel leaks or seepage at connections, float bowl gaskets, carb vents, etc.  It doesn't take much fuel seepage to be create an odor (fuel or otherwise).  You can use some dry spray-on foot powder or thin tissue to help identify the leak site.  My money is on overweight floats, sticking floats, or defective/obstructed float valve causing excess fuel to exit out the vent line.

ps -- Depending on your type of aircraft and the location of its fuel tank vents, you might be smelling fuel venting from fuel tank vents?  An unbalanced engine (e.g., poorly synced carbs) could also cause fuel to splash around inside the carbs and flow out the vents.