While on a leasurely sight seeing trip along the Mississippi, fuel began pouring into the cockpit. It was not a drip. It was a flow. It hit my feet, soaking my Hush Puppies. The A&P at the our emergency landing field could find no leak. He suggested we try flying with the electric fuel pump off. Turning it on only to return the header to 80-90% full each time it registered 1/2 empty. The trick worked and we flew home. The first time the indicator said full (just about the same time we trimed out after the climb out) the leak started. Turning the pump off yielded an almost instantaeous halt to the leak.
My home field A&P can find NO leak. No bad fittings, no cracked lines, no split seams, holes, corrosion, nothing. A presuure test with a full tank was negative. We spent the morning today running high speed taxi tests up to take off speeds with the electric pump on and the header tank full. After twenty minutes we got nothing. I've had a fuel smell in the cockpit off and on for the past three years that no one could pin down. Flying home with the electric pump off, there was no fuel smell. During the high speed tests today there was a slight fuel smell. The problem flight was the first long flight I had made after installing a new header tank gas cap and gasket, the type with the glass covered fuel level indicator. The FBO owner and one of the most respected aviation old timers in the area, suspects the fuel pump is building up a pressure so that fuel is being forced out the vent hole in the front of the cap. In a hundred mile per hour wind stream, it is almost instantly forced down and under the cowling where it makes its way over and around the tank, eventually pouring over my feet. There is no doubt the flow stops immediately after the fuel pump is turned off. Does anyone have any ideas on how to proceed? Had a similar experience? The negative results from the pressure test have me stumped. Bert Hampton N99618 at 3K6
