"Cut it off at the source" is excellent advice.
This spring the smell of gas was driving me nuts camping with my gf at the Grand Canyon. There were at least two sources : 1) I had purchased a new filler cap from W&N but it fit so tightly that I was not closing it all the way. Making the effort to do so helped. 2) I removed the gas tank cover in order to verify that the fuel line to the sender was good: I replaced it. Then I noticed that if I pushed down on the center of the gas tank, there was air escaping from the seal where around the top of the sender where it contacts the gas tank : I could hear it. I removed the sender and put "the right stuff" gasket sealer on the round rubber gasket that seals the interface between the sender and the tank. I don't think that it is an 0 ring, it had a rectangular profile if I remember correctly, and I'm pretty sure that it was original -- When I pushed down on the tank I could no longer hear air escaping but I noticed that the metal of the tank surrounding the sender sort of glistened when I pushed down. Air/vapor was till escaping. I was in a hurry to get this fixed, camping in the middle of the Navajo res, at Canyon de Chelly, so I went the Hack Mechanic kluge route. I found a hardware store and purchased a round shower rubber drain gasket that was just a bit larger in diameter than the original gasket. I removed the sender, cleaned the gasket and the surfaces, layed a new layer of "The Right Stuff'" around the hole where the sender goes into the tank and round the sender surface, and put it sender back through the two concentric gaskets. That sealed it so that nothing escaped. I've been meaning to get a new gasket and do this the way it should be done on a 35k car going up 5% a year, but the kluge is holding up. Will the concour's judges deduct points ?
John in Montreal