My 1989 Homelite-Jacobsen mower with B&S 3.5 HP with vacuum-pulse carb leaks fuel out of the carb onto the top of the fuel tank when its not running. I think its haunted! It defies gravity as it will leak down a tank of gas as the mower sits in the shed but the gas is on the top of the tank - there is no leak in the tank. Do you think it could be the tank cap? Its just the standard original cap with no apparent obstructions. Years ago I had to put a diaphragm in it and it continues to start easily and runs like a new one. I'm just looking for ideas - I have to do something before the thing catches fire. I'd junk it but its in such great shape!

To re-cap, the tank top stays dry while its running. A few hours after turning it off the top of the tank will be wet even if there is not much fuel in it. This is how I know its somehow getting up the pick-up tubes and then to the outside of the carb.