Try leaving your fuel tank cover off just in case you have a vaccum. Simple and eliminates that possibility although it's not likely. Tom's suggestion two posts earlier is more in line. The check is when pumping the pump no fuel should be coming out there. If there is quite a bit leaking out certainly replace the hand pump. If fuel leaks out air can leak in. It's less than 20.00 for the new improved type if test indicates it is required.