Abstract: A method for feeding fuel in a fuel system is disclosed in its most preferred form utilizing a device including a valve stem which is reciprocally received through a bore in a foam rubber ball. The valve stem includes a plate which may be pulled against the ball to seal the valve stem in the bore. The ball is of solid cross section and has a size for overfitting and abutting with the fill opening of a fuel tank. The ball is deformable to conform to the perimeter of the fill opening for sealingly engaging the perimeter of the fill opening and has a firmness for transmitting a force applied to the ball in the direction of the fill opening into a sealing force applied by the ball to the fill opening to balance opposing forces created by the introduction of air pressure into the fuel tank through the valve stem and for allowing an excessive air pressure to escape from the fill opening around the ball.