[john walker's workshop]

the area under the cap would be full of fuel normally, being that the pump is filling it with fuel, and the bowl is full and the float valve won't let anymore in.. if the cap leaks it's not tight enough or the sealing ring is damaged, being that the fuel is under some pressure. and pump covers warp at the corners, so everything is normal. you might need a fresh diaphram if it's torn or separating. be careful not to fold it anywhere when you reinstall the pump cover. fix the issues and you're off.