How is it wired ? When both batteries
are off and the key
Is also off the pump should still work you should have 2 one on the key the other always on wired directly to hot wire
Check your vent maybe blocked or the fill line is kinked or try putting a SMALL like 7/16 or 3/8 line down the fill line But don’t let it go in the fuel just to release air and try to put fuel if that works then you no it’s a vent problem