I went through two pumps on two combines this fall. Mine however would always run just not pump. I blamed it on the switch to B-2 Biodiesel and I think I am right. I changed more filters on more tractors this fall than I ever have before. But it sounds like to me you have a lousy ground. As close as the pump is to the Battery I would ground it direct back to the neg post on the battery and see what happens. Good luck I hope this helps. Will