My 89 F150 has an interesting gas gauge problem. When I got the truck the gauge was pinned full. Did research and found either shorted wire or open wire both answers. That was OK because I will just trouble shoot it. However I put in about 4 gallons recently from empty and it seems that the gauge is now moving beyond F, like F is it's starting point. I have an aftermarket gauge I am going to temporarily hook up. Anyone ever had this problem? I was thinking that maybe I got the wrong pump but with the old tank and pump I still showed F all the time. Thanks. Jim