1996 Ford f250 with a 351W gasser. Less than a year ago the rear in take fuel pump went out, so I replaced it with a new one. It worked great for a while then a few months ago it stopped working again. The truck was down for a little while for a new crate engine and some minor body work. That work included pulling the bed off the frame. Some time after that it stopped working again. Yesterday I pulled the bed and checked all made sure it was plugged in. I then went ahead and installed another brand new in tank fuel pump. And, it still no work. The switch appears to work fine. The truck will run on the front tank but when I hit the switch it sputters and dies. What should I look for? Does the rear pump have a separate relay or fuse? What else could cause this problem? I am on a tight dead line this truck has to be on the road heading south in a day.