Hello. My grandfather has a 1996 Ford F-150, and he's asked for my internet assistance. He's having trouble with his two fuel tanks. He says he'll fill up both tanks, front and rear. He'd select the rear tank fine, but when he selects to have fuel from the front tank, the car dies. He says there's two versions of the truck, one with plastic tanks and fuel pumps in the tanks, and one with metal tanks with the fuel pumps on the fuel lines. He has the latter, with the pumps on the fuel lines. It's fuel injected. There's no problem with the fuse he says, but i'm wondering if anybody has any ideas? Thanks.