I have a 1990 F150 with two gas tanks... I have started to use the rear gas tank instead of using the front one. The rear gas tank has only been used once in a while.

Whenever I switch to the rear tank, I notice a performance difference in acceleration response time. Could this be from a dirty tank and lines, or could it be somthing else, like a fuel pump that's on its last legs?

Randall Clark

 

Having gone unused, anything is possible, but I would suspect the valve is not switching fully. Try measuring the volume from the front and rear tanks before the valve. If there is a noticeable difference, then I would say the pump, if not, it's the valve.

 

Sounds like a problem I was having with my 1989 F150 .
It was real pigged out when I ran it on the front pump so I use the rear and dont worry about the front!
I feel that the intank pum is not putting out enough volume for the engine to make the power it should .
I would replace the intank pump and be sure to clean out the tank and replace the fuel filter!