I have a 1988 f250 with the 302 engine and dual tanks. The rear is filling up the front. I have read some of the topic questions and i believe it says the main pump has two valve to direct the return and that one is stuck open or the oring is bad. Can you find the seals at a parts store or are they a ford item only? The front tank hasn't worked for quite a while even thoug it sounds like it is pumping. Will run about 10 to 15 minutes and then die, switch it to the rear and it fires up and will run just fine. One other problem is the gas that is coming out the front smells bad but most of it is new gas as it only has less than a quarter of a tank when I quit using it about a year ago. I really have nowhere to get rid of it, can I put stabilizer in it and use it over? Am I right in my understanding of the pump and valves?

 

I might be wrong here - different years have different setups... My 91 did this, and it was a bad fuel pump on the tank that was being filled. The valve/seal/whatchamacallit is internal in the pump assembly, so the whole front tank pump needed to be replaced.

Someone will chime in with accurate info for your year if it's different.

On the fuel thing, I wouldn't try to run year old fuel through my truck. And to swap the fuel pump you'll either need to drop the tank or remove the bed. To drop the tank, you'll want to siphon all the gas out first, or it'll weigh a ton... When I removed my front tank, I gathered up some fuel cans from a few friends/neighbors, and gave them a free fill up for their lawn mowers.

 

The '87-'89s have a different fuel system. According to Ymeski it's opposite on those trucks so the tank that doesn't get the fuel when it's supposed to has the weak pump. The rear pump isn't producing enough pressure to move the valve to return the fuel to the rear tank. Or I suppose the valve (dual function reservoir or DFR) could be bad. Me, I would fix the front tank pump and run the old gas. As a matter of fact, I still need to do that. Your truck has a frame mounted pump also so that's the pumping you hear when the front tank is selected.

 

I'm having the front tank feed my rear in my 88. I'm picking up a new valve for $78 from a buddy at a ford dealer this weekend. I'm not sure how these things work but is there a chance they could get stuck half way? I've gotten worse gas milage and my idle issue started around the time it went out.