I have an 88 f150 with duel fuel tanks. My front tank is constantly being refilled from the back tank to the point of overflowing. Any tech advice would be appreciated.

 

The check valve on the in-tank fuel pump in your front tank has failed and will need to be replaced.

I will tag @Steve83 and see if he can provide diagrams for repair.

 

On pre-'90 EFI trucks, it's a different system, and a different failure. It's the O-rings inside the DFR, which is explained in the captions of this album:


(phone app link)

 

^^^Crap I don't know how I missed it was 88 - this is why I tag you.

 

IDK what tagging is - I just browse the forums now & then, and look for threads I think I might help with.

 

You can tag a user by putting the @ in front of his/her name and it will send that user a PM - so if someone wants to get your attention you will receive a notification. I've done it with a few other users but it is still a new feature so they might be working out the bugs. See my first post in this thread where I tagged you. And this thread.

 

I probably have PMs turned off. They got abused on several forums I've used in the past, so I usually do that when I'm setting up my accounts now.

 

I have a newer truck but in my friend's 1996 f150 he has the same issue. We discovered it to be the fuel rail return which only vents to the 'main' tank. He discovered the issue since his front tank pump has failed and was only using the rear tank, and one day he looked in his mirror and saw fuel spraying from his front tank fill nozzle.