I have a 1993 f250 long bed with a 460, when I got it I replaced the front fuel pump because it was bad. Recently my rear gas tank started leaking out of the gas cap and I replaced the rear fuel pump to see if that would fix it. At first it was still leaking but that was because I didn’t seal the pump properly, so now I just dropped the tank again and resealed the pump properly but when I turned it on (running off the front tank and the rear tank is completely empty) it started SPEWING gas everywhere out of the rear tank. I’ve heard it could be the fuel tank selector valve but I looked under the truck and can’t find anything like that so I don’t even know if my truck has that part. But even if it is that and I just missed it, I’m still confused why it’s leaking because the rear tank is 100% empty and sealed. Any suggestions? Any advice is helpful at this point.

 

Hi Nathan,
So we are are on the same page,,,,,,,,,,,,,,, there is usually a locking ring that holds the fuel pump and sending unit in place on the tank.
There is supposed to be a rubber ring between the tank and the sending unit. That is what seals the pump and sending unit to prevent fuel from leaking out.
If the lines are not connected all the way to the unit that could be what might be leaking. Can you see exactly where the fuel is coming out?

Need to take things one at a time so we don't overlook anything. Are you OK with this ?

 

I can’t tell exactly where it’s leaking from but the rubber seal is in the the lock ring is nice and tight. I plan on taking the bed off to really see what’s going on

 

Taking the bed off is a lot of work and may need new insulators.
If you lower the tank , not completely, you might be able to see with a flashlight and small mirror.

There are other considerations, but is the rear tank overfilling ?