Apologies if I’ve missed a forum that captures my situation, but I have yet to find one just like my situation. I have a 1993 F350 Crew cab long bed with a 7.5l gasser. The problem I’m having is that the rear tank fills the front tank. I know the main issue is a faulty check valve in the front tank, but I’ve very recently replaced both tanks’ pumps and still having the same issue. I even replaced the front one again a few days ago thinking maybe I got a dud on the last one.

My question is this, is there anything else besides the check valve that would cause this to happen? I know there’s a shuttle valve for the return line, could that be faulty or do I have the worst luck with getting faulty check valves with new pumps?

Not sure if this helps somehow, but the fuel gauge when using my rear tank shows over full for a few minutes then finally starts to register the right amount.

Thanks in advance

 

I need some addl info from you.
When you state you replaced the front tank pumps,did you replace only the pump or the entire module?
If you only replaced the pump , that could be why you still have the problem. You need to replace the entire front fuel pump module assy .
Which did you do, and if I might ask, where did you purchase the replacement parts,,,,,,,,,,,,,,,,,,,,,,you know where this is going !

 

I replaced the entire FDM. To be clear I didn’t replace the rest of the housing cause as far as I can tell the rest of the assembly is just the wiring connection and metal fuel lines that plug into the FDM. I could be missing something about it though aka if there’s some hidden check valve built into the tubing. I bought the FDM at Autozone. I didn’t get the best one, but I’ve used different parts from that manufacturer with good results.

I read about the recall for these 1993 trucks and wondering if I might have a bad fuel pressure regulator that keeps blowing the check valves cause it allows too much pressure. Could this be the issue? I’m going to test the fuel pressure this weekend, but until then just speculation I guess. Just trying to rule things out.

Also I do still have the last fuel pump that was new, but just replaced thinking I got a dud. Can I put an air hose to the high pressure line and if it holds then my check valve is good?

thanks

 

To be clear,
There is a FDM Fuel pump driver module
AND a fuel pump module assy , has the fuel gauge as part of it.
Which did you replace and there are internal check valves, but there is a switching valve assy attached to the frame that when one tank is sending fuel the switching valve blocks off the other tank internally..

 

I replaced the pump assembly which has the internal check and shuttle valves (see attached pic). I kept the original fuel gauge float assembly.
I don’t have the selector valve on the frame, it’s just controlled by the selector switch on the dash. I believe they did away with those pre-90’s, but either way no selector valve on the truck.