Fuel Flow Between Tanks
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Fuel Flow Between Tanks
I have seen a couple other threads relating to this but they got so long I had a hard time sorting through them to find the pertinent info.
I have a '93 F150 351W with 73k original miles and dual tanks. When I ran the rear tank the return fuel kept overfilling the front tank but I didn't fix it. Now the front tank is overfilling the rear as well so I have to do something.
The check valve recall was already performed on my truck twice and I've replaced the fuel pressure regulator. I believe I need to replace the fuel pumps in both tanks but some posts have said replace the whole fuel delivery module, not just the pump. What is the difference?
Any help is greatly appreciated!
I have a '93 F150 351W with 73k original miles and dual tanks. When I ran the rear tank the return fuel kept overfilling the front tank but I didn't fix it. Now the front tank is overfilling the rear as well so I have to do something.
The check valve recall was already performed on my truck twice and I've replaced the fuel pressure regulator. I believe I need to replace the fuel pumps in both tanks but some posts have said replace the whole fuel delivery module, not just the pump. What is the difference?
Any help is greatly appreciated!
Lead Driver
Joined: Nov 2002
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From: Concord, NC
The fuel delivery module contains the fuel pump, shuttle valve assembly, and the fuel level sender. The shuttle valve assembly is what has failed, so the FDM needs to be replaced in both tanks.
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I can't seem to find anything by the name of FDM, is that all rolled into the pump? I see the pump, the hanger, and the float assembly.
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More specifically, I see the pump, sender(or hanger), float and strainer. Do I need to replace it all or just the pump?
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Lead Driver
Joined: Nov 2002
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From: Concord, NC
I haven't had one of these apart, but I think the shuttle valve is contained within the white plastic fuel pump assembly and not the hanger. I think the member "subford" has an exploded view of the shuttle valves somewhere.
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Here a couple pictures of an FDM which contains the pump and check valves, the fuel level sender(float) is attached to the outside of the FDM resovoir.
The check valves are contained in the piece at top left below and the actual pump is the steel cylinder top middle.
However when you buy a "pump" aftermarket you usually get the complete FDM with the resovoir that contains the check valves and a new pump.
The check valves are contained in the piece at top left below and the actual pump is the steel cylinder top middle.
However when you buy a "pump" aftermarket you usually get the complete FDM with the resovoir that contains the check valves and a new pump.
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Great! The pictures helped a ton.
How do I find out what size fuel tanks I have? When I look up these pumps even after narrowing it down by make/model/year there are still multiple different pumps for different tank sizes shown. I can't seem to find any markings on the tanks saying what their capacity is & when I used an online VIN decoder it just said fuel capacity is 34.7gal, not what the individual tank sizes are.
How do I find out what size fuel tanks I have? When I look up these pumps even after narrowing it down by make/model/year there are still multiple different pumps for different tank sizes shown. I can't seem to find any markings on the tanks saying what their capacity is & when I used an online VIN decoder it just said fuel capacity is 34.7gal, not what the individual tank sizes are.
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My truck is 4x4 with the super cab but I have a 17gal front and 18gal rear. I called the dealer today to verify before buying the pumps(I've been super busy and haven't had a chance)and they told me the sizes based on my VIN. Hopefully this weekend I can replace at least one of the pumps.
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I have had the cross flow problem with my gas tanks before and my issue has stopped. I haven't replaced a thing in the truck other then runnign some seafoam through both tanks a few times. That seemed to resolve my issue so far at least. Will this work on everyones truck I doubt it but it worked in mine.
Edit: I ran one full bottle per tank and I've never really filled the tanks on my truck as I don't really drive it all that much.
Edit: I ran one full bottle per tank and I've never really filled the tanks on my truck as I don't really drive it all that much.
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I replaced the rear fuel pump module and it appeared to solve the return from the front going to the back for a while but it's back to the same old problem again, $130 and a couple hours worth of work later. I think I'm just going to leave it, I don't know what else to do. Everyone says replace the fuel pump module because that's where the check valve is.
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