Alright all, here’s a bit of a puzzle to me. I have a 1995 F150 5.8 Eddie Bauer. Both tanks “work” (except for this issue) and both pumps were replaced last year. I recently filled both, as I usually do, and I usually use the rear to a 1/4 then switch. Well in the process of a week or so driving my gauge (which is accurate for both tanks) would go down while driving (like normal) then next time I drove the vehicle even if just sitting for a few hours, it would indicate higher than it was when I shut it off, like an 1/8 of a tank more. Eventually it got down to a 1/4 tank, I switched to the front, and it was indicating empty. I figured it might be a gauge issue, so I ran with it and it died on me, empty tank. Switched back to rear, which indicated higher than the 1/4 tank it was just a few minutes ago, and it ran fine. Overall the rear tank alone did like 250 miles, so clearly it was feeding off the front tank also.

So front tank is filling rear tank when rear tank is selected and rear pump is running.

I also have a rough idle and laggy acceleration ( but this is most likely a vacuum leak from the EGR that I am working on) and a noticeable smell of gas.

Any help is appreciated. Deleting tanks is not my preferred option.

 

It’s a bad check valve in the pump assembly. You can add these and it should stop. If you have a lifetime warranty on pump, swap it. That’s a 50/50 crap shot it don’t blow again. Mine did the next day.. if your rear is the one filling, I belong it’s the rear that needs to be changed. Someone wiser will come in on that hopefully.

 

Those are what you need 2 of, one on each supply (pressure) line on the pumps
The short ones are for the plastic lines with a removable clip to remove
The long ones are for the metal lines with the internal release clip
If you put a short one on a metal line, you'll have trouble. You will have a real hard time ever getting it off again (no room for the tool to be inserted)
Glad they are making them again, not happy about the price
I still search every Ford at the junkyard I see from 93 to 95 or 96 for used ones that are still good

 

you said those (or the ones 90project5.0 posted) go on the pressure line? Just checking because the ones he sent from Amazon are labeled “return”.

 

His set, which you will only find in a junkyard, went on supply and return lines. They are obsolete. The return side is what causes the cross flow usually. You put one on each tank.

 

That's Amazon for you
They go on the pressure side
Also
They are 3/8 and the return is 5/16

 

My return is 3/8, not 5/16.
None aftermarket sell the supply side.

 

If you want to try just on one tank…

https://www.ebay.com/itm/28722595396...7XE2ZW4BWG0SJ0

 

You better check that again
You have one big one and 1 small one on the tank and they are 3/8 and 5/16
You will see the big one squirt pressure (supply) and it's the 3/8 one

 

I know I bought 5/16 fuel injection hose for my supply line and that’s what’s on it. It wasn’t over extended putting it on there. Prior to that, i found a patch job on the plastic line that failed. A 5/16” compression line fitting is what I used to fix it.

 

Fuel filter inlet is 5/16” as well.