95 F250 backfeeding gas to the rear tank

I'm gonna buy this truck from my wifes nephew. He had the fornt tank replaced, and always just kept 20 miles worth in the rear tank in case he ran out. I found out how low he left it when I started driving it and had to use it up, and put another few gallons in at the station. It had a leak about 1/4 way up, now it's at the bottom too so I ran it dry and was just using the front tank. Now every now & then I notice gas running out of the back tank so I'll switch to that tank and drive for 20-40 miles before it'll start chugging again, and then after another day driving on the front tank it'll be leaking out the back again.

Where would the problem be? I plan to replace the rear tank as well, but I'm just wondering what else I need to do or have done?

It also needs ball joints in the front and probably a few other components, which will slowly get taken care of as I can afford them. First, I gotta get the title from his girlfriends dad (he's in the Navy now, and down in Florida) and get it switched over to my name, transfer the insurance from my old truck, etc...

BTW- Anybody need a 4.9 w/ Mazda 5 speed out of an 89 F150? It's a 2wd truck w/ around 200,000 on original engine, trans, and clutch. Engine would need at the least some bearings. KNocks and low oil pressure unless you run 15-40 in it.

The rest of that truck is shot.

Donovan from Wisconsin

I am guessing some one has switched the return lines. You are running out of one tank, but the fuel that is not be used is returning to the other tank. The return fuel should be going back into the same tank you are on. This happened to me in a Brand New 1984 F350 Diesel.

Don,
Ford had problems with that, their solution was to put one way check valves in line.There was a later improvement,but off the top of my head I can't remember what it was. The valves stopped the backfeed to the non used tank. Have a 92 and that was done when I got it,so didn't have to worry about it. Just changed the tanks to the poly type so I didn't have to worry about rusting out again.Shame they didn't think about it when they built it,but you know the story.Keeps returning customer base coming back for more.lol
LOU

There was a common problem with that on that era of Ford trucks. the fix is putting a check valve in one of the lines on the rear tank.

This is why I had to stay at a motel for the FENA meet, rather than my '88 Ford E150 campervan.
A neighbor and his dorf addicted uncle are working on it as we speak.
They are rarely confused, they are very confused. Seems a poorly designed experiment at best.
I had to quit using it because the front tank constantly overflowed- dangerous situation eh? Then I removed the front tank altogether... now, it quits when it feels like it for as long as it feels like it.
They are re-inventing the spin on filter,that is where the pressures drop, before the high pressure pump.
While we are taking a day to get back to it... I am thinking what people told me in passing... one tank is for driving, one just for a pinch... front or back is main? Daydreaming this.... rear tank full, front tank full. Use front tank until nearly empty... because with the return line from the injectors constantly coming back in, if it already has a lot in there, it will overflow out the filler etc. But then, the rear tank will drain faster, because the return doesn't seem to go there.... so the excess is refilling the front-main tank... so now you got to flip the switch and pray for a gas station soon...now there is just 'some' in each???
this is like a history lesson??? Amelia Aerhart getting lost cause she didn't switch wing tanks on time? ... oh come on! This is a poster child for buying Japanese in 1989 ....

Easy fix- the check valves in the fuel pumps go bad. Just put in-line check valves in both supply lines and you"re done.

In that era, Dorf had a low pressure pump in each tank and a high pressure pump in the frame rail AND a proprietary doomaphagee that was to determine where the return fuel went. (Which did NOT always work out well.)

Unless you like spending $$$$$$ and enjoying MISERY RUN, do not WALK away from that vehicle!

Each tank has a check valve in the line on my 96.I replaced both tanks.If I run on the rear tank the front tank gains fuel.That means the front tank check valve is leaking back.I use the rear tank as a reserve most of the time.Leaving alky gas sit in the rear tank for a long time may cause trouble so I switch between tanks.The fuel lines look expensive so replacing them doesnt make sense.The fuel system in these trucks prove Ford engineers are idiots.Take a close look at the cross member just forward or the rear tank.Mine was rusted thin.The fuel and gauge lines lay on top of the sharp edge.Ford put a bit of plastic tape on the cross member.Nice places for sparks with a leaky gas tank.You cant buy a new cross member and junk yards want 50 bucks for one that looks the same as my original.I made one with steel I had on hand.Change the rear tank fast.Take a close look at the spring hangers and spring shackles and the chassis from the cab to the rear bumper before you spend more money on that truck.

I have the diesel version of that truck (95 F250). Mine doesn't have that probelm, yet, but i am expecting it. Friend with the same truck and same problem found it was the tank switch. Seems part of the switch fails and the return lines all dump into the rear tank. Mine has 240K+ on it and runs like a champ.

Don, each tank has a fuel pump. Each fuel pump has a shuttle
valve. The idea is that the tank and pump supplying fuel forces
on the shuttle and allows return fuel back into the tank it came
from. Without fuel pressure coming out of the tank return fuel
would not be allowed into the tank. If the shuttle seizes up you
have this problem.
Later Bob

You need base part Number 9J274 valve kit.
The are pricey & come in a package of 2, one
for each pressure line.. It's just a one way
check valve. I not at the at work but I think
the Part Number your looking for is 1L3Z-
9J274AA.

That was a common problem that I saw a lot (as a cert mechanic in those days) and it even happened to my twin tank van. Never fixed one because it was a factory recall and they fixed mine and all the others for free. You might want to check into it.

Jim

been a couple of years ago, but ford still honored a no charge repair on neighbors truck, cause it was a safety recall.

no that was 87-89 only that had the frame rail pump. 90 and up had the hig pressure pump that was in the tank.

and this is a very common problem for these trucks. search the ford truck forums they have lots of posts with answers with this problem

(quoted from post at 08:43:07 08/28/13) That was a common problem that I saw a lot (as a cert mechanic in those days) and it even happened to my twin tank van. Never fixed one because it was a factory recall and they fixed mine and all the others for free. You might want to check into it.

Jim

Click to expand...

(quoted from post at 10:51:54 08/28/13) been a couple of years ago, but ford still honored a no charge repair on neighbors truck, cause it was a safety recall.

Click to expand...

Yep, a guy here had one fixed by the dealer not long ago, no charge.