I just got this truck and it has fuel issues. First of all it has 2 tanks. The smaller front tank leaks. When I put gas in the rear tank which seems to not leak it somehow makes it way to the front tank and leak out. My question is what are my options? Can I eliminate something to only use 1 tank? Im trying to do this as cost efficient as possible. Im going to need a front tank, where would be a good place to look for a platic tank? Any advice you guys can give me would be great. I did alot of searching and found some info but not much.

Thanks guys!
-Justin

 

You have a bad selector valve on the frame, it has shaft "O" rings in it that are stuck on the shaft.
Struck "O" ring:
http://i54.photobucket.com/albums/g91/subford/Fuel/DSC02400.jpg

Some 88 photos and diagrams.
Fuel System Diagrams for the 88 F series:

Electrical:
http://i54.photobucket.com/albums/g91/subford/Fuel/fuel-sel1987-89FSeries.gif

Mechanical
http://i54.photobucket.com/albums/g91/subford/Fuel/88Fuelsystem.gif

Selector Valve 1:
http://i54.photobucket.com/albums/g91/subford/Fuel/dfres.gif

Selector Valve 2:
http://i54.photobucket.com/albums/g91/subford/Fuel/FuelRes1.gif

Selector Valve 3:
http://i54.photobucket.com/albums/g91/subford/Fuel/FUELRES2.gif

Selector Valve 4:
http://i54.photobucket.com/albums/g91/subford/Fuel/Fuelselectorvalve.jpg

In Tank Fuel Pump:
http://i54.photobucket.com/albums/g91/subford/Fuel/1989FuelPump2.jpg

High Pressure Fuel Pump + Filter:
http://i54.photobucket.com/albums/g91/subford/Fuel/FuelPumpFilter88.jpg

Fuel Pressure Regulator:
http://i54.photobucket.com/albums/g91/subford/Fuel/fpr02.gif

Fuel Manifold:
http://i54.photobucket.com/albums/g91/subford/Fuel/Fuelmanifold.jpg

Fuel Pumps test ground at the Test Connector:
http://i54.photobucket.com/albums/g91/subford/Fuel/DataLinkConn.jpg

Inertia switch location 87-89:
http://i54.photobucket.com/albums/g91/subford/Fuel/1989InertiaSwLocation.gif

 

Is this something I can fix, or is it something that just needs to be replaced? Are they expensive?

 

Most of the guys just replace it but I had to know what made the fuel go to the front.
If you look at the first link above the bottom "O" is for the rear tank the top "O" ring is for the front tank.
As you can see the front "O" gets stuck on the shaft from non switching for a while and there is no way to free it without tearing the valve apart and most do not want to do that. I do not know where you can get a set of "O" rings to repair it.
You would have to special order it from your Ford guy as auto parts stores do have them. They are about $110.00 I think.

 

is there a picture of what the actual part looks like? does it have a pigtail of wires on it?

 

There are no wires on the selector valve, just hoses. There are photos of it above the links I posted.

 

Is there a way to by pass the valve and just use the bigger rear tank?

 

I just called my buddy up at autozone. I aksed him if he could get the selector valve. He use to be a Ford tech until he hurt his back. Anyhow, he says they can get a "universal" one for 49 bucks. Has anyone used one of those before? Like I said, is there a way to just bypass this?

 

http://www.directfordparts.com is a sponsor of this forum and sells the selector valve for around $55.00 plus shipping.

F1UZ-9B263-B

The front tank should be larger than the rear tank by a couple gallons.

I had a problem like you describe on my 88. Some of the return fuel was being dumped back into the wrong tank. I purchased the selector valve and installed it but the problem didn't change. Ended up being a weak in tank pump. I know that doesn't seem logical but that's what cured my problem.

The only explanation I can think of is the valves in the selector valve weren't completely switching due to weak fuel pressure from the defective fuel pump.

 

Well 55 is much better that 110. Where is the valve located? Do I have to drop the rear tank to see it? I got under the truck tonight but couldnt find it. when I did some inspecting of the side gas tank I noticed the sending unit looks brand new. All gold and shiney, the complete opposite of the truck. It stuck out like a sore thumb.

 

Click on the links provided and you'll see what the selector valve looks like.
It's black and round and mounted a little bit forward towards the middle of the inside driver side frame rail.

It has 4 input lines. 2 from each tank (an input from the in tank pump and the return line.) The front of the selector valve has a output that goes to the high pressure fuel pump mounted on the driveside frame rail and a line coming back which is the return line.

To remove the hoses, you pry up on the plastic clip half way and the hose should pull off. To reinstall the hose, push the clip back down and push the hose back on. If you break a clip, they sell them at Pep Boys and I think Autozone. **Note: There are two different size clips used.

As was mentioned. The selector valve is mechanical. The fuel pressure from the intank pump is what moves the valves inside the selector valve.