Please move if incorrect forum- If there is an old F250 or fuel system forum, I missed it.

My '88 efi F250 draws fuel only from the front tank. When I flip the dash switch to the rear tank, the gauge goes to empty- even though the tank is full- and the pump continues to draw from the front tank.
From the Haynes manual I picked up, it looks like this model has a single, frame-mounted pump and a "fuel tank selector" to vary the tank drawn from.

Did a search and it looks like dual tank issues are fairly common. There are separate in-tank sending units, and there are check valves to prevent one tank from filling the other.

So, it appears I may have two problems: a bad sending unit and tank selector. Since the front tank empties regardless of switch position and the fuel guage registers differently, am I correct in assuming I don't have a check valve, dash switch or some sort of relay causing one or both problems?

Also (and here's the bigger reason for this post), if the tank selector is bad, what's my best bet for replacing it? The manual states it's not serviceable and the parts stores I've called don't carry it. Not crazy about going to the dealer or buying a 15 year old used part. Has anyone found a cheaper alternative for a new or remanufactured one?

Brock

 

I've seen it posted several times that the valve is a dealer-only item.

As for the sending unit, replace the valve first, and see if it fixes the problem. You may or may not have to drop the tank. Or you can do what I did - drive it on the tank that doesn't read until it dies, then flip it over to the one where the gauge works.

 

Hi! I had the same problem with my 88 F150. It actually has three fuel pumps-one in each tank and one on the frame. The pump in the tank pushes fuel to the selector valve on the frame which operates by fuel pressure and closes off the tank that is not being used.The fuel then goes to the pump on the frame which increases the pressure and pumps fuel to the motor.If the pump in the tank (the rear tank in my case)doesn't work it will not send the pressure to the selector valve to switch tanks! The pump on the frame can still draw fuel from the front tank since the valve is still open.So even though I was switching tanks at the selector switch on the dash- I was still drawing fuel from the front tank.Since your guage goes to empty when you switch tanks- I would first check to see if the wire harness is tight on top of your tank and check to see if the ground wire from the harness has a good connection to the frame, and check for power to the pump.

 

Call around to smaller Ford dealers and ask if you can get for the best price. Net price should be about $65.00. Also if you unscrew the bottom of your old fuel selector valve you should find a couple of 1/4" black o rings. If you find them at the bottom, then you know it's bad. Same thing happened on mine, there's not much more it could be besides that selector valve. You may have other problems to, with your rear tank. Its easy to replace, two 10 mm bolts and 6 fuel lines. relieve the fuel pressure first. You may want to pick up two bolts, both of mine brock off, with it being rusted.

 

Thanks for the replies!

I looked a little closer last night and re-read the Haynes manual. It appears I do have the 3-pump setup. So, two more questions:

First, if I unscrew the bottom of the selector valve as you suggest, Mike, will it damage it? I would assume not, so perhaps a better question is, why does a non-serviceable unit come apart? Is there a filter inside? If so, I'll want to replace it at the same time.

Second (or fourth, I guess), there is a test procedure in the manual using compressed air to test the valve. But since the fuel gauge doesn't read, and I have the selector valve with no electronics, I suspect the rear pump. I'd like to test it first. The in-tank pumps apparently only run when that tank is selected (this makes sense). I'm thinking about disconnecting the lines from the rear tank at the valve, switching to the rear tank, and turning the key on. The system should prime and fuel should run out of the line if the back pump is working. Correct?

Maybe I'll get lucky and my initial guess is correct. The valve is hella easier to get to, and I don't care much about the fuel gauge as long as the front tank works.

Brock