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1991 Ford club wagon fuel system

I am having an issue with by club wagon and am looking for some suggestion. I have tried taking this to a local ford dealer, but if you can’t plug something into it that tells you what is wrong and how to fix it…they are lost.

This vehicle has dual tanks. The front tank doesn’t work (and never has since I purchased it a couple of years ago…bad fuel pump I am guessing}.

A couple of months ago the fuel pump went out on the rear tank and I had it replaced. I now have a peculiar problem. Fuel is coming out of the front tank fill spout when the engine is running. There seems to be a tremendous amount of pressure building up in the front tank…even though I am not using it. I would seem as though fuel is being pumped out of the rear tank and into the front tank to a certain pressure point, and then on to the engine. One solution would seem to be to remove the front tank completely from the system, but I don’t know how to do that, or if it should be done. After driving and coming to a stop, fuel is pouring out through the gas cap on the front tank. I. Don’t need to use the front tank as I am just using this as a work truck.

Any ideas would be appreciated.

It sounds like the dual function reservoir is leaking. This contain the switching valve for the fuel tanks. If the dual function reservoir leaks internally the fuel pressure from one tank could enter the other or the pressure return from the engine could go to the wrong tank.

The dual function reservoir replaces the six port selector valve, used on earlier models. The dual function reservoir switches the tank from which the engine draws fuel mechanically, instead of electrically.
The dual function reservoir operates as follows:
Fuel pressure created by the selected in-tank fuel pump exerts force on a 3 inch fluoro-silicon diaphragm which is in turn connected to a T-bar and two shafts. This force moves the valve shaft, simultaneously opening and closing supply and return ports. When the alternate fuel tank is selected, pressure is exerted on the opposite side of the diaphragm, moving the valve shafts to open the alternate fuel tank ports.

It’s a fairly easy job to isolate the front fuel tank from the rear tank. I’ve done this a couple of times in the past. Once on a dual tank pickup truck and once on a motor home on the side of the road. It cost less than $50 to accomplish the task on either vehicle. Find a good independent mechanic and they will solve your problem.

Suggest to carry a fire extinguisher until this is resolved.

That truck has a fuel pressure relief valve at the engine that dumps excess pressure back to the tank that is feeding the engine. The diverter valves switches the pressurized fuel supply from one tank to the other and also switches the return hose to the proper tank. If the return diverter gets stuck on one tank or bleeds over from one port to the other fuel will dump into the unused tank and could become highly pressurized. As @missileman suggested a good independent shop should eliminate the diverter altogether and make it safe to operate on one tank, hopefully it is the larger one.

And what a coincidence. That F-150 that I junked out last month had dual tanks and everything was working like new. The valve is quite accessible and simple to remove. Oh well, My neighbors would complain if I start hoarding again.