Tanks draining each other?

[vegas39]

Can the fuel tanks on our trucks drain off each other? My brother in law has an 86 and he says his rear tank was full yesterday and the front tank ran empty, he switched to the rear tank and today, the rear tank is bone dry and the front tank is full! Is it possible for the switching valve to go bad and do this kind of thing? He stopped this morning and topped up both tanks.

Update. He just called me back again and said he has fuel ******* out of his rear tank, says he cant even take the cap off, under pressure. He cant drive the truck, no matter what he switches the valve to, fuel is pouring out of the back tank. Thanks!!

 

[Wicked97]

Yes thats what happens when the switching valve goes bad.

 

[Mulochico]

That's exactly what mine started to do when the valve went bad.

 

[vegas39]

Well dang! It sounds like it's drawing fuel from one tank and the returning it to the other.

The real ***** is, now I have to get in my car and drive to frigin Utah and disco the fuel valve for him!

 

[icanfixall]

Sadly thats what has happened and... Filling both tanks was just adding to the problem. Changing tanks might solve the overfull tank but the switching valve needs to be repaired or replaced. It will be costly too if Ford is the only place that has one. Many auto parts stores have a generic replacement but from all the readings here its hell to install with the multibalr wire connections that needs to be matched up. You could just run either tank directly by bypassing the tank switching valve. Cutting off the lines and adding some 5/16 return line rubber hose and some 3/8 supply line will work but its only going to be for a one tank usegae. Plug off the other tanks lines at or near the switching valve too so that unused tank wont drain to the road.. Might be able to cut the lines farther from the switching valve in attempts of saving those fitting if you ever find a Ford replacement valve.

 

[vegas39]

Sadly thats what has happened and... Filling both tanks was just adding to the problem. Changing tanks might solve the overfull tank but the switching valve needs to be repaired or replaced. It will be costly too if Ford is the only place that has one. Many auto parts stores have a generic replacement but from all the readings here its hell to install with the multibalr wire connections that needs to be matched up. You could just run either tank directly by bypassing the tank switching valve. Cutting off the lines and adding some 5/16 return line rubber hose and some 3/8 supply line will work but its only going to be for a one tank usegae. Plug off the other tanks lines at or near the switching valve too so that unused tank wont drain to the road.. Might be able to cut the lines farther from the switching valve in attempts of saving those fitting if you ever find a Ford replacement valve.

Thanks Gary. I had to do the same thing on my truck right after I bought it. I've been running off my front tank only for the last four years.
He's just gonna have to deal with using one tank from now one, he doesnt travel with it anyway, just works in town with it.

 

[icanfixall]

Well kenny tell him how to cut and splice in some 5/16 and 3/8 fuel line rubber hose but do it away from the switching valve. Then all he needs to do is get a factory valve and a short length of hose and 4 clamps. then reconnect the lines and be done with it.. Caution is to be used with diesel fuel running down you arms.. It reall burn the underarm pits big.... I guess it wouldn't have hurt me so bad had I not just shaved my pits for the GMM model shots.... Oh... The cost of being famous all the time...

 

[92F350CC]

My switch has been bad ever since I bought the truck. I took it on a trip the first time I got it and noted that it had decent mileage.....but on the return trip it was terrible

While running on my rear tank, it will pump fuel into the front tank. This isn't a problem for me though, I just remember to run the front tank first, then the rear, and then the front again. The only time it ever overflows is if I run the rear tank while the front is full. With the price of fuel, it didn't take me more than once to learn not to do that. I would spend more on the valve than I will ever lose in fuel....so f*** it.

 

[79jasper]

Could also take the valve off and make sure nothing is blocking it. (Like a piece of broken shower head) But couldn't the return lines be put on backwards???

 

[icanfixall]

I don't feel anyone has worked on the fuel tank switching valve so I'm not seeing how any lines might be on the wrong sides. But it is a good question that has not been addressed...

 

[79jasper]

I don't feel anyone has worked on the fuel tank switching valve so I'm not seeing how any lines might be on the wrong sides. But it is a good question that has not been addressed...

He didn't state how long the bro in law had the truck so I wasn't sure.

 

[MIDNIGHT RIDER]

But couldn't the return lines be put on backwards???

That is my diagnosis.

I don't see it being mechanically possible for the valve to fail in such a way as to act as described.

It either switches BOTH the DRAW and RETURN as it should, or stays stuck with both DRAW and RETURN on one tank, or goes dead and defaults to center position = no tank.

I had so many electric valves to fail and cause me extreme grief that I will never trust an electric valve again; hence is why I run no-nonsense manual valves.