Dual fuel tank problems
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Dual fuel tank problems
Have a 92 f150 inline six, with a fuel tank issue. The rear tank is pumping gas to the front tank at a rate of about 1/4 tank every 8 miles. Took the truck to the dealership and had a new check valve put in under a recall. Still having the same problems. Any ideas or suggestions as to what is going on with the rear tank would be greatly appreciated. 
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Joined: May 2002
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From: Broken Arrow, OK
Does the front pump still work properly? I'm not sure about the 92's, but some years have a fuel selector valve, others don't. On the ones that don't a bad fuel pump can allow flow between tanks.
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Think I got it figured out. Each pump has a shuttle valve that allows unused fuel to return to the tank only if that pump has power. The front tank shuttle valve is most likely stuck open and allowing fuel to be pumped into it. 
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Time for a new front fuel pump
Time for a new front fuel pump. Easiest way to gain access is to take tailgate off, disconnect fuel filler hoses, take out the bed bolts and lift the bed off or just slide it back until you can gain access to the top of the front tank. Takes two to lift the bed off, but only one BOB (big old boy, like me) to shift the bed backwards. Much easier that dropping the tank. The pump costs about $100, maybe less than that now and isn't hard to install. Did mine 2-3 years ago and no probs yet...other than a peeling factory paint job. Always wanted an appaloosa!
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I had the same exact problem and it was because the front fuel pump was bad and not holding pressure allowing for the crossflow to occur, I replaced the front fuel pump and it has fixed everything.
I left the bed on and just dropped the tank it was pretty easy, I had it done in 2 hours.
I left the bed on and just dropped the tank it was pretty easy, I had it done in 2 hours.
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Shuttle valves
Don't know about a 95, but on the 86-93's (I think) the shuttle valve is an integral part of each fuel pump in each tank. When they crap out, unburned fuel from the engine bypasses the tank it came from and should return to and gets pushed into the second tank...which can cause potentially dangerous overflow if that tank is pretty close to full. Quite a sight to look in the rear view and see your rear tank filler spewing gas down the road. Exciting too. I fixed mine by replacing both in-tank fuel pumps, just for good measure. Might be different on a 95 though, a dealer parts guy could probably tell you.
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From: Saddle Brook United State
Hi, your gas tank problem is a common one, there is a recall on it. You might even be able to get ford to fix it due to the fact yours is a 95. Now to the problem. The check valve in the pump in the tank that the gas goes into is bad allowing gas from the return line to go into that tank. There is a fix that doesn't involve a new $200 pump,If you can't get it fixed for free, Ford has inline check valves that install between the return line and the pump. You remove the return line from the pump and snap the check valve on and replace the return line , it will now go to the other end of the check valve. You have to go to a Ford dealer and get him to look up the check valves ( he won't want to do it but hound him, they were part of a kit) and do a search to find out if anyone in your area has one. If you have rubber arms you can do it with the tank in the truck, I had the tank out because of a leak and while I was putting the new tank back I added the check valve because I had the same problem as you and it fixed the problem.
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stractor
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From: Langhorne, PA
Make the dealer try again. I don't think they did it right, your problem is exactly what the recall was all about. I also have a 92 w/I6 and had the same exact problem. The dealer performed the recall repair and installed the new parts and it has worked fine for 6 years. I hope you get it fixed for free.
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When I first experience my crossflow problem I went to the dealership and had the recall repair done. Did not fix my problem. The check valve and the shuttle valve are two different valves within the pump. The check valve is replaceable and the shuttle is not, requiring a new pump. Both valves can produce the crossflow problem. From what I have read, if it is the check valve, then it is the pump that is in the tank which is pumping the gas into the other (which is usually the rear tank according to my local ford dealer). If it is the shuttle valve it is the pump in the tank in which the gas is getting pumped into. There is a nice picture of the inside guts of a pump in my Haynes repair manual. Here is another theory to this confusing problem.
http://www.misterfixit.com/dualtank.htm
http://www.misterfixit.com/dualtank.htm
Last edited by zerocash; Jul 17, 2004 at 10:01 PM.
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Here is anothr reply i found.
"Your problem is similar to the fuel cross flow problem on the 1990-93's with dual tanks. That safety recall fix didn't work well either. Problem is, Ford only has a 12/12 warranty on their recall fixes. I see that NHTSA is investigating this recall (90-93) because of so many complaints of ineffective repairs; and now customers have to pay for the correct fix, which is usually replacing one or both fuel pumps ($$$)"
"Your problem is similar to the fuel cross flow problem on the 1990-93's with dual tanks. That safety recall fix didn't work well either. Problem is, Ford only has a 12/12 warranty on their recall fixes. I see that NHTSA is investigating this recall (90-93) because of so many complaints of ineffective repairs; and now customers have to pay for the correct fix, which is usually replacing one or both fuel pumps ($$$)"
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From: kingman az
dual fuel tank question
i have a 86 f250 with a stock 19 gal tank.i put in a 50 gal bed tank but i dont want to put in a 100.00 selector valve.i want to run a metal line from the 50 gal to the stock tank all the emmission hoses have been un hooked.can i use the fuel return hose to pump from the 50 gal to the stock tank .i only get 10 mpg even with a good tuneup so i need the extra fuel.
thank you
lrd56
thank you
lrd56
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