I own a '91 Ford F150, 4.9 liter with duel tanks. If my front tank fuel pump went out would that cause the back tank to flow into the front tank therefore causing it to overflow? If so, will replacing the front tank fuel pump solve this problem?

 

I have a 96 XLT with the 4.9L 300 with dual tanks. I've always suspected my front pump is bad. I occassionally have problems starting the truck when I'm on my front tank, switching to the rear starts me right up, then while driving switching to the front makes the truck stall and sputter until enough fuel is pushed to the engine.

But, I also have the problem of the "magical transferring fuel syndrome."

I will top off both tanks, drive the front empty, drive the rear to almost empty, switch to the front and have half a tank. I have no idea why.

And I really don't know if a new pump will fix your problem of "back flow", which should be "front flow", but just wanted to know that you're not alone with this problem.

n

 

There are two possible reasons for crossflow between tanks: a defective diaphragm in the dual tank selector valve or a defective check valve in the pump unit in the fuel receiving tank.
kfrazier: Can't help you on the pump problem. I wouldn't know if the check valve would still work without the pump. I know it's one, non-serviceable unit, but I haven't taken mine out yet.


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1988 F-150, V8, 5.0L (302ci), 5spd, SuperCab. Shorty headers, K&N filter, MSD 6a ignition, Accell 300 8.8mm race wires, Accell supercoil, Accell rotor+cap, Bosch +4 Platinum plugs, RanchHand bumper. Soon: Dual exhaust.
http://brembs.net/cars/FordPU.html

 

I just purchased a 94 F150 with dual tanks. The previous owner mentioned that I should not fill the rear tank because it will automatically transfer all the fuel to the front tank. Aparently regardless if the front tank has gas in it or not. If the front tank has fuel in it, the excess will spill out of the filler neck. I have read a lot of posts here about various dual tank problems. This post seems to be the closest to my problem. What is the problem? Is it the front or rear fuel pump? Switch? Did you ever get the problem fixed?

 

Hey U guys - I fixed my problem with these darn tanks...

I replaced the rear pump and dropped the front tank.

After dropping the front, I removed the pump but left the metal hose assembly installed plugged up with clamped on aftermarket fuel lines from inside then shoved a bolt in each supply and return and clampped the hose on the bolt!!!

Voila! One less tank to fill and no more gas rain on tailgatters!
Plus, The truck seems to have alot more power??? Most likely because the pressure is higher at the injectors now...

BTW. I have a 93 f150 str6 Auto - Duel Tank Hell!

I have a better Idea later to try when I have some more money..

Here it is

Drop the front again but where the fuel lines connect to the pressure fittings I would like to install an "IN-LINE CHECK VALVE"

Basically I would be adding another check valve to all four hoses in the tanks but the back and front flow problems shold cease!

If anyone knows if there is such a upgrade please let me know..
mdudik(No Email Addresses In Posts!)

If no upgrade I intend to have these short check valve hoses made.

 

I don't fully understand what you did. You simply plugged all the lines with bolts? Which means you don't use the tank anymore? Or have you connected the tanks so that the pump in the rear tank also pulls fuel from the front tank, making it one big tank?

 

There have been three recalls associated with this problem, NHTSA numbers 93V125000, 94V169000 and 00V424000. You can check them out by clicking on "Recalls/TSBs" in the right-hand column of this page and following the links. The upshot is that you should be able to have the repairs made by your dealer for free.

Regards,
Bob P.

 

It generally means the check valve in the tank that overflows is bad. The check valve is a built-in, non-serviceable part of that in-tank fuel pump. But changing your pump is not hard. An aftermarket pump will cost you about $200, and it takes about 2 hours of your time. I dropped my rear tank to change the pump there and found out what a hassle that is. So I just pulled the bed off instead when I had to do the front pump. Take off the bed bolts and tailgate, loosen the clamps on both the fuel filler hoses, and disconnect the tail-lights and put the wires out of the way. Now you and a friend can stand at each wheel well and lift and scoot the bed back to gain access to the front tank/pump. Don't even have to take the bed off the frame unless you just want to. After you do this the pump swap is easy. Ford did a safety recall/refit for this problem and last July sent out a refund/recall letter on it. I managed to collect for the cost of replacing my front fuel pump, but it took several weeks, a nasty letter to Ford corporate and a lot of frustration. Their people handling the recall/refund in the field don't seem to understand that the failed check valves in the pumps can cause this problem. Anyway, good luck changing out your front pump...and hope you have good dealings with Ford if you go the recall route.

 

Those pump/sending units seem to be a really bad design! I'm going to try to find one at a wrecker (only the sending unit or floater is bad on mine). What year would fit in my truck? I know my 88 is in the 87-91 lineage, but would newer ones fit, too? Until what year?