1.My rear tank fills my front tank, i have a 1994F150 duel tank 5.0 automatic

and

2. I have correct fuel pressure when truck is running with and without vac. line off or on FPR, but as soon as you shut the motor off it goes to zero in 1-2seconds

(i know FPR is good and the injectors are good)

3. I was just curious if anyone else had a fuel pressure problem along with a bad checkvalve, or checked there fuel pressure drop off rate when they had this condition

4. I searched this forum for two hours and know one else complained a bout a fuel pressure problem when they had there crossflow problem, they all acted like there truck always ran fine during all stages of driving. Does a bad Check Valve cause Fuel Pressure Problems

5. I think I have a bad check valve and weak fuel pump condition at the samt time, my truck bucks and falls on its face when cruising down highway when trying to give it a little gas, and when i take off from a stop light, but the truck runs fine when i give it 3/4 or full throttle.

I will being replace my front pump soon enough but I am just curious if in the end will it fix my fuel pressure problem to,

Let me know your experiences guys

Thanks Nate

 

I've never heard of the rear tank filling the front one. I'm not saying its never happened. I've just heard of the front tank fillin the rear. I'd check your fuel valve. You shouldnt lose fuel pressure instantly like that.

 

My front tank fills my rear tank. Very common for one to fill the other on dual tank trucks. Even after the recall that replaced check valves. Also had a fuel pump replaced. I just make sure there is room for fuel in my back tank when using the front. There are tons of threads in this forum on the duel tank issues. Gary

 

I was just getting ready to post a question on this. My friend has a 93 150 w/dual tanks. The when feeding off the aft tank the return must be going into the front tank, because it will over fill. Where are the check valves that you speak of? Also, at times when the truck is running off the aft tank it runs as if it has bad gas. Could the check valve for the front tank be hung open and dropping the fuel pressue and causing this condition? Steve

 

but how does your guys truck run when you have the overflow problem. my checkvalve is located in side the tank, part of the Fuel Pump Assembly

Nate

 

I haven't been able to correlate drivablility issues with the aft tank return fuel getting thru the fwd tank check valve, because the only time I am sure it is transferring fuel is when it comes out the filler neck!!!

 

To replace the check valve, do I have to replace the fuel pump or is it available as a separate part?

 

Ford had a recall om this issue. I believe they installed check valves in the fuel lines. Depending on your mileage, ford may still do the recall service.

 

87-91 have check valve on frame rail next to fuel tanks, 92-96 have check valve inside of the tank, it is part of the fuel pump assembly (FDM) (Fuel Delivery Module)
unless you know how to get around it, you have to replace the whole fule pump assembly, this is how the Auto Parts Stores sell it, i think you can just buy the pump from NAPA but, its worth the extra $50 to just replace the whole assembly

the recall is only good up to 12years or 150,000 miles from the build date of the truck

i am out of luck because mine is 94 with 162,000miles on it.

I think i have a weak pump along with my fuel pressure issue, thats why my truck runs like it does, (I hope replacing the front fuel pump is enough to fix it)

Nate

 

Some fuel pressure testers have a bleeder valve to relieve pressure. (and usually a hose to run to a container)
See if yours is open, if you have one. Some have a plunger type release, you should not be pressing it during testing.

it sure is perplexing...
Popa Tim

 

I have the crossflow problem on my truck, front tank fills the back tank.

My truck runs fine while it is doing this.

300/ 1991 f150.

 

on my truck if you push the pin down on the schradervalve, hardly nothing comes out, its like a little volcano spilling down the sides, it will not shoot anything out. also with fuel pressure tester hooked up engine off with fuel pump grounded making 40-42psi,(it takes a couple of seconds to get up to that) i push the pressure release button on fuel pressure tester and it comes out very slow out the line like a leaking faucet,

i have done this on my 5.0 Mustangs and it comes out with some force, i even have to watch the line because it could spray fuel everywhere and come out of the container i have the line going to.

I am pretty sure the fuel pump is weak to.

I bought the new front tank pump last night and will install it in the next couple of days.

Hopefully this will solve my problem

Nate