Here's something interesting happening to my fuel tanks that isn't causing a performance or safety problem, but I'd like to know if anyone has encountered and fixed this.

With the forward fuel tank needle near E and switching to rear tank, the rear tank consumption is just a little greater than the forward tank. However, after runnning the rear tank nearly empty, switching to the forward tank reveals about 3/4 tank!

My questions are: Where is the cross-feed occuring and what is causing it?

Thanks!

-- Jay

94 F-150 XLT Super Cab w/302, AOD-E, 8.8" 3.55
98 Exploder, 4WD POS

 

There is either a recall or a TSB out for this problem. It has to do with a check valve in the in tank pumps I think. Check with Ford, and the Recalls/TSB link on the right.

 

Gas guages on these trucks bite. That why the trip odometer is standard equipment.

 

[updated:LAST EDITED ON 01-14-03 AT 05:05 PM (EST)]Hi-
Do you have the black fuel swithching thing on the driver's side framerail with the 3 "ins" and 3 "outs"?
Mine does the same thing and more, if your truck is identical I can definitely elaborate...

 

There should be no selector valve in the fuel lines. At least as early as 92, Ford went to high pressure in tank fuel pumps with integrated check/crossflow prevention valves. They have no selector valve, just two fuel lines "y"ed into one going to the fuel filter and the fuel rail. If one of the check valves fails, you will get a cross flow of fuel, I want to say on the return side, but it may be on the send as well. I remember seeing a TSB or a recall out for this problem, as it was issued for my dad's 92. I'm pretty sure this is your problem. Check with Ford, and check the "Recalls/TSBs" link on the right.

 

Elaborate on the fuel switching valve. I am having problems with my 88. Valve will not open for the rear tank. Pumps all check out, and still will not open up.

 

[updated:LAST EDITED ON 01-14-03 AT 09:17 PM (EST)]On the '88, if it's like my '87, there is a pressure operated valve which switches due to the pressure from the in tank fuel pumps. Make sure the rear fuel pump is coming on first (EDIT: woops, you said they were fine). If it's not, something in that circuit is probably your problem or possibly the electric switch in the dash. If it works check the switching valve, the valve is a black canister like device with 6 fuel lines attached to it. That would be the next place to check. Hope this helps.

 

>There should be no selector valve in the fuel lines. At
>least as early as 92, Ford went to high pressure in tank
>fuel pumps with integrated check/crossflow prevention
>valves. They have no selector valve, just two fuel lines
>"y"ed into one going to the fuel filter and the fuel rail.
>If one of the check valves fails, you will get a cross flow
>of fuel, I want to say on the return side, but it may be on
>the send as well.

I think you've hit the nail on the head here. It's not a problem right now, since fuel's still getting tot he engine. Something to fix when I have a lot of time on my hands.

>I remember seeing a TSB or a recall out
>for this problem, as it was issued for my dad's 92. I'm
>pretty sure this is your problem. Check with Ford, and
>check the "Recalls/TSBs" link on the right.

 

Hi-
My truck is an 86 with the 302 and fuel injection. It has a device that after inspection and disassembly i've concluded works on pressure. The truck has the 3 fuel pumps, one in each tank that are not very high pressure, and then the one on the fuel rail that you can hear whine for a couple seconds with the ignition on.
I'm not sure what Ford calls it, let's call it the tank switcher/fuel filter housing just for this thread. It has one large diaphram over the top and this diaphram controls two valves. One for the fuel inlet from each tank, and one for the return to each respective tank. As far as I can tell, when it senses pressure from the low side in tank pumps, if it's working right it will shut off draw from the tank not in use and simultaneously shut off return to the tank not in use.
When mine started to mess up I was running the back tank and started to smell gas. When I got out to look gas was squirting out of an overfilled front tank through it's gas cap. I haven't replaced the fuel switching thing but I now have to deal with using the full contents of the front tank first to prevent the return flow from over filling it. I assume just because of proximity to the switcher that it only does this when running the rear tank with a near full front tank.
By the way the 3 "ins" are front and rear tank inlets and the single return line from the engine. The 3 "outs" are the returns for each tank and the single supply line to the high pressure frame rail mounted pump.
Hopefully someone will tell us what Ford calls it and how much they want for it

 

It's called the "dual-function reservoir" on 2-tank trucks, and the "single-function reservoir" on single-tank trucks. You can read all about it here: