I bought a 1990 F150 new that year and kept it for 19 years. I had the fuel diverter replaced at least 3 times - Ford did it for free. I bought a 1994 F150 stretch cab a few months ago and the front tank is filling up to overflow, so the diverter is gone on this one. I read that Ford replaces them for 12 years, then I'm on my own.
I bought the part: Ford F1UZ9B263B
Now, where is it on the Chassis? Unless it's on top of the front tank, I don't have a clue. I've searched the frame from engine to bumper and I can't find it. I bought an online alleged copy of the Ford manual [1994 F150] and it has no section on fuel.

 

You do not have that item on your truck.
You have a bad Fuel Delivery Module (FDM) inside the front tank.
The last year that a F1UZ9B263B was used on a ford F-series truck was 1989.
The E-series used it through 1991.

 

Not according to the Ford Dealer and a score of threads I've seen on this site.
I may be wrong, but the Ford dealer believes my truck has it.

How would a bad fuel delivery module in the front tank send fuel from the rear tank to the front? It behaves exactly as my 1990 did. It runs on both tanks, but the front tank overflows. Perhaps the incorporated this unit into the front tank fuel pump?
If so, it's strange that this part is sold for 1986 - 1996 F150s.

 

Your Ford Dealer does not know what he is talking about.
The threads you have seen are for the 1986-1989 F-series trucks.
That part was only used in 1986-1989 F-series truck.
If you had one of these on your truck you did not have a 1990 truck.
The problem with the FDM is the high pressure check valve or the the return shuttle valve is bad.
Any body that say that part was used in 1986-1996 F-150s does not know what they are talking about.

 

Good thing.. because that part doesn't exist on a truck of that year. What Ford likely changed/installed was an exterior check valve on one or both of the in-tank delivery modules, they had a service bulliten at the time to address this crossflow problem on dual tank trucks. It's a little fitting that goes on the high pressure send line right at the tank that you probably wouldn't even notice if you weren't looking for it.

 

I've found references for F150's 1986-1996 that refer to an external diverter, including one that cited this forum's past moderator as a source for the part [he was a retired Ford part manager].
I've seen about as many references indicating that it is integral to the fuel pumps, or just the front pump.
There is one mechanic in town I trust: I'll ask him.
The part I purchased is a passive 6-connector device with a resevoir. Allegedly it bolts to the frame just in front of the front tank. I reasoned out how it would work. I don't see how independent pumps in separate tanks can avoid a cross-over. At some point before the injector they have to meet. Unless Ford connected the tanks somehow - the external valve is simpler.
But so far I have equal evidence for both arguments.

 

As usual Steve83 has some info on the Fuel Cross-flow TSB: Steve83 - fsa01m05fuelcrossflow

 

The Ford F-series fuel system 1986-1989:


The Ford fuel system from 1990 on:


The FDM that you have in that truck:


/

 

To add some more to Bill's photo:


Electric Fuel Delivery Module (FDM)

The electric fuel delivery system used on the 4.9L, 5.0L, 5.8L and 7.5L Electronic Fuel Injection (EFI) engines consists of a fuel delivery module (FDM) assembly. The FDM unit includes a high pressure fuel pump, venturi jet pump, supply check valve, and a shuttle selector valve located internally to an in-tank reservoir assembly mounted from the fuel tank sender flange.

The following provides a brief description and function of each of the FDM internal components.

High Pressure Fuel Pump: The high pressure fuel pump is located inside the flange-mounted, reservoir assembly internal to the fuel tank.

Shuttle Selector Valve: The shuttle selector valve opens the return line to the tank and the return flow is directed to the appropriate tank on vehicles equipped with dual tanks.

Supply Check Valve: The supply check valve, which is normally closed, opens when the outlet pressure from the energized pump exceeds the opposing check valve spring force. When the pump is de-energized (i.e., engine is shut off), the supply check valve closes to maintain pump prime and fuel supply line pressure.

Venturi Jet Pump: A portion of the high pressure flow from the pump is diverted to operate the venturi jet pump. The venturi pump draws fuel from the tank into the ITR reservoir to augment the engine return flow. This process ensures an adequate fuel supply to the pump during extreme vehicle maneuvers and steep vehicle attitudes with low-tank fill levels.

The inlet of the venturi pump has a nylon filter on it to prevent dirt and other particulate matter from entering the system. Water in the fuel tank can pass through the filter without restriction.

 

Now I have two diagrams showing disparate solutions, if I understand the diagrams. One shows an external check valve at each tank. The other shows the check valve integral to the fuel pump.
I liked the external six-hole diverter better: It didn't require that I lift the bed or drop the tanks.

 

You are correct, there are several references to the the Single or Dual Function Reservoir on this forum. You will also see it only applies to 1986 to 1989 F-series trucks. 1990 and older Ford trucks adopted a different fuel supply system. Albeit, it was also a stinker design that was susceptible to the same type cross-flow issue.

 

Ford added the band-aid fix of an external check valve to "fix" the crossflow problem. They did not want to drop the tanks or remove a bed either.

They never did change the internal check valve design on forward production trucks of that era. If a customer complained of the cross flow issue they added the external checked valve in retrospect.

I have owned 3 1992-1993 Ford trucks. None of them ever got the external check valve even though both 1993 trucks were in the affected model year of the recall because I did not have the cross-flow problem.

 

The old system (1986-1989) had the check valve inside the high pressure pump. The 1990 on system had a high pressure check valve and a shuttle valve inside the FDM in each tank.
I do not know what you mean by "Now I have two diagrams showing disparate solutions".

The only time Ford put on external check valve at each tank was for the 1993 truck when the they had a bad run of fuel pressure regulators that caused the high pressure check valve in the non selected fuel tank to go bad. They took the cheap way out of the problem by putting on the check valves on the high pressure line at each tank and replaced the fuel pressure regulator.
Some were put on other years to satisfy customers but 1993 was the bad year.

 

This is why I ask about the part that is so ardently decried here.
This is from this site in the past:

NumberDummy


No external switching valve? So..what would you call the following?

F1UZ9B263B This is what Ford calls it: FUEL TANK SELECTOR VALVE & RESERVOIR ASSY. Fits: 1994/96 F150.

__________________
Bill // Retired Ford Parts Manager // SoCal Chapter member // Part Number Research: 1928/2001 FoMoCo vehicles.

Later posts on this site say this same part fits 1986 - 1996 F150, gas or diesel. And Tallahassee Ford said this part fits my truck. I am not sure if this is the current after-market fix or not. On my 1990 it was fixed under Ford's policy for free, but my 1994 is beyond the 12-year limit.

 

From the same sender on this site [NumberDummy], Posted 03-03-2009, 06:45 AM

FIUZ9B263B replaced: E7TZ9B263A, FOUZ9B263A and FIUZ9B263A, so it actually fits 1987/96, not just 1994/96.

He gave a person to contact -FTE sponsor - but he no longer exists.

On the strength of his statement I called Tallahassee Ford: They said it fit my truck and cost $235. I bought it from another dealer for $150.