'85-89 Fuel Systems
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For Type 2 SFR, read this page & the NEXT several:



For Type 4 DFR, read this page & the NEXT several:



See also:

Single-Function Reservoir Installation
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NOTE: The frame mounted fuel filter was repositioned to between the fuel pump and engine in February, 1986.

To permanently eliminate the reservoir, use these Dorman fuel tubes.

See also:
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Hi-Pressure Fuel Pump, Filter, & Dual-Function Reservoir F1UZ-9B263-B for '84-89 EFI
IF THE IMAGE IS TOO SMALL, click it.



NOTE: The frame mounted fuel filter was repositioned to between the fuel pump and engine in February, 1986.

To permanently eliminate the reservoir, use these Dorman fuel tubes.

Early High-Pressure Fuel Pump & Filter
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'85 5.0L In-Tank (Low-Pressure) Fuel Pump, Level Sender, & Tank Plate (Tank Hanger Assembly)
IF THE IMAGE IS TOO SMALL, click it.

Low-Pressure In-Tank Fuel Pump for '84-89 EFIs
The large (~3") mounting plate shown is for '88-89
IF THE IMAGE IS TOO SMALL, click it.

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The pre-'87 fuel level sender operates through a range of 10.5 Ohms (full) to 72.8 Ohms (empty).
The '87-up sender is 160 Ohms (full) to 16 Ohms (empty).

The fuel pump is a motor with an impeller assembly, much like an oil pump, so it will allow fuel to leak backward into the tank when it's not running. This behavior is VITAL to the operation of the dual-function reservoir. Inexpensive aftermarket solenoid-stlye fuel pumps do not allow fuel to leak backward, and so inhibit the DFR. To use one or more solenoid pumps, replace the DFR with a SFR and this style of valve:

Plastic Fuel Line Clips
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Do not use silicone grease anywhere near the fuel system.

'86 F-series Fuel Tanks
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For wheelbase, see this:


For pickup tank access, see this:


For newer trucks:

'88 Single-Function Reservoir

Used on '88-89 Broncos & F-series/E-series/Rangers/others with single tank dual-pump EFI. In this version, the only moving part is the tank-side inlet check valve. The return ports flow freely and are NOT connected to the reservoir. The engine-side supply port is open to the reservoir.

To test it, unplug the frame fuel pump, disconnect the engine-side supply (large) line, and cycle the key. If fuel flows out of the reservoir nipple, the reservoir is working normally. If not, disconnect the tank-side supply (large) line, and cycle the key. If fuel flows out of the line, the reservoir check valve is probably stuck, or its internal filter is clogged.

A reservoir marked "DO NOT REMOVE CUP" does not contain a filter. For a replacement O-ring for the cup, buy a Wix 33268, NAPA 3268, Fram CG3862, Purolator F50126, CarQuest 86268,or equivalent filter.

To permanently eliminate the reservoir, use these Dorman fuel tubes.

GO TO THE NEXT PIC.

See this caption:

'86-87 Single-Function Reservoir (SFR) Fuel Flow
IF THE IMAGE IS TOO SMALL, click it.

Fuel flows in through the larger tank-side supply nipple from the in-tank pump to the inlet check valve, which allows it into the reservoir. As the cup fills, fuel moves through the filter, up the pickup tube, & out the larger engine-side supply nipple. Unused fuel enters the engine-side return nipple, mingles with any unused fuel coming through the check valve from the reservoir, and exits the tank-side return nipple.

The only fault that would cause a noticeable problem would be for the inlet check valve to stick closed, blocking any fuel from entering the reservoir, but this isn't likely. With the cup removed (have a replacement cup O-ring in-hand before attempting), a sharp pick can be used to pull the valve downward & open. The valve cannot be removed from the reservoir body.

A more common fault (but less noticeable) is for the check valve O-rings to fall out or split, reducing the pressure to the frame pump. This might make the engine slightly harder to start, especially after the tank runs dry.

The Ford engineering number on the filter is E6TZ-9365-A. A reservoir marked "DO NOT REMOVE CUP" does not contain a filter. For a replacement O-ring for the cup, buy a NAPA 3268, Fram CG3862, or equivalent filter.

GO TO THE NEXT PIC.

See also:

'88-91 Single-Function Reservoir (SFR) Fuel Flow
IF THE IMAGE IS TOO SMALL, click it.

Fuel flows in through the larger tank-side supply nipple from the in-tank pump to the inlet check valve, which allows it into the reservoir. As the cup fills, fuel moves up the pickup tube & out the larger engine-side supply nipple. Unused fuel enters the engine-side return nipple, bypasses the blocked-off check valve ('88 revision) and exits the tank-side return nipple.

The only fault that would cause a noticeable problem would be for the check valve to stick closed, blocking any fuel from entering the reservoir, but this isn't likely. With the cup removed (have a replacement cup O-ring in-hand before attempting), a sharp pick can be used to pull the valve downward & open. The valve cannot be removed from the reservoir body.

A reservoir marked "DO NOT REMOVE CUP" does not contain a filter. For a replacement O-ring for the cup, buy a NAPA 3268, Fram CG3862, or equivalent filter.

Dual-Function Reservoir F1UZ-9B263-B
IF THE IMAGE IS TOO SMALL, click it.

If available, priced from $90-300 plus sh Ford F1UZ-9B263-B, Dorman 911000, or any knock-off copy like this one or this other or this third...

A reservoir marked "DO NOT REMOVE CUP" does not contain a filter. For a replacement O-ring for the cup, buy a NAPA 3268, Fram CG3862DP, or equivalent filter.

To semi-permanently eliminate the reservoir and use only 1 tank, use these Dorman fuel tubes.

See also:

. . .

Go to the NEXT page...

Dual-Function Reservoir F1UZ-9B263-B
If available, priced from $90-300 plus sh Ford F1UZ-9B263-B, Dorman 911000, or any knock-off copy like this one or this other or this third...

Used on '84-89 F-series/E-series/Rangers/others with dual tank dual-pump EFI. NOT used on Broncos.

If the engine only runs on one tank, but dies after a minute running on the other, AND both tank fuel pumps are known to be good, the reservoir's switching valve mechanism is probably stuck. Remove its 2 mounting bolts & clean it thoroughly BEFORE disconnecting any lines. Replace the reservoir on the frame & loosen (but do not remove) the reservoir cup BEFORE removing the reservoir assembly from the vehicle. See the NEXT several pics & captions...

To semi-permanently eliminate the reservoir and use only 1 tank, use these Dorman fuel tubes.

A reservoir marked "DO NOT REMOVE CUP" does not contain a filter. For a replacement O-ring for the cup, buy a NAPA 3268, Fram CG3862DP, or equivalent filter.

See this caption:

Dual-Function Reservoir Assembled (replaced by F1UZ-9B263-B)

After thoroughly cleaning the outside of the reservoir assembly and loosening the cup, remove the reservoir from the vehicle & re-clean it. Do not allow anything other than carb cleaner into the nipples. Do not use silicone grease anywhere near the fuel system. Use only clean motor oil to lubricate any fuel system components.

If available, priced from $90-300 plus sh Ford F1UZ-9B263-B, Dorman 911000, or any knock-off copy like this one or this other or this third...

A reservoir marked "DO NOT REMOVE CUP" does not contain a filter. For a replacement O-ring for the cup, buy a NAPA 3268, Fram CG3862DP, or equivalent filter.

Dual Function Reservoir Cover

Remove the 8 screws from the diaphragm cover & lift it off carefully. Do not distort the orange diaphragm or the tiny black O-ring.

Dual Function Reservoir Diaphragm

Without distorting the diaphragm, remove the phillips screw from the diaphragm top plate & lift them off carefully. Place the diaphragm on a clean surface so it remains unwrinkled.

Dual Function Reservoir Plate

Using needle-nose pliers, push the valve pushrods out of the clips in the bottom plate (by rotating the plate) & remove it.

Dual Function Reservoir O-ring

Without distorting it, remove the tiny O-ring from the edge of the body. Re-install the phillips screw by hand halfway into the detent rod.

The main cause for the valve NOT to switch is the tiny O-ring that allows fuel to the top of the diaphragm swelling shut (because of ethanol in modern gas). This prevents the valve from moving, and if it does move, it can stop halfway, causing the engine to stall.

To fix it, slide the O-ring onto a 1/16" drill bit in a STOPPED variable-speed drill, hold onto the O-ring gently, and slowly bring the drill up to full speed, as you slide the O-ring off.

Dual Function Reservoir Detent

Using the screw as a handle, pull the detent rod out.

Dual Function Reservoir Rings

Using a clean, sharp pick, carefully pry each tab of the lock rings up one-at-a-time working slowly around each ring to release it without bending it. Avoid scarring the valve bores.

Dual Function Reservoir Switching Valve

Noting their orientations, extract each valve from its bore. If they remain, carefully remove the white O-rings without distorting them.

The valves must be reinstalled facing the correct direction.

Dual Function Reservoir Switching Valve
IF THE IMAGE IS TOO SMALL, click it.

Without distorting any rubber parts, slide each component off the top end of the valve stem, keeping them in order.

If the valve assembly must be disassembled, remove the E-ring from the bottom end & carefully slide each component off. Do not use silicone grease anywhere near the fuel system. The only acceptable lubricant is clean motor oil.

Dual Function Reservoir Exploded F1UZ-9B263-B $90-200 plus sh
IF THE IMAGE IS TOO SMALL, click it.

Thoroughly clean & inspect each part. Replace any that are worn or damaged. Apply a light film of clean motor oil to each part before assembly. Do NOT use silicone grease on any fuel system component. The only acceptable lubricant is clean motor oil.

If the valves' upper &/or lower O-rings split, crack, or leak, fuel can be transferred from one tank to another, possibly resulting in overflow & fire.

Dual Function Reservoir Check Valve

The check valves are glued into the reservoir body and should not be removed. If the supply check valve O-ring slips off, the valve's spring will pull it into the reservoir body.

To permanently eliminate the reservoir, use these Dorman fuel tubes.

A reservoir marked "DO NOT REMOVE CUP" does not contain a filter. For a replacement O-ring for the cup, buy a NAPA 3268, Fram CG3862, or equivalent filter.

I could tell these O-rings were swollen when I rebuilt this DFR, but I didn't realize they would blow off the valves while I was test-driving. And I CERTAINLY didn't expect the engine to just STALL. But after a tow-truck ride, and some foul language, I came up with this.

I drilled a 1/16" pilot hole ~1//4" into each valve's center. Then I widened it with the drill tip of this standard Ford trim screw. I found out the hard way that even this short screw is too long, so I cut a pair down to ~2 threads, and installed them to keep the O-rings on the valves.

To permanently eliminate the reservoir, use these Dorman fuel tubes.

A reservoir marked "DO NOT REMOVE CUP" does not contain a filter. For a replacement O-ring for the cup, buy a NAPA 3268, Fram CG3862, or equivalent filter.

Dual Function Reservoir Check Valve

WIth the supply switching valve removed, a bent probe can be used to push the check valve out far enough to reinstall the O-ring.

If the return check valve falls or leaks, it cannot be accessed.

To permanently eliminate the reservoir, use these Dorman fuel tubes.

Dual-Function Reservoir (DFR) F1UZ-9B263-B Fuel Flow - Top Tank Ports

When the tank connected to the top ports is selected by the dash switch, pressure from it flows to the top of the diaphragm through the tiny O-ring, pushing the switching valves down. The detent rod holds them in this position. The tops of the switching valves open, allowing fuel from the upper tank-side supply (large) port to flow to the supply check valve which opens, filling the reservoir. As it fills, fuel is forced up the pickup tube & out the engine-side supply port.

(Note the lower diagram shows the opposite side of the reservoir.)
All fuel returning from the engine flows to the return check valve which allows any excess into the reservoir. Because both switching valves are connected to the lower diaphragm plate, the return valve also opens its top seat, allowing fuel to flow to the top return port & back to that tank.

A leak at the switching valves' O-rings can allow fuel from one tank to return to both tanks, giving the appearance of high fuel consumption (low MPG), and possibly overflowing one tank.

Dual-Function Reservoir (DFR) F1UZ-9B263-B Fuel Flow - Bottom Tank Ports

When the tank connected to the bottom ports is selected by the dash switch, pressure from it flows to the bottom of the diaphragm through a journal in the body, pushing the switching valves up. The detent rod holds them in this position. The bottoms of the switching valves open, allowing fuel from the lower tank-side supply (large) port to flow to the supply check valve which opens, filling the reservoir. As it fills, fuel is forced up the pickup tube & out the engine-side supply port.

(Note the lower diagram shows the opposite side of the reservoir.)
All fuel returning from the engine flows to the return check valve which allows any excess into the reservoir. Because both switching valves are connected to the lower diaphragm plate, the return valve also opens its bottom seat, allowing fuel to flow to the bottom return port & back to that tank.

A leak at the switching valves' O-rings can allow fuel from one tank to return to both tanks, giving the appearance of high fuel consumption (low MPG), and possibly overflowing one tank.

Dual-Function Reservoir Installation
IF THE IMAGE IS TOO SMALL, click it.

NOTE: The frame mounted fuel filter was repositioned to between the fuel pump and engine in February, 1986.

To permanently eliminate the reservoir, use these Dorman fuel tubes. The lack of a reservoir MAY cause rough running when the tank is low (bubbles in the fuel rail), and of course, only 1 tank can be connected.

See also:

'84-89 Dual-Function Reservoir
IF THE IMAGE IS TOO SMALL, click it.

The engine supply line feeds the high-pressure frame-mounted fuel pump, which goes to the in-line fuel filter, which then supplies the fuel rail.

A reservoir marked "DO NOT REMOVE CUP" does not contain a filter. For a replacement O-ring for the cup, buy a NAPA 3268, Fram CG3862, or equivalent filter.

For more info, see this album:
http://www.supermotors.net/vehicles/registry/2742/66025

'84-86 5.0L Fuel Pump & Filter under driver's floorboard (A5/FU)
IF THE IMAGE IS TOO SMALL, click it.

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NOTE: The frame mounted fuel filter was repositioned to between the fuel pump and engine in February 1986.

Reservoir
This is a dual-function reservoir F1UZ-9B263-B from an '88 F150, but 2 ports are blocked off and only one tank is connected.

A reservoir marked "DO NOT REMOVE CUP" does not contain a filter. For a replacement O-ring for the cup, buy a NAPA 3268, Fram CG3862, or equivalent filter.

Eventually, I realized that the problem with the DFR was the aftermarket solenoid-style fuel pumps. Because they didn't allow fuel to bleed back into the tanks (like the original impeller-style pumps), the DFR was unable to switch, and it would jam midway, blocking all fuel flow.

So I replaced the DFR with these valves from NAPA, and a SFR. There have been no fuel problems since.

The solenoids are carefully plumbed so that, when UNpowered, they default to the same tank. Wiring them is simple: they're parallel to the OTHER tank's pump, meaning, when the pump for the other tank runs, the valves are energized & direct fuel to & from the other tank.

Even though this section is strictly for low-pressure fuel, I still chose to use EFI-rated fuel hose.

'88 Inertia Switch Location

firewall forward of the e-brake & clutch pedals
B5FO on this chart:



Later inertia switch location: in the R kick panel below the dash


See also:

SOLD Rear tank for EFI pickups. Low-pressure in-tank pump ('84-89 EFI) available. Clean, dry; no rust, dents, or leaks.

'87 EFI Small-hole Fuel Tank Connections