Fuel Pump Upgrades

On the XR we have two fuel pumps, the in-tank and the in-line. One upgrade is to put 12v on the pump rather than the stock ~10v, the other solution is to upgrade the in tank pump and delete the external one.

Hi Output Fuel Pump Upgrade

The high output in-tank pump (255lph) replaces BOTH stock pumps.You want the High-pressure 255lph for a Mustang.

Check out http://www.autoperformanceengineering.com/
Part number FPF003 for '85-'97 Ford Mustang.

If you read the footnote, it says it also works for XR4Tis.

The stock in-line pump (next to the left rear tire) is replaced with a longer filter without modification to the fuel lines. The filter part number is FOTZ-9155-B.

The 255lph pump is a little longer than the stock piece. What I did was to hold the new pump (with the filter sock on it) up to the XR4 and marked the the bracket and the 255 pump. removed the stock pump, bend the stock clamps ( you will see what I am talking about once you get the pump off) and used a hose clamp to hold the 255 in place. On mine the outlet of the pump is right at the inlet (outlet whatever you want to call it) tube. I used cone shaped sanding wheel to open the inlet of the metal tube. When the factory cut the tube, it left the tube somewhat closed off, you see what I am talking about. Install the fuel "sock" filter just before putting the pump in the tank. Be sure the sock is not touching the side of the tank. Change the electrical connector. The hole project is a 10 minute job. Thats not counting the time it took to get the fuel tank out of the car. No big deal there either....

There are two styles of 255 pumps a standard and a high pressure. The standard pressure is set up to run 40 psi, the high pressure one will flow well up 110 psi. If you get one, make damn sure that you get the high pressure one. (If you get the standard pressure pump it will not live long and may take your engine with it.) You can get the high pressure 255 walbro pumps and wiring kit for $105 + shipping all you need to do is email (Ron Gregory) sale@apeusa.com and tell him what you are doing... He will know what high pressure pump will fit in the XR4. (I have purchased many pumps from Ron and have never had a service problem. Randy Schultz)

There is a "resistor wire" on the ground side of the in-tank pumps wiring, that will need to be removed. The resistor wire (RW) is soldered in the ground wire (actually is a section of the ground wire). If you take the carpet out of the trunk you will see the wire harness coming from the tank. The RW section starts were the pump wiring joins the harness. It extends the width of the trunk, between the tail lights. I just cut the wire before the RW and grounded the pump to the body of the car.

Other items:

1. The electrical connector at the pump needs to be changed. A new one comes with the pump.

2. The filter with the longer ends is for a ?? (NOT a 90 Ford Ranger )(you can get one a Pep Boys or where ever you buy parts) it will go in place of the external pump/filter assembly. Remove the compete assy. The long filter will rest in the stock filter bracket.

Fuel Pump ReWire ( it is easier to put a larger capacity pump in , ed)

Did the fuel pump re-wire this weekend, and got the results that I expected. Now, with the fuel pump drawing power directly off the alternator output, I get one LED "richer" on the Air/Fuel meter at WOT with accessories running.

Get another relay for the fuel pump. I have an '87 XR, so I don't know if there are any differences in fuse box configuration between years. I can only comment on my experience with my '87. First of all, take the NEW relay and carefully & slowly bend the #30 blade around and up the side of the relay case. If you lean over the driver side fender looking into the fuse box (with fuse rows along top and right side), then the #30 blade is the one which plugs into the top slot of the fuel pump relay socket. I've seen relays with metal cases, which might pose a potential short problem, but my relay case was plastic so this wasn't an issue.

Next, attach a wire to this blade. Use a minimum 12 ga wire. You can use a crimp on type blade connector or just solder the wire on there directly. I used a blade connector, which makes a tight fit between the fuel pump and adjacent relay. It does fit if you bend the blade correctly.

Drill a small hole in the side of the fuse box (dia of your wire) and run this into the engine compartment. I recommend applying sealant around the wire where it exits the fuse box to keep things weather proof.

Finally, just unscrew the alternator output nut and attach the new fuel pump "hot" wire with a crimp on lug (I always soldier them also). I'd recommend cleaning up the terminals real good. To be safe, disconnect the battery before doing any of this to prevent an early 4th of July display of sparks.

This approach is very simple, effective, and still retains the rest of the stock fuel pump circuit. We still keep the fuse and inertia switch (turns off fuel pumps in case of a crash) in the circuit, so it should be a very safe change. If you later decide you want to change back to the stock configuration, then just unplug the modified relay, remove the additional wire, and plug another in another relay.


For those who are contemplating putting a 190 lph or larger fuel pump in the tank be sure and bypass the resistor in the ground circuit. Here's why.

I used a 190 lph pump on my 3.8SC swap and at first did not bypass the ground. When starting the car after sitting overnight I would turn the key on to the run position and let the fuel system charge until the pump timed out. I would then crank the engine. For the first moment or two the engine would run rough before clearing up and idling as it should. If I turn the key to the run position, charge the fuel line, turn the key off and then back on to charge the fuel system a second time the car would start up and run fine. I suspected the pump was not putting out as it should and sure enough when I bypassed the resistor on the ground side of the pump wiring the pump ran much faster. When cold the car started as it should.

The 3.8SC has a longer fuel rail system and the pump running on reduced voltage did not supply enough fuel during the second or so it would run when the key was first turned on. I suspect output was weak at full throttle as well, but I was able to correct the problem during the motors break in before I tried any power runs.

I bypassed the ground up inside the hatch area. When the jack cover is pulled up one can see the wire harness to the pump running from the rear harness to a rubber grommet in the trunk floor. The pump harness has two brown ground wires, one for the fuel sender and one for the pump. The dark brown resistor wire extends across the length of the rear hatch area, and the connection with the light brown ground wire from the fuel pump is wrapped in black cloth tape. I pulled some of the tape back and snipped the light brown wire close to where it connects with the resistor wire, providing as much free length of wire as possible. I then put a ring connector on the end and attached under a ground screw on the rear panel by the tail lights.