New Fuel Pump Help

The Walbo 255 is normally an in tank pump that is a 1 for 1 swap with the stock pump. I would stick to a Walbro155 unless you plan on a supercharger, turbo or NO2.

Copied from the FORD RACING PERFORMANCE PARTS catalog:
Safe “Horsepower Capacity” @ 40 PSI with 12 Volts
60 Liter Pump = 95 LB/HR X .9 = 86 LB/HR, Safe for 170 naturally aspirated Horsepower
88 Liter Pump = 140 LB/HR X .9 = 126 LB/HR, Safe for 250 naturally aspirated Horsepower
110 Liter Pump = 175 LB/HR X .9 = 157 LB/HR, Safe for 315 naturally aspirated Horsepower
155 Liter Pump = 246 LB/HR X .9 = 221 LB/HR, Safe for 440 naturally aspirated Horsepower
190 Liter Pump = 302 LB/HR X .9 = 271 LB/HR, Safe for 540 naturally aspirated Horsepower
255 Liter Pump = 405 LB/HR X .9 = 364 LB/HR, Safe for 700 naturally aspirated Horsepower

Note: For forced induction engines, the above power levels will be reduced because as the pressure required by the pump increases, the flow decreases. In order to do proper fuel pump sizing, a fuel pump map is required, which shows flow rate versus delivery pressure.

Fuel Pump Replacement
Here are some useful tips...

I have done the tank removal three times, and the main issues are getting the car up on jack stands and getting the gas out of the tank. DO NOT try to do this job without jack stands. Becoming a pancake is not part of the repair process.

Pumping out the old gas:
If the old pump still works, you can use it to pump the tank out.
1.) Separate the pressure line (the one with the Schrader valve on it) using the fuel line tools.
Look in the A/C repair section for the fuel line tools. They look like little plastic top hats. You will need the 1/2" & 5/8" ones. The hat shaped section goes on facing the large part of the coupling. Then you press hard on the brim until it forces the sleeve into the coupling and releases the spring. You may need someone to pull on the line while you press on the coupling.


Use a piece of garden hose to run from the pressure line to your bucket or gas can. Make sure it is as leak proof as you can make it. Fire and explosion are not part of the repair process...

2.) Jumper the fuel pump test point to ground.



Turn the ignition switch to the Run position. the fuel pump will pump the tank almost dry unless the battery runs down first.

Some 5 gallon paint pails lined with garbage bags are good to hold the gas. The garbage bags provide a clean liner for the pails and keep the loose trash out of the gas so you can reuse it. If you decide to use a siphon, a piece of 1/2" garden hose stuck down the filler neck will siphon all but a gallon or so of the gas.

Remove the filler neck bolts and put them in a zip bag. Disconnect the supply & return lines by removing the plastic clips from the metal tubing. If you damage the clips, you can get new ones form the auto part store for just a few dollars. I have used tie-wraps, but that is not the best choice. Then you remove the two 9/16" nuts that hold the T bolts to the straps. Put the nuts in the zip bag with the filler bolts. Pull the plastic shield down and away from the tank. Once the tank drops a little bit you can disconnect the wiring for the pump & fuel quantity sender.

The pump assembly comes out by removing a large metal ring that unscrews from the tank. You are supposed to use a brass punch to tap on the ring so that you don't make sparks. Look closely at the rubber O ring gasket when you remove the sender: it is very easy to damage on reinstallation. If it gets damaged, the car will smell like gasoline when you fill the tank up. The pump assembly requires some twisting and turning to get it out the hole.
Late Model Restoration will have all the parts you need – fuel pump, rubber fuel pump seal, lock ring for the fuel pump and just about any other parts.
See https://lmr.com/products/79-93-Mustang-Fuel-Pump

Look very closely at the electrical wiring. The stock fuel pump wiring can overheat and melt the insulation. Mine had some really crummy plastic tubing slid over the quick disconnects. If the wires ever got together, there would be sparks inside the fuel tank and no more Mustang. I eliminated the splice in the middle of the wiring and went straight from the pump to the feed through connectors for the wiring. It required some soldering and crimping of new tabs on the wires, but it made a neater job.

Inspect the pump mount to metal tubing bracket. Mine broke and I couldn't get it to solder back together. I drilled a small hole for a machine screw & self locking nut to hold the clamp and bracket together.

The pump is easy to get off the mount but is somewhat difficult to get back it the tank without damaging the sock filter or tearing it on the tank baffle. When you install the metal ring that holds the pump in place, watch out for the gasket O ring. Some RTV may be helpful if the ring is not in excellent condition.

The tank to filler pipe seal is a large rubber grommet. Inspect it for hardening, tears and damage. At $20 from the Ford dealer, it might be a good idea to replace it.

I used a floor jack to help lift the tank back in place. You may find that it is the only time you really can make good use of a helper.[/b]

Dyno12 said:

So I can get the Walbo 155 inline pump? It has an aftermarket tank in it with the fuel exiting at the very bottom of tank on the rear. There is no spot for an in tank pump.

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I have not seen a Walbro external pump, so I can't answer that question.

I would keep the aeromotive unit personally. It's a high quality piece and any external electric pump is going to be "noisy".

Change to a 130 amp alternater. Should solve any voltage issue

A5literMan said:

I would keep the aeromotive unit personally. It's a high quality piece and any external electric pump is going to be "noisy".

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Not the old A1000.
Noisy as hell and people would burn them out in a few thousand miles.
Not sure I've ever known anyone that had one last. I think outside the tank they run too hot and self destruct.

You can get walbro inline pumps.
I think the gsl393 (155lph but you can find any size you want) would work. If you plan on an SC in the future, get the hp255 version, if not, get the 155.

Walbro inline pumps are about 80% quieter than an a1000.

Since the inline pumps are cheap and you won't have to do any wiring, if you do indeed have an a1000, I personally would swap it out. Probably sell the aeromotive pump and make money on the project. Much less likely to leave your stranded.

Just curious why the inline pump and not an in tank unit?

stykthyn said:

Just curious why the inline pump and not an in tank unit?

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Sounds to me like he bought a car that was once heavily modified.
Back in the day you went to a sumped tank and an a1000 pump.

2000xp8 said:

Sounds to me like he bought a car that was once heavily modified.
Back in the day you went to a sumped tank and an a1000 pump.

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Kind of what I was thinking, but there was no mention of a power adder or anything suggesting the need for that kind of fuel.

The good news is that with that pump (which I think is for a boat, according to summit racing) you can run another 1200hp through it, lol.
I can only imagine how much fuel is being dumped back in the tank if it runs like a typical return system.

You don't run a pump like that unless you were into more than 600rwhp.
It's also more powerful than the a1000.

I would think with the right fittings you could just swap it out for a gsl392 walbro.

How do your torque boxes look?

Looks like it's already connected to an aeromotive filter, If it is you can just buy another internal filter for it.
Probably aint going to be cheap.