January 14, 2014

Fuel injection systems utilize high-pressure fuel pumps that run between 40-60 psi (depending upon the application). These high-pressure pumps were frame-rail-mounted in the pioneering days of factory EFI, including some of the first fuel injected Fox Mustangs. However, as manufacturers learned about EFI and implemented changes to their model lineup, the high-pressure EFI fuel pump eventually made its way to the inside of the fuel tank. This in-tank mounting had several benefits, including packaging, noise reduction, and fuel pump life (the fuel itself is a cooling medium). Unfortunately, placing the fuel pump inside the fuel tank does make a fuel pump replacement or upgrade a little more challenging than removing a couple of bolts and swapping out pumps. In some vehicles, you can actually access the fuel pump through a large body plug directly over the tank (Ford started doing this with the '05 and up Mustang), but for the Fox-era Mustang it requires removal of the fuel tank from the vehicle to access the fuel pump assembly. This is still very much a DIY project that can be accomplished with basic hand tools in your driveway. You just have to remember you are dealing with a flammable material and to ensure you are using safe procedures. Replacement fuel pumps are available in stock flow and high-flow models. If your Mustang is completely stock, then a stock pump is fine. However, if you have performance upgrades or are planning said upgrades, a higher flow fuel pump should be on your shopping list. There are a few other “gotchas” we'll discuss in the captions, but this is indeed a project you can tackle easily. See how in the photos with the help of National Parts Depot's Fox Mustang catalog.

1. To make the removal of the tank a bit easier, it is recommended to have no more than a quarter tank of gas. This makes the tank easier to maneuver and keeps the fuel level below the filler neck opening. If the pump is dead and you can’t drive the car, you’ll have to siphon the fuel out. Once the fuel level is OK, disconnect the battery and the fuel pump wiring at the rear bumper.
2. With the fuel tank supported by a floor jack or other means, remove the two retaining bolts found on the inboard end of the tank straps, just aft of the axle housing.
3. Lower the tank a few inches to access the tank’s fittings. You will have three hoses to disconnect—pressure and return at the fuel pump, and a push-on hose at the vapor vent valve. The return line requires a Ford fuel line disconnect tool that you can pick up from any parts store. Once the lines are disconnected, the fuel tank can be lowered further and then slid to the driver’s side, allowing the fuel filler pipe to separate from the tank’s opening.
4. Using a plastic or brass drift (something that will not create sparks; we improvised with a brass hammer), knock the lock ring free from the fuel pump so the pump can be removed. The pump will require rotating of the assembly as it comes out of the opening to clear the tank’s baffling.
5. On a workbench, you can see the main pump assembly mounted in the fuel pump hanger (with our new 255-lph pump next to it). To install the new pump, disconnect the original pump’s outlet hose and wiring, pry the filter sock off the end, and unbolt the pump bracket from the pump hanger.
6. Carefully reassemble the fuel pump hanger and bracket with the new pump in place. The wiring for the new pump will need to be trimmed to length and connected to the factory wiring. Solder and shrink wrap are best, but we’ve used crimp connectors as well with no issues.
7. The upgraded fuel pump assembly can now be reinstalled into the tank. Be sure to use a new O-ring seal as well. The pump will require a little twisting and turning to seat properly and to locate the filter screen in the tank’s baffled area.
8. The owner’s fuel level sender functions properly, but if you have any doubts about yours, NPD offers a nice replacement complete with a new O-ring and lock ring.
9. Whenever a Fox fuel tank is removed for repairs/upgrades, it is strongly urged to pick up a filler neck seal as well. These seals, over time, take a set to the diameter of the filler neck tube and will leak. Do yourself a favor and pick one up with your other fuel system parts.
10. While not often as big an issue as the filler neck seal, this rubber gasket that seals the tank’s filler neck to the trunk/hatch floor can sometimes be damaged by road debris or tear with age. NPD not only has this seal in stock but they also offer replacement fasteners. Just take note the seal must be installed before the tank is reinstalled.
11. Another quick and easy part to add to your shopping list is a new fuel filler cap. Over time, the cap retainer cracks and fails, leaving the cap free to be left behind at your last fill up. We’ve also seen the larger rubber seal crack and fall out as well, so just pick up a new one and save yourself the hassle.
12. Using the new fuel line retaining clip provided with the fuel pump kit, prepare the fuel pump feed line by installing the clip with the point facing away from the line opening. Reinstall the fuel pump feed and return lines along with the fuel vapor vent line and reinstall the tank with a generous application of silicone spray lube on the fuel filler neck seal. Slide the tank over the filler neck and secure the tank with the two retaining straps.
13. Another must buy item when servicing/upgrading your fuel system is a replacement fuel filter. If your pump failed, there’s a good chance your filter is full of particulate. The filter only takes a few minutes to swap out (one hose clamp retainer and two fuel line retaining clips).

NPD Parts Used
Fuel Filter M-9155-5 $14.95
Filler Pipe Seal M-9072-2A $14.95
Filler Pipe Seal M-9008-2A $32.95
Filler Pipe Seal Fasteners M-9008-1K $1.95
Vent Valve Seal F-9B076-1 $7.13
Gas Cap F-9030-28 $24.25
Pump/Sender O-Ring 9276-1 $0.99 (x2)
Fuel Level Sender M-9275-13A $54.95
255-lph Fuel Pump M-9A406-1B $134.95