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98-04 Ford Mustang Fuel Pump

By Chris Myer
(Have another year Mustang? Too easy! Visit our Fuel Pumps Finder!)

The fuel pump for the 98-04 Ford Mustang is an unusual beast. So much so that Walbro did not offer a high performance fuel pump for this application until 2011. If you're interested in what made this so difficult or why this is such a big deal, read our 98-04 Mustang Technical Background

Walbro has finally released their wildly anticipated High Performance Fuel Pump kit for the 98-04 Ford Mustang. It flows an amazing 290 liters per hour (See the Walbro Mustang HP Fuel Pump Flow Chart, below.) Use this handy guide to select the right pump for your year and Engine Combination:

Year Engine Size (VIN 8th Digit) Notes OE / HP
1998 All w/o California Emissions*:
3.8L (4) Exc. California
4.6L (X) Exc. California
Cobra 4.6L (V) Exc. California
1998 All w/ California Emissions*:
3.8L (4) California,
4.6L (X) Califonia,
Cobra 4.6L (V) California
1999-2000 3.8L (4) TU228
1999-2000 4.6L (X) Incl. '99 Cobra 4.6 (V) TU228
2001-2002 3.8L (4) TU229
2004 3.9L (6) TU229
2001-2004 4.6L (X) Incl. 01, 03 Cobra (V, X) TU229
2003-2004 3.8L (4) TU229
2003-2004 4.6L (R) TU229
*Typically only vehicles originally sold new in the state of California will have California emissions. Look for a plate near the strike plate on the driver's-side door to confirm.

Compare character in (parenthesis) to the 8th digit of your VIN to confirm fitment! NOTE! Walbro does not make a fuel pump tank unit for the Mustang with a 'Y' in the 8th digit of the VIN Code! These Mustangs are equipped with dual fuel pumps. To upgrade these, please contact us for special instructions.

Generally, it is best to select the OE replacement fuel pump unless you have modified your Mustang in such a way that will greatly increase the horsepower. The Walbro OE Replacement Fuel Pumps listed here are capable of producing fuel for an additional 5-10% horsepower. So, if you've added an intake and an exhaust, the Walbro OE fuel pump will work great.

On the other hand, if you have serious power adders, such as a supercharger kit or nitrous, opt for the HP fuel pump. Remember that the Walbro HP fuel pump does not itself add horsepower. But, if you upgrade the horsepower capability of your engine without upgrading the fuel flow with a high performance fuel pump, you risk running your engine lean and DESTROYING IT! No risk is associated with running the HP version of the Walbro fuel pump in your Mustang, just a bit more initial cost. If in doubt--call us. We're thrilled for the opportunity to talk to and assist our customers.

Is it true that these new Walbro Tank Units for the 98-04 Mustang flow MORE than 255 LPH?

Believe it! Because these tank units for the 98-04 Mustang use the new Walbro DCSS 39/50 turbine fuel pump and not the 255 LPH gearotor pump, they flow an amazing 290 liters per hour against the normal 43 psi with a typical 13.5 volts (your charging system provides 13.5 volts when the alternator is turning.) Take a look at the fuel pump flow graph below for a closer look. (Graph is in gallons per hour--multiply by 3.785 to get liters per hour.)

Walbro TU229HP High Performance Mustang Tank Unit Flow Graph (Other 98-04 Mustang HP Tank Units Similar.)

Some place tried to sell me a Walbro GSS341 / GSS342 for my Mustang. Is that wrong?

Completely. And, until just a short time ago, that was one (wrong) way to approach the problem. Don't get us wrong. The Walbro GSS341 and GSS342 are great fuel pumps! In most applications, these fuel pumps do great! Apply 12 volts, externally regulate them, and you're all set with 255 liters per hour of fuel, enough to fuel 540 (turbo/supercharged) or 670 (NA) HP.

But fuel pressure regulation in the 98-04 Mustang is entirely different. Instead of sending a straight 12 volts to the pump, they send a pulsed voltage that will cause the GSS341/GSS342 Gearotor pump to cog and fail--permanently. The pumps above, however, are designed to work with the pulse-width modulated (PWM) pressure output to provide over 255 LPH without the failure that is inevitable in a gearotor pump. Read on to learn more about why this is so important.

98-04 Mustang Technical Background

Prior to January 2011, we didn't list a high performance 255 LPH fuel pump for the 1998 and later Ford Mustang. Some companies will sell you the same kit used on the 96-97 Cobra, but there are a list of reasons why you should consider this option very carefully.

The '98 and later Mustangs do not use a standard mechanical-style fuel pressure regulator. Instead, the computer senses the fuel pressure and controls it by sending a "pulse wave modulated" (PWM) signal to the fuel pump. To simplify, this means that it alters the voltage to control the pressure output by the fuel pump. This works well with many turbine-style fuel pumps, but the Walbro 255 LPH fuel pumps are gearotor-style. The low voltages that PWM-controlled systems generate cause them to start "cogging", which can result in reduced pump longevity. One solution to this would be to simply install a 12 VDC power to the fuel pump, switched to "on" when the key is in the on or start position, then add a mechanical fuel pressure regulator. This disables the cability of the ECU to control the fuel pressure (which is considered by most to be a positive feature.)

Assuming that the installation of a switched 12 VDC power supply to the fuel pump was done correctly (and ignoring the obvious safety considerations of failing to do that,) there are yet other issues to consider. The 98+ Mustang's fuel pump sits down in a resevoir that holds the fuel around the pickup during cornering. That is not unusual. However, the resevoir for the 98+ Mustang is shorter, vertically, than that of the 96-97 Cobra, so the fuel pump does not fit into that resevoir as well. If you overcome that issue, then there is the fact that the Walbro fuel pump can quickly out-flow the jets that allow fuel to flow into the resevoir. This means that, at a high-fuel useage situation in a heavily modified Mustang, starvation could occur, particularly at lower fuel levels when passive filling (fuel running over the sides of and into the resevoir) is not available. One solution that has been developed to this problem is to drill holes in the resevoir to allow additional fuel to flow into the resevoir. However, this is not an all-positive solution, as this also allows fuel to run out of the resevoir, effectively limiting the fuel baffling purpose for which it was designed.

The right answer? Unfortunately, until Walbro released their 255 LPH High Performance Walbro fuel pump that fits properly into this application (mentioned at the top of this article) there wasn't one. The Walbro OE-replacement TCA903 turbine-style pump provides roughly 180 liters per hour of fuel at the standandard 45 psi / 12 vdc that the unit sees in an unmodified Mustang. 180lph is conservatively capable of fueling 470 naturally-aspirated horsepower--380 if the horsepower is turbo- or supercharger produced. Now, if you're sure that you need more fuel then the new 255 LPH 98-04 Mustang Fuel Pump can provide, then we have another alternative for you. We highly recommend the Fore Precision Fuel Hat, which allows you to install two PWM-style fuel pumps side-by-side in the fuel tank. Alternatively, for such a high-performance requirement, consider having an aftermarket fuel cell installed in the car. This will allow you to use something like the Walbro 255 LPH inline fuel pump that is available from Fuel-Pumps.Net, along with a mechanical fuel pressure regulator.

Walbro Warranty InformationUse this handy lookup feature to find the right fuel pump for your car right now!

By Chris Myer

For warranty purposes, Walbro fuel pumps are broken down into two categories: original equipment replacement and high performance. High performance fuel pumps sold by Fuel-Pumps.Net are labled as such, and include any fuel pump kit that includes a GSS341, GSS342, F20000169 and, in some cases, the GSL392. (If in doubt, please ask.)

OE replacement fuel pumps are covered by a 90 day / 4,000 mile warranty. Details of this warranty are below. Returning a fuel pump for warranty takes time--usually 4-6 weeks for shipping, testing, and determination. You will be given the option of returning the fuel pump to us and waiting for the outcome of the test or buying a new fuel pump first and then receiving a credit for the original pump if warranty is given.

Strictly speaking, Walbro offers no warranty on their high performance fuel pumps. However, we're so confident of the quality of Walbro fuel pumps, that if you'll pay for the testing fee ($40), and if it turns out that the fuel pump was defective, we will GIVE you a new fuel pump.

In any case, before you send a fuel pump to us (whether a warrantied OE fuel pump or a non-warrantied HP fuel pump), be absolutely sure it has failed, and that your tank is not the cause of the failure. When the fuel pump is sent to Walbro, they will put it on their test bench to test for flow and pressure. A surprising number of the fuel pumps sent back to us as "dead" meet all manufacturers specifications--there is nothing wrong with them. When the pump fails this test, Walbro cuts the pump in half. If it has debris in it, then it is not eligible for warranty. Usually, on the very rare occasion that we receive a fuel pump that has actually "died", it has foreign matter inside the pump. The Walbro pumps are built to such exact tolerances that failure to properly filter the pump will put debris in the gerotor, and the pump will fail.

Walbro Warranty Statement

TI Automotive will accept Walbro OE Replacement fuel pumps for a defective credit consideration against defects in material and workmanship for a period of ninety (90) days or four thousand miles (whichever comes first) to the first user of the product. TI Automotive's obligation is limited to products that, to the Company's reasonable satisfaction, are deemed defective in material and/or workmanship and will replace defective products at their discretion. This defective credit acceptance does not cover a product which has been damaged by accident, misuse, or neglect, and it does not cover a product which has been repaired, altered, or mutiliated outside of TI Automotive's factory in a matter which, in the judgement of TI Automotive, impairs its ability to function properly. In addition, nothing will be allowed for labor charge incurred in the removal, disassembly, ro reinstallation of the product. The warranty described in this paragraph shall be IN LIEU OF any other warranty, express or implied, including but not limited to any implied warranty of Merchantability or fitness for a particular purpose.

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