In 1998, the Ford Mustang was available with a 3.8-liter or 4.6-liter engine. Both power plants rely on a sequential fuel injection system to provide the fuel used in the combustion chamber to generate horse power. The fuel pump resides inside the gas tank and sends gas forward, through the in-line fuel filter, to the fuel injection system atop the engine. While Ford had no set fuel filter maintenance interval in 1998, in the mid-2000s Ford began recommending replacing the filter every 15,000 miles.
Open the trunk and pull back the trunk liner on the left side to reveal the inertia switch, sometimes called the fuel pump cutoff switch. Pull wiring connector off the base of the switch.
Crank the Mustang's engine for 20 seconds to relieve the pressure in the fuel lines. Open the hood. Disconnect the negative battery cable using a battery wrench.
Block the left-front tire with two wheel chocks to hold the Mustang in place. Lift the rear end of the Mustang with a floor jack. Place two jack stands under the rear axle, just inboard from the rear wheels on both sides and lower the Mustang onto the stands with the floor jack.
Crawl under the rear end of the Mustang and follow the fuel line forward from the gas tank until you encounter the fuel filter, mounted on the rear cross-member.
Loosen the fuel filter retaining clamp with a screwdriver. Position the drain pan directly underneath the fuel filter. Release the fuel line retaining clips, located in the fuel lines where they meet the filter, with the fuel-line disconnect tool.
Pull the lines off the old filter. Remove the old filter from the retaining clamp and set it in the drain pan.
Slide the new filter into the retaining band, with the fuel flow arrow aiming forward toward the engine. Place the fuel lines on the new filter and push the clips down into place in the line ends. Tighten the retaining clamp with the screwdriver.
Crawl out from under the Mustang. Lift it off the jack stands with the floor jack, move the stands and then lower the Mustang to the ground.
Reconnect the inertia switch wiring connector to the switch. Close the trunk. Reconnect the negative battery cable and close the hood.
Turn the ignition cylinder to the run position, count to 10 and then shut it off. Do this once more before cranking the engine to start the Mustang. Move the wheel chocks away from the car before driving.
