Replacing A Fuel Pump Fuse In A Fox Body Mustang

If you're having issues with your Fox Body Mustang's fuel pump, you may need to replace the fuse. However, it's important to note that there is no actual fuse for the fuel pump in 87-93 Mustangs. Instead, there is a fusable link, which is a wire near the battery that is designed to burn out in the event of too much draw. This wire can be inspected for damage and replaced if necessary. Additionally, there are other components that may need to be checked, such as the inertia switch in the trunk, and the fuel pump relay, which could be located under the driver's seat, under the dash, on the firewall, or near the headlights.

Check if the fuel pump fuse is melted

To check if the fuel pump fuse is melted, you will need to locate the fuse box. In a Fox Body Mustang, the fuse box is located in the engine compartment, usually on the driver's side fender. Once you have located the fuse box, follow these steps:

• Open the fuse box by releasing the clips or screws that hold it in place.
• Look for the fuel pump fuse, which is typically labeled as such or marked with a fuel pump symbol.
• Visually inspect the fuse for any signs of melting or damage. A melted fuse will often appear distorted or have a burnt smell.
• If the fuse appears damaged, carefully remove it using fuse pullers or needle-nose pliers.
• Examine the fuse more closely to confirm if it is melted. A melted fuse will have a broken or damaged wire inside.
• If the fuse is indeed melted, replace it with a new one of the same type and rating.

It is important to note that the fuel pump fuse in a Fox Body Mustang is not a standard blade-type fuse but a "fusible link." This is a wire that is designed to burn out in the event of too much current draw. To inspect a fusible link:

• Look for any visible damage to the wire.
• Feel the wire to see if it is hollow, which indicates that the internal fuse has melted.
• If the fusible link is damaged, cut it out and replace it with an inline fuse.

Check the inertia switch in the trunk

To check the inertia switch in the trunk of a Fox Body Mustang, you'll need to locate the switch and then perform some tests to check it's functioning correctly.

Locating the Inertia Switch

The inertia switch is located in the trunk, on the driver's side. It should be between the carpet and taillights, a little to the left of the licence plate when facing the trunk. It may be covered by a black rubber plug that pops out, or it might be behind some plastic trim.

Testing the Inertia Switch

You can use a voltmeter to test the inertia switch. Check both sides of the switch for power. There should be power on the dark green/yellow (inertia switch input) and brown/pink wire (inertia switch output). If there is power on the dark green/yellow wire and not on the brown/pink wire, this means the switch is open. Press the red plunger to reset it to the closed position.

If the switch is faulty, you can bypass it, but this is not recommended as it is a safety feature. If your fuel line is ever severed, you want the switch to cut off the fuel pump to prevent a fire.

Check the fuel pump relay

To check the fuel pump relay on a Fox Body Mustang, you must first locate it. For 1986-91 Mustang models, the fuel pump relay is located under the driver's seat. For 1992-93 Mustang models, the fuel pump relay is usually located under the MAF (Mass Air Flow) sensor, although some earlier 1992 models may still have it under the driver's seat.

Once you have located the fuel pump relay, you can perform the following checks:

• Check for power at the fuel pump. The fuel pump has a connector at the rear of the car with a pink/black wire and a black wire that goes to the fuel pump. The pink/black wire should be hot when the test connector is jumped to the test position. If there is no voltage when jumped, check the fuel pump relay and fuse links.
• Check the power feed. Look for 12 volts at the pink/black wire (the power source for the fuel pump relay). If there is no voltage or low voltage, this could be due to a bad fuse link, bad wiring, or connections.
• Check the relay. Turn on the key and jumper the ECC test connector. Look for 12 volts at the dark green/yellow wire (relay-controlled power for the fuel pump). If there is no voltage, the relay has failed or there is a broken wire in the relay control circuit. Be sure to check the condition of the relay, wiring, and socket for corrosion and damage.

If you are experiencing issues with your fuel pump relay, it is recommended to refer to a professional mechanic or a detailed wiring diagram for further guidance.

Check the fuel pump for power

To check the fuel pump for power, you can use a multimeter or a test light to verify that there is power at the fuel pump.

Firstly, locate the fuel pump relay. For 1986-1991 Mustang year models, the fuel pump relay is located under the driver's seat. For 1992-1993 Mustang year models, the fuel pump relay is usually located under the MAF (Mass Air Flow) sensor, although some earlier 1992 models may still have it under the driver's seat.

Once you have located the fuel pump relay, the next step is to check for power at the fuel pump. The fuel pump has a connector at the rear of the car with a pink/black wire and a black wire that goes to the fuel pump. The pink/black wire should be hot when the test connector is jumped to the test position. To trick the fuel pump into running, find the ECC test connector and jump the connector in the lower RH corner to ground. If there is still no voltage, check the fuel pump relay and fuse links.

If you are still experiencing issues with the fuel pump not receiving power, it may be due to a faulty inertia switch. The inertia switch is located on the driver's side by the taillight. Look for a black rubber plug that pops out or, if you can't find it, loosen the plastic trim. Check for voltage on both sides of the switch. If there is voltage on both sides, then check the pink/black wire on the fuel pump relay, which is the power feed to the fuel pump. If there is good voltage there, then the fuel pump may be the culprit.

Check the fuel pump for ground

To check the fuel pump for ground on a Fox Body Mustang, you will need to locate the fuel pump relay and the fuel pump driver module. The fuel pump relay is located either under the driver's seat or on the passenger side fender well in front of the shock tower. The fuel pump driver module can be found on the underside of the luggage compartment.

Once you have located the fuel pump relay, you can check the ground by following these steps:

• Turn the ignition key to the "On" position but do not start the engine.
• Locate the fuel pump relay and remove it from its housing.
• Check the fuel pump relay for any signs of corrosion or damage.
• Inspect the wiring and socket for any damage or loose connections.
• Ensure that the ground wire from the fuel pump relay is securely connected to the chassis ground.

If the fuel pump relay appears to be in good condition and the ground wire is securely connected, you can move on to checking the fuel pump driver module:

• Locate the fuel pump driver module under the luggage compartment.
• Check the pins on the fuel pump driver module for any signs of corrosion or damage.
• Ensure that the ground wire from the fuel pump driver module is securely connected to the chassis ground G400, which is located on the left rear of the luggage compartment.

If there are no issues with the fuel pump relay or the fuel pump driver module, then the problem may lie elsewhere in the fuel system or engine. It is recommended to consult a professional mechanic or seek further troubleshooting advice if the issue persists.

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