2004 Ford Explorer Sport Trac Fuel Pump Relay Location: The Complete Owner’s Guide

The fuel pump relay on a 2004 Ford Explorer Sport Trac is located in the Power Distribution Box (PDB) under the hood, on the driver’s side, near the firewall behind the battery. This is the most common location across the Sport Trac lineup from 2001 through 2010. The relay is typically labeled on the underside of the PDB cover, and in most cases it sits in a slot that is clearly marked with either "Fuel Pump" or "FP". If you are dealing with a no-start condition or suspect your fuel pump is not receiving power, this relay is the first component you should check before you even think about dropping the fuel tank.

The relay itself is a small, rectangular electrical component with four or five pins that controls the power supply to the electric fuel pump. When you turn the ignition key to the "ON" position, the relay closes and sends 12 volts to the fuel pump, which then pressurizes the fuel system. If the relay fails, the pump will not run, and your engine will crank but will not start. The good news is that the relay is inexpensive and relatively easy to replace. The bad news is that finding it in a crowded engine bay can be tricky if you do not know exactly what you are looking for. This guide will walk you through the exact location, how to access it, how to test it, and what to do if the relay turns out to be fine.

Why the Fuel Pump Relay Matters

The fuel pump relay is a small but critical part of your Sport Trac’s electrical system. Without it, the fuel pump simply will not operate. The relay acts as a heavy-duty switch that allows a low-power signal from the engine computer to control a high-power circuit that feeds the fuel pump. When the relay fails, you will typically experience one or more of the following symptoms:

1. Engine cranks but will not start – This is the most common symptom of a failed fuel pump relay. You turn the key, the starter spins the engine over, but the engine never fires up because there is no fuel pressure.
2. No fuel pump priming sound – When you turn the ignition to the "ON" position (without cranking), you should hear a faint humming noise coming from the fuel tank area for about two to three seconds. If you hear nothing, the relay may not be sending power to the pump.
3. Intermittent starting issues – If the relay is failing intermittently, you may find that the truck starts fine sometimes and then refuses to start other times. This is often caused by a relay with worn contacts that work when cold but fail when hot.
4. Engine stalls while driving – If the relay fails completely while you are on the road, the engine will lose fuel pressure and die. You will not have any warning, and the truck will simply shut off.

Step-by-Step: Locating the Relay

Step 1: Open the Hood and Find the Power Distribution Box

The Power Distribution Box is a black plastic box that houses most of the fuses and relays for your Sport Trac. On the 2004 model, it is located in the engine compartment on the driver’s side, close to the firewall and directly behind the battery. It is a rectangular box with a removable lid that has a diagram printed on the underside showing the location and function of every fuse and relay inside.

Step 2: Remove the PDB Cover

Press the release tabs on the sides of the cover and lift it straight up. The cover is not bolted down, so it should come off easily. Once removed, flip it over and look at the diagram printed on the underside. You are looking for a relay labeled "Fuel Pump" or one that is identified with the abbreviation "FP".

Step 3: Identify the Correct Relay

The relay is a small, cube-shaped component that plugs into the fuse box. It is usually black or dark gray and has either four or five metal prongs on the bottom. On most 2004 Sport Trac models, the fuel pump relay is located near the middle of the fuse box, but the exact position can vary depending on the trim level and optional equipment your truck has. If the diagram on the cover is not clear, consult your owner’s manual for the specific relay slot.

Step 4: Check the Label on the Relay Itself

Some relays have a small label or marking on the top that indicates what circuit they control. If the relay is labeled, this is the fastest way to confirm you have the right one. If it is not labeled, compare it with the diagram on the underside of the PDB cover.

Testing the Fuel Pump Relay

Once you have located the relay, you need to determine whether it is actually the cause of your problem. There are several ways to test it, and you do not need to be a professional mechanic to do this.

Method 1: The Swap Test

This is the quickest and easiest way to test a relay. Find another relay in the same fuse box that has the same part number and configuration – the horn relay is usually a good candidate. Pull out the suspect fuel pump relay and plug in the known-good relay in its place. Then turn the ignition to the "ON" position and listen for the fuel pump priming sound. If you hear the hum, the original relay is bad and needs to be replaced. If you still hear nothing, the problem is elsewhere.

Method 2: Listen for the Priming Cycle

With the relay in place, turn the ignition key to the "ON" position without cranking the engine. You should hear a faint hum from the fuel tank area for two to three seconds. This is the fuel pump running to pressurize the system. If you do not hear this sound, the relay may not be sending power to the pump.

Method 3: Check for Voltage

If you have a multimeter, you can check for voltage at the fuel pump connector. The pump is located inside the fuel tank, and you can access the electrical connector near the top of the tank. With the ignition in the "ON" position, you should read approximately 12 volts at the connector. If you have voltage, the relay is working and the problem is the pump itself. If you have no voltage, the issue could be the relay, a blown fuse, or a wiring problem.

Method 4: Check the Fuse

Before you replace the relay, check the fuel pump fuse as well. On a 2005 Explorer Sport Trac, the fuel pump fuse is a 20-amp mini fuse located in the Power Distribution Box under the hood, and it is typically fuse number 30. The 2004 model uses a similar configuration. A blown fuse will cause the exact same symptoms as a failed relay, and replacing a fuse is even cheaper than replacing a relay.

What If the Relay Is Fine?

If the relay tests good and the fuse is not blown, the problem could be one of several other components. Do not assume the fuel pump itself is bad just yet. Work through these possibilities in order.

1. Check the Fuel Pump Driver Module (FPDM)

The 2004 Sport Trac uses a returnless fuel system that incorporates a Fuel Pump Driver Module. This module controls the speed of the fuel pump based on demand from the engine computer. On the Sport Trac, the FPDM is mounted under the vehicle on the passenger side, near the front of the fuel tank. It is exposed to the elements and often fails due to corrosion and moisture intrusion. If the module is corroded or cracked, it will not send power to the fuel pump, and you will have the same symptoms as a failed relay. Inspect the module for signs of corrosion, especially on the back of the aluminum housing.

2. Check the Inertia Fuel Shutoff Switch

Ford vehicles are equipped with an inertia switch that cuts power to the fuel pump in the event of a collision. In some models, this switch is located on the right side of the passenger footwell, behind the kick panel. If the switch has been tripped, it will need to be reset. Press the reset button on top of the switch to restore power to the fuel pump.

3. Check the Wiring and Connectors

Corroded or damaged wiring between the relay, the FPDM, and the fuel pump can cause intermittent or complete loss of power. Inspect the wiring harness for signs of fraying, melting, or rodent damage. Pay special attention to the connector at the fuel pump itself – a melted or corroded connector indicates a serious electrical issue.

4. Test the Fuel Pump

If all the electrical components check out, the fuel pump itself may be failing. The pump is located inside the fuel tank, and testing it requires either a fuel pressure gauge or a multimeter. Connect a fuel pressure gauge to the Schrader valve on the fuel rail and check the pressure with the ignition in the "ON" position. The pressure should read between 30 and 60 PSI, depending on the engine. If the pressure is low or zero, the pump is likely bad and will need to be replaced.

How to Replace the Fuel Pump Relay

Replacing the fuel pump relay is one of the simplest repairs you can do on your Sport Trac. It takes about five minutes and requires no special tools.

1. Disconnect the negative battery cable – This is a safety precaution that prevents accidental shorts while you are working with electrical components.
2. Remove the PDB cover – Press the release tabs and lift the cover off.
3. Pull the old relay out – Grasp the relay firmly and pull it straight up. It may take a little effort, but it will come out of the socket.
4. Plug in the new relay – Align the prongs with the socket and press down firmly until the relay is fully seated.
5. Reconnect the battery – Reattach the negative battery cable and tighten the terminal.
6. Test the system – Turn the ignition to the "ON" position and listen for the fuel pump priming sound.

Where to Buy a Replacement Relay

You can purchase a replacement fuel pump relay from your local Ford dealer, an auto parts store like AutoZone or O'Reilly, or online through retailers like PartsGeek. The relay is a generic automotive relay that is used across many Ford models, so it is widely available and inexpensive. When purchasing a replacement, make sure you get one that matches the amperage rating of the original.

Final Thoughts

Finding the fuel pump relay on your 2004 Ford Explorer Sport Trac is a straightforward process once you know that it lives in the Power Distribution Box under the hood on the driver’s side, behind the battery. Start by testing the relay before you do anything else. If the relay is good, move on to the fuse, the FPDM, and the pump itself. Most fuel delivery problems are caused by one of these four components, and working through them in order will save you time and money. Do not drop the fuel tank until you have ruled out every other possibility.

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