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

The bottom line: On a 2004 Ford Explorer Sport Trac, the fuel pump relay lives inside the Power Distribution Box (PDB) under the hood, on the driver’s side, near the firewall and behind the battery. It is commonly identified as relay #48, and the matching 20-amp fuel pump mini fuse is labeled #26 in the same box. In some Sport Trac variants, the relay may sit in a rectangular black plastic box next to the horn relay in the same engine bay area. If your Explorer cranks but won’t start, or you hear no fuel pump hum when you turn the key, the relay is one of the first things to check.

This guide walks you through the exact location, how to confirm the relay is bad, how to bypass it for testing, and what to do if the relay is not your problem. You will also find a reliable replacement recommendation near the end. No guesswork, just the steps.

1. Where the Fuel Pump Relay Is Located

The Power Distribution Box is the main fuse and relay center in the engine bay. On the 2004 Explorer Sport Trac, this box sits on the driver’s side, close to the battery and the firewall.

Steps to find the relay:

  1. Open the hood and look to the driver’s side, near the back of the engine bay.
  2. Locate the black plastic Power Distribution Box. It has a removable cover.
  3. Remove the cover and look at the underside of the lid for a diagram. It should show relay positions.
  4. Find relay position #48. This is the fuel pump relay.
  5. The 20-amp fuel pump fuse is mini fuse #26, also in this box.

Some owners report the relay in a separate small black box beside the horn relay, still in the engine bay on the driver’s side. Either way, you are looking for a standard 4-pin relay. If the diagram on the lid is faded, check your owner’s manual or search online for the 2004 Explorer Sport Trac Power Distribution Box layout.

2. Symptoms That Point to a Bad Fuel Pump Relay

A failing fuel pump relay usually shows clear warning signs. If you notice any of the following, the relay is worth testing before you replace the fuel pump itself:

  1. Engine cranks but will not start — the most common symptom.
  2. No fuel pump prime noise — when you turn the key to the “ON” position (without cranking), you should hear a faint hum from the fuel tank for 2 to 3 seconds. If you hear nothing, the relay may not be sending power.
  3. Engine dies while driving and then restarts after cooling down — a classic relay failure pattern.
  4. Sputtering, hesitation, or loss of power under load.
  5. Long crank times before the engine fires up.

These symptoms can also point to a bad fuel pump, a clogged fuel filter, or a failed fuel pump driver module. So test the relay first. It is the cheapest and easiest check.

3. How to Test the Fuel Pump Relay

You do not need special tools for a basic relay test. Just follow these steps:

  1. Turn the ignition off and disconnect the negative battery terminal. This prevents accidental shorts and keeps you safe when working with electrical parts.
  2. Remove the fuel pump relay (relay #48) from the Power Distribution Box.
  3. Use a multimeter set to measure resistance (ohms).
  4. Check the coil side of the relay — terminals 85 and 86 should show some resistance (typically 50 to 120 ohms). If the reading is infinite or zero, the relay coil is dead.
  5. Check the switch side — terminals 30 and 87 should show no continuity when the relay is at rest. If they show continuity, the relay is stuck closed.

If the relay fails any of these checks, replace it. Relays are not expensive, usually between $30 and $50.

4. How to Bypass the Fuel Pump Relay for Testing

If you want to confirm the fuel pump itself works, you can bypass the relay temporarily. This is a common trick used by mechanics and DIY owners.

Follow these steps carefully:

  1. Remove the fuel pump relay from the Power Distribution Box.
  2. Look at the relay socket. You will see four terminals: 30, 85, 86, and 87.
  3. Use a short piece of wire with the ends stripped, or a paperclip, to jump terminals 3 and 5 (which correspond to relay pins 30 and 87 in this socket layout).
  4. Turn the ignition to the “ON” position without cranking the engine.
  5. Listen near the fuel tank for the pump hum. If the pump runs, the relay is the problem. If it stays silent, the pump or its wiring is the issue.

Important safety note: Do not leave the jumper in place while driving. The purpose is only to test. Remove the jumper and reinstall the relay once you are done.

5. The Fuel Pump Driver Module (FPDM) — Another Common Culprit

On the 2004 Explorer Sport Trac, there is a part called the Fuel Pump Driver Module (FPDM). This module controls the fuel pump speed. It is separate from the relay and a known failure point on these trucks.

  • Location on Sport Trac: The FPDM is mounted under the vehicle, on the passenger side, near the front of the fuel tank. Because it is exposed to the elements, it often fails due to corrosion and moisture intrusion.
  • Location on Explorer SUV: If you drive the SUV version, the FPDM is inside the cargo area, behind the interior trim panel on the passenger-side rear quarter panel.

If your relay checks out but the fuel pump still does not run, test the FPDM. You will need a multimeter and the vehicle’s wiring diagram. Look for trouble codes like P1233 through P1237, which point to fuel pump control circuit problems.

6. Fuel Pump Fuse and Inertia Switch

Fuel Pump Fuse:
The 20-amp mini fuse for the fuel pump is in the same Power Distribution Box as the relay. It is fuse #26. A blown fuse is a common and cheap fix. Always check the fuse before condemning the relay or the pump.

Fuel Pump Inertia Switch:
The inertia switch is a safety device that cuts power to the fuel pump in a collision. On the 2004 Explorer, it is located behind the passenger side kick panel — that is, in the right front passenger footwell area. If the switch is tripped, the engine will crank but get no fuel. Press the reset button on top of the switch to restore power.

7. How to Replace the Fuel Pump Relay

Replacing the relay is a five-minute job. Here is how:

  1. Buy the correct relay. Most auto parts stores stock the standard 4-pin relay that Ford uses. Bring the old one for comparison.
  2. Disconnect the battery negative cable.
  3. Remove the relay by pulling it straight out of the socket.
  4. Insert the new relay in the same position. Push it down until it clicks into place.
  5. Reconnect the battery and test the system.

Turn the key to the “ON” position and listen for the fuel pump prime hum. If you hear it, the job is done.

8. What If the Relay Is Fine? Next Steps

If the relay, fuse, and inertia switch all check out, and you still have no fuel pressure, move on to the fuel pump itself. On the 2004 Explorer Sport Trac, the electric fuel pump is inside the fuel tank. Accessing it requires either removing the tank or using an access hole on top of the tank.

Steps to access the pump:

  1. Relieve fuel system pressure by pressing the Schrader valve on the fuel rail with the ignition off.
  2. Raise the vehicle safely on jack stands.
  3. Remove the skid plate and disconnect the fuel lines and electrical connector.
  4. Lower the tank and remove the locking ring to pull the pump module out.

This job is labor-intensive. If you are not comfortable working with fuel systems, have a professional do it. Expect the total cost for a new fuel pump installed to range from $600 to $900.

9. KEMSO Fuel Pump — A Smart Replacement Option

If your fuel pump is bad and you are replacing it, consider a KEMSO brand fuel pump. KEMSO builds high-performance fuel pumps that are OEM replacements. That means they match the original equipment specifications for fit and function.

Why choose KEMSO:

  1. High performance — designed to meet or exceed factory flow and pressure specs.
  2. OEM replacement — drop-in fit, no modification needed.
  3. Lifetime warranty — KEMSO stands behind its products.

KEMSO makes fuel pumps for a wide range of vehicles, including motorcycles, ATVs, and cars. You can browse their selection and order directly at their official website:

https://www.kemsoracing.com/

Before you buy a fuel pump, verify the exact part number for your 2004 Explorer Sport Trac so you get the right fit.

10. Final Words

The fuel pump relay on your 2004 Ford Explorer Sport Trac is easy to find and easy to replace. Start with the Power Distribution Box under the hood, check relay #48 and fuse #26, and test the relay before spending money on parts. If the relay is not the issue, check the inertia switch and the FPDM. Only then move on to the pump itself.

A bad fuel pump relay is a small problem that can stop your truck cold. Knowing where to look and how to test will save you time and money. And if you do end up replacing the fuel pump, KEMSO offers a solid, reliable option backed by a lifetime warranty.

For replacement fuel pumps, visit KEMSO at:
https://www.kemsoracing.com/


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