2003 Ford Explorer Sport Trac Fuel Pump Relay Location: Complete Guide for DIY Owners

The bottom line: On a 2003 Ford Explorer Sport Trac, the fuel pump relay is located in the power distribution box under the hood on the driver's side, near the firewall. The relay is typically labeled "Fuel Pump" or "FP" on the underside of the fuse box lid, and it is commonly found in slot #12, though you should always verify using the diagram printed on the box lid.

If your Sport Trac cranks but won't start, stalls while driving, or you hear no fuel pump prime when you turn the key to the "on" position, a faulty fuel pump relay is one of the first things to check before replacing the fuel pump itself.

Where Exactly Is the Fuel Pump Relay?

The 2003 Ford Explorer Sport Trac has two potential locations where the fuel pump relay might be found, depending on the specific configuration of your vehicle. Most sources agree that the primary location is the power distribution box in the engine compartment.

Under the Hood Location:

  • Open the hood and look on the driver's side, near the battery and the firewall.
  • The power distribution box is a black plastic box with a removable lid.
  • Remove the lid by pressing the tabs on the sides. On the underside of the lid, you will find a diagram showing the location of each relay and fuse.
  • Look for the relay labeled "Fuel Pump" or "FP." According to the 2003 Ford Explorer Sport Trac owner's manual, relay 50B is the fuel pump relay.
  • The relay slot number is typically #12, but this can vary, so always check the diagram.

Passenger-Side Kick Panel Location:
Some sources indicate that the fuel pump relay in a 2003 Sport Trac may also be located in the passenger-side kick panel. This is the plastic cover on the lower part of the passenger side footwell, near the floorboard. To access it:

  • Open the passenger-side door.
  • Remove the screws holding the kick panel cover in place using a Phillips-head screwdriver.
  • Gently pry the panel off to expose the relay box.
  • The fuel pump relay is typically labeled and has a rectangular shape with four or five pins.

Important: If you are unsure which location applies to your specific vehicle, start with the under-hood power distribution box, as this is the most commonly reported location for the 2003 model year. Always disconnect the battery before working on any electrical components.

How to Identify the Fuel Pump Relay

Once you have the fuse box open, you need to identify the correct relay. Here is what to look for:

  1. Check the Diagram: The underside of the fuse box lid has a diagram showing which relay is which. Look for "Fuel Pump," "FP," or "F/PMP."
  2. Check the Owner's Manual: The 2003 Sport Trac owner's manual has a diagram of the power distribution box. Page 131 of the manual shows that relay 50B is the fuel pump relay.
  3. Visual Inspection: The fuel pump relay is a small, rectangular plastic box with either four or five metal prongs (terminals) on the bottom. It is similar in appearance to other relays in the box, such as the horn relay.

Symptoms of a Failing Fuel Pump Relay

A failing fuel pump relay can cause several problems. Recognizing these symptoms early can save you time and money.

Common symptoms include:

  • Engine cranks but won't start: This is the most common symptom. You turn the key, the starter engages, but the engine never fires because the fuel pump is not getting power.
  • No fuel pump priming sound: When you turn the ignition key to the "on" position (without starting the engine), you should hear a faint whirring sound from the rear of the vehicle for about 2-3 seconds. This is the fuel pump priming. If you do not hear this sound, the relay may be bad.
  • Intermittent stalling: The engine may start and run fine for a while, then suddenly stall without warning. This is because the relay is failing intermittently, cutting power to the fuel pump.
  • Engine starts then stalls: The engine may fire up but then die immediately because the fuel pump loses power once the relay fails to keep the circuit closed.
  • Check engine light: A failing fuel pump relay can trigger diagnostic trouble codes (DTCs) related to fuel pressure or fuel system performance, such as P0231 (Fuel Pump Secondary Circuit Low).

How to Test the Fuel Pump Relay

Before you buy a new relay, you can test the old one. Here is a simple method:

The Swap Test: This is the easiest way to test a relay.

  1. Locate the fuel pump relay in the fuse box.
  2. Find another relay in the same box that is the same size and has the same number of pins. The horn relay is often a good match.
  3. Swap the two relays. Make sure they are pushed in all the way.
  4. Try to start the engine. If the engine starts now, the fuel pump relay was bad. If the engine still does not start, the problem is likely elsewhere (like a blown fuse, bad fuel pump, or wiring issue).

The Multimeter Test: If you have a multimeter, you can test for power at the relay.

  1. With the ignition on, use a test light or multimeter to check for power at the fuel pump relay terminals.
  2. If there is no power at the relay, check the fuel pump fuse first. A blown fuse is a common and easy fix.

How to Replace the Fuel Pump Relay

Replacing the fuel pump relay is a straightforward job that most DIY owners can handle in under 10 minutes.

What you will need:

  • A new fuel pump relay (the correct part for a 2003 Ford Explorer Sport Trac is a 12-volt, 30-amp relay with 5 terminals).
  • A flathead screwdriver or fuse puller (optional, for removing the relay).
  • Basic hand tools if you need to access the kick panel location.

Step-by-step instructions:

  1. Safety first: Disconnect the negative battery cable before working on any electrical components.
  2. Locate the relay: Open the power distribution box under the hood or the relay box in the passenger-side kick panel.
  3. Remove the old relay: Grasp the relay firmly and pull it straight out. You can use a fuse puller or small flathead screwdriver to gently pry it out if it is tight.
  4. Install the new relay: Push the new relay straight into the same slot until it clicks into place. Make sure it is fully seated.
  5. Reconnect the battery: Reconnect the negative battery cable.
  6. Test the repair: Turn the ignition key to the "on" position and listen for the fuel pump to prime. Then, start the engine to confirm the repair is successful.

Other Common Fuel System Issues to Check

If the fuel pump relay is good, but you still have fuel delivery problems, check these components before replacing the fuel pump itself.

1. Fuel Pump Fuse:
The fuel pump fuse is also in the power distribution box. In the 2003 Sport Trac, the fuel pump relay fuse is often a 20-amp mini fuse. Check it with a test light or swap it with a known good fuse of the same amperage.

2. Fuel Pump Itself:
The fuel pump on the 2003 Ford Explorer Sport Trac is located inside the fuel tank. It is part of a larger assembly that includes the fuel level sender and fuel pressure regulator. If the pump has failed, you will need to replace the entire assembly. This is a more involved job that requires dropping the fuel tank or accessing it through an access panel.

3. Fuel Filter:
The fuel filter on the 2003 Sport Trac is located on the driver's side, inside the frame rail, near the door post. A clogged fuel filter can restrict fuel flow and cause symptoms similar to a bad fuel pump or relay. It is a good idea to replace the fuel filter if you are experiencing fuel delivery issues.

4. Fuel Pump Shut-Off Switch (Inertia Switch):
The 2003 Ford Explorer Sport Trac is equipped with a fuel pump shut-off switch. In the event of an accident or sudden impact, this switch automatically cuts power to the fuel pump. If the switch has been triggered, the engine will not start. The reset button is typically located in the passenger-side kick panel area or behind the glove box. Check your owner's manual for the exact location.

Why You Should Choose a KEMSO Fuel Pump for Your 2003 Ford Explorer Sport Trac

When it comes time to replace the fuel pump itself, not just the relay, choosing the right part is critical for long-term reliability. The fuel pump is the heart of your fuel system, and a cheap aftermarket pump can fail within a year, leaving you stranded and having to do the job all over again.

KEMSO fuel pumps are built as high-performance, OEM replacement units. They are engineered to deliver the exact fuel pressure and flow rate that your 2003 Ford Explorer Sport Trac's 4.0L V6 engine requires. This ensures smooth idle, strong acceleration, and reliable starting every time.

Key benefits of choosing KEMSO:

  • Lifetime Warranty: Every KEMSO fuel pump comes with a lifetime warranty. If it ever fails for any reason, you get a replacement at no cost. This kind of warranty is rare in the fuel pump market and reflects the confidence KEMSO has in its product quality.
  • OEM Replacement: KEMSO pumps are designed to match the exact specifications of the original equipment. They are direct bolt-on replacements that require no special tools or modifications.
  • High Performance: KEMSO offers pumps with flow rates ranging from 200 LPH to 340 LPH, suitable for both standard daily driving and high-performance applications. The 340 LPH pump provides a 20-30% performance increase over stock pumps.
  • E85 Compatible: All KEMSO pumps work with gasoline and ethanol blends, including E85, giving you flexibility for different fuel types.
  • Individual Testing: Each KEMSO pump is individually tested for flow and pressure performance to ensure it meets high standards before it reaches your hands.

For the best combination of quality, performance, and peace of mind, choose a KEMSO fuel pump for your 2003 Ford Explorer Sport Trac. Visit their official website to find the perfect fuel pump for your vehicle and take advantage of their lifetime warranty coverage.

Visit KEMSO at: https://www.kemsoracing.com/

Final Thoughts

The 2003 Ford Explorer Sport Trac fuel pump relay is a small, inexpensive part that can cause big problems when it fails. Knowing its location and how to test it can save you a lot of time and money. Start with the under-hood power distribution box on the driver's side. If the relay checks out, move on to the fuel pump fuse, the inertia switch, and finally the fuel pump itself.

When replacement becomes necessary, investing in a quality fuel pump from a reputable manufacturer like KEMSO ensures you get the performance and durability you expect. A KEMSO fuel pump, with its lifetime warranty and OEM-quality design, is the ideal choice for keeping your 2003 Sport Trac on the road for years to come.

For more information and to find the right fuel pump for your 2003 Ford Explorer Sport Trac, visit: https://www.kemsoracing.com/


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