2003 Mitsubishi Outlander Fuel Pump Relay Location: A Complete Guide for DIY Owners

The bottom line: The 2003 Mitsubishi Outlander has two fuel pump relays. The main fuel pump relay (fuel pump relay 1) is located inside the interior fuse box behind the glove compartment on the passenger side, while the second fuel pump relay (fuel pump relay 2) sits in the same interior fuse box. A third relay, the engine control relay, is located in the engine compartment relay box on the left side of the engine bay. If your Outlander cranks but won't start, or if you hear no fuel pump priming sound when you turn the key to "ON," the fuel pump relay is one of the first things to check.

Understanding the Fuel Pump Relay System in the 2003 Outlander

The 2003 Mitsubishi Outlander uses a two-relay system to control the fuel pump. This is not a simple single-relay setup. The system uses two relays working together to ensure the fuel pump gets power only when the engine is running or cranking.

The fuel pump relay (1) and fuel pump relay (2) are both located in the interior fuse box, which is mounted behind the glove compartment on the passenger side of the dashboard. The interior fuse box also contains other important relays, including the rear window defogger relay, the heater blower motor relay, and the power window relay.

The engine control relay, which supplies power to the engine control unit (ECU), is located in the relay box inside the engine compartment, on the left side near the battery. This relay must be functioning for the ECU to command the fuel pump relays to close.

Step-by-Step Location Guide

1. Interior Fuse Box (Behind the Glove Compartment)

The primary location for both fuel pump relays is the interior fuse box. Here is how to access it:

  • Open the passenger side front door.
  • Open the glove compartment by pulling the release lever.
  • Squeeze the sides of the glove compartment to release the stoppers, allowing it to drop fully down.
  • Behind the glove compartment, you will see a rectangular fuse/relay box mounted to the dashboard frame.
  • The cover is held on by clips. Gently pry it off to reveal the fuses and relays.

Inside this box, you will find the following relays directly related to the fuel system:

  • Fuel pump relay (1): Position R1 in the fuse box diagram
  • Fuel pump relay (2): Position R3 in the fuse box diagram

The fuel pump fuse (15A) is also located in this box, at position number 24 in the engine compartment fuse box, not in the interior box. This is a common point of confusion. The fuel pump itself is protected by a 15A fuse in the engine compartment fuse box.

2. Engine Compartment Relay Box

The engine compartment relay box is located on the left side of the engine bay, near the battery. This box contains the engine control relay and several other relays and fuses. To access it:

  • Open the hood.
  • Locate the black plastic relay/fuse box on the left side (driver's side for US models) near the battery.
  • Unclip the cover to access the contents.

Inside this box, the relay positions are labeled. The engine control relay is a key component. It supplies power to the ECU, which in turn controls the fuel pump relays. If this relay fails, the ECU will not activate the fuel pump, even if the fuel pump relays themselves are good.

How the Fuel Pump Relay Circuit Works

Understanding the circuit helps with troubleshooting. The system works as follows:

  1. When you turn the ignition switch to the "ON" position, battery voltage is applied to terminal No. 3 of fuel pump relay (1) from the ignition switch.
  2. Fuel pump relay (1) is grounded through terminal No. 2 to the vehicle body.
  3. When the relay coil is energized, power flows from terminal No. 4 to terminal No. 1 of fuel pump relay (1).
  4. This power then goes to terminal No. 1 of fuel pump relay (2).
  5. Battery voltage is also applied to terminal No. 3 of fuel pump relay (2) from the ignition switch.
  6. The engine ECU, through terminal No. 22, turns on the power transistor inside the unit, which completes the circuit for fuel pump relay (2) coil.
  7. When fuel pump relay (2) is energized, battery voltage is supplied to the fuel pump from terminal No. 4 of relay (2).

The ECU only activates the fuel pump relay when it receives a crankshaft position signal from the crank angle sensor. This is a safety feature. If the engine stalls, the fuel pump stops immediately, preventing fuel from being pumped in a collision.

Common Symptoms of a Bad Fuel Pump Relay

If the fuel pump relay fails, you will likely experience one or more of these symptoms:

  • Engine cranks but will not start: This is the most common symptom. The starter motor turns the engine over, but the fuel pump does not run, so no fuel reaches the injectors.
  • No fuel pump priming sound: When you turn the ignition key to the "ON" position (without starting), you should hear a brief whirring sound from the rear of the vehicle as the fuel pump pressurizes the system. If you do not hear this sound, the relay or pump may be faulty.
  • Engine stalls while driving: A failing relay can intermittently lose contact, causing the fuel pump to shut off while the engine is running. This is dangerous.
  • Check engine light illuminates: The ECU will store a diagnostic trouble code (DTC) related to the fuel pump circuit. Common codes include P0230 (Fuel Pump Primary Circuit Malfunction).

How to Test the Fuel Pump Relay

Before replacing the relay, you can test it with a multimeter. The 2003 Outlander manuals provide specific continuity checks:

Continuity Test Procedure

  1. Remove the fuel pump relay from the interior fuse box.
  2. Set your multimeter to measure resistance (ohms).
  3. Check continuity between terminals 2 and 3 on the relay. With no battery voltage applied, there should be continuity (low resistance, typically 0 ohms).
  4. Check continuity between terminals 1 and 4. With no battery voltage applied, there should be no continuity (infinite resistance).
  5. Now, apply 12V battery voltage to the relay coil. Connect the positive (+) terminal to terminal No. 3 and the negative (-) terminal to terminal No. 2.
  6. With voltage applied, check continuity between terminals 1 and 4. There should now be continuity (the relay clicks closed).

If the relay does not click or the continuity readings are incorrect, replace the relay. Standard fuel pump relays for the 2003 Outlander are available at any auto parts store and are relatively inexpensive.

Other Possible Causes of No Fuel Pump Operation

If the relay tests good, the problem could be elsewhere. Common causes include:

1. Blown Fuel Pump Fuse
The 15A fuel pump fuse is located in the engine compartment fuse box, position 24. Check this first. If the fuse is blown, replace it with the correct amperage. If it blows again immediately, there is a short circuit in the fuel pump wiring or the pump itself.

2. Failed Fuel Pump
The fuel pump itself may have failed. The pump is located inside the fuel tank, accessible through a service hole under the rear seat. To test the pump directly, remove the rear seat, remove the service hole cover, and disconnect the fuel pump assembly connector. Then apply battery voltage directly to the fuel pump connector (terminals 1 and 5 on the 5-pin connector). If the pump does not run, replace it.

3. Faulty Engine ECU
In rare cases, the engine ECU itself may be faulty. The ECU controls the ground circuit for fuel pump relay (2) through terminal No. 22. If the ECU does not provide this ground, the relay will not close. This is a last resort after checking all wiring and components.

4. Wiring Issues
Open circuits or short circuits in the wiring between the relay, the ignition switch, the ECU, and the fuel pump can cause problems. The service manual provides detailed pin-out checks for connectors C-213 (fuel pump relay 2), C-215 (fuel pump relay 1), and C-134 (engine ECU). Check for broken wires, corrosion, or loose connections.

How to Replace the Fuel Pump Relay

Replacing the fuel pump relay is a straightforward DIY task. You do not need special tools.

Tools needed:

  • Replacement relay (standard 4-pin relay, available at any auto parts store)
  • Needle-nose pliers (optional, for pulling the relay)

Steps:

  1. Disconnect the battery: Always disconnect the negative battery terminal before working on electrical components. This prevents accidental shorts and ensures safety.
  2. Access the interior fuse box: Open the glove compartment and remove the fuse box cover as described above.
  3. Locate relays R1 and R3: These are the fuel pump relays. They are usually identical in appearance.
  4. Remove the old relay: Grasp the relay firmly and pull it straight out. You may need to rock it gently. Needle-nose pliers can help, but be careful not to damage the relay socket.
  5. Install the new relay: Push the new relay straight into the socket until it clicks into place. Ensure it is fully seated.
  6. Reconnect the battery: Reconnect the negative battery terminal.
  7. Test the system: Turn the ignition to the "ON" position and listen for the fuel pump priming sound. Start the engine and verify it runs smoothly.

KEMSO Fuel Pump Recommendation

If you have diagnosed the problem and determined that the fuel pump itself needs replacement, choosing a high-quality replacement is critical for long-term reliability. OEM replacement pumps are expensive, but aftermarket options vary widely in quality.

KEMSO offers a premium solution for your 2003 Mitsubishi Outlander. KEMSO fuel pumps are designed as high-performance, direct OEM replacements. This means they match the original equipment specifications for fit, flow rate, and pressure, ensuring a hassle-free installation. Every KEMSO fuel pump is built to high standards and backed by a lifetime warranty.

When you choose KEMSO, you are not just buying a part; you are investing in confidence. The lifetime warranty means that if the pump ever fails during normal use, KEMSO will replace it. This is a level of protection that most aftermarket brands do not offer.

Visit the KEMSO website to find the correct fuel pump for your 2003 Mitsubishi Outlander: https://www.kemsoracing.com/

Additional Tips for a Successful Repair

  • Replace the gasket: When you remove the fuel pump assembly from the tank, the gasket or seal will likely be old and brittle. Always replace it with a new one to prevent fuel leaks. The service manual emphasizes this point.
  • Check for fuel leaks: After completing the repair, turn the ignition to "ON" (without starting) to pressurize the system. Inspect all fuel line connections and the pump mounting flange for any signs of leakage. The manual recommends following specific leak check procedures.
  • Use the correct tightening torque: When reinstalling the fuel pump assembly, tighten the lock ring or mounting bolts to the specified torque. The service manual specifies 8.8 ± 1.9 N·m for the fuel pump assembly. Over-tightening can damage the gasket or the pump housing.
  • Relieve fuel pressure first: Before disconnecting any fuel lines, you must relieve the fuel system pressure. The manual provides a specific procedure: remove the rear seat, access the service hole, disconnect the fuel pump connector, start the engine, and let it run until it stalls. This reduces the risk of fuel spray.

Final Thoughts

The 2003 Mitsubishi Outlander fuel pump relay location is straightforward once you know where to look. Both fuel pump relays are in the interior fuse box behind the glove compartment. The engine control relay, which is also essential for fuel pump operation, is in the engine compartment relay box.

By understanding the two-relay system and following the diagnostic steps outlined above, you can quickly determine whether the relay is the problem or if the issue lies elsewhere. Always start with the simplest checks: the fuse and the relay. If those are good, move on to testing the fuel pump itself.

For a reliable, long-lasting fuel pump replacement, choose KEMSO. Visit https://www.kemsoracing.com/ to browse their selection of high-quality, lifetime-warranty fuel pumps for your 2003 Mitsubishi Outlander and many other vehicles.


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