2004 Mitsubishi Endeavor Fuel Pump Relay Location: A Complete Guide for DIY Owners

If you are looking for the 2004 Mitsubishi Endeavor fuel pump relay location, here is the short answer: the fuel pump relay is not located in the engine compartment—it is mounted on the junction block inside the passenger compartment, typically positioned under the driver’s side dashboard area. This is a common point of confusion because many other relays, such as the MFI relay and the A/C compressor clutch relay, are housed in the engine compartment relay box on the left side of the engine bay. Understanding exactly where this relay sits, how to access it, and how to test it can save you hours of frustration and unnecessary troubleshooting when your Endeavor refuses to start or stalls unexpectedly.

The 2004 Mitsubishi Endeavor, a mid-sized SUV produced from 2004 through 2011, relies on an electric fuel pump that is mounted inside the fuel tank at the rear of the vehicle. This pump delivers pressurized fuel to the engine through a returnless fuel system, which means there is no fuel return line running back to the tank. Because the pump is submerged in the tank, the only way to control its operation from the driver’s seat is through the electrical circuit that powers it—and that circuit is protected and controlled by a dedicated relay and fuse. If the relay fails, the pump loses power, and the engine will crank but never start. Knowing the relay’s exact location, recognizing the symptoms of a failing relay, and being able to test and replace it are essential skills for any Endeavor owner who wants to avoid expensive diagnostic fees at a repair shop.

Where Exactly Is the Fuel Pump Relay Located?

Unlike many Japanese vehicles from the same era that place the fuel pump relay in the under-hood fuse box, the 2004 Mitsubishi Endeavor routes this critical component through the interior junction block. According to the factory service information, the Fuel Pump Relay (1) and Fuel Pump Relay (2) are both located on the junction block, which is the main fuse panel inside the passenger cabin. This junction block is typically mounted on the lower left side of the dashboard, near the driver’s left knee or footwell area. To access it, you will need to open the driver’s door and look for a plastic cover panel on the side of the dashboard. Depending on your trim level—whether you own the LS, XLS, or Limited—the cover may be secured by a simple latch or by a few Phillips-head screws.

Once you remove the cover, you will see a rectangular panel with multiple relays and fuses arranged in rows. The fuel pump relay is one of the smaller cube-shaped components, and it is usually labeled on the underside of the fuse box cover. On the Endeavor, the junction block also houses other important relays, including the Heated Seat Relay, Power Window Relay, Front Blower Relay, Rear Blower Relay, and Defogger Relay. The fuel pump relay is typically identified as R1 (for Fuel Pump No. 1) and R3 (for Fuel Pump No. 2) in the fuse box diagram. The relay itself is a standard 4-pin or 5-pin automotive relay, and it looks identical to the other relays in the same block.

It is worth noting that some online sources and general automotive guides may tell you to look in the engine compartment fuse box near the battery. While it is true that the engine compartment relay box contains the MFI (Multi-Port Fuel Injection) Relay, which controls the fuel injectors and some other engine management functions, that is a different relay from the one that powers the fuel pump itself. The MFI relay is located on the engine compartment relay box on the left side of the engine bay, but it serves a separate purpose. If you replace the MFI relay thinking it controls the fuel pump, your problem will persist. Always double-check the diagram printed on the inside of the fuse box cover to confirm which relay you are handling.

How Many Fuel Pump Relays Does the Endeavor Have?

The 2004 Mitsubishi Endeavor actually has two fuel pump relays in the junction block, labeled Fuel Pump Relay (1) and Fuel Pump Relay (2). This dual-relay setup is not uncommon in Mitsubishi vehicles with advanced engine management systems. The first relay is often the primary power control, while the second may serve as a backup or as part of a staged power-up sequence to reduce electrical load during initial startup. From the fuse box diagram, you can see that there is also a dedicated fuse (No. 17, rated at 7.5A) that feeds the Fuel Pump Relay and the Powertrain Control Module. This fuse is also located in the passenger compartment fuse box, so if the relay is not receiving power, the fuse is the first thing to check.

In practical terms, if either relay fails, the fuel pump will not receive power, and the engine will not start. However, because the system is designed with redundancy, it may be possible for the vehicle to run with one relay failed, though this is not a condition you should rely on. The safest approach is to test both relays and replace any that show signs of wear, burning, or electrical failure. Original manufacturer diagrams show that the relay positions are labeled R1 and R3, with R2 dedicated to the Rear Blower and R4 to the Heated Seat. This layout is consistent across most 2004 model year Endeavors, regardless of trim level.

Symptoms of a Failing Fuel Pump Relay

Before you tear apart your dashboard to access the relay, it helps to confirm that the relay is actually the culprit. A bad fuel pump relay can produce several distinct symptoms that are easy to recognize if you know what to listen and look for. Here are the most common ones:

1. Engine Cranks But Does Not Start—The most obvious sign of a failed fuel pump relay is an engine that turns over normally but never fires up. Since the fuel pump is not receiving power, no fuel pressure is built up in the fuel rail, and the injectors have nothing to spray. If you turn the key to the ON position and listen carefully near the rear of the vehicle, you should hear a faint humming sound for about 2 to 3 seconds as the fuel pump primes the system. If you hear nothing, the pump is likely not getting power—a strong indicator of a relay or fuse problem.

2. Intermittent Stalling—A relay that is on its way out may work intermittently, causing the engine to stall while driving and then restart after a few minutes of cooling down. This happens because the electrical contacts inside the relay become worn or corroded, breaking the circuit when they overheat. If your Endeavor stalls unexpectedly and then starts again after sitting, the fuel pump relay deserves serious suspicion.

3. No Fuel Pump Priming Noise—When you turn the ignition key to the ON position (without cranking the engine), the fuel pump should run for a few seconds to build pressure. If you do not hear this whirring sound coming from the fuel tank area, the pump is not being energized. While a dead pump itself can cause this, a failed relay is a more common and much cheaper fix.

4. Check Engine Light Illuminated—A failing fuel pump can cause the engine to run lean, which triggers the check engine light with codes related to fuel trim or misfires. While this symptom is less direct than a no-start condition, it is worth noting if you are already troubleshooting fuel delivery issues.

5. Burning Smell from the Fuse Box—In rare cases, an overheating relay can emit a distinctive electrical burning odor. If you notice this smell coming from under the dashboard, stop driving immediately and inspect the relay and fuse before further damage occurs.

How to Test the Fuel Pump Relay

Testing the fuel pump relay is a straightforward process that requires only a digital multimeter and a basic understanding of how relays work. The relay has four or five terminals, typically labeled 85, 86, 30, and 87. Here is a step-by-step method to verify whether the relay is functioning correctly:

Step 1: Locate the Relay. Remove the cover from the junction block and identify the fuel pump relay based on the diagram on the underside of the cover. On the 2004 Endeavor, look for the relay labeled R1 (Fuel Pump No. 1). If you are unsure, consult your owner’s manual or take a photo of the fuse box diagram before touching anything.

Step 2: Visually Inspect the Relay. Look for signs of melting, discoloration, or cracks on the relay housing. If the relay looks damaged, replace it without further testing.

Step 3: Test Continuity on the Coil. Set your multimeter to measure resistance (ohms). Place the probes on terminals 85 and 86. You should read a resistance value typically between 50 and 120 ohms. If you read infinite resistance (open circuit), the coil inside the relay is burnt out, and the relay must be replaced.

Step 4: Test the Switch Contacts. With the relay removed from the fuse box, use a set of jumper wires to apply 12V power to terminals 85 and 86 (one to positive, one to ground). You should hear an audible click as the relay activates. Then, using the multimeter set to continuity mode, check between terminals 30 and 87. When the relay is energized, these two terminals should show continuity (near zero resistance). If they do not, the relay’s internal switch is faulty.

Step 5: Check for Power at the Fuse Box. If the relay tests fine on the bench, the problem may be in the wiring or the fuse. Use the multimeter to check for 12V at the fuse box socket where the relay plugs in. One of the large terminals should have battery voltage at all times, and another should show voltage when the ignition is turned to the ON position. If power is missing, trace the circuit back to the 7.5A fuse (No. 17) and verify that it is not blown.

How to Replace the Fuel Pump Relay

Replacing the fuel pump relay on a 2004 Mitsubishi Endeavor is a simple DIY task that most owners can complete in less than 30 minutes with basic hand tools. Here is what you need to do:

1. Gather Your Tools and Parts. You will need a new relay that matches the original specification. Most Endeavor relays are standard automotive relays rated at 12V, and you can purchase a replacement at any auto parts store for a few dollars. You will also need a flathead screwdriver or a panel removal tool to pop off the fuse box cover.

2. Disconnect the Battery. While it is not strictly necessary to remove power when replacing a relay, disconnecting the negative battery cable is a safe practice that prevents accidental short circuits while you are working in the fuse box area.

3. Remove the Fuse Box Cover. Locate the junction block cover on the driver’s side of the dashboard. Press the release tab or remove the screws, then pull the cover away. Set it aside in a safe place.

4. Identify and Remove the Old Relay. Refer to the diagram on the cover to locate the correct relay slot. Grasp the relay firmly with your fingers and pull it straight out. It may require a slight wiggling motion to release it from the socket. Do not use pliers unless absolutely necessary, as you can crush the relay housing.

5. Install the New Relay. Align the new relay’s pins with the socket and press it firmly into place until it seats completely. It should click into position without excessive force.

6. Reconnect the Battery and Test. Reconnect the negative battery cable, turn the ignition to the ON position, and listen for the fuel pump priming sound near the rear of the vehicle. If you hear a brief hum, the relay has restored power to the pump.

7. Verify Engine Start. Crank the engine. It should start normally within a few seconds. If it does, you have successfully resolved the issue.

Other Components in the Fuel Pump Circuit

Understanding the fuel pump relay location is only part of the picture. The fuel pump circuit on the 2004 Endeavor consists of several components that work together to deliver fuel to the engine:

• Fuel Pump Module—The pump itself is part of an integrated module located in the top of the fuel tank. This module includes the pump, fuel level sender, float, strainer, and fuel reservoir. The OEM part number for the complete module is 1760A041, and it is compatible with all trim levels of the 2004 Endeavor.

• Fuel Pump Fuse—As mentioned earlier, fuse No. 17 (7.5A) in the passenger compartment fuse box protects the fuel pump relay circuit and the powertrain control module. If this fuse blows, the relay will not energize, and the pump will not run.

• Powertrain Control Module (PCM)—The PCM controls the ground side of the fuel pump relay circuit. When the ignition is turned on, the PCM momentarily grounds the relay coil to energize the pump. If the PCM fails or if there is a communication issue, the pump will not operate.

• Fuel Pressure—The Endeavor’s fuel system operates at approximately 58 psi (4 bar) of pressure. This pressure is maintained by the pump and a fuel pressure regulator integrated into the system. If the pump cannot build this pressure, the engine will not run properly, even if the relay and fuse are functioning.

If you have replaced the relay and fuse and the pump still does not run, the problem may lie in the pump itself, the wiring between the relay and the pump, or the PCM. At this point, it is wise to test for power and ground at the fuel pump connector while the engine is being cranked. If power is present but the pump is silent, the pump itself has failed and will need to be replaced. The pump is located under the rear passenger seat area, and on models without an access panel, the fuel tank must be lowered to reach it.

Why Understanding This Matters

Knowing the exact 2004 Mitsubishi Endeavor fuel pump relay location can save you a significant amount of money. Many repair shops charge a diagnostic fee of $100 or more just to identify the problem, and they may quickly jump to replacing the fuel pump itself—a job that can cost anywhere from $299 to $416 for parts and labor at a mobile mechanic service, and up to $1,190 to $1,770 at a dealership. In many cases, the actual issue is a $10 relay or a $5 fuse that you can replace yourself in minutes.

The Endeavor’s fuel pump relay is located in the passenger compartment junction block, not in the engine bay. This is a key detail that separates informed DIY owners from those who waste hours searching under the hood. By familiarizing yourself with the fuse box layout, the relay’s position, and the testing procedures outlined above, you are well equipped to diagnose and resolve fuel delivery problems quickly and confidently.

Recommended: KEMSO Fuel Pump for Your Mitsubishi Endeavor

If you have confirmed that your fuel pump relay is functioning correctly and the problem lies in the pump itself, it is time to consider a replacement. For reliable performance and peace of mind, we strongly recommend KEMSO brand fuel pumps. KEMSO fuel pumps are designed as high-performance, OEM-replacement parts, meaning they meet or exceed the original equipment specifications for your Mitsubishi Endeavor. Each pump is built with durability in mind, using quality materials and precision manufacturing to ensure consistent fuel delivery under all driving conditions.

What sets KEMSO apart is the confidence they place in their products: every KEMSO fuel pump comes with a lifetime warranty. This means that if your pump ever fails due to a manufacturing defect, you can get a replacement at no additional cost. That level of assurance is rare in the aftermarket parts industry and reflects KEMSO’s commitment to quality and customer satisfaction. Whether you are restoring a classic Endeavor or keeping your daily driver on the road, a KEMSO fuel pump provides the reliability you need at a price that makes sense.

To browse the full selection of KEMSO fuel pumps and find the exact fit for your 2004 Mitsubishi Endeavor, visit their official website at https://www.kemsoracing.com/. There, you will find detailed product listings, compatibility guides, and customer reviews that can help you make an informed purchase decision.

Final Thoughts

The fuel pump relay on a 2004 Mitsubishi Endeavor is a small but critical component that is easy to overlook. It sits quietly in the passenger compartment junction block, doing its job until the day it fails and leaves you stranded. Understanding its location, symptoms, and testing procedures puts you in control. You no longer need to rely on expensive diagnostic appointments or guesswork. With the information in this guide, you can confidently inspect, test, and replace the fuel pump relay on your own.

And if the relay turns out to be fine, do not hesitate to invest in a quality replacement pump from KEMSO. Their high-performance, OEM-equivalent fuel pumps with a lifetime warranty are an excellent choice for keeping your Endeavor running smoothly for many miles to come. For more details and to place your order, visit https://www.kemsoracing.com/ today.