2001 Mitsubishi Eclipse Fuel Pump Relay Location: Complete Guide for Owners
The fuel pump relay on a 2001 Mitsubishi Eclipse is located inside the engine compartment fuse box, which is positioned on the left side of the engine bay next to the battery. This is the most important thing you need to know before starting any diagnostic work on your fuel system. The relay is a small black plastic component that plugs directly into the fuse box, and it controls the electrical current that powers your fuel pump. If your Eclipse cranks but won't start, the fuel pump relay is one of the first things you should check.
Understanding the Fuel Pump Relay and Its Role
Every time you turn the ignition key in your 2001 Mitsubishi Eclipse, the fuel pump relay activates. This relay sends an electrical current to the fuel pump, which then delivers gasoline from the tank to the engine. The engine control module (ECM) controls the relay, ensuring the pump gets power only when needed . Unlike the fuel pump itself, which runs continuously while the engine is on, the fuel pump relay only works at startup and when you shut off the ignition. Once the car is running, the fuel pump continues to operate on power received from other sources like the oil pressure sending unit .
The fuel pump relay is also known as the relay switch, and its function is similar to that of an automotive fuse. It is a plastic component, typically black, set in a small box with a wiring harness attached to its underside. The relay's sprockets attach to the engine assembly .
Exact Location of the Fuel Pump Relay
For the 2001 Mitsubishi Eclipse, the fuel pump relay is located in the engine compartment fuse box. This fuse box sits on the driver's side of the engine bay, right next to the battery. The relay is part of the main fuse and relay panel mounted in that area .
To access the relay:
- Open the hood and secure it properly.
- Locate the fuse box on the left side of the engine compartment, near the battery.
- Remove the cover of the fuse box by pressing the retaining clips or lifting the latch.
- Look for the relay labeled for the fuel pump. On many models, the fuel pump relay is identified as the MFI relay or MPI relay, which stands for MultiPort Fuel Injection .
According to multiple sources, the fuel pump relay part number for the 2001 Eclipse is MR312504 . Some owners also refer to this as the ASD (Auto Shut Down) relay, which controls power to the fuel pump, ignition coil, and fuel injectors .
How to Identify the Correct Relay in the Fuse Box
The engine compartment fuse box on the 2001 Mitsubishi Eclipse contains multiple relays and fuses. Here is how to identify the fuel pump relay specifically:
Fuse box layout: The engine compartment fuse box (Type 2 for 2001 models) has a diagram on the underside of the cover. The fuel pump is protected by fuse number 24, which is a 15-amp fuse . The actual relay for the fuel pump is often labeled as the MFI relay or Engine Control Relay.
Relay identification: The MFI relay is typically one of the larger relays in the box. It is rectangular and has four or five prongs on the bottom. If you are unsure, consult your owner's manual or look for a diagram printed on the fuse box cover.
Passenger compartment fuse box: Some sources mention that the fuel pump relay can also be located behind the dashboard on the passenger side, though this is less common for the 2001 model year . For the 2001 Eclipse, the primary location remains the engine compartment fuse box.
Common Symptoms of a Bad Fuel Pump Relay
A failing fuel pump relay can cause several noticeable problems. Here are the most common symptoms to watch for:
1. Engine cranks but does not start. This is the most common symptom. When you turn the key, the starter motor engages and the engine turns over, but it never fires up. This happens because the relay is not sending power to the fuel pump, so no fuel reaches the engine .
2. Engine starts intermittently. Sometimes the car starts fine, and other times it cranks endlessly without firing. This intermittent behavior is a classic sign of a failing relay that works sporadically.
3. Car stalls while driving. If the relay fails while you are on the road, the engine will suddenly lose power and shut off. You may be able to restart the car after a few minutes once the relay cools down, but this is a dangerous situation that should be addressed immediately .
4. No sound from the fuel pump. When you turn the ignition to the "on" position (without starting the engine), you should hear a brief humming sound from the rear of the car. This is the fuel pump priming. If you hear nothing, the relay or the pump itself may be faulty.
5. Engine runs rough or hesitates. A failing relay may not provide consistent power to the fuel pump, causing the engine to run poorly, hesitate during acceleration, or struggle to maintain speed .
How to Test the Fuel Pump Relay
Before replacing the relay, you can test it to confirm it is the problem. Here is a simple step-by-step process:
Step 1: Locate the relay. Open the engine compartment fuse box and find the fuel pump relay.
Step 2: Listen for the click. Have a helper turn the ignition key to the "on" position while you listen near the relay. You should hear a distinct click sound as the relay activates. If you hear no click, the relay may be bad.
Step 3: Swap the relay. If you have another relay of the same type in the fuse box (such as the horn relay or cooling fan relay), you can swap them. If the car starts after swapping, the original relay was faulty.
Step 4: Check for power. Use a multimeter to test for voltage at the relay terminals. With the ignition on, you should see 12 volts at the power terminal. If you have power but the relay is not clicking, the relay is likely bad.
Step 5: Test the fuel pump directly. You can apply direct 12-volt power to the fuel pump connector to see if the pump itself works. If the pump runs with direct power but not through the relay, the relay is the problem .
How to Replace the Fuel Pump Relay
Replacing the fuel pump relay on a 2001 Mitsubishi Eclipse is a straightforward job that most DIYers can handle in under 30 minutes. Here is how to do it:
What you will need:
- Replacement fuel pump relay (part number MR312504 or equivalent)
- Safety glasses
- Gloves
Step 1: Safety first. Make sure the engine is off and the key is removed from the ignition. Disconnect the negative battery terminal to prevent any accidental electrical shorts.
Step 2: Access the relay. Open the hood and locate the engine compartment fuse box on the left side near the battery. Remove the fuse box cover.
Step 3: Remove the old relay. The fuel pump relay is typically a plug-in type. Grasp the relay firmly and pull it straight out of its socket. You may need to use a small amount of force, but do not twist or rock it excessively.
Step 4: Install the new relay. Line up the prongs on the new relay with the socket and push it firmly into place until it clicks. Make sure it is fully seated.
Step 5: Reconnect the battery. Reconnect the negative battery terminal.
Step 6: Test the system. Turn the ignition key to the "on" position and listen for the fuel pump to prime. Then start the engine and check for proper operation. Take the car for a short test drive to confirm everything is working .
Cost of Replacement
The cost to replace the fuel pump relay on a Mitsubishi Eclipse varies depending on whether you do it yourself or hire a mechanic. On average, the total cost for a professional replacement is around $104, with about $9 for parts and $95 for labor . However, prices can vary significantly based on your location and the specific model year. For a 2001 Mitsubishi Eclipse, shop or dealer prices can range from $128 to $170 for the complete service .
If you do the replacement yourself, the relay itself costs between $10 and $30 from most auto parts stores. This is a very affordable repair that can save you a trip to the mechanic.
Other Related Components to Check
If replacing the fuel pump relay does not fix your problem, there are other components you should inspect:
Fuel pump fuse: The fuel pump is protected by a 15-amp fuse located in the engine compartment fuse box (fuse number 24) . A blown fuse will cause the same symptoms as a bad relay. Check this fuse first before replacing the relay.
MFI relay (Engine Control Relay): Some sources refer to the MFI relay as the ASD relay. This relay provides power to the fuel pump, fuel injectors, and ignition system. If this relay fails, the engine will not start at all . The MFI relay is also located in the engine compartment fuse box.
Crank position sensor: If the ECM does not receive a signal from the crank position sensor, it will not activate the fuel pump relay. This is a common issue on the 2001 Eclipse and can cause the same symptoms .
Fuel pump itself: If the relay and fuse are good but the pump is not working, the fuel pump may have failed. This is more common on high-mileage vehicles. The fuel pump is located inside the fuel tank .
Why Your Fuel Pump Relay May Fail
Fuel pump relays can fail for several reasons. Understanding these causes can help you prevent future problems:
1. Age and wear. The relay contains mechanical contacts that open and close every time you start the car. Over time, these contacts can wear out, burn, or become pitted. This is the most common cause of failure.
2. Corrosion and oxidation. The relay can oxidize or rust over time, especially in humid climates or if the engine bay is frequently washed. Corrosion on the relay terminals can prevent proper electrical contact .
3. Electrical overload. If the fuel pump draws too much current due to a failing pump or a short circuit, the relay can overheat and fail. This is why it is important to check the entire fuel system if the relay fails repeatedly.
4. Heat damage. The engine compartment gets very hot, and the relay is exposed to this heat. Over time, the internal components can degrade due to thermal stress.
Maintenance Tips for Your Fuel System
Keeping your fuel system in good working order can extend the life of your fuel pump relay and other components. Here are some practical tips:
Check the relay regularly. Have the fuel pump relay inspected every time you change your brakes or have routine maintenance done . This is a quick check that can prevent a breakdown.
Keep the fuel tank at least a quarter full. Running the tank low can cause the fuel pump to overheat and fail prematurely. The fuel in the tank helps cool the pump .
Replace the fuel filter. A clogged fuel filter puts extra strain on the fuel pump and can cause the relay to fail. Replace the filter according to the manufacturer's schedule.
Use quality fuel. Poor quality fuel can contain contaminants that clog the fuel system and cause damage to the pump and relay.
When to Call a Professional
While replacing the fuel pump relay is a simple DIY job, there are times when you should call a mechanic. If you have replaced the relay and the fuse, but the car still will not start, the problem may be more complex. Issues with the ECM, crank sensor, or wiring harness require professional diagnostic equipment . Additionally, if you are not comfortable working with electrical components, it is always safer to have a professional handle the repair.
Why You Should Choose a KEMSO Fuel Pump for Your 2001 Mitsubishi Eclipse
If you have diagnosed your fuel system and determined that the fuel pump itself needs replacement, the quality of the pump you choose matters. A failing fuel pump can cause the same symptoms as a bad relay. When it comes time to replace your fuel pump, you want a product that offers reliability, performance, and peace of mind.
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Final Thoughts
The fuel pump relay on your 2001 Mitsubishi Eclipse is a small but critical component. When it fails, your car will not start, and you may be stranded. Knowing the location of the relay and how to test and replace it can save you time and money. The relay is located in the engine compartment fuse box next to the battery, and replacing it is a simple DIY task that takes just a few minutes.
If you are experiencing symptoms like the engine cranking but not starting, intermittent stalling, or no fuel pump noise, start by checking the relay and the 15-amp fuel pump fuse. If those are good, move on to testing the MFI relay and the crank position sensor. And if the problem turns out to be the fuel pump itself, trust KEMSO to deliver the quality and performance you need.
For more information about KEMSO fuel pumps and to find the right replacement for your vehicle, visit https://www.kemsoracing.com/ today.