Mitsubishi Fuel Pump Relay Location: Find and Fix Fast

The Mitsubishi fuel pump relay location varies significantly by model and year, but it is almost always found in one of the primary interior fuse boxes or the engine compartment fuse/relay box. The most common spots are under the dashboard near the driver's knees (left kick panel), behind the glove compartment, or under the hood in the main power distribution center. Identifying the correct relay requires consulting your owner's manual or fuse box diagram.

Finding a faulty fuel pump relay is essential when diagnosing a Mitsubishi that cranks but won't start. This critical relay controls power to the fuel pump, and when it fails, your pump won't activate, leaving the engine without fuel. Knowing where to look saves hours of frustration during repairs.

Understanding Fuse and Relay Boxes in Mitsubishi Vehicles

Modern Mitsubishis have multiple fuse and relay boxes. These contain the fuses protecting individual circuits and the relays controlling major components like the fuel pump, headlights, cooling fans, and horn. Relays are switches that allow a low-current signal from the car's computer or a switch to control a high-current device; the fuel pump relay handles the significant electrical load needed to run the fuel pump motor. The primary boxes are typically located:

  1. Interior Fuse Box (Left Kick Panel): Positioned under the dashboard, on the driver's side, often near where your left knee rests while driving. Access usually involves removing a plastic cover that snaps off or is held by screws.
  2. Interior Fuse Box (Behind Glove Box): Found behind the glove compartment in some models. Access involves removing the glove box by pressing in the sides to let it drop down fully.
  3. Engine Compartment Fuse/Relay Box (Power Distribution Center): Located under the hood, typically near the battery or along one of the fenders. This box houses larger fuses and relays for high-draw engine and accessory components.

Why Knowing the Exact Location Matters

Mitsubishi designs its wiring harnesses and fuse box layouts model-specifically and often updates them between generations. A relay positioned near the driver's knees in one Outlander might be behind the glove box in the next. An Eclipse might have it under the hood, while a similar-year Lancer positions it inside. Relying solely on a forum post about a different model will likely lead you astray. Consulting the definitive source for your specific Vehicle Identification Number (VIN) is paramount.

Methods to Find Your Mitsubishi Fuel Pump Relay

  1. Owner's Manual: Your first and best resource. Locate the index section for "fuses" or "relays," find the relevant fuse box diagram pages (often near the manual's end), and look for the legend identifying the "Fuel Pump Relay," "FP Relay," "Main Relay," or sometimes "Circuit Opening Relay." The diagram shows its exact position within the chosen box.
  2. Fuse Box Lid/Cover Diagrams: If you lack the manual, examine the plastic lids covering each fuse box in your vehicle. They almost always have a printed or embossed diagram listing every fuse and relay slot number or position and its function. Look for the labels mentioned above. Pay attention to symbols as well as text.
  3. Online Vehicle-Specific Resources: Use parts dealer websites like MitsubishiPartsDeals or Partsouq. Enter your full VIN, navigate to the Electrical section, then Fuse Boxes or Relays. Diagrams showing relay locations for your exact model and year are usually available. Factory repair manuals (available through subscriptions like AllDataDIY or Mitchel1) offer the most detailed exploded views and component locations.
  4. Systematic Relay Identification: If diagrams are unavailable, methodically inspect each relay in the main interior and engine bay boxes. Listen for a faint click near relays when an assistant turns the ignition key to the "ON" position (before cranking). The fuel pump relay should typically click once to prime the system during this step. Note: Other relays may also click. Compare similar-looking relays; swapping with a known non-critical relay of the same type (like the horn relay) is a common diagnostic step but refer to methods below for verification.

Physical Identification of the Fuel Pump Relay

Once you locate the likely box, identify the specific relay. Standard automotive relays in Mitsubishis are usually small plastic cubes measuring roughly 1 inch square. They plug into sockets with typically 4 or 5 metal prongs visible underneath. Look for markings molded onto the relay body:

  • Manufacturer Codes: Companies like DENSO, Omron, Panasonic make most OEM relays.
  • Part Numbers: May be full Mitsubishi numbers (e.g., MRxxxxxx) or generic manufacturer numbers matching the specs.
  • Specifications: Key details like coil voltage (12V), contact arrangement (SPST, SPDT - Fuel pump is usually SPST), and switching current rating (often 20A, 25A, or 30A).
  • Terminal Numbers: Labeled on the relay itself (e.g., 30, 85, 86, 87, 87a). The diagram below explains their function.

Understanding Relay Terminal Functions

  • Terminal 85: Coil Negative (-). Typically connected to ground through the ECU or PCM.
  • Terminal 86: Coil Positive (+). Receives the control signal (12V) from the ignition switch or ECU when activated.
  • Terminal 30: High-Current Input (+). Connected directly to the battery positive via a fuse.
  • Terminal 87: High-Current Output (+). Switched output that sends power to the fuel pump when the relay is energized.
  • Terminal 87a: Only on SPDT relays. Normally Closed (NC) contact that disconnects when the relay is energized. Fuel pump relays are usually SPST (Terminals 30 and 87 only).

Testing the Mitsubishi Fuel Pump Relay

Testing verifies function:

  • Auditory Test: With the ignition OFF, listen near the relay while an assistant turns the key to "ON." You should hear a distinct single click as the relay energizes. No click suggests a potential problem with the relay's coil or the control signal. Do this quickly to avoid draining the battery.
  • Swap Test: Find a relay in the same box with the exact part number or markings. Common choices are the horn relay, headlight relay, or radiator fan relay. Swap their positions. If the suspected fuel pump relay was the issue, the component whose relay you moved (horn, etc.) will now stop working, and your fuel pump should start functioning. If the horn and fuel pump still don't work after swapping, the original relay might be good, pointing to another problem. If the horn stops working in its new position, but the fuel pump starts working, the moved relay was faulty. Do not swap with critical relays like the Engine Control Unit (ECU) relay.
  • Basic Power Check (Simple Multimeter): Set to DC volts. Ground the black probe. With ignition OFF, probe pin 30 - it should show battery voltage (around 12.6V). Probe pin 86 with ignition in "ON" - it should show battery voltage momentarily. Probe pin 87 with ignition "ON" should also show battery voltage momentarily if the relay is good. If voltage is missing at 30, check the main fuse supplying the box. If voltage is missing at 86 with key "ON", suspect a control circuit issue (ECU, wiring). If voltage is missing at 87 with key "ON" and voltage present at 86 & 30, the relay is likely faulty.
  • Resistance/Continuity Check (Off-Car Multimeter): Remove the relay. Set the multimeter to Ohms (continuity).
    • Check between pins 85 and 86: Should show resistance (e.g., 50-150 ohms). Infinite resistance means an open coil - relay bad.
    • Check between pins 30 and 87: Ignition OFF position - should show no continuity (infinite resistance). Place 12V across pins 85 (+) and 86 (-). You should hear a click, and continuity should appear between pins 30 and 87 (low resistance, near 0 ohms). If no continuity appears after applying 12V, the contacts are bad - replace the relay.

Replacing a Faulty Mitsubishi Fuel Pump Relay

  1. Disconnect the Battery: ALWAYS disconnect the negative battery terminal before servicing any electrical components to prevent shorts, sparks, or potential damage to sensitive electronics like the ECU.
  2. Locate Relay: Confirm location using the methods above.
  3. Remove Old Relay: Relays pull straight out of their sockets. Do not twist or bend them; grip firmly and pull vertically. If stuck, carefully wiggle slightly while pulling.
  4. Inspect Socket: Visually check for corrosion, bent pins, or melted plastic in the relay socket before inserting the new one. Clean corrosion gently with electrical contact cleaner and a small brush.
  5. Install New Relay: Ensure the new relay matches the old one exactly in pin configuration and part number/specs. Orient it correctly using the keying in the socket (often a small tab or offset pin pattern). Push firmly straight down until fully seated.
  6. Reconnect Battery: Securely tighten the negative battery clamp.
  7. Test Operation: Turn the ignition key to "ON" and listen near the fuel tank filler neck for the brief hum of the pump priming. Then attempt to start the engine. If it starts, let it run briefly to confirm. Recheck fuse box diagrams to ensure no related fuses need replacing.

Critical Safety Precautions

  • Battery Disconnection: Mandatory before handling relays or fuses.
  • Fire Risk: Fuel pump circuits carry significant current. Shorts can cause sparks and fires. Ensure tools never bridge terminals accidentally. Avoid metal jewelry near terminals.
  • Hot Surfaces: Engine compartment components can be extremely hot. Allow the engine to cool before working under the hood.
  • Electrical Shock: While standard car voltages (12V) are generally safe, exercise caution around damaged wiring or components.
  • Fuel Vapors: Highly flammable. No smoking or open flames nearby when working on fuel system components, even indirectly.

Diagnosing "Cranks But No Start" Beyond the Relay

If replacing the relay doesn't solve the problem, the issue lies elsewhere in the fuel delivery or ignition systems. Continue diagnostics:

  1. Check Fuel Pump Fuse: Usually located in the same fuse box as the relay or potentially in the main engine bay box. Locate its exact position via diagrams and test or visually inspect for a broken filament. Replace if blown, but investigate why it blew.
  2. Listen for Fuel Pump: At key "ON" (before cranking), listen for the pump priming near the fuel tank (approx 2-3 seconds). No sound means no pump activation (circuit issue, pump itself dead) or faulty relay connection.
  3. Check Fuel Pressure: Requires a fuel pressure gauge adapter specific to your model. Connecting it to the fuel rail schrader valve will confirm if pressure exists. Low or zero pressure points to pump failure, clogged filter, or leaky pressure regulator even if the relay clicks.
  4. Inspect Wiring: Visually trace wiring from the relay socket to the pump connector (often inside the cabin or trunk near the tank hatch). Look for obvious damage, chafing, or corrosion.
  5. ECU Diagnostic Trouble Codes (DTCs): Scan the ECU using an OBD-II scanner. Codes related to fuel pump circuits (P0230, P0627) or immobilizer issues provide crucial clues. Immobilizer problems can prevent fuel pump enablement even with a good relay and pump.
  6. Aftermarket Alarm/Stereo Consideration: Poorly installed aftermarket systems can interfere with factory wiring, including fuel pump circuits or immobilizer bypasses. Temporarily disable such systems as a test if suspected.

Model-Specific Mitsubishi Fuel Pump Relay Location Highlights

  • Mitsubishi Lancer / Lancer Evolution (Various Generations):
    • Common 2008-2017: Primarily located inside the vehicle. Check the interior fuse box behind the glove compartment. You will need to fully lower the glove box (press sides inward) for access. The relay is usually a standard cube type.
    • Older Lancers: Verify fuse box diagrams carefully; some may use the driver kick panel box or potentially an under-hood location.
    • EVOs: Check diagrams meticulously. Locations vary between generations and market variants. Often in the kick panel or behind glove box.
  • Mitsubishi Outlander / Outlander Sport (ASX / RVR):
    • Modern Outlanders (e.g., 2014+): Focus on the interior driver's side kick panel fuse box. Remove the cover, locate via the diagram on the lid. Often near the top or middle section.
    • First Generation Outlanders: Tend to have it within the interior fuse box, possibly also the kick panel.
    • Outlander Sport (ASX/RVR): Consistently located in the interior fuse box behind the glove compartment. Lower the glove box for access.
  • Mitsubishi Eclipse / Eclipse Spyder (3rd & 4th Gen, 2000-2012):
    • Highly likely to be located in the engine compartment fuse/relay box near the battery. Consult under-hood labels carefully. Distinguish it from the main EFI relay which is usually close by. Earlier models may differ slightly.
  • Mitsubishi Galant (Late Models):
    • Primarily found inside the car within the driver’s side kick panel fuse box. Lid diagrams are essential.
  • Mitsubishi Mirage / Space Star:
    • Concentrate on the interior fuse box behind the glove compartment. Glove box removal is straightforward.
  • Mitsubishi Montero / Montero Sport / Pajero:
    • Montero Sport: Varies by generation. Later models likely follow the trend for interior placement (kick panel or behind glove box). Older models need diagram verification.
    • Montero (Full Size): Due to age and global design variations, verification is critical. Common spots include interior driver kick panel and under-hood boxes. Owner's manual is essential.
  • Mitsubishi i-MiEV (Electric): Electric vehicles do not have a fuel pump or its relay. The concern is invalid for pure EVs.

Conclusion: Key to Finding the Mitsubishi Fuel Pump Relay

While a specific location cannot be guaranteed for every Mitsubishi without the VIN, the fuel pump relay consistently resides within the primary interior fuse boxes (driver kick panel or behind glove box) or the engine compartment power distribution center. Your owner's manual or the diagram on the fuse box lid is the definitive, model-year specific source. Locating and testing the relay is the critical first step in resolving a cranking no-start condition potentially linked to fuel delivery failure. Remember to always disconnect the battery before handling electrical components. If the relay proves good, systematically check fuses, listen for pump activation, inspect wiring, and scan for diagnostic trouble codes to pinpoint the underlying issue. Persistence using accurate resources solves this common problem.

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