2012 Ford Fusion Fuel Pump Relay Location: The Complete Guide

The fuel pump relay in your 2012 Ford Fusion is located in the Battery Junction Box (BJB), commonly known as the engine compartment fuse box, specifically in slot #3. This relay is crucial for delivering power to your car's fuel pump when you turn the ignition on, priming the system for starting and maintaining fuel flow while driving.

Understanding precisely where this relay is and how to handle it is essential for diagnosing no-start conditions or poor running related to fuel delivery. Locating the relay is the first step in checking or replacing it. Let's break down everything you need to know to find and work with the 2012 Ford Fusion's fuel pump relay.

1. The Key Spot: Battery Junction Box (BJB)

  • Location: Open the hood of your Fusion. The Battery Junction Box (BJB) is the large, black plastic box situated relatively close to the battery. On the 2012 Fusion, it's typically found towards the rear of the engine bay on the passenger side. Sometimes referred to as the under-hood fuse box or engine compartment fuse/relay center.
  • Identifying the BJB: It's a rectangular box with a removable lid (cover). You'll often see large power cables running into or out of it, connecting to the battery positive terminal and the alternator.
  • Access: To get to the relay, you simply need to remove the plastic cover. This usually involves pressing down on a clip or squeezing tab(s) on the sides or ends of the cover and lifting it straight up.

2. Pinpointing Relay Slot #3

  • Visual Guide: The inside of the BJB cover is your best friend. Look on the underside of the lid you just removed. There should be a detailed diagram showing the layout and function of every fuse and relay position inside the box.
  • What to Look For:
    • Find the diagram section labeled "Relays" or similar.
    • Locate the relay identified as Slot #3.
    • Look for labels like "Fuel Pump," "PCM Relay," "PCM Power," or "Fuel Pump Relay" next to slot #3 or listed in a legend associated with it. This is your target relay. Note: Ford sometimes labels relays by their primary function for the Powertrain Control Module (PCM) rather than specifically "Fuel Pump," as the PCM controls the relay that powers the fuel pump.
  • Inside the Box: Look inside the BJB itself. You'll see numerous fuses (smaller, mostly colored plastic components) and several larger, square or rectangular, usually black components – these are the relays.
  • Confirming Slot #3: The slot positions are typically numbered clearly on the plastic housing inside the fuse box. Find the spot labeled "3". The relay you see plugged into that socket is the one controlling the fuel pump. It will be a standard automotive ISO mini or micro relay (commonly black, sometimes other colors).

3. What the Fuel Pump Relay Looks Like

Understanding what you're looking for helps confirm you've found the right component before testing or replacing:

  • Standard Automotive Relay: The fuel pump relay in the 2012 Fusion will be a standard black plastic cube-shaped module.
  • Size: Approximately 1 inch square (or slightly rectangular).
  • Terminals: You'll see 4 or 5 metal terminal pins protruding from the bottom that plug into the fuse box socket.
  • Diagram: The relay itself often has a small diagram on its top or side showing the internal wiring schematic (typically showing terminals 85, 86, 30, 87, and sometimes 87a) and sometimes a part number.

4. Why You Might Need to Access the Fuel Pump Relay (Common Symptoms)

Knowing the relay's location becomes critical if you experience problems indicating a potential fuel pump or power delivery issue:

  • Engine Cranks But Won't Start: The most classic symptom of a failed fuel pump relay (or fuel pump). The starter spins the engine, but no fuel reaches the engine.
  • No Power to the Fuel Pump: When you turn the key to the "On" position (before starting), you should normally hear a faint humming sound from the rear of the car (where the fuel tank is) lasting about 2-3 seconds. If you hear no sound, it could indicate no power reaching the fuel pump – potentially caused by a bad relay (but also possibly a fuse or fuel pump itself).
  • Engine Stalls Intermittently or After Running: A relay with internal corrosion or failing contacts might work briefly or intermittently, causing the engine to suddenly lose power and stall while driving, only to potentially restart later.
  • Diagnosis Step: Checking/swapping the relay is a simple, inexpensive diagnostic step when troubleshooting no-start or fuel delivery issues, before condemning the more expensive fuel pump.

5. How to Test the 2012 Fusion Fuel Pump Relay

If you suspect an issue, testing the relay is straightforward:

  • Tools: A multimeter capable of testing continuity and DC voltage is best. A basic test light can sometimes work for simple checks.
  • Simple Swap Test (Easiest Method):
    1. Locate another identical relay in the BJB that powers a non-critical system (common choices include the horn relay, rear defogger relay, A/C relay – consult the diagram on the fuse box lid to find one with the same part number).
    2. Pull out the suspected fuel pump relay (Slot #3) and the identical donor relay.
    3. Install the donor relay into Slot #3.
    4. Turn the ignition key to the "On" position and listen near the rear of the car for the fuel pump priming hum. If the pump now primes (or the car starts), the original relay in Slot #3 is likely bad. Replace it.
    5. Remember to put the original donor relay back in its correct slot.
  • Testing with a Multimeter (Bench Test):
    1. Remove the relay from Slot #3.
    2. Identify the terminals:
      • 85 & 86: Coil control terminals (low current circuit).
      • 30: Constant battery power input (always hot).
      • 87: Switched power output (to fuel pump).
      • (87a, if present, is usually unused in fuel pump circuits).
    3. Test Coil Resistance: Set multimeter to Ohms (Ω). Touch probes to terminals 85 and 86. You should read resistance, typically between 50-120 Ohms. An infinite reading (OL) means the coil is open (bad). A reading of zero means the coil is shorted (bad).
    4. Test Switch Contacts: Set multimeter to Continuity (beep) or Ohms.
      • Terminals 30 and 87 should have NO CONTINUITY when the relay is at rest.
      • Apply 12 volts to terminals 85 (positive) and 86 (ground). You can use small jumper wires connected to the vehicle battery or a 9V battery (though 9V might not reliably activate all relays, 12V is better).
      • While 12V is applied to 85 and 86, test between 30 and 87. You should now have CONTINUITY (low or zero Ohms). If not, the contacts are faulty (bad relay).
      • Remove the 12V power from 85/86, continuity between 30 and 87 should disappear.

6. How to Replace the Fuel Pump Relay

If testing confirms the relay is faulty, replacement is simple:

  1. Buy the Correct Relay: Find the appropriate replacement relay. Your auto parts store (AutoZone, O'Reilly, NAPA, Advance Auto Parts, RockAuto) can look it up by vehicle make, model, year, and engine. Specify you need the fuel pump relay or PCM relay for the Battery Junction Box (under hood). Using the same part number as the original is ideal.
  2. Location Confirmation: Go back to Slot #3 in the Battery Junction Box.
  3. Removal: Firmly grasp the old relay and pull it straight up out of its socket. It might be snug; use a slight rocking motion if necessary.
  4. Installation: Take the new relay and orient it correctly (match the terminal pattern to the socket). Push it firmly straight down into Slot #3 until it clicks or is fully seated.
  5. Test: Turn the ignition key to "On" and listen for the fuel pump prime (2-3 second hum). If heard, try starting the engine. Confirm normal operation.
  6. Replace Lid: Snap the cover back onto the Battery Junction Box.

7. Important Safety Precautions

  • Battery: Always disconnect the negative battery terminal before performing any electrical work to prevent short circuits or accidental sparks. Reconnect it after you've finished replacing or testing relays.
  • Tools: Avoid using metal tools unnecessarily around the fuse box to prevent shorting terminals.
  • Replacement: Use only a relay with the correct specifications (amperage rating, pin configuration) for your vehicle. Incorrect relays can cause electrical problems or fire hazards.
  • Diagnosis: While a failed relay is common, remember that a lack of fuel pump operation could also be due to a blown fuse, wiring fault, bad ignition switch, or a failed fuel pump itself. Consider checking the relevant fuel pump fuse (usually labeled in the BJB diagram, possibly slot #15 or similar – ALWAYS confirm with your lid diagram) if replacing the relay doesn't solve the issue.
  • Corrosion: Inspect the fuse box socket and the relay terminals for any signs of corrosion or overheating (melting, discoloration). Clean contacts carefully if needed or consult a professional if damage is found.

8. Beyond the Relay: Next Steps if Replacement Doesn't Help

If replacing the relay doesn't resolve your no-start or fuel pump issue, further diagnosis is needed:

  • Check the Fuel Pump Fuse: Locate the fuse associated with the fuel pump circuit in the BJB (again, consult your lid diagram – often slot #15 but varies). Remove it and inspect the thin metal strip inside the plastic housing. If it's broken or melted, the fuse is blown. Replace it with one of the exact same amperage rating (e.g., 20A).
  • Listen for Pump Prime: Have a helper turn the key to "On" while you listen carefully near the fuel tank filler neck. No sound points to a power supply problem (fuse, relay again, wiring) or a dead pump.
  • Check Fuel Pressure: Requires a special gauge attached to the fuel rail Schrader valve. Lack of pressure despite a new relay points towards a failed fuel pump, clogged filter, or other significant fuel system blockage.
  • Check for Power at Fuel Pump Connector: If possible to access the fuel pump wiring harness connector (often near the tank), test for battery voltage on the appropriate wires during the prime cycle. No voltage means a problem in the circuit before the pump (relay, fuse, wiring).
  • Consult a Professional: Electrical diagnosis beyond basic fuse/relay checks often requires specialized tools and knowledge. If you've exhausted the simple checks or lack confidence, seeking help from a qualified mechanic is strongly recommended. They have the tools (advanced scanners, pressure gauges) to pinpoint issues like PCM control signal problems or internal wiring faults efficiently.

Conclusion

Knowing that the 2012 Ford Fusion fuel pump relay location is in the Battery Junction Box (BJB) under the hood, specifically slot #3, empowers you to tackle a common cause of starting problems quickly. By referencing the diagram on the fuse box lid, identifying the correct relay, and following safe testing and replacement procedures, you can often resolve fuel pump power issues yourself. Remember the simple swap test with another identical relay is a powerful diagnostic tool. While replacing a faulty relay is generally straightforward, persistent fuel delivery problems after replacement signal the need for deeper investigation into fuses, wiring, the fuel pump itself, or professional diagnostic assistance. Addressing fuel pump relay concerns promptly ensures your Fusion starts reliably and continues to run smoothly.

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