2000 Mustang Fuel Pump Relay Location: Diagrams & Easy Access Guide

Finding the fuel pump relay in your 2000 Ford Mustang is straightforward: It's located in the engine compartment's Central Junction Box (CJB), specifically in position number 9. Located near the brake master cylinder and firewall on the passenger side, this black plastic box houses critical fuses and relays, including the one vital for delivering power to your fuel pump. Knowing its exact spot is key if you suspect fuel delivery problems causing no-start issues.

What The Fuel Pump Relay Does (And Why Its Location Matters)
The fuel pump relay is a crucial electrical switch controlled by your Mustang's Powertrain Control Module (PCM). When you turn the ignition key to the "Run" position (before cranking), the PCM briefly energizes the relay for a few seconds to prime the fuel system. As you crank the engine, the PCM receives a signal from the crankshaft position sensor and continues powering the relay. This allows battery power to flow through the relay's internal contacts directly to the fuel pump, located inside the fuel tank. A failed relay means no power reaches the pump, resulting in a no-start condition. Knowing precisely where it is saves significant diagnostic time and hassle when troubleshooting fuel-related problems.

Pinpointing the Central Junction Box (CJB) in the 2000 Mustang
The Central Junction Box (CJB), sometimes called the engine compartment fuse box or power distribution box, is the large black plastic housing containing the fuel pump relay for your 2000 Mustang. Forget looking under the dash – for this generation Mustang, it's exclusively under the hood.

  • Location: Open the hood and stand on the passenger side of the vehicle. Look towards the rear (firewall side) of the engine compartment.
  • Landmarks: You'll see the brake master cylinder (silver metal component). The CJB is mounted vertically on a bracket, positioned immediately behind the brake master cylinder and directly adjacent to the engine compartment firewall. It's a prominent, rectangular, black box.
  • Visual Confirmation: The CJB has a removable cover secured by clips or small bolts. It typically has labels molded into the lid indicating the fuse and relay layout.

Relay Position: Identifying Slot #9 (SPDJB-4C018-AA)
The 2000 Mustang CJB holds numerous fuses and relays. Identifying the correct spot is critical.

  1. Locate the Cover Diagram: Remove the CJB cover by unclipping the latches or removing the retaining bolts/screws using the proper size socket or screwdriver (often a 7mm or 8mm socket for bolts, or clips just needing firm pressure). Flip the cover over.
  2. Find the Layout Guide: The underside of the cover features a detailed diagram, either molded into the plastic or printed on a sticker. This diagram maps out the specific position and amperage rating of every fuse and the function of every relay slot within the box.
  3. Identify Slot #9: Carefully scan the diagram. Look for labels like "Fuel Pump," "FP," or specific relay numbers. Crucially, the relay for the fuel pump in the 2000 Mustang (all V6 and V8 models) is designated by the diagram as position number 9 (typically written as "9" or "Relay 9").
  4. Spotting Slot #9 in the Box: With the cover off, look inside the junction box. The slots are clearly numbered. Find the position labeled "9" molded into the plastic near a relay socket. Physically, slot 9 is usually located in the middle or slightly upper-middle section of the CJB's relay bank, often near other key relays like the EEC/PCM power relay (slot 10) or the cooling fan relays.
  5. The Relay Itself: The standard fuel pump relay installed at the factory in a 2000 Mustang is a black, cube-shaped relay commonly referred to by Ford part number SPDJB-4C018-AA (or compatible aftermarket equivalents like Motorcraft DY-1007). It typically has four or five blade terminals on the bottom. A generic 30-40 amp ISO mini relay (also known as a micro relay) matching the terminal pattern (often with pin numbers 30, 85, 86, 87, and sometimes 87a) is functionally identical and commonly used as a replacement.

Visual Reference: Crucial for Confidence
Verifying visually is always recommended:

  • Photo of CJB Location: Imagine a photo showing the engine compartment passenger side, clearly highlighting the black CJB behind the brake master cylinder and near the firewall. (Note: Describing the exact visual context helps readers spot it quickly).
  • Photo of Open CJB Diagram: Visualize the underside of the CJB cover focusing on the layout diagram, circling "Slot 9" and its "Fuel Pump" label. The diagram usually lists items like:
    • 1: Starter Relay
    • 2: Ignition Coil Fuse (?)
    • 3: ABS Motor Relay
    • 4: ABS Valve Relay
    • 5: Powertrain Control Module (PCM) Relay
    • 6: Air Conditioning Clutch Relay
    • 7: High Speed Cooling Fan Relay (if equipped)
    • 8: Low Speed Cooling Fan Relay (if equipped)
    • 9: FUEL PUMP RELAY (CIRCLED for emphasis)
    • 10: EEC/PCM Power Relay
  • Photo of Relay in Slot #9: Picture a close-up photo of the relay plugged into socket #9 within the CJB itself. This relay looks identical to the PCM/EEC relay (slot 10) and the standard Ford micro relays.

Testing the 2000 Mustang Fuel Pump Relay (Simple Method)
If you suspect a relay failure, a simple swap test is the quickest diagnostic:

  1. Identify Known Good Relay: Locate another relay in the CJB with the exact same part number and physical shape as the one in slot #9. Common candidates are the PCM/EEC Power Relay (usually slot #10) or the horn relay (often slot #13). Confirm the swap candidates are identical by part number and terminal configuration.
  2. Swap Procedure: Carefully pull the suspected fuel pump relay (#9) straight out of its socket. Pull one of the identical relays (e.g., from slot #10) straight out. Plug the relay from slot #10 into slot #9. Plug the original relay from slot #9 into slot #10.
  3. Test Operation: Turn the ignition key to the "Run" position (but do not crank). Listen carefully near the rear of the car for the distinct, brief (2-3 second) humming sound of the fuel pump priming. If you now hear the pump prime (where it didn't before the swap), the original relay in slot #9 was faulty. If you still don't hear the pump, the relay in slot #10 might also be bad (less likely, but possible), or the problem lies elsewhere (fuse, wiring, pump, PCM).
  4. Relay Bench Test (Optional): Using a multimeter, you can test relay continuity between specific terminals when applying power to the coil terminals (generally 12V to terminal 85, ground to 86). It should connect 30 to 87 when powered and be open between them when not powered. A non-functional relay needs replacing.

Replacing the Fuel Pump Relay
If testing confirms failure:

  1. Source Replacement: Purchase a new relay matching the Ford SPDJB-4C018-AA, F6TZ-14B192-AA, Motorcraft DY-1007, or a standard ISO 30/40A Mini/Micro Relay (4 or 5 pin). Available at Ford dealers, auto parts stores (O'Reilly, AutoZone, NAPA, Advance Auto Parts), or online retailers. Confirm the pin pattern matches your existing relay before buying.
  2. Remove Old Relay: With the CJB cover off and ignition OFF, firmly grasp the faulty relay plugged into socket #9 and pull it straight upwards out of the socket.
  3. Install New Relay: Orient the new relay correctly using the terminal pattern and any keying tabs on the relay body and socket. Press it firmly straight down into socket #9 until it's fully seated.
  4. Test: Turn ignition to RUN and confirm you hear the fuel pump prime. Start the engine. If successful, replace the CJB cover.

Important Fuse Check: Fuse #11
The fuel pump relay receives power through a specific fuse:

  • Location: Also in the Central Junction Box (CJB). The diagram will show fuse positions and amperage.
  • Critical Fuse: Fuse #11 (or fuse #17 in some models if labeled differently - CHECK THE DIAGRAM!) is the fuse supplying power to the fuel pump relay coil and the PCM's control circuit for the relay. This is often a 15 Amp or 20 Amp fuse, clearly labeled on the diagram.
  • Action: ALWAYS verify fuse #11 (or its equivalent per your specific diagram) is intact whenever troubleshooting fuel pump relay or no-start issues. A blown fuse will cause symptoms identical to a bad relay. Locate the fuse, visually inspect the wire element inside, or test it with a multimeter for continuity. Replace it with the correct amperage fuse if blown and investigate what caused the overload.

When Troubleshooting Points Beyond the Relay
If the relay tests good and the fuse is intact, but the fuel pump doesn't run:

  1. Inertia Switch: The 2000 Mustang has an inertia safety switch located on the passenger-side kick panel (toe board), near where the front passenger's feet would rest. This switch cuts power to the fuel pump in a collision. Check if it's tripped (red button popped up). Press the button firmly down to reset it if tripped. Test for pump operation.
  2. Fuel Pump Itself: The pump inside the fuel tank can fail. Testing its direct power and ground requires more advanced diagnostics. Listen for priming noise near the gas tank filler neck or rear underbody. Use test lights or multimeter probes on the fuel pump wiring harness connector accessible near the tank or in the trunk near the pump access panel. Significant noise during pump operation suggests impending failure.
  3. Wiring Harness: Damage, corrosion, or breaks in the wiring between the CJB, inertia switch, and fuel pump can occur. Inspect visible sections near connectors.
  4. PCM Control Signal: The PCM commands the relay ON. A faulty PCM, a missing crankshaft position sensor signal, or wiring issues preventing the PCM from grounding the relay coil circuit can cause no operation. Requires specialized scan tools to diagnose control circuit signals.
  5. Fuel Level: Ensure there's adequate fuel in the tank! An empty tank or a faulty fuel level sender can cause similar issues, though the relay would still click/energize. The gauge reading may not be accurate.

Emergency "Hack" (Use With Extreme Caution)
If a new relay isn't immediately available and you MUST get the car running or moved (short-term solution ONLY):

  1. Disconnect Battery (Optional but safer): Consider disconnecting the negative battery terminal.
  2. Locate Relay Socket #9: Remove CJB cover. Find socket #9.
  3. Identify Terminals: The socket has exposed metal terminals. You need to identify terminals 30 (Constant Battery Power - usually fused directly from the battery) and 87 (Output to Fuel Pump). Consult a detailed wiring diagram for your Mustang if possible. In a pinch for Ford relays: Terminal 30 is often the last terminal in one row, and Terminal 87 is the opposite corner terminal in the other row. MISIDENTIFYING TERMINALS CAN DAMAGE WIRING.
  4. The "Jump": EXTREME CAUTION: Using a small gauge insulated wire with female spade terminals, plug one end firmly into the socket hole for Terminal 30, and the other end into the socket hole for Terminal 87. Alternatively, using insulated pliers, carefully insert a short piece of heavy gauge wire or a folded paper clip to create a solid metal bridge ONLY between the specific metal sockets for Terminal 30 and Terminal 87 within the relay socket cavity. DO NOT BRIDGE TO ANY OTHER TERMINALS.
  5. Reconnect Battery: Reconnect the negative battery terminal if disconnected.
  6. Immediate Action: Turn the ignition to RUN/ON. The fuel pump should run continuously as long as the ignition is on, bypassing the relay and inertia switch. START THE ENGINE IMMEDIATELY. This method provides power to the pump but removes safety controls and can cause overheating if run excessively without the engine operating or cooling fuel flow. Move the car only as far as necessary. DISCONNECT THE JUMPER OR BRIDGE AS SOON AS POSSIBLE AND DO NOT DRIVE NORMALLY LIKE THIS. It presents a fire and electrical hazard. This is strictly a last-resort, short-distance emergency tactic to move a disabled vehicle.

Special Considerations & FAQ

  • 1999-2004 Models: While generally similar, always double-check the diagram under the specific CJB cover for your model year. Early New Edge models or exports might have slight variances. Generally 1999-2001 have very similar CJB layouts to 2000.
  • Different Engines? (V6 vs. V8): The Central Junction Box location and relay position (#9) is identical for all 2000 Mustang models (3.8L V6, 3.8L V6 Premium, 4.6L GT). The relay function doesn't change between engine types.
  • Relay Confusion with PCM Relay: The PCM Relay (EEC/PCM Power Relay, slot #10) looks identical. Ensure you are swapping or testing the correct relay position #9 (Fuel Pump), not #10 (PCM). They are distinct components.
  • Relay Continuously Running? If the fuel pump runs non-stop whenever the ignition is on (not just priming for 2-3 secs), the relay contacts might be welded closed internally. This requires relay replacement.
  • Clicking Relay: A rapid clicking sound from the CJB when trying to start often indicates a weak battery or poor power connection preventing the relay coil from staying energized, not necessarily a bad relay itself. Check battery voltage and terminals. Clicking alone without the pump running suggests the relay is activating but no power is getting to the pump fuse or the pump itself may be faulty.

Knowing the 2000 Mustang fuel pump relay location (CJB Position #9) empowers you to tackle one of the most common causes of no-start frustration quickly and effectively. Always start diagnosis by checking fuse #11 and visually locating/testing the relay itself using the swap method outlined above. Armed with the diagrams and steps here, you can save significant time, money, and get your Mustang back on the road faster.

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