1999 Ford Explorer Fuel Pump Relay Location: Find & Fix It Fast (Complete Guide)

The fuel pump relay for your 1999 Ford Explorer is located inside the vehicle's central Power Distribution Box (PDB), positioned near the driver's side kick panel under the dashboard.

Knowing exactly where to find the fuel pump relay in your 1999 Ford Explorer is crucial when facing a no-start situation or fuel delivery issues. This critical electrical component acts as a switch, controlling power flow to the fuel pump. A faulty relay is a common cause of fuel pump failure symptoms. This definitive guide provides the precise location, step-by-step access instructions, identification tips, testing procedures, and replacement details to get your Explorer running reliably again.

Understanding the Power Distribution Box (PDB) Location

1. Position Inside Cabin: Forget the engine compartment fuse box. For the 1999 Explorer, the Power Distribution Box (PDB) housing the main fuses and relays, including the fuel pump relay, is located inside the passenger compartment.
2. Driver's Side Kick Panel: Specifically, the PDB is mounted on the driver's side of the vehicle, low down near the floor.
3. Below the Dashboard: It is installed behind the driver's side kick panel, the vertical trim piece situated just to the left of the brake and accelerator pedals and slightly below the dashboard.
4. Physical Characteristics: The PDB is a large, typically black or dark grey plastic box, measuring roughly 6-8 inches wide and several inches tall. It will have a removable plastic cover.

Step-by-Step Guide: Accessing the Relay

Performing this task safely and correctly requires preparation:

1. Ensure Safety First:
   • Turn the Ignition OFF: Ensure the key is completely removed from the ignition.
   • Set the Parking Brake: Prevent accidental rolling.
   • Disconnect the Negative Battery Terminal: This is a critical safety step. Use an appropriate sized wrench (usually 8mm or 10mm) to loosen the nut on the negative (-) battery terminal clamp. Carefully lift the clamp off the terminal post and secure it away from the battery to prevent accidental contact. This eliminates the risk of electrical shorts or sparks while handling relays and fuses.
2. Locate the Driver's Side Kick Panel: Sit in the driver's seat and look towards the area immediately to the left of your feet, adjacent to the door sill. You will see a textured plastic panel running vertically from near the dash down towards the floor. This is the kick panel.
3. Remove the Kick Panel:
   • Locate Fasteners: Examine the kick panel. It is typically secured by plastic clips or push-pin fasteners, often near the top and sometimes near the bottom or center. Sometimes a single screw (often a Phillips head) is present near the top behind where the hood release lever may partially obscure it. You might need to gently pry the hood release lever trim aside.
   • Remove Screws: If a screw is present, carefully remove it using a Phillips screwdriver. Set the screw aside safely.
   • Release Clips/Pins: Using your fingers or a plastic trim tool (highly recommended to avoid scratching the panel or dashboard), carefully pry or pull the panel straight towards you, releasing the retaining clips or push-pins. Start near the top and work down. Apply firm but steady pressure. Avoid excessive force which could break the clips or the panel itself.
   • Set Panel Aside: Once all clips/pins are released, gently set the kick panel aside out of your workspace.
4. Identify the Power Distribution Box (PDB): Behind the kick panel, you will now see the large, rectangular Power Distribution Box mounted to the vehicle's structure. It may be slightly angled.
5. Remove the PDB Cover:
   • Locate Cover Tabs: The PDB has a removable plastic lid or cover. Inspect its edges for plastic tabs or hooks securing it in place.
   • Release Tabs: Simultaneously press in on the securing tabs or hooks while carefully lifting the cover upwards and away from the base. Some covers may simply pull straight off once tabs are clear.
   • Set Cover Aside: Place the cover in a safe location where it won't get damaged or stepped on.

Identifying the Fuel Pump Relay within the PDB

With the PDB cover removed, you will see an array of fuses and relays inside. Relays are typically cube-shaped, black plastic components with multiple electrical prongs on the bottom that plug into sockets. Fuses are generally smaller and flatter.

1. Consult the Diagram: This is the single most reliable identification method. The underside of the PDB cover you just removed has a detailed diagram molded into the plastic or printed on a sticker. This diagram maps out the precise location and function of every fuse and relay socket within the PDB box.
2. Locate the Relay Legend: Carefully examine this diagram. Look for the legend, typically listed numerically by fuse/relay position number or listed by function.
3. Find "Fuel Pump" Relay: Scan the legend for terms like "Fuel Pump," "FP," "Fuel," or sometimes "PCM Relay" (though PCM relay is usually distinct). The diagram will clearly indicate the specific socket position for the fuel pump relay. This location is consistent across most 1999 Explorers.
4. Physical Identification: While the diagram is essential, the fuel pump relay itself is commonly one of several identical-looking relays within the PDB. Never rely solely on visual position guessing. Cross-reference the location shown in the diagram on the cover with the sockets in the actual box.
5. Verify Position: Find the relay socket designated as the Fuel Pump relay on the diagram. Note any nearby relays/fuses as landmarks. Visually confirm you are looking at the correct socket location within the opened PDB.

What the Fuel Pump Relay Does

Understanding its function aids troubleshooting:

1. High Current Control: The fuel pump motor draws significant electrical current to operate. The relay allows a tiny control signal from the Powertrain Control Module (PCM - the engine computer) to switch on a much larger current flow needed by the pump.
2. Safety and Logic: When you turn the ignition key to "Run" or "Start," the PCM provides a brief ground signal to the relay coil. This activates the relay internally, closing its high-current switch contacts.
3. Power Flow: With the relay activated, battery power flows from the PDB through the relay's closed contacts, out to the fuel pump harness, and powers the pump.
4. Fused Protection: Power to the fuel pump relay is supplied by a large fuse within the PDB (or possibly an engine bay fuse). Check your cover diagram for the fuel pump fuse (e.g., 30 Amp Mini fuse) and verify its condition simultaneously when checking the relay.

Symptoms of a Faulty Fuel Pump Relay

A failing relay can manifest identically to a bad fuel pump or other electrical issues:

1. Engine Cranks but Won't Start: The most common symptom. The starter works, turning the engine over, but no fuel is delivered because the pump isn't getting power.
2. No Fuel Pump Prime Noise: When you turn the ignition key to "Run" (before cranking), you should normally hear a distinct buzzing/humming sound from the rear of the vehicle for 1-2 seconds as the pump pressurizes the fuel rail. Complete absence of this sound is a strong indicator of relay (or fuse) failure, pump failure, or wiring issues.
3. Engine Stalling: A relay that's intermittently failing might cause the engine to abruptly stall while driving, as if the fuel was suddenly cut off. It may or may not restart immediately.
4. Intermittent No-Start: The vehicle may start normally sometimes and fail to start at other times, often correlated with ambient temperature (heat/cold affecting the relay internals).
5. Complete Electrical Failure Signs (Less Common): A severely failed relay could potentially cause other symptoms depending on how it fails, though usually only pump operation is lost.

Testing the Fuel Pump Relay

Swapping with an identical relay is often the fastest diagnostic test.

1. Locate a Compatible Relay: Inside the PDB, find another relay identical in size, shape, and markings to the suspected fuel pump relay. Common interchangeable relays in the '99 Explorer might include the Horn relay, A/C Compressor Clutch relay (if equipped), or Blower Motor relay. Crucially, verify using the cover diagram that the function of this "test relay" socket is NOT critical for engine operation or safety before you remove it.
2. Swap the Relays:
   • Grip Firmly: Grasp the suspected bad fuel pump relay firmly.
   • Pull Straight Up: Pull it straight upward with steady pressure. It should release from its socket without excessive force.
   • Insert Test Relay: Take the known working identical relay (from, say, the horn socket), and plug it securely into the fuel pump relay socket.
   • Insert Suspect Relay: Plug the suspected bad relay into the horn (or other donor) socket.
   • Reconnect Battery: Reconnect the negative battery terminal.
   • Test for Prime Sound: Turn the ignition key to the "Run" position (do not crank). Do you hear the fuel pump prime sound now? If yes, the original relay in the fuel pump socket was likely faulty.
   • Test Donor Function: If the pump now primes, also test the function of the donor circuit (e.g., sound the horn). If the horn doesn't work, the suspect relay is bad and caused both the pump failure and now the horn failure because you moved the bad relay. If the horn works, it merely confirms the donor socket is functioning; your fuel pump relay diagnosis holds.
3. Using a Multimeter (For Advanced Users):
   • Set to Ohms (Resistance): Disconnect the relay. Set your multimeter to measure resistance (Ohms, Ω).
   • Find Coil Terminals: Consult the relay case diagram or search online for "standard automotive 4 or 5 pin relay diagram." Identify the two terminals for the control coil (typically 85 & 86).
   • Measure Coil Resistance: Place multimeter probes on terminals 85 and 86. You should read a resistance value, typically between 50-150 Ohms. A reading of infinity (OL, Open Loop) indicates a bad coil. A reading near zero Ohms indicates a shorted coil. Either means the relay is faulty.
   • Set to Continuity/Diodes: Switch the multimeter to Continuity (which beeps) or Diode Test.
   • Identify Switch Terminals: Find the terminals for the switched high-current contacts (typically 30 & 87, sometimes 87a).
   • Test Open State: Probe terminals 30 and 87. With no power applied to the coil, there should be no continuity (no beep, high resistance).
   • Test Closed State (Requires Power): To test if the contacts close properly, you need to power the coil. You can do this carefully by applying 12 volts (using fused jumper wires, if skilled) to terminals 85 (+) and 86 (-). You should hear/feel a distinct "click." While powering the coil, probe terminals 30 and 87 again. There should now be continuity (beep, low resistance). If contacts don't close, the relay is bad.

Replacing the 1999 Ford Explorer Fuel Pump Relay

Once confirmed faulty, replacement is straightforward:

1. Purchase the Correct Relay:
   • The relay type is a standard ISO micro/miniature automotive relay. Ford part numbers were often F5DZ-14B192-AA or similar, but parts change. Do not rely solely on model year online listings.
   • Take the Old Relay: This is the absolute best practice. Remove the faulty relay and take it with you to the parts store (AutoZone, O'Reilly, NAPA, Advance Auto Parts, Ford Dealer Parts Counter). Match the physical size, shape, pin configuration (number and arrangement of blades), and amperage rating (usually marked on top, like "20A" or "30A"). Common brands include Bosch, Tyco, Omron. Expect to pay around $15-$30.
   • Identify Key Attributes: Count the pins (4 or 5), note the base configuration (standard "mini ISO" pattern), and note the amperage rating printed on top. Mention "Fuel Pump Relay for 1999 Ford Explorer PDB." Have the parts counter verify cross-references.
2. Install the New Relay:
   • Disconnect Battery Negative: Reconnect battery if necessary, then disconnect Negative terminal again before installation.
   • Identify Socket: Ensure you are inserting it into the CORRECT socket identified via the PDB cover diagram as the Fuel Pump Relay socket.
   • Align Properly: Relays have pins of specific sizes/shapes, and the socket has guides (tabs or asymmetrical holes). Align the relay correctly over its socket. Do not force it.
   • Press Firmly: Push the relay straight down into the socket until it clicks and seats fully. Give it a gentle tug upwards to confirm it's locked in.
3. Reassemble:
   • Replace PDB Cover: Snap the cover securely back onto the Power Distribution Box. Ensure all tabs engage properly.
   • Reattach Kick Panel: Align the driver's side kick panel back into position over the PDB area. Starting from the bottom or top, press firmly to engage all the plastic clips or push-pins back into place. If a screw was present initially, reinsert and tighten it securely but do not overtighten.
   • Reconnect Battery: Reconnect the negative battery terminal and tighten the clamp nut firmly.
4. Test Operation:
   • Turn the ignition key to the "Run" position. You should clearly hear the fuel pump prime for 1-2 seconds.
   • Start the engine. It should start normally.
   • If applicable, test the function of the relay you swapped from earlier (e.g., honk the horn).

Common Mistakes and Troubleshooting Tips

• Ignoring the Diagram: Assuming the relay position without checking the cover diagram is the most frequent error. Fuse/relay layouts changed even within the same year model sometimes.
• Not Disconnecting Battery: Risk of shorts or sparks near sensitive electronics is real. Always disconnect the negative terminal.
• Forcing the Relay: If it doesn't seat easily, the relay is likely misaligned. Forcing can break the socket or relay pins. Double-check orientation.
• Testing Without Power Applied: When testing with a multimeter for coil activation or contact closure, you must apply 12V to the control coil terminals to properly simulate its operation.
• Assuming Relay is the Only Issue: While the relay is a common failure point, a missing fuel pump prime noise could also mean a blown fuse, a bad fuel pump, damaged wiring (especially the inertia switch), or a faulty PCM command. Test systematically.
• Check the Inertia Switch: The 1999 Explorer has a Fuel Pump Inertia Safety Switch, usually located on the passenger side kick panel or floor area behind a cover. If triggered (e.g., after a bump), it cuts power to the fuel pump. Make sure it's reset (push the button on top).
• Confirm Fuel Pump Fuse: Locate and visually inspect the main fuel pump fuse in the PDB as indicated on the cover diagram. It will be a larger fuse (e.g., 20A, 30A). Look for a broken filament inside the clear plastic top or significant discoloration.

Importance of a Quality Relay

Using a cheap, no-name relay is a risk. Fuel pumps demand consistent, high current. Inferior relays:

• Burn Out Faster: May fail prematurely under load.
• Can Develop Intermittent Faults: Lead to frustrating stalls or no-starts.
• May Cause Voltage Drop: Reduce efficiency or lifespan of the fuel pump itself.
• Poor Heat Tolerance: Engine bay proximity heat can affect low-quality internals.

Stick with known brands like Ford Motorcraft (OEM), Bosch, TYC, Standard Motor Products, or high-quality store brands.

Conclusion

Diagnosing and replacing a faulty fuel pump relay in your 1999 Ford Explorer is a manageable DIY repair. Remember the critical steps: disconnect the battery negative terminal, carefully remove the driver's side kick panel, locate the Power Distribution Box, remove its cover, consult the diagram on the cover to identify the fuel pump relay socket, test or swap the relay, install a high-quality direct replacement, reassemble meticulously, and reconnect the battery. Armed with this detailed location guide and procedure, you can quickly resolve fuel delivery issues caused by a bad relay, saving time and money compared to a mechanic visit. Always prioritize safety by disconnecting the battery before handling electrical components and double-check relay identification via the PDB cover diagram.