1999 Ford Explorer Fuel Pump Reset Switch: Location, Purpose, and Step-by-Step Reset Guide

The 1999 Ford Explorer fuel pump reset switch, often called an inertia switch, is a crucial safety device. Its primary function is to cut power to the fuel pump instantly in the event of a significant impact or collision, reducing the risk of post-crash fire. However, it can sometimes trip during hard bumps or jolts, causing your Explorer to stall unexpectedly and refuse to restart. Resetting this switch is straightforward: locate it behind the front passenger-side kick panel near the floor, firmly press its red reset button, and verify normal fuel pump operation.

If resetting the switch doesn't restore operation, the stall is likely caused by a failed fuel pump, a blown fuse, wiring issues, or another fuel system problem. Understanding this switch's role and how to properly reset it is vital for diagnosing a sudden no-start condition in your 1999 Explorer. This guide provides exhaustive details on finding, resetting, and troubleshooting this critical component.

What Exactly is the Fuel Pump Reset Switch and Why Does Your '99 Explorer Have One?

The fuel pump reset switch is an inertia-activated safety switch mandated on most vehicles since the mid-to-late 1980s. Its core purpose is fire prevention. During a collision or severe impact that might damage fuel lines or the fuel tank, the sudden deceleration or force causes a mechanism inside the switch (either a ball bearing or a pendulum) to move, triggering an internal spring-loaded switch that opens the electrical circuit powering the fuel pump.

This action stops the pump from delivering fuel under pressure to the engine compartment. If fuel lines were ruptured in the crash, a running fuel pump would continue spraying highly flammable gasoline, creating an extreme fire hazard. The switch acts as an automatic electrical kill switch for the fuel pump.

On the 1999 Ford Explorer, the switch is installed in the fuel pump's power feed circuit, positioned to sense impacts effectively. It's intentionally designed as a single-use, resettable device. After minor impacts or shocks where no actual fuel system damage occurs (like driving over a deep pothole at speed or a forceful bump during off-roading), the switch might trip unnecessarily. That's why Ford equipped it with a simple red reset button accessible to the owner, preventing unnecessary service visits for a simple reset. It's not a diagnostic tool or a routine maintenance item; it's purely a safety sentinel that occasionally needs resetting after a false alarm.

Detailed Location of the Fuel Pump Reset Switch in a 1999 Ford Explorer

Finding the switch is simple, but knowing precisely where to look saves time. Forget engine compartments or trunk areas. The 1999 Ford Explorer fuel pump reset switch is located inside the passenger compartment:

1. Front Passenger Footwell: Start seated in the front passenger seat.
2. Locate the Kick Panel: Look to your right, towards the lower section of the door sill area. You'll see a vertical plastic panel running along the lower edge of the side wall, where your feet rest near the door. This is the kick panel. It protects the vehicle's wiring and components running along the rocker panel from feet and debris.
3. Identify Access Features: The kick panel covering the switch usually differs slightly. It may have a small finger notch molded into its top rear edge, or it might be slightly shorter than the surrounding trim pieces, making its removal easier. On some models, it's secured by a single screw at the top front corner; others use plastic push-pin clips.
4. Remove the Kick Panel:
   • If secured by a screw: Use a Phillips screwdriver to remove it.
   • If clipped in: Insert a small flat-head screwdriver or plastic trim removal tool behind the top rear edge (near the finger notch, if present). Gently pry it away from the metal body of the vehicle. The panel should pop out. It may remain connected by wiring for courtesy lights, so handle it carefully.
5. Expose the Switch: Once the kick panel is removed, the inertia switch is immediately visible. It's typically a small, black, rectangular plastic module (about 2-3 inches wide and tall, and 1-1.5 inches deep) mounted securely to the vehicle's inner rocker panel sheet metal, pointing upwards. A prominent red button protrudes from the top center or top surface of this module. You will also see the electrical wiring harness plug connected to its base. This is the fuel pump reset switch.

Clear Signs Your Fuel Pump Reset Switch Needs Resetting

A tripped inertia switch manifests through very specific, often sudden, symptoms:

1. Sudden Engine Stall While Driving: The most common indicator. The engine will cut out abruptly, mimicking running out of gas, immediately after a significant jolt. This could be hitting a deep pothole, a curb, railroad tracks aggressively, a minor collision, or even a severe bump while off-roading. The stall happens instantly with the impact.
2. Failure to Restart After the Stall: This is the key symptom differentiating it from other fuel pump failures. The engine will crank normally but will not start. You will not hear the brief 2-3 second fuel pump priming sound when you first turn the ignition key to the "Run" position (before cranking). Without pump pressure, no fuel is delivered to the injectors.
3. No Fuel Pump Priming Sound: As mentioned, turn the ignition key to the "Run" position (not to "Start"). Normally, you should hear a distinct whirring or humming sound coming from the rear (near the fuel tank) for 1-3 seconds as the pump builds initial pressure. If the inertia switch is tripped, you will hear nothing at all during this key phase. This is a crucial diagnostic step.
4. Accompanied by Recent Impact: Symptoms directly following a bump, jolt, or jarring event strongly suggest the switch as the prime suspect. If the stall happened on smooth pavement with no impact, other causes are more likely.

Step-by-Step: Exactly How to Reset the 1999 Ford Explorer Fuel Pump Switch

Resetting is simple, but follow these precise steps:

1. Park Safely: Ensure the vehicle is in Park (automatic) or Neutral with the parking brake firmly applied.
2. Turn Off Ignition: Remove the key from the ignition switch.
3. Access the Switch: Follow the location guide above to remove the front passenger kick panel and expose the inertia switch module with the red button.
4. Locate the Red Reset Button: Identify the prominent red button on the top of the black plastic module.
5. Press the Button Firmly: Place your thumb or finger squarely on the center of the red button. Press it downward firmly and completely until you feel it click or bottom out. Hold it down for about 1 second. You don't need excessive force, but a solid push is required. There's typically no need to hold it for an extended period.
6. Listen for Pump Activation: Have an assistant turn the ignition key to the "Run" position (not Start). Immediately after pressing the reset button, you should hear the distinct fuel pump priming sound for a few seconds from the rear of the vehicle. If you hear this, the reset was successful. If you don't hear it, the pump circuit is still open (switch didn't reset, or another problem exists).
7. Attempt to Start the Engine: Turn the ignition key to the "Start" position. The engine should crank and, if the switch was the only issue, start normally. A slight delay might occur as fuel pressure rebuilds fully.
8. Reinstall Kick Panel: Once the engine is running normally, carefully snap the plastic kick panel back into place or secure it with its screw. Make sure no wiring is trapped behind it.

Troubleshooting: What If Resetting Doesn't Work?

Failure of the reset procedure to restore fuel pump operation indicates a more complex problem. Systematically check these components:

1. Verify Switch Reset: Did you press the button firmly enough and feel/hear it click? Did you actually hear the fuel pump prime after pressing it? Confirm carefully. The reset process is immediate.
2. Check Fuel Pump Fuse: The fuel pump circuit relies on a separate fuse. Locate the fuse box (usually under the dashboard near the driver's door or in the engine compartment). Consult your owner's manual or the fuse box lid diagram for the exact fuse location (commonly labeled "Fuel Pump," "FP," "PCM Power," or similar). Visually inspect the fuse element for a break. Replace it with a fuse of identical amperage rating even if it looks intact, as hairline cracks can be invisible. Test with a multimeter for continuity if unsure.
3. Confirm Fuel Pump Grounds: Poor electrical grounding points can interrupt the circuit. Trace wiring diagrams for the fuel pump circuit grounds, typically found on the frame rails near the fuel tank or engine compartment. Clean any corrosion at ground terminals/brackets with a wire brush.
4. Test Fuel Pump Relay: The relay acts as the high-power switch for the pump. Locate the fuel pump relay in the power distribution box (usually under the hood). Swap it with a known-good, identical relay (like the horn relay - verify pin compatibility first). If the pump works with the swapped relay, replace the original one.
5. Check for Power at the Reset Switch (Intermediate Skill):
   • Set multimeter to DC Volts (20V range).
   • Locate the wire harness plug connected to the inertia switch base. With the key OFF, unplug this connector.
   • Identify the two heavier gauge wires in the plug/harness (typically thicker than the ground wire). The switch breaks the power feed to the pump.
   • Turn ignition key to "Run". Carefully probe the socket terminal in the harness plug connector that receives power from the fuse/relay using the multimeter's red probe. Ground the black probe to clean metal on the car body.
   • One terminal should show battery voltage (approx 12V) with the key in Run. If no voltage is present, the problem is upstream (fuse, relay, wiring fault from relay/fuse to switch, bad ignition switch, or PCM control issue). If voltage is present...
6. Test Switch Continuity (Intermediate Skill):
   • Key OFF.
   • Measure resistance (Ohms) across the two main power terminals on the inertia switch module itself using a multimeter.
   • Normally (After Reset): Should show very low resistance, near 0 Ohms (closed circuit).
   • Tripped: Should show infinite resistance or "OL" (open circuit).
   • Press the reset button and re-test. It should close the circuit. If it remains open after resetting, the switch is likely faulty internally.
7. Test Voltage at the Fuel Pump (Advanced Skill): Accessing the pump wiring near the tank requires safety precautions and technical skill.
   • Disconnect the fuel pump harness plug near the tank (often under the vehicle).
   • Turn key to "Run". Measure voltage between the power wire in the vehicle harness side (consult wiring diagram for color, often Pink w/ Black stripe) and a good ground. Should be battery voltage momentarily. If yes, the pump or its wiring from the plug is faulty. If no, the fault lies between the inertia switch and this plug.
8. Direct Fuel Pump Test (Advanced): Apply 12V directly to the fuel pump's power terminal briefly (use fused jumper wires) to see if it runs. Extreme caution required due to spark risk near fuel.
9. Listen For Pump Noise Without Electrical Help: Have an assistant place an ear near the fuel filler neck while you turn the key to "Run". Sometimes the pump sound is faint but audible if you listen directly at the tank.
10. Consider Fuel Pump Failure: If all electrical checks pass (power and ground reach the pump, inertia switch is reset), the fuel pump motor itself has likely failed and needs replacement. This requires dropping the fuel tank in most Explorers. A fuel pressure gauge test (connected to the fuel rail Schrader valve) provides definitive confirmation (should see 35-45 PSI for a healthy system on a push-start test cycle).

Common Misconceptions and Mistakes About the Reset Switch

• "It's a Fuse": While related, the inertia switch is not a fuse. It's an impact sensor that interrupts the circuit. A fuse protects against electrical overload; the inertia switch protects against collision damage.
• "It Needs Frequent Resetting": A properly functioning switch should only trip due to a genuine impact or severe jolt. If it trips repeatedly under normal driving, there's an underlying problem:
  • The switch itself is loose, faulty, or overly sensitive.
  • The mounting bracket is loose or cracked, transmitting excessive shock to the switch.
  • Severe vibration issues or worn suspension components causing excessive jolting. Address these root causes to prevent nuisance tripping.
• "Tapping on the Fuel Tank Fixes It": This "trick" occasionally jolts a failing pump motor's brushes into contact, allowing it to run briefly. It does not reset the inertia switch. If tapping the tank temporarily allows restarting, it strongly points to a failing pump, not a tripped switch.
• "The Reset Switch Should Be Disabled for Reliability": This is dangerous and illegal. Disabling or bypassing the inertia switch removes a critical safety feature, leaving the fuel pump running in a crash and increasing fire risk significantly. Never bypass it permanently.
• "The Pump Won't Run At All If The Switch is Tripped": Correct. It completely opens the circuit.
• "The Switch Protects Against Electrical Surges": Its design protects against physical impacts, not electrical problems like voltage spikes. Fuses and relays handle electrical circuit protection.

Preventive Measures: Keeping Your Explorer Reliable

While the inertia switch itself needs no routine "maintenance," you can minimize nuisance trips:

1. Ensure Secure Mounting: Occasionally (e.g., during oil changes), quickly inspect the switch behind the kick panel. Ensure it's firmly bolted/screwed to the body and the bracket isn't cracked or loose. Tighten if necessary. A loose switch vibrates excessively and trips more easily.
2. Address Suspension Issues: Worn shocks, struts, bushings, or ball joints allow more severe jolts to transmit through the vehicle's structure. Replacing these parts improves ride quality and reduces the shock loads that could trip the switch unnecessarily.
3. Drive Mindfully: Be vigilant over rough roads, railroad crossings, and potholes. Reducing speed minimizes impact force.
4. Know the Location: Familiarize yourself with finding the switch before you have a breakdown. Save time in a stressful situation.
5. Carry Essential Tools: Keep a small Phillips screwdriver and a flashlight in your Explorer to access the switch easily on the roadside. Consider including the relevant fuse.

Costs Involved: From Reset to Replacement

• DIY Reset: Cost: $0. Time: 2-5 minutes. Skill Level: Beginner.
• Replacing a Blown Fuse: Cost: $1-$5 for a pack of fuses. Time: 2-5 minutes. Skill Level: Beginner.
• Replacing the Inertia Switch Itself:
  • Part Cost: Typically $15-$40 USD for a new OEM-style switch. (Prices fluctuate - always confirm compatibility for 1999 Explorer).
  • Labor Cost (Shop): Usually 0.3 - 0.5 hours shop time ($30-$75) plus part cost. Very quick replacement.
  • DIY Skill Level: Beginner/Intermediate (locating connector, unplugging old, plugging in new, securing). No special tools beyond a screwdriver.
• Diagnosing/Fixing Other Problems: Costs vary significantly.
  • Fuel Pump Replacement: Parts: $100-$300+ depending on brand/quality. Labor: 2-5 hours ($200-$500+) due to tank removal. Total: $300-$800+.
  • Relay Replacement: Part: $10-$30. Labor: 5-15 min ($10-$25 shop min).
  • Wiring Repair: Cost depends on issue complexity ($50-$500+).
  • PCM Diagnosis/Failure: High cost ($500+).

Conclusion: Empower Yourself with Knowledge

The 1999 Ford Explorer fuel pump reset switch is a vital safety component designed to protect you in a collision. While its primary function is critical, its unintended consequence – stalling your engine after a significant bump – can be frustrating. The good news is resetting it is a quick, free, and simple task any owner can perform. By knowing its location behind the front passenger kick panel and understanding the reset process (firmly press the red button), you can potentially get your Explorer running again in minutes.

Always remember the key diagnostic step: Listen for the fuel pump prime after resetting the switch. The absence of that sound demands further investigation into fuses, the relay, wiring, or ultimately, the fuel pump itself. Resist the temptation to disable the switch permanently; your safety isn't worth the risk. With the information in this guide, you possess the knowledge to confidently identify and resolve a tripped inertia switch and understand when the problem points to a more serious issue requiring additional repair. This empowers you to maintain your 1999 Explorer reliably and safely for the long haul.