How to Reset the Fuel Pump on a 1999 GMC Jimmy: A Simple, Step-by-Step Guide

Resetting the fuel pump on your 1999 GMC Jimmy is a straightforward process achieved by pressing the small red reset button located on the inertia switch. This switch is typically found mounted low on the passenger-side kick panel, near the floor just forward of the door opening. Pressing this button restores power to the fuel pump after it has been automatically shut off due to a significant impact or collision safety system activation. This procedure requires no tools, takes less than one minute to complete, and is the standard troubleshooting step if your Jimmy cranks but won’t start following a jolt or minor collision.

Understanding the Fuel Pump Reset Function

General Motors installed an inertia switch in the fuel pump circuit on the 1999 Jimmy and similar vehicles. Its primary purpose is safety. During a moderate to severe impact, such as a collision, the inertia switch triggers. This immediately cuts electrical power to the fuel pump. Cutting power stops fuel delivery to the engine. This action reduces the risk of fuel leakage and potential fire if a fuel line or component is damaged in the crash. The switch essentially acts as a circuit breaker for the fuel pump. It requires manual resetting once it has been activated. Sometimes even a hard bump or jolt while driving, hitting a large pothole sharply, or even aggressively slamming a door can cause the inertia switch to trigger inadvertently.

Exact Location of the 1999 GMC Jimmy Fuel Pump Reset Button (Inertia Switch)

Locating the inertia switch is critical for the reset process. On the 1999 GMC Jimmy, this component is not under the hood or near the fuel tank. Instead, you need to look inside the vehicle’s passenger compartment. Open the front passenger door. Look down at the area where the side of the dashboard meets the floor. This vertical panel is called the kick panel. The inertia switch is mounted low on this kick panel, near the floor. You may have to slightly move the front passenger seat back for better access. Visually identify a small, rectangular, often black or gray plastic module approximately 1.5 to 2 inches wide by 2 to 3 inches tall. A bright red button protrudes slightly from the center or top of this module – this is the reset button you need to press.

Step-by-Step Guide to Resetting the 1999 GMC Jimmy Fuel Pump

Performing the reset is incredibly simple. Follow these precise steps:

  1. Prepare the Vehicle: Ensure the Jimmy is parked safely on level ground. Set the parking brake firmly. Turn the ignition key completely to the OFF position. Remove the key. Ensure any passengers exit the vehicle for safety.
  2. Access the Inertia Switch: Walk around to the passenger side and open the front passenger door fully. Kneel or crouch outside the vehicle looking into the passenger footwell area. Locate the inertia switch module low on the kick panel near the floor.
  3. Press the Reset Button: Identify the distinct red button on the module. Using your fingertip, press the red button firmly downward. You should feel a distinct click as the button locks into its reset position. This audible or tactile click confirms the reset mechanism has engaged. Do not hold the button down; a single, firm press is sufficient.
  4. Verify Reset: After pressing the button, return to the driver’s seat. Insert the key and turn it to the ON position (but do not start the engine). Listen carefully. You should hear the fuel pump motor run for approximately 2 seconds as it primes the fuel system. This priming hum near the rear of the vehicle confirms the fuel pump is receiving power again.
  5. Attempt to Start: Turn the key fully to the START position. If the reset was necessary and the inertia switch was the only issue, the engine should now crank and start normally. Allow the engine to idle for a moment to confirm stable operation.

Troubleshooting If the Reset Doesn’t Work

If pressing the reset button does not result in the fuel pump priming noise and the engine still won’t start, further diagnosis is required:

  1. Confirm Prime Sound: Recheck steps 2-4. Ensure you pressed the button until it clicked. Listen intently from outside the vehicle near the rear wheels when turning the key to ON – the fuel pump hum should be audible. If not, the problem likely lies elsewhere.
  2. Check Fuel Pump Fuse: Locate the vehicle’s under-hood fuse box. Consult the diagram on the fuse box lid to identify the specific fuse protecting the fuel pump circuit (often labeled "FUEL PUMP" or "FP", and typically a 15A or 20A fuse). Remove this fuse and inspect it visually. The thin metal strip inside the clear plastic housing must be intact. If the metal strip is broken or melted, the fuse is blown. Replace it with an exact amperage replacement.
  3. Inspect Fuel Pump Relay: While in the under-hood fuse box, locate the fuel pump relay. Consult the lid diagram. Try swapping it with an identical, known good relay from another circuit (like the horn relay). Attempt to start the vehicle. If it starts, the original fuel pump relay is faulty and needs replacement.
  4. Verify Fuel Level: It sounds obvious, but ensure the fuel gauge is not malfunctioning. Check that there is more than 1/4 tank of fuel in the tank. A critically low fuel level can sometimes prevent proper pickup, especially if the truck is parked on an incline.
  5. Listen for Fault Codes: If the truck starts but runs poorly, or if the Service Engine Soon light is illuminated, have the diagnostic trouble codes (DTCs) read using an OBD-II scanner. Specific fuel system-related codes (like those pointing to the fuel pressure regulator or pump circuit problems) can provide crucial clues.
  6. Consider Fuel Pump Failure: If power (fuse, relay) is confirmed good and the inertia switch is reset, but the pump makes no sound, the fuel pump itself may have failed. This is a common failure point on aging vehicles. Testing fuel pressure at the fuel rail schrader valve (if equipped) using a rental gauge from an auto parts store is the definitive test. No pressure strongly points to a failed fuel pump or related wiring/ground issue.

Safety Precautions When Resetting or Diagnosing Fuel Issues

Always prioritize safety when working near fuel systems:

  • No Smoking/Flames: Absolutely never smoke or bring any open flame or spark near the vehicle during or immediately after fuel system work. Vapors are highly flammable.
  • Ventilation: Work in a well-ventilated area. Gasoline fumes can accumulate and pose health and explosion risks.
  • Fire Extinguisher: Keep a suitable (Class B) fire extinguisher readily accessible whenever working on fuel system components.
  • Avoid Electrical Sparks: Disconnect the battery’s negative terminal before performing any electrical tests or repairs near the fuel tank or pump if directed by service manuals. Be cautious with test light probes.
  • Protect Eyes/Skin: Wear safety glasses. Gasoline is an irritant; avoid contact with skin and eyes. Have clean water available for rinsing.
  • Stable Vehicle: Ensure the parking brake is firmly set and wheels are chocked.

Distinguishing Inertia Switch Reset from Major Fuel Pump Replacement

Resetting the inertia switch is a simple, exterior procedure taking only moments. Replacing the fuel pump itself is a major repair. The pump assembly is located inside the fuel tank. Replacement requires safely depressurizing the fuel system, lowering the fuel tank (which often necessitates supporting the vehicle securely on jack stands and disconnecting drivetrain/exhaust components), draining the tank, disconnecting multiple fuel lines and electrical connectors, removing the old pump module, installing a new one, and reassembling everything. This job is complex, messy, and best left to experienced DIY mechanics or professionals. The cost difference is significant: resetting costs nothing; pump replacement involves the cost of the pump assembly and several hours of labor. Always attempt the reset and check fuses/relays before assuming the pump itself is bad.

When Professional Diagnosis is Necessary

Seek help from a qualified automotive technician if:

  • The reset procedure was performed correctly, but the fuel pump still doesn’t prime or run.
  • Fuses blow repeatedly after replacement.
  • You suspect a wiring harness issue (damaged wires, corrosion).
  • Visible fuel leaks are present anywhere on the vehicle.
  • Fuel pressure testing confirms inadequate pressure.
  • The vehicle starts after reset but dies shortly after.
  • The Service Engine Soon light is illuminated.
  • You lack the tools, confidence, or safe environment to proceed beyond basic resetting and fuse/relay checks.

Maintaining a Healthy Fuel System

To minimize chances of encountering fuel pump issues:

  • Prevent Running Low: Avoid consistently driving the Jimmy with less than 1/4 tank of fuel. The fuel pump relies on gasoline for lubrication and cooling. Low fuel levels increase heat stress.
  • Fuel Filter Service: Replace the engine’s inline fuel filter according to the maintenance schedule (often every 30,000 miles). A clogged filter forces the pump to work harder, shortening its life.
  • Quality Fuel: Use reputable fuel stations. Contaminated or poor-quality fuel stresses the pump and can cause premature wear.
  • Address Starting Issues Promptly: Don’t ignore symptoms like hard starting, loss of power, or sputtering under load. These can indicate fuel system problems which, left unaddressed, can overload and damage the pump.

Knowing how to locate and press the fuel pump inertia switch reset button empowers 1999 GMC Jimmy owners to resolve a common starting issue quickly and confidently in many situations. This simple procedure bypasses a safety shutdown designed to protect you. Remember to systematically check fuses, relays, and fuel levels if a simple reset doesn’t solve the problem, and never hesitate to consult a professional mechanic when safety or complexity becomes a concern.

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