1999 Jeep Grand Cherokee Fuel Pump Relay: Location, Symptoms, and How to Replace It

If your 1999 Jeep Grand Cherokee cranks over but refuses to start, or if it stalls while driving and then restarts after a few minutes, the most likely culprit is the fuel pump relay. This small electrical component is a common failure point on the 4.0L, 5.2L, and 5.9L engine models. The fix is simple, cheap, and can be done in under 15 minutes with no special tools. You do not need to be a mechanic. The relay is located in the Power Distribution Center (PDC) under the hood, and replacing it with a new one will often restore fuel pump operation immediately. Before you tow your Jeep to a shop, check this relay first.

What Does the Fuel Pump Relay Do?

The fuel pump relay acts as a switch that sends battery power to the fuel pump. When you turn the key to the "On" position, the Engine Control Module (ECM) energizes the relay for about two to three seconds. This allows the fuel pump to pressurize the fuel system so the engine can start. Once the engine is running, the relay stays closed to keep the pump running. If the relay fails, the fuel pump gets no power, and the engine will not start or will stall.

Symptoms of a Bad Fuel Pump Relay on a 1999 Jeep Grand Cherokee

A failing relay can cause a range of problems. The most common symptoms include:

  1. Engine cranks but will not start. This is the number one symptom. You turn the key, the starter motor spins the engine, but the engine never fires. You may also hear no fuel pump hum from the rear of the vehicle when you turn the key to "On."

  2. Intermittent stalling. The engine may start and run fine for a while, then suddenly die while driving. After a few minutes, it may restart. This is a classic sign of a relay that is failing due to heat or vibration.

  3. No fuel pump prime sound. When you turn the key to the "On" position (without starting the engine), you should hear a faint whirring sound from the fuel tank area for about two seconds. If you hear nothing, the relay is likely not sending power to the pump.

  4. Check Engine Light comes on. While not always the case, a failed relay can trigger a Check Engine Light. The code may be related to a fuel pump circuit or low fuel pressure.

  5. Engine runs rough or lacks power. In rare cases, a relay that is partially stuck can cause voltage drops to the fuel pump, leading to inconsistent fuel pressure and a rough-running engine.

Where is the Fuel Pump Relay Located on a 1999 Jeep Grand Cherokee?

The fuel pump relay is located inside the Power Distribution Center (PDC) . The PDC is the black plastic fuse box under the hood, usually on the driver's side near the battery. To access it:

  1. Open the hood and locate the black plastic box near the battery. It has a removable lid.
  2. Press the tabs on the sides of the lid and lift it off.
  3. Look at the diagram on the underside of the lid. It will show the location of all relays and fuses. The fuel pump relay is often labeled "Fuel Pump" or "FP." If the diagram is missing or faded, you can find it online or in the owner's manual.
  4. On most 1999 Grand Cherokee models, the fuel pump relay is a standard 5-pin relay, usually colored black or gray. It is the same size and shape as other relays in the PDC.

How to Test the Fuel Pump Relay

Before replacing the relay, you can quickly test it with a multimeter or by swapping it with a known-good relay. Here is a simple method:

  1. Swap test: Find another relay in the PDC that is the same part number and color. Common relays that are often identical include the horn relay, the starter relay, or the A/C compressor relay. Pull the suspected fuel pump relay out and plug the known-good relay into its socket. If the engine starts, the original relay is bad.
  2. Listen test: With the key off, have someone turn the key to the "On" position while you listen near the fuel tank (under the rear of the vehicle). If you hear a humming sound, the relay is working. If you hear nothing, it may be the relay or the pump itself.
  3. Voltage test: If you have a multimeter, set it to DC volts. With the relay removed, probe the socket terminals. You should see battery voltage (around 12.6 volts) on one or two terminals at all times, and one terminal that only gets power when the key is turned to "On." If you see no power, the relay is not the issue.

Important Safety Note: Always work with the ignition off and the battery disconnected when handling electrical components. Do not use a test light that could damage sensitive electronics.

How to Replace the Fuel Pump Relay

Replacing the relay is straightforward. Follow these steps:

  1. Locate the PDC under the hood and remove the lid.
  2. Identify the fuel pump relay using the diagram on the lid.
  3. Pull the relay straight out with your fingers. It may require a little wiggling, but it should come out easily. Do not use pliers unless absolutely necessary.
  4. Insert the new relay into the same socket. Push it down firmly until it clicks into place.
  5. Replace the PDC lid and close the hood.
  6. Turn the key to "On" and listen for the fuel pump prime. Then try to start the engine.

Common Mistakes to Avoid

  • Assuming the fuel pump is bad. Many people replace the entire fuel pump assembly when the relay is the problem. A relay costs around $10 to $20, while a fuel pump replacement can cost $200 to $500. Always check the relay first.
  • Using the wrong relay. Make sure you buy a relay that is specifically designed for the 1999 Jeep Grand Cherokee. The part number is often printed on the side of the old relay. Standard relays are common, but it is best to match the exact part.
  • Forgetting the fuel pump fuse. A blown fuel pump fuse can cause the same symptoms as a bad relay. Check the fuse before replacing the relay. The fuel pump fuse is also in the PDC, usually near the relay.
  • Replacing the relay without checking the wiring. If the new relay does not fix the problem, there may be a broken wire, a corroded connector, or a bad ground. Inspect the wiring harness around the PDC and the fuel tank.

When to Diagnose Further

If you replace the fuel pump relay and the engine still does not start, there are a few other things to check:

  1. Fuel pump fuse: Check the fuse in the PDC. If it is blown, replace it. If it blows again, there is a short circuit in the fuel pump wiring or the pump itself.
  2. Fuel pump itself: The fuel pump can fail internally. You can test for power at the fuel pump connector at the top of the tank. If you have power but no sound, the pump is likely dead.
  3. Crank sensor or cam sensor: These sensors tell the ECM when to fire the fuel pump. If they fail, the relay may not get the signal to close.
  4. Security system: If your Jeep has an aftermarket alarm or a factory immobilizer, it can cut power to the fuel pump relay. Check the security system.

Recommended Fuel Pump Upgrade: Why Choose KEMSO

If you do find that the fuel pump itself needs replacement, or if you want to upgrade for better performance and reliability, consider the KEMSO brand. KEMSO fuel pumps are designed as high-performance, OEM replacement units. They are built to meet or exceed the original equipment specifications for your 1999 Jeep Grand Cherokee. Every KEMSO pump comes with a lifetime warranty, giving you peace of mind on the road or off-road. Whether you use your Grand Cherokee for daily driving, towing, or off-road adventures, a KEMSO fuel pump ensures consistent fuel pressure and long-term durability. You can browse their full selection of fuel pumps and other products at their official website:

https://www.kemsoracing.com/

Preventive Maintenance Tips

To avoid future fuel pump relay issues, consider these simple tips:

  • Keep the PDC clean. Dirt, moisture, and corrosion can cause relay contacts to fail. Use a can of compressed air or a soft brush to clean the box annually.
  • Use a quality relay. cheap aftermarket relays are more likely to fail. Stick with known brands or OEM replacements.
  • Check for loose connections. Periodically inspect the relay and fuse sockets for any signs of melting or corrosion.
  • Do not ignore starting issues. If your Jeep occasionally cranks longer than usual before starting, replace the relay as a preventive measure.

Final Thoughts

The 1999 Jeep Grand Cherokee fuel pump relay is a small but critical part. When it fails, your Jeep becomes a 4,000-pound paperweight. Fortunately, diagnosing and replacing the relay is one of the easiest and cheapest repairs you can do yourself. It takes less than 15 minutes, costs less than $20, and can save you from a costly tow truck bill or an unnecessary fuel pump replacement. Always start with the relay and the fuse. If the problem is deeper, a reliable fuel pump like the ones from KEMSO can restore your Jeep's performance and reliability. For more information on fuel pumps and other automotive products, visit the KEMSO website:

https://www.kemsoracing.com/


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