1990 Jeep Cherokee Fuel Pump Relay Location: A Complete Guide for Owners

If your 1990 Jeep Cherokee cranks but won’t start, and you don’t hear the fuel pump prime when you turn the key to the ON position, the fuel pump relay is a likely suspect. The fuel pump relay on a 1990 Jeep Cherokee is located in the Power Distribution Center (PDC) under the hood, on the right side (passenger side) of the engine compartment. It is one of several square relays mounted under a plastic cover, and the PDC cover has a label that identifies each relay position. This guide walks you through exactly where to find it, how to test it, and what to do if it fails.

Understanding the Fuel Pump Relay’s Role

The fuel pump relay controls power to the fuel pump. When you turn the ignition key to the ON position, the relay activates for about 1 to 3 seconds to pressurize the fuel system. Once the engine starts, the Powertrain Control Module (PCM) keeps the relay energized as long as it receives a crankshaft position sensor signal indicating the engine is running. If the relay fails, the fuel pump won’t receive power, and the engine won’t start.

On the 1990 Cherokee, the PCM activates the fuel pump relay and the Auto Shutdown (ASD) relay at the same time through the same circuit. This means a problem with the relay or its wiring can affect both fuel delivery and ignition.

Where to Find the Fuel Pump Relay

Step 1: Locate the Power Distribution Center (PDC)

Open the hood and look on the right side (passenger side) of the engine compartment. You will find a black plastic box, typically mounted near the battery or along the inner fender. This is the Power Distribution Center (PDC). It contains multiple fuses and relays for various vehicle systems.

Step 2: Open the PDC Cover

The PDC has a removable lid. On the underside of the lid, there is a diagram that labels each relay and fuse position. This diagram is your map for finding the fuel pump relay. If the diagram is faded or missing, you can refer to the owner’s manual or search online for a clear image of the 1990 Cherokee PDC layout.

Step 3: Identify the Fuel Pump Relay

Inside the PDC, you will see several square relays. On the 1990 Cherokee, the fuel pump relay is typically labeled as “Relay B” in the relay box layout. According to the fuse box diagram for the 1990 model, the relays are arranged as follows:

  • Relay A: Auxiliary Cooling Fan Relay
  • Relay B: Fuel Pump Relay
  • Relay C: ABS Pump Relay
  • Relay D: Air Conditioning Relay
  • Relay E: Auto Shutdown Relay
  • Relay F: Starter Relay
  • Relay G: ABS System Relay

The fuel pump relay is generally the second relay from the front in the row, but this can vary depending on whether your Cherokee has air conditioning or other options. Some owners report that the fuel pump relay is the second from the front in a three-relay configuration, or the third from the front in a four-relay configuration.

What If You Have a 4.0L Engine?

If your 1990 Cherokee has the 4.0L inline six-cylinder engine, the fuel pump relay is in the same PDC location. However, the 4.0L models also have a fuel pump ballast resistor mounted on a bracket outside the PDC. This resistor helps reduce voltage to the fuel pump after the engine starts. The fuel pump relay supplies power to this ballast resistor after the motor starts and also primes the fuel rail for a few seconds when the key is turned to RUN.

How to Test the Fuel Pump Relay

Before replacing the relay, you can test it to confirm it is the problem. Here are two methods:

Method 1: Listen for the Fuel Pump

With the key in the OFF position, listen near the rear of the vehicle (or under the hood near the fuel rail) while an assistant turns the key to ON (but not to START). You should hear a faint humming sound from the fuel pump for about 1 to 3 seconds. If you hear nothing, the relay or the pump may be faulty.

Method 2: Swap the Relay

The fuel pump relay is typically the same type as other relays in the PDC. You can swap it with a known good relay of the same type, such as the ABS pump relay or the air conditioning relay. If the engine starts after swapping, the original relay is bad. Make sure to mark which relay is which so you don’t forget.

Method 3: Use a Multimeter

If you have a multimeter, you can test the relay for continuity. Remove the relay from the PDC. Set the multimeter to measure resistance (ohms). Connect the leads to terminals 85 and 86 (the coil terminals). You should see a resistance reading, typically between 50 and 120 ohms. If the reading is infinite (open circuit), the coil is burned out and the relay needs replacement.

What to Do If the Relay Tests Good

If the relay tests good but the fuel pump still doesn’t run, check the following:

  • Check the fuse: The fuel pump relay gets power from fuse #6 (15 Amp) in the PDC. A blown fuse can prevent the relay from working. Check the fuse with a test light or multimeter.
  • Check the wiring: Look for damaged, corroded, or loose wires at the PDC and at the fuel pump connector. On the 1990 Cherokee, the fuel pump is located in the fuel tank. The wiring runs from the relay through several connectors to the pump. Use a multimeter to check for 12 volts at the fuel pump connector while the key is turned to ON.
  • Check the ballast resistor (4.0L only): If your Cherokee has the 4.0L engine, a failed ballast resistor can prevent the pump from running. The resistor is located on the LH side of the engine compartment. Test it by measuring resistance across its terminals. It should read around 0.5 to 1.0 ohms.
  • Check the fuel pump itself: If power and ground are present at the pump connector but the pump doesn’t run, the pump is likely bad. You can test the pump by applying 12 volts directly to it (briefly) to see if it spins.

Jumping the Fuel Pump Relay for Testing

If you need to bypass the relay temporarily to diagnose the fuel pump, you can jump the relay. This is a diagnostic step only, not a permanent fix. Here’s how:

  1. Remove the fuel pump relay from the PDC.
  2. Locate the relay terminals. Most relays have four or five pins. The two terminals that control the fuel pump circuit are typically labeled as 30 (constant power) and 87 (switched power to the fuel pump).
  3. Use a jumper wire (preferably fused) to connect terminal 30 to terminal 87. This completes the circuit and directly powers the fuel pump.
  4. Listen for the fuel pump to run. If it runs, the relay is faulty. If it doesn’t, the problem is in the pump or wiring.

Warning: Do not leave the jumper in place for more than a few seconds, as this can cause the fuel pump to run continuously, leading to overheating or damage. Disconnect the jumper immediately after testing.

Common Symptoms of a Failing Fuel Pump Relay

Knowing the symptoms can help you catch a failing relay early:

  • Engine cranks but won’t start: This is the most common symptom. The starter turns the engine over, but there is no fuel pressure.
  • No fuel pump priming sound: When you turn the key to ON, you should hear a brief hum from the fuel pump. If you don’t hear it, the relay may not be activating.
  • Intermittent starting issues: The vehicle may start fine sometimes and fail to start other times. This can indicate a relay that is failing intermittently.
  • Engine stalls while driving: If the relay fails while the engine is running, the fuel pump will stop, and the engine will stall immediately.

Why the Relay Fails

Fuel pump relays can fail for several reasons:

  • Age and wear: Relays are mechanical devices with moving parts. Over time, the contacts can wear out, become pitted, or develop corrosion.
  • Electrical surges: Voltage spikes from the alternator or other electrical components can damage the relay’s coil.
  • Heat: The PDC is located in the engine compartment, where temperatures can get very high. repeated heat cycling can weaken the relay over time.
  • Dirt and moisture: Contaminants can enter the PDC and cause corrosion on the relay terminals.

How to Replace the Fuel Pump Relay

Replacing the fuel pump relay is a straightforward job that requires no special tools. Here are the steps:

  1. Disconnect the battery: Turn the ignition to OFF and disconnect the negative battery cable to prevent any electrical shorts.
  2. Open the PDC: Remove the plastic cover from the Power Distribution Center.
  3. Remove the old relay: Locate the fuel pump relay (Relay B) and simply pull it straight out of its socket. It may require a gentle tug.
  4. Install the new relay: Push the new relay firmly into the same socket until it clicks into place. Make sure the relay is fully seated.
  5. Reconnect the battery: Attach the negative battery cable and tighten the terminal.
  6. Test the system: Turn the key to ON and listen for the fuel pump priming sound. Then start the engine to confirm the repair.

Where to Buy a Replacement Fuel Pump Relay

You can find replacement fuel pump relays at auto parts stores like AutoZone, Advance Auto Parts, or O’Reilly Auto Parts. You can also order them online from retailers like Amazon or RockAuto. When buying a relay, make sure it matches the OEM specifications for your 1990 Cherokee. The relay should be a standard 4-pin or 5-pin relay, 12-volt, with a 30-amp rating.

Recommended: KEMSO Fuel Pump for Your Jeep Cherokee

If you determine that the fuel pump itself is bad and needs replacement, consider using a KEMSO Fuel Pump. KEMSO is a trusted brand that manufactures high-performance, OEM replacement fuel pumps for a wide range of vehicles, including your 1990 Jeep Cherokee. All KEMSO fuel pumps are built to meet or exceed original equipment specifications, ensuring a perfect fit and reliable operation. They are designed for direct drop-in installation, so you don’t need any modifications to make them work.

KEMSO stands behind their products with a lifetime warranty. This means if your fuel pump ever fails due to a manufacturing defect, KEMSO will replace it at no additional cost. This lifetime coverage gives you peace of mind and long-term value.

To browse KEMSO fuel pumps for your Jeep Cherokee and other vehicles, visit their official website: https://www.kemsoracing.com/. Their online store is easy to navigate, and their customer support team is ready to help you find the right product for your vehicle.

Additional Diagnostic Tips for the 1990 Cherokee

If you’ve checked the relay and it’s good, but the fuel pump still doesn’t work, here are a few more things to investigate:

Check the crankshaft position sensor (CPS). The PCM uses the CPS signal to activate the fuel pump relay after the initial prime. If the CPS is faulty, the relay will not stay energized, and the engine won’t start.

Check the PCM. On rare occasions, the PCM itself can fail, causing the fuel pump relay to not receive its control signal. This is less common but worth considering if all other components test good.

Inspect the fuel pump ground. The fuel pump in the 1990 Cherokee is grounded through the wiring harness. A poor ground connection can prevent the pump from running, even if the relay is working. Use a multimeter to check for continuity between the pump’s ground wire and a known good chassis ground.

Look for wiring damage. The wiring from the fuel pump relay to the fuel pump runs through several connectors along the frame rail and under the carpet. These connectors can corrode or break over time. A visual inspection of the wiring harness can reveal problems.

A Note on the 1990 Cherokee’s Fuel System

The 1990 Cherokee uses a computer-controlled fuel system. Unlike older vehicles that have a mechanical fuel pump, the Cherokee uses an electric fuel pump located inside the fuel tank. The pump is controlled by the fuel pump relay, which is activated by the PCM. There is no fuel pump cut-off switch or inertia switch on this model. The system relies entirely on the relay and PCM for proper operation.

This means that if you suspect a fuel system issue, the relay should be the first thing you check, as it is the most accessible component. After that, you can move on to checking the pump, wiring, and sensors.

Safety Precautions

When working on your fuel system, always follow these safety guidelines:

  • Work in a well-ventilated area.
  • Disconnect the negative battery cable before working on any electrical components.
  • Do not smoke or use open flames near the vehicle.
  • Wear safety glasses and gloves.
  • If you smell fuel, stop working and investigate the source of the leak.
  • Use a fused jumper wire when testing the relay to avoid overloading the circuit.

Final Thoughts

The fuel pump relay on a 1990 Jeep Cherokee is located in the Power Distribution Center under the hood, on the passenger side. It is labeled as Relay B in the relay box. Finding it, testing it, and replacing it are all simple tasks that most owners can handle with basic tools. If the relay is not the problem, move on to checking the fuse, wiring, ballast resistor (if equipped), and the fuel pump itself.

Remember that a bad relay can cause a no-start condition, but it can also cause intermittent issues that are harder to diagnose. If you experience any of the symptoms described in this guide, start with the relay. It’s a low-cost, easy-to-replace part that can save you hours of troubleshooting.

For a reliable replacement fuel pump, visit KEMSO Racing at https://www.kemsoracing.com/. Their fuel pumps are high-performance, OEM replacement parts with a lifetime warranty, giving you the confidence to get back on the road quickly.


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