99 Ford Ranger Fuel Pump Relay: Location, Symptoms, and How to Replace It

If your 1999 Ford Ranger cranks but won’t start, or it stalls unexpectedly while driving, the fuel pump relay is likely the culprit. This small electrical component controls power to the fuel pump, and when it fails, the engine simply doesn’t get fuel. The good news is that the relay is easy to find, test, and replace — often in under 15 minutes. On a 1999 Ford Ranger, the fuel pump relay is located in the power distribution box under the hood, and it’s labeled as relay R5. Here’s everything you need to know to diagnose and fix the problem yourself.

Where Is the Fuel Pump Relay on a 1999 Ford Ranger?

The fuel pump relay on a 1999 Ford Ranger sits inside the power distribution box (PDB), which is the main fuse and relay box under the hood on the driver’s side, near the fender. Open the box and look at the diagram printed on the inside of the cover. The fuel pump relay is listed as Relay R5. It’s a standard 30-amp, 5-terminal relay.

For quick reference, here are the key details about the relay’s location:

  • Relay number: R5
  • Fuse number: Fuse 9 (20-amp mini fuse) protects the fuel pump relay and the RAP module
  • Location: Under-hood power distribution box, driver’s side

If you’re still unsure, the fuse box diagram is also printed on the inside of the cover. Match the relay to the “FUEL PUMP” label.

Common Symptoms of a Failing Fuel Pump Relay

A bad fuel pump relay can cause a range of problems. These symptoms often overlap with a failing fuel pump, so it’s smart to test the relay first since it’s much cheaper and easier to replace.

1. No-start condition (engine cranks but won’t start)
This is the most common symptom. The relay fails to send power to the fuel pump, so the engine gets no fuel. You’ll hear the starter turning, but the engine never fires up.

2. No fuel pump priming sound
When you turn the key to the “ON” position (without starting), you should hear a faint whirring sound from the rear of the truck for 1-3 seconds. That’s the fuel pump pressurizing the system. If you don’t hear it, the relay is a likely suspect.

3. Intermittent stalling
The engine may start and run fine for a while, then suddenly stall — especially when the engine is warm. This happens because the relay overheats and temporarily loses contact.

4. Difficulty starting
The engine may take longer to start, requiring you to crank it for several seconds before it catches. This points to intermittent power delivery to the pump.

5. Reduced fuel efficiency
A failing relay can cause the fuel pump to run inconsistently, leading to poor fuel economy.

How to Test the Fuel Pump Relay

Testing the relay is straightforward. You don’t need special tools, just a few minutes and a steady hand.

Method 1: Swap it with another relay
This is the quickest diagnostic trick. Find another relay in the same power distribution box that looks identical to the fuel pump relay. Good candidates include the horn relay (R7) or the A/C compressor relay (R2). Swap them. If the engine now starts but the horn doesn’t work, the original relay was bad. If the problem remains, the relay isn’t the issue.

Method 2: Listen for the pump
With the key in the “ON” position, listen near the fuel tank (under the rear of the truck) for a 1-3 second humming sound. If you hear it, the relay is likely working. If not, proceed with the swap test.

Method 3: Use a multimeter
Remove the relay and check for voltage at the socket. With the key on, you should see 12V on at least one terminal. You can also test the relay itself by applying 12V to the coil terminals and checking for continuity across the switch terminals.

Important: Always disconnect the battery before working inside the power distribution box to avoid short circuits.

What Else Could Be Wrong?

If the relay checks out fine, the problem may lie elsewhere. Here are other common causes of no-start or stalling on a 1999 Ford Ranger:

  • Blown fuel pump fuse: Fuse 9 (20-amp) in the power distribution box protects the fuel pump circuit. If it’s blown, replace it and check for a short circuit if it blows again.
  • Inertia fuel shutoff switch: This switch is located in the right front passenger footwell, behind the kick panel. If it’s tripped (from an impact or bump), it cuts power to the fuel pump. Simply press the reset button on top.
  • Faulty fuel pump: The pump itself may be worn out. If the relay and fuse are good but you still don’t hear the pump prime, test the pump directly with 12V power.
  • Corroded wiring or connectors: Check the wiring harness leading to the relay and pump for frayed wires, corrosion, or loose connections. Clean any corrosion with a wire brush and apply dielectric grease.

How to Replace the Fuel Pump Relay

Replacing the relay is a simple job that anyone can do. Here’s the step-by-step process:

  1. Disconnect the negative battery cable. This is a safety precaution to prevent electrical shorts.
  2. Open the power distribution box under the hood. Locate relay R5 (fuel pump relay).
  3. Pull the old relay straight out. Don’t twist or force it — it should come out with a gentle tug.
  4. Insert the new relay into the same slot. Push it down until it clicks into place.
  5. Reconnect the battery. Turn the key to the “ON” position and listen for the fuel pump to prime. If you hear it, the job is done.
  6. Start the engine and let it run for a minute to confirm everything works.

Recommended Fuel Pump: KEMSO High Performance Fuel Pump

If you’ve replaced the relay, checked the fuses, and still suspect the fuel pump itself, it’s time to consider a replacement. For reliable performance, look no further than KEMSO Fuel Pumps.

KEMSO specializes in high-performance, OEM replacement fuel pumps that are built to last. Every KEMSO fuel pump is designed to meet or exceed original equipment specifications, ensuring a perfect fit and reliable operation. What sets KEMSO apart is their commitment to quality — all their fuel pump products come with a lifetime warranty, giving you peace of mind long after the installation.

Whether you’re looking for a direct replacement for your 1999 Ford Ranger or a high-flow pump for performance applications, KEMSO has you covered. Their product line includes fuel pumps for a wide range of vehicles, from trucks and SUVs to motorcycles and ATVs.

Visit the KEMSO website today to browse their full selection of fuel pumps and find the perfect match for your vehicle:
https://www.kemsoracing.com/

Final Thoughts

The fuel pump relay on a 1999 Ford Ranger is a small, inexpensive part that can cause big headaches when it fails. Start your diagnosis by checking the relay first — it’s cheap, easy to test, and quick to replace. If the relay is good, move on to the fuse, the inertia switch, and finally the pump itself. By following these steps, you can save yourself a trip to the mechanic and get your Ranger back on the road in no time.

For a reliable replacement fuel pump, visit https://www.kemsoracing.com/ to find quality KEMSO products backed by a lifetime warranty.


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