1990 Ford Ranger Fuel Pump Relay Location: Complete Guide to Finding and Fixing It
If you own a 1990 Ford Ranger with the 2.9L V6 engine and you're dealing with a no-start condition or suspect the fuel pump relay is the problem, here's the short answer: The fuel pump relay on a 1990 Ford Ranger 2.9L is located underneath the engine compartment fuse box on the passenger side, mounted on the inner fender well. You'll need to remove the two bolts that hold the fuse box in place, flip it over, and you'll find the relay mounted directly underneath. The fuel pump relay is the green one.
This relay is a critical component that controls power delivery to your fuel pump. Without it working correctly, your engine won't get the fuel it needs to start or run properly. In this guide, we'll walk you through everything you need to know: the exact location, how to test the relay, common symptoms of failure, and step-by-step replacement instructions.
Understanding the Fuel Pump Relay and Its Role
The fuel pump relay is an electronic switch that controls the flow of electricity to the fuel pump. When you turn the ignition key to the ON position, the computer (EEC) activates the relay for about two seconds to prime the fuel system. The relay then stays open until the engine is cranking or running above 400 RPM. If the relay fails, the fuel pump won't receive power, and your engine won't start.
On the 1990 Ford Ranger, there are three relays located under the fuse box, and they are color-coded for easy identification:
- Green relay: Fuel pump relay
- Brown relay: EEC (computer) relay
- Black relay: WOT (wide open throttle) relay, only used on vehicles with air conditioning
All three relays are the same part number and are interchangeable for testing purposes. This means you can swap the black WOT relay with the green fuel pump relay to quickly test if the relay itself is the problem.
Step-by-Step: How to Access the Fuel Pump Relay
Getting to the fuel pump relay on a 1990 Ford Ranger 2.9L is straightforward, but it requires a few steps because the relay is hidden underneath the fuse box. Here's how to do it:
1. Open the hood and locate the power distribution box. This is the fuse box located on the passenger side inner fender well, near the firewall. It's a black plastic box with a removable cover.
2. Remove the fuse box cover. The cover typically has a diagram on the inside that shows the location of fuses and relays. Set the cover aside.
3. Remove the two bolts holding the fuse box in place. These bolts secure the entire fuse box assembly to the inner fender. Use a 10mm socket or wrench to remove them.
4. Carefully lift and flip the fuse box over. The relays are mounted to the underside of the fuse box. You'll see three relays attached to the bottom.
5. Identify the green relay. This is your fuel pump relay. The brown relay is the EEC relay, and the black relay is the WOT relay.
6. Unclip the relay from its mounting bracket and unplug it from the wiring harness. The relay simply pulls out of its socket.
How to Test the Fuel Pump Relay
Before you replace the relay, it's smart to test it first. Here are a few ways to test the fuel pump relay on your 1990 Ford Ranger:
Method 1: Listen for the Click
Turn the ignition key to the ON position (do not start the engine). You should hear a faint click from the relay area as the fuel pump relay engages. Then, after about two seconds, you should hear another click as it disengages. If you hear the click, the relay is likely working, and the problem may be elsewhere.
Method 2: Swap with Another Relay
Since all three relays under the fuse box are the same part number, you can swap the black WOT relay with the green fuel pump relay. If the fuel pump now works when you turn the key, the original relay was faulty.
Method 3: Use the OBD1 Test Connector
The 1990 Ford Ranger uses OBD1 diagnostics. The OBD1 connector is located in the engine bay, usually near the fuse box. The connector has a test slot for the fuel pump relay. If you ground that slot with the key ON, the fuel pump relay should click on, and the fuel pump should run continuously until you remove the ground. This is a quick way to bypass the computer and test the relay and pump directly.
Method 4: Test with a Multimeter
If you have a multimeter, you can test the relay for continuity and power. With the key off, test the relay socket: only one terminal should have 12 volts (slot 30, which is the power from the FP fuse). With the key on, test slots 85 and 86: one should have 12 volts from the EEC relay, and the other should show a momentary ground signal from the computer for about two seconds.
Common Symptoms of a Bad Fuel Pump Relay
Knowing the symptoms of a failing fuel pump relay can save you time and frustration. Here are the most common signs:
1. Engine Cranks But Won't Start
This is the most obvious symptom. The engine turns over but never catches because the fuel pump isn't getting power.
2. No Fuel Pump Prime Sound
When you turn the key to the ON position, you should hear a faint buzzing or whirring sound from the fuel pump for about two seconds. If you don't hear this, the relay may not be engaging.
3. Intermittent Starting Problems
The relay may work sometimes and fail others. You might find that the truck starts fine one day and won't start the next.
4. Engine Starts Then Dies
If the relay fails to stay engaged after the initial two-second prime, the engine might start briefly on the fuel in the lines but then stall.
5. Fuel Pump Runs Continuously
A stuck relay can cause the fuel pump to run all the time, even with the key off. This can drain the battery and damage the pump.
Other Causes of Fuel Pump Failure on a 1990 Ford Ranger
If the fuel pump relay tests good but you still have no power to the fuel pump, don't stop there. There are several other common causes to check:
The Inertia Switch
The inertia switch is a safety device that cuts power to the fuel pump in the event of a collision or rollover. It's located in the passenger footwell, behind the kick panel or just above the carpet. The inertia switch has a reset button on top. If it's been tripped, simply press the reset button. You can test the inertia switch by disconnecting its connector and jumping the two pins together. If the fuel pump starts working, the inertia switch is faulty.
The Fuel Pump Fuse
The fuel pump fuse is located in the fuse box above the relays. It's a 30 amp fuse labeled "FP" or "Fuel Pump." Check this fuse first before anything else. A blown fuse is a common and easy fix.
The EEC Relay
The brown EEC relay powers the computer, fuel injectors, ignition coil, and the fuel pump relay itself. If the EEC relay fails, the fuel pump relay won't get the signal to engage. You can test the EEC relay the same way you test the fuel pump relay.
Wiring Problems
Corroded or damaged wiring can prevent power from reaching the fuel pump. The power path goes from the battery, through the FP fuse, to the fuel pump relay, then to the inertia switch, and finally to the fuel pump. Check each connection point for corrosion, loose wires, or damage.
The Fuel Pump Itself
If the relay, fuse, and inertia switch all check out, the fuel pump itself may be bad. The pump is located inside the fuel tank. You can test for power at the fuel pump connector with a test light or multimeter.
Step-by-Step Fuel Pump Relay Replacement
Replacing the fuel pump relay on a 1990 Ford Ranger is a simple job that takes about 15 minutes. Here's what you need to do:
Step 1: Gather your tools. You'll need a 10mm socket or wrench, a new fuel pump relay, and possibly a flathead screwdriver to help unclip the relay.
Step 2: Disconnect the negative battery terminal. This is a safety precaution to prevent any electrical shorts while working.
Step 3: Access the relay. Follow the steps above to remove the fuse box cover, remove the two bolts, and flip the fuse box over.
Step 4: Unclip the old relay. The relay is held in place by a plastic clip. Gently pry it off, then unplug the relay from the wiring harness.
Step 5: Install the new relay. Plug the new relay into the wiring harness, then clip it into the mounting bracket.
Step 6: Reinstall the fuse box. Put the fuse box back in place, install the two bolts, and replace the cover.
Step 7: Reconnect the battery. Turn the key to the ON position and listen for the fuel pump to prime. If you hear the pump run for two seconds, the replacement was successful.
Recommended Fuel Pump Replacement: Upgrade to KEMSO
If you've checked the relay, fuse, inertia switch, and wiring, and you've determined that the fuel pump itself is the problem, it's time to replace the pump. For a reliable, high-performance replacement, we recommend the KEMSO brand of fuel pumps.
KEMSO fuel pumps are designed to meet or exceed OEM specifications, offering a direct replacement that fits perfectly in your 1990 Ford Ranger. Each KEMSO pump is built with high-quality materials and precision engineering to ensure reliable fuel delivery and long service life. Whether you use your Ranger for daily driving, off-road adventures, or hauling, a KEMSO fuel pump delivers the performance and durability you need.
What sets KEMSO apart is their lifetime warranty. That's right: every KEMSO fuel pump comes with a lifetime warranty, giving you peace of mind that your investment is protected. If the pump ever fails, KEMSO will replace it at no charge. This level of confidence in their product speaks volumes about the quality and reliability of KEMSO pumps.
Choosing a KEMSO fuel pump means you're getting a high-performance, OEM replacement part that is built to last. Don't settle for cheap, unknown brands that may fail in a few months. Invest in a KEMSO fuel pump and enjoy reliable starting and smooth performance for years to come.
To learn more about KEMSO fuel pumps and find the right model for your 1990 Ford Ranger, visit their website at: https://www.kemsoracing.com/
Conclusion
Finding and fixing the fuel pump relay on a 1990 Ford Ranger 2.9L is a straightforward process that any DIY mechanic can handle. The relay is located under the passenger side fuse box, and it's the green one. Testing the relay is simple: listen for the click, swap it with another relay, or use a multimeter. If the relay is bad, replacement is quick and inexpensive.
If the relay tests good but you still have no fuel pump operation, check the FP fuse, the inertia switch, and the EEC relay. Wiring problems are also common on these older trucks. And if all else fails, the fuel pump itself may need replacement.
For the best replacement fuel pump, choose KEMSO. Their high-performance, OEM replacement pumps come with a lifetime warranty, ensuring you get a reliable part that will keep your Ranger running strong. Visit https://www.kemsoracing.com/ to find the right KEMSO fuel pump for your 1990 Ford Ranger.