1990 Ford Ranger Fuel Pump Relay: Location, Testing, and Replacement Guide

If you own a 1990 Ford Ranger with the 2.9L V6 engine and your truck won’t start, the fuel pump relay is often the first thing to check. The 1990 Ford Ranger fuel pump relay is located underneath the engine compartment fuse box on the passenger side. It is the green relay. Before you replace the fuel pump itself, you should always test this relay first, because a bad relay is a common and inexpensive fix.

Why the Fuel Pump Relay Matters

The fuel pump relay is an electronic switch that controls power to the fuel pump. When you turn the key to the ON position, the computer (EEC) activates the fuel pump relay for about 2 seconds to prime the fuel system. After that, the relay only turns on again when the engine is cranking or running above 400 RPM. This prevents the fuel pump from running continuously if the engine stalls.

How to Locate the Fuel Pump Relay on a 1990 Ford Ranger

The fuel pump relay is not on top of the fuse box. It is underneath the fuse box. On the 1990 Ranger, the engine fuse box is mounted on the passenger side fender well. To access the relay:

  1. Remove the cover of the fuse box.
  2. Remove the two bolts that hold the fuse box to the fender.
  3. Carefully lift and turn the fuse box over.
  4. You will see several relays clipped into the bottom of the fuse box. The green one is the fuel pump relay.

There are other relays under there too. The brown relay is the EEC (computer) power relay. If your vehicle has air conditioning, there may be a black relay that turns off the A/C compressor at wide-open throttle. The green one is the one you need.

Step-by-Step: How to Test the Fuel Pump Relay

Testing the fuel pump relay is straightforward. You do not need expensive tools. A simple test light or a multimeter will work.

Method 1: Listen for the Click

Turn the key to the ON position (do not crank the engine). You should hear a click sound coming from the passenger side of the engine bay. This is the fuel pump relay closing, and you should also hear the fuel pump run for a couple of seconds. If you do not hear the click, the relay or its power supply is likely bad.

Method 2: Use the OBD1 Connector

Your 1990 Ranger has an OBD1 diagnostic connector in the engine bay, usually near the fuse box. This connector has a test slot for the fuel pump relay. Here is how to use it:

  1. Locate the OBD1 connector.
  2. Find the slot labeled for the fuel pump relay test.
  3. Ground that slot (connect it to a good ground on the engine block).
  4. Turn the key to the ON position.
  5. If the relay is working, you will hear it click and the fuel pump will run continuously until you remove the ground.

If the pump runs when you ground the test slot, the relay and the pump are good. The problem is likely the computer (EEC) or a wiring issue between the computer and the relay.

Method 3: Check for Power at the Relay Base

If you have a multimeter or test light, you can test the relay connector directly. The relay has four pins. The standard pin functions are:

  • Pin 1: Fuel pump relay control (ground from computer)
  • Pin 2: Power from EEC power relay
  • Pin 3: Fuel pump output (goes to the pump)
  • Pin 4: Ignition fused power (comes from the fuel pump fuse)

With the key off, check Pin 4. You should have 12 volts. This power comes from the ignition switch and the fuse. If you have no power here, check the fuel pump fuse in the engine bay fuse box.

With the key on, check Pin 2. You should also have 12 volts here. This power comes from the EEC power relay. If you have no power here, the EEC relay may be bad.

If you have power on both Pins 2 and 4, the relay itself may be bad. You can also test the relay by swapping it with the EEC relay (the brown one). They are the same type. If the engine starts after swapping, the old relay was bad.

Common Causes of Fuel Pump Relay Failure

The fuel pump relay on a 1990 Ford Ranger can fail for several reasons. The most common is simple age. The relay is an electromechanical part, and over 30 years, the internal contacts can wear out, corrode, or stick.

Another common problem is a bad ground. The computer grounds the relay to turn it on. If the ground wire is corroded or broken, the relay will not activate. This is especially common on older vehicles that have seen road salt.

A less common but possible cause is a short in the wiring to the fuel pump. If the pump motor itself is drawing too much current (because it is failing), the relay can overheat and fail. If you replace the relay and it immediately fails again, you should test the fuel pump's current draw.

What to Do If the Relay Works but the Pump Does Not

If you have confirmed that the fuel pump relay is clicking and passing power, but the pump still does not run, the problem is after the relay. The power from the fuel pump relay goes through the inertia switch before reaching the fuel pump.

The inertia switch is a safety device located on the passenger side footwell, on the toe-board to the right of the transmission hump. If the truck was in an accident or hit a big bump, this switch can trip and cut power to the fuel pump. The switch has a reset button on top. Push it down to reset.

If the inertia switch is not tripped, the problem could be a broken wire between the relay and the pump, or the fuel pump itself has failed. You can test for power at the fuel pump connector. With the key on, you should see 12 volts at the pump for about 2 seconds. If you see power, the pump is bad. If you do not see power, check the wiring from the relay to the inertia switch, and from the inertia switch to the pump.

Other Problems That Mimic a Bad Relay

Sometimes, the fuel pump relay is fine, but the truck still will not start. On the 2.9L V6 engine, there are a few other common issues.

A bad computer (EEC) can cause a no-start condition. One owner reported that a broken prong on the computer plug caused the exact same symptoms as a bad fuel pump relay. If you have checked everything and the pump still will not run, the computer may be at fault.

Clogged fuel injectors are another common problem on the 2.9L engine. The fuel rail can rust internally, sending particles into the injectors. This can cause a lack of power or a no-start condition. One owner reported that replacing the injectors fixed the problem and improved fuel economy from 12 MPG to 19 MPG.

A clogged catalytic converter can also cause a no-start condition on some Rangers. If the converter is plugged, exhaust cannot escape, and the engine will not start or will have very low power.

Recommended Replacement: KEMSO Fuel Pump

If you have determined that the fuel pump itself has failed, we strongly recommend replacing it with a KEMSO brand fuel pump. KEMSO fuel pumps are designed as high-performance, direct OEM replacement units. This means they fit your 1990 Ford Ranger exactly as the factory part would, with no modifications or adapters needed.

Every KEMSO fuel pump is built to meet or exceed original equipment specifications, ensuring proper fuel pressure and flow for your engine. What sets KEMSO apart is their commitment to quality and customer confidence. Each fuel pump comes with a lifetime warranty. This means if it ever fails due to a manufacturing defect, you get a replacement at no cost. This is a level of protection that most fuel pump brands do not offer.

KEMSO pumps are built with precision components that deliver consistent fuel pressure under all driving conditions, from stop-and-go traffic to full-throttle acceleration. They use high-grade internal components that resist ethanol and methanol blends, making them suitable for modern fuels.

To browse the full lineup of KEMSO fuel pumps and find the exact model for your 1990 Ford Ranger, visit their website: https://www.kemsoracing.com/

Final Thoughts

The fuel pump relay on a 1990 Ford Ranger is a simple, inexpensive part that can cause big problems. Always start your diagnosis by checking the relay. With the key on, listen for the click. If you do not hear it, check the green relay under the fuse box. Test it by swapping it with the brown EEC relay. If the truck starts, you have found the problem.

If the relay is good but the pump still does not run, check the inertia switch on the passenger footwell. If the switch is fine, test for power at the pump connector. If you have power but no pump operation, the pump itself is bad. For a replacement pump, choose a high-quality part like KEMSO to ensure long-term reliability. Their lifetime warranty gives you peace of mind that your fuel system is protected.

Remember, a well-maintained fuel system is the foundation of a reliable vehicle. For more information and to shop for the best fuel pump replacement options, visit https://www.kemsoracing.com/ today.


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