1990 Jeep Wrangler Fuel Pump Relay Location: The Complete Guide to Finding and Fixing It
If your 1990 Jeep Wrangler with the 2.5L four-cylinder engine cranks but won't start, the fuel pump relay is one of the first things you need to check. The relay is located in the engine compartment, on the upper right-hand side near the rear area, mounted to the inner fender next to the battery. Unlike later models that use a full Power Distribution Center (PDC) box, the 1990 YJ has individual relays bolted directly to the fender well. This guide will walk you through exactly where to find it, how to test it, and what to do if it's the problem.
Why the Fuel Pump Relay Matters
The fuel pump relay is a small electrical switch that controls power to the fuel pump. When you turn the key to the ON position, the relay energizes and sends battery voltage to the fuel pump so it can prime the system. If the relay fails, the pump never gets power and the engine won't start. A bad relay is a common cause of no-start conditions on these older Jeeps, and it's far cheaper to replace than a fuel pump.
Where to Find the Fuel Pump Relay on a 1990 Jeep Wrangler
The exact location of the fuel pump relay on a 1990 YJ is:
Under the hood, on the passenger side (right side) of the engine compartment, mounted to the inner fender near the battery.
On the 1990 model, there is no large plastic fuse box like you see on newer Jeeps. Instead, the relays are individual units bolted to the sheet metal. Look for two or three small, cube-shaped relays mounted to the inner fender between the battery and the firewall. The fuel pump relay is usually one of these. It is often interchangeable with the horn relay, so you can use that as a quick test.
How to Test the Fuel Pump Relay
Before you buy a new relay, you should test the one you have. Here is a step-by-step procedure that works on the 1990 Wrangler 2.5L.
Step 1: Check for Power at the Relay
Locate the fuel pump relay connector. Using a voltmeter, check for battery voltage at terminal 30 (the Red wire). If you have no voltage here, check the fusible links and battery connections.
Step 2: Check for Output Voltage
Connect the voltmeter to the F22 wire at terminal 87 (Orange wire). Have a helper turn the ignition key to the START position and crank the engine. If you see battery voltage here during cranking, the relay is functioning normally.
Step 3: Check the Control Signal
If you had no output voltage in step 2, check the F17 wire at terminal 86 (Orange/White wire). Turn the key to the RUN position. You should see input voltage from the ECU here. If not, there may be a wiring issue or a problem with the ECU itself.
Step 4: Test the Ground Side
Connect the voltmeter to the 11 wire at terminal 85 (Yellow wire). Crank the engine. The voltage should be present and then drop to less than 1 volt within 2 seconds. If it doesn't drop, the relay may be stuck or the ECU is not grounding it properly.
Step 5: Swap the Relay
The easiest test is to swap the fuel pump relay with another relay of the same type, like the horn relay. If the fuel pump starts working after the swap, you know the original relay was bad.
What to Do If the Relay Checks Out
If the relay tests fine but the fuel pump still doesn't run, you need to check the pump itself. On a 1990 Wrangler, the fuel pump is located inside the gas tank. To access it, you must drop the tank or cut an access hole in the floor. Before you do that, check the wiring harness at the top of the tank. The connector has three wires: a ground (usually Orange), a fuel gauge sender wire (Dark Blue), and a power wire to the pump (Black). Use a multimeter to test for power and ground at this connector when the key is turned ON.
Common Causes of Fuel Pump Relay Failure
Relays don't last forever. Here are the most common reasons they fail on a 1990 Jeep Wrangler:
- Current overload: If the fuel pump draws too much current, the relay contacts can burn out.
- Short circuit: A short in the wiring can cause a current spike that damages the relay coil or contacts.
- Age and vibration: Over 30 years of use, the internal components simply wear out.
When to Replace the Fuel Pump
If you have confirmed the relay is good and you have power at the pump connector, but the pump does not run, the pump itself is likely bad. Other signs of a failing fuel pump include a whining noise from the tank, difficulty starting, or the engine stalling while driving.
The Best Fuel Pump Upgrade for Your 1990 Jeep Wrangler
When it's time to replace your fuel pump, you want a part that is reliable, performs well, and is backed by a solid warranty. That's where KEMSO comes in.
KEMSO offers high-performance, direct OEM replacement fuel pumps that are designed to be a perfect fit for your 1990 Jeep Wrangler. Whether you are replacing a stock pump that has failed or you want to upgrade for better performance, KEMSO has you covered. Their pumps are high-flow units capable of supporting up to 700-800 horsepower, making them ideal for everything from daily driving to off-road adventures.
One of the best things about KEMSO is their lifetime warranty. Every KEMSO fuel pump is serialized and comes with a lifetime guarantee, meaning you only buy it once. They are built to strict quality standards, and each pump is individually tested before it leaves the factory. If you want peace of mind and a pump that will last, KEMSO is the smart choice.
Visit the KEMSO website at https://www.kemsoracing.com/ to find the perfect fuel pump for your Jeep Wrangler and take advantage of their lifetime warranty.
Final Thoughts
Finding the fuel pump relay on a 1990 Jeep Wrangler is straightforward once you know where to look. It's mounted to the inner fender on the passenger side, near the battery. Testing it is easy with a multimeter or by swapping it with another relay. If the relay is good but the pump still won't run, the pump itself is likely the problem. And when you need a replacement, choose a quality brand like KEMSO for a reliable, long-lasting fix.
For more information and to find the right fuel pump for your vehicle, visit https://www.kemsoracing.com/ today.