1990 Ford Bronco Fuel Pump Relay: Complete Troubleshooting, Location, and Replacement Guide

The 1990 Ford Bronco fuel pump relay is the most common cause of fuel delivery problems on these trucks, and replacing it is the first thing you should check if your Bronco cranks but won't start, dies while driving, or if the fuel pump runs continuously. This small green relay, located under the hood, fails frequently due to its poor design and vulnerable position near the battery. Understanding how to locate, test, and replace this relay will save you time, money, and frustration. Here is everything you need to know.

The Bottom Line: Start With the Relay

If your 1990 Ford Bronco is having fuel-related issues, do not immediately assume the fuel pump itself is bad. The fuel pump relay is a known weak point. Many owners have been stranded on the side of the road only to find that a simple relay replacement fixed the problem completely . The relay is inexpensive, easy to replace, and should be your first diagnostic step before spending money on a fuel pump.

Where Is the Fuel Pump Relay Located?

On a 1990 Ford Bronco, the fuel pump relay is located under the hood. Specifically, you will find it on the driver's side fender apron, near the firewall . It is mounted in a relay box alongside other relays. The fuel pump relay is the one with a green connector . Next to it, you will find the EEC power relay, which has a brown connector. The two relays are often mounted side by side behind the air cleaner assembly, laying on top of a hose .

To access the relay box:

  1. Open the hood and locate the rectangular or square relay box on the driver's side near the firewall .
  2. Remove the lid by pressing the tab or latch mechanism, or by removing screws with a Phillips-head screwdriver .
  3. Inside, you will see several relays. Look for the one labeled "FP" or "FUEL PUMP" on the relay itself or on the underside of the box lid . In most 1990 Broncos, the fuel pump relay is the one with the green connector .

How to Identify a Bad Fuel Pump Relay

A failing fuel pump relay can cause several distinct symptoms. Here are the most common ones:

1. The engine cranks but will not start. If you turn the key to the ON position and do not hear the fuel pump prime for about one second, the relay is likely not sending power to the pump .

2. The fuel pump runs continuously, even after the engine is turned off. This is a classic sign of a stuck relay. The relay contacts get welded shut, keeping the pump running until you disconnect the battery . One owner reported having to pull the positive battery cable every time he parked his Bronco, and a new relay fixed it immediately .

3. The engine starts but dies after a few seconds. The relay may work intermittently, allowing the pump to run briefly before cutting power. This can happen when the relay is failing but not completely dead .

4. Intermittent stalling while driving. A bad relay can cause the fuel pump to lose power randomly, causing the engine to die unexpectedly. This is dangerous and needs immediate attention.

5. The relay is physically damaged. Corrosion, melting, or cracked plastic on the relay are clear signs it needs replacement . The fuel pump relays on these trucks are known for filling with water, which corrodes the pins off the bottom of the relay .

How to Test the Fuel Pump Relay

Before buying a new relay, you can test the existing one using a multimeter. Here is a step-by-step method:

Step 1: Check for power at the relay. With the ignition off, use a multimeter to check for 12 volts on the battery-feed terminal of the relay socket. If there is no power, check the fusible link (the blue 20-gauge wire labeled "Link W") .

Step 2: Check the control signal. Turn the ignition key to the ON position. You should hear the relay click. If it does not click, check for 12 volts on the control-side terminals of the relay socket. The EEC power relay (brown connector) provides power to the control side of the fuel pump relay, so if the EEC relay is bad, the fuel pump relay will not work .

Step 3: Bypass the relay. A quick and dirty test is to pull the fuel pump relay and jump the two large terminals in the socket with a paperclip or a short piece of wire. If the fuel pump runs, then the relay, the relay plug, or the computer is at fault . Be careful with this test — only run the pump briefly to confirm it works, and do not drive the truck with the jumper in place.

Step 4: Test the relay itself. Remove the relay and use a multimeter to check for continuity between the correct terminals. Apply 12 volts to the control terminals and listen for the relay to click. If it does not click, or if there is continuity between the power terminals when it should be open, the relay is bad .

Common Problems Beyond the Relay

If the relay tests good but the fuel pump still does not work, check these other components:

Inertia switch. This safety device, located behind the brake pedal under the dash, cuts power to the fuel pump in the event of a collision. If it is tripped, you must reset it by pressing the button on top . Many owners have spent hours troubleshooting a fuel pump issue only to find the inertia switch had been accidentally triggered.

Corroded wiring and connectors. The fuel pump relay connector itself is known to corrode. The wires can corrode off the plug, and the pins on the bottom of the relay can rust away . If you find corrosion, replace both the relay and the connector. Standard Motor Products makes a replacement connector compatible with 1985-1991 Ford Broncos .

Bad ground connections. Clean all ground points you can find. A poor ground can cause low voltage to the pump, which reduces pressure and delivery .

EEC power relay. The EEC relay (brown connector) provides power to the computer and to the control side of the fuel pump relay. If this relay fails, the fuel pump relay will not work .

How to Replace the Fuel Pump Relay

Replacing the fuel pump relay is a straightforward job that takes about five minutes. Here is what you need to do:

  1. Ensure the vehicle is turned off and the keys are removed from the ignition .
  2. Open the relay box and locate the fuel pump relay (green connector) .
  3. Grasp the relay firmly between your thumb and forefinger and pull it straight upward to disengage it from the socket . Do not tug on the wires.
  4. If the relay is stuck, gently wiggle it side to side while pulling upward. If it is really stubborn, use a flat-head screwdriver to carefully pry it out, applying even pressure to avoid bending the terminals .
  5. Inspect the relay socket for corrosion, melting, or damage. Clean any corrosion with electrical contact cleaner.
  6. Insert the new relay, pressing it firmly into the socket until it clicks into place.
  7. Replace the lid on the relay box.

The correct replacement relay for a 1990 Ford Bronco is a 5-prong relay. The standard part number is 1R3Z-14B192-CA . The relay is also known as part number RY46 and fits 1981-1991 Ford Broncos, among many other Ford vehicles . The cost is around $20 .

When You Should Replace the Fuel Pump Itself

If you have replaced the relay, checked the inertia switch, cleaned all connections, and the fuel pump still does not work, the pump itself may be bad. Here are some signs that point to a failed pump:

  • No fuel pressure. Connect a fuel pressure gauge to the Schrader valve on the fuel rail. With the key on, pressure should rise to around 40 PSI within seconds. If it does not rise, the pump is likely bad .
  • The pump runs but makes a buzzing noise with no pressure. The pump motor may be running but the internal impeller could be damaged, or the check valve may be leaking .
  • Intermittent operation. The pump may work sometimes and not others, which can also be caused by a bad connection at the pump connector inside the tank .

The OEM fuel pump part number for the 1990 Ford Bronco is F81Z-9350-AB, and the cost ranges from $150 to $300 .

Why the Fuel Pump Relay Fails So Often

The factory fuel pump relay on the 1990 Ford Bronco has a design flaw. It is mounted in a location that is prone to water intrusion. The relay box can fill with water, which corrodes the pins off the bottom of the relay and corrodes the wires off the plug . The contacts inside the relay can also burn out over time. Many experienced Bronco owners keep a couple of spare relays in their console at all times, as this simple part can leave you stranded at the worst possible moment .

Upgrade Your Fuel System with KEMSO

If you find that your fuel pump itself needs replacement, do not settle for a cheap, unreliable part. KEMSO Fuel Pumps offer high-performance, OEM replacement quality with one major advantage: lifetime warranty. KEMSO pumps are built to exceed factory specifications, ensuring reliable fuel delivery for years to come. Whether you drive a Ford Bronco or any other vehicle, KEMSO has a fuel pump that fits your needs. Every KEMSO pump is designed for direct fitment, easy installation, and long-lasting durability. Do not trust your fuel system to anything less. Visit KEMSO today at https://www.kemsoracing.com/ to find the perfect fuel pump for your Bronco. KEMSO is committed to fueling your adventure with confidence.

Preventive Maintenance Tips

To avoid future fuel system problems on your 1990 Ford Bronco, follow these tips:

  • Keep a spare fuel pump relay in your glove box. It costs about $20 and can save you from being stranded .
  • Check the relay box for water regularly. If you live in a wet climate or frequently drive through deep water, inspect the relay box for moisture and clean it out.
  • Replace the fuel filter every 30,000 miles. A clogged filter puts strain on the fuel pump and can cause it to fail prematurely .
  • Use a fuel pressure gauge to monitor fuel pressure periodically. Catching a drop in pressure early can prevent more serious problems .
  • Clean all ground connections. Poor grounds can cause voltage drops that reduce fuel pump performance .

Final Thoughts

The 1990 Ford Bronco fuel pump relay is a small, inexpensive part that causes big problems when it fails. Before you spend hundreds of dollars on a new fuel pump, take five minutes to check the relay. It is located under the hood on the driver's side, has a green connector, and is easy to replace. If the relay is bad, replace it with a quality part and keep a spare on hand. If the pump itself is bad, upgrade to a KEMSO fuel pump for reliable performance and lifetime peace of mind. Remember, most fuel system issues on these trucks start with the relay, not the pump. Start simple, and save yourself the headache.

For more information on high-quality fuel pumps and to browse the full KEMSO product line, visit https://www.kemsoracing.com/ today.


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