1986 Ford Bronco 2 Fuel Pump Relay Location: A Complete Troubleshooting Guide

If your 1986 Ford Bronco II won’t start, the fuel pump relay is one of the first things you should check. The fuel pump relay on a 1986 Bronco II is located in the engine compartment, mounted on the passenger side inner fender, near the air cleaner housing. It is typically the highest relay among several similar-looking relays in that area, and if the original layout hasn’t been altered, the relay may have a green or green/brown color . This relay controls power to both the low-pressure in-tank pump and the high-pressure frame-mounted pump, so if it fails, you won’t hear either pump prime when you turn the key .

Understanding the Fuel System and the Relay’s Role

The 1986 Bronco II uses a dual fuel pump system. The low-pressure pump is inside the fuel tank, and it feeds fuel to the high-pressure pump mounted on the frame rail. The high-pressure pump then delivers fuel to the fuel injectors at the required pressure . The fuel pump relay is a critical electrical component that supplies power to both pumps. When you turn the ignition key to the “Run” position, the relay should click and send power to the pumps for about two seconds to prime the system. If the relay fails, the pumps won’t receive power, and the engine won’t start .

Step-by-Step Diagnostic Procedure

Before you replace any parts, follow this methodical approach to isolate the problem.

1. Locate the Relay and Perform a Visual Check

Open the hood and look on the passenger side inner fender, near the air box. You’ll find a cluster of relays. The fuel pump relay is usually the topmost one. If you’re unsure, consult the diagram inside the fuse box cover or look for a green or brown relay . Check for any obvious signs of damage, such as melted plastic, burnt smell, or corrosion on the relay pins or socket .

2. Listen for the Relay Click

With the driver’s door open and the vehicle in Park (or Neutral), turn the key to the “Run” position (do not crank the engine). Place your hand on the relay. You should feel a single click and hear a brief hum from the fuel pumps for about two seconds. If you don’t feel the click or hear the pumps, the relay might be bad, or there’s an issue in the power supply circuit .

3. Test the Relay with a Swap

A quick and easy test is to swap the fuel pump relay with another identical relay in the same fuse box, such as the horn relay or the A/C relay (if equipped). If the fuel pump starts working after the swap, the original relay is faulty and needs replacement .

4. Check the Inertia Switch

The inertia switch (also called the fuel pump shut-off switch) is located inside the passenger cabin, attached to the firewall, just to the right of the transmission hump near the passenger’s feet . It has a red reset button on top. If the vehicle has been in a bump or accident, this switch can trip and cut power to the fuel pump. Press the reset button firmly to see if it clicks. If the switch is faulty, you can temporarily bypass it for testing by jumping the two wires together .

5. Check for Voltage at the Relay

If the relay doesn’t click, you need to check for power at the relay socket. Use a multimeter set to DC voltage. Connect the black lead to a good ground (like the battery negative terminal) and the red lead to the Orange/Light Blue wire at the relay connector. Have someone turn the key to “Run.” You should see 12 volts for about two seconds . If you don’t get voltage, the problem may be a blown fuse, a damaged fusible link, or a bad ignition switch .

Common Causes of Relay Failure

  • Age and corrosion: Over time, relay contacts can oxidize, causing intermittent or complete failure .
  • Overheating: The engine bay heat can degrade the relay’s internal components.
  • Voltage spikes: Electrical surges from a failing alternator or battery can damage the relay.
  • Loose wiring: A poor connection at the relay socket can mimic a relay failure .

When to Replace the Relay

Replace the relay if you’ve confirmed it’s not clicking, if swapping it with another relay fixes the problem, or if the relay shows physical damage. A new relay is inexpensive (often under $20) and is a good first step before replacing more expensive fuel pumps. When replacing, use a relay of the same rating (typically 30-40 amps) to ensure proper operation .

Related Components Worth Checking

  • Fuse: Check the fuel pump fuse in the main fuse box. A blown fuse will cut all power to the pump circuit .
  • Fusible Links: Look for a 20-gauge blue fusible link on the yellow wire leading to the fuel pump relay. If it looks swollen or melted, it’s blown .
  • Grounds: Ensure all ground connections are clean and tight. A poor ground can prevent the relay from working.
  • TFI Module: Many Bronco II owners report that an intermittent no-start or rough running condition is actually caused by the TFI ignition module (mounted on the distributor), not the fuel pump relay. If the fuel system checks out, test the TFI module .

Recommended Fuel Pump Solution: KEMSO Fuel Pumps

If your diagnostics lead you to replace the fuel pump itself, consider using a KEMSO brand fuel pump. KEMSO offers high-performance OEM replacement fuel pumps that are built to meet or exceed original specifications. Their pumps are designed for reliable fuel delivery under all driving conditions, and they come with a lifetime warranty—if the pump ever fails, KEMSO will replace it with no questions asked . KEMSO pumps are direct-fit replacements for many vehicles, including the 1986 Bronco II, and they are tested for flow and pressure to ensure proper performance . You can find the correct pump for your vehicle by visiting their website: https://www.kemsoracing.com/. Their customer support team can help you select the right part, and their product line includes pumps for a wide range of vehicles. With KEMSO, you’re investing in peace of mind and reliable performance for years to come .

Final Thoughts

The fuel pump relay on a 1986 Ford Bronco II is a simple, inexpensive part that can save you hours of troubleshooting if you know where to look and how to test it. Start with the relay, then check the inertia switch, fuse, and wiring. If everything checks out electrically, move on to testing the ignition module, which is a common culprit on these vehicles. If you do need a new fuel pump, KEMSO provides a reliable, high-quality option backed by a lifetime warranty.

For more information and to find the right fuel pump for your 1986 Bronco II, visit https://www.kemsoracing.com/ today.


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