1986 Ford F150 Fuel Pump Fuse: Complete Troubleshooting Guide

If your 1986 Ford F150 has no power to the fuel pump, the problem is rarely a blown fuse—it’s more likely a faulty relay, a tripped inertia switch, or a burned fusible link. The 20-amp fuel pump fuse in the interior fuse panel is only one piece of a larger electrical puzzle. This guide will walk you through every step to diagnose and fix the issue, from checking the fuse box to testing the computer ground circuit, so you can get your truck running again.

Understanding the 1986 Ford F150 Fuel Pump Electrical System

The 1986 Ford F150 uses a complex fuel delivery system that relies on multiple electrical components working together. The system includes a high-pressure fuel pump mounted on the frame, and in some configurations, a low-pressure pump in the tank. The power to these pumps flows through a relay, a fuse, an inertia switch, and several fusible links. The computer (EEC) controls the relay by grounding the coil circuit. If any part of this chain fails, the pump won’t run.

The 20-amp fuse (position 16) in the interior fuse panel protects the horn and cigar lighter, but it does not directly power the fuel pump. The fuel pump gets its power from a separate yellow wire that comes from the starter relay battery terminal through a fusible link. This is a common point of confusion for owners troubleshooting a no-start condition.

Step 1: Check the Fuse Panel First

Locate the interior fuse panel under the dashboard on the driver’s side. The 1986 Ford F150 has one fuse box. Look for the following fuses related to the fuel system:

  • 10A Fuse (position 15) – Auxiliary Fuel Tank Selector
  • 15A Fuse (position 18) – Electric Fuel Pump Control (7.5L engine only)

Inspect both fuses visually and with a test light. If the 10A fuse for the auxiliary tank selector is blown, the pump may not operate when that tank is selected. The 15A fuse for the pump control circuit is critical for the 7.5L engine. Replace any blown fuses with the correct amperage rating.

Tip: Even if the fuse looks good, test it with a multimeter. A fuse can appear intact but have an internal break.

Step 2: Test the Fuel Pump Relay

The fuel pump relay is located on the driver’s side firewall near the brake booster. The relay has four pins, and the wiring is as follows:

  • Yellow wire – Power from a fusible link (constant 12V)
  • Pink/Black wire – Power out to the inertia switch
  • Red wire – EEC power (key-on power)
  • Tan/Light Green wire – Ground signal from the computer

To test the relay, follow these steps:

  1. Turn the key to the ON position (do not start the engine).
  2. Listen for a click from the relay. The pump should run for 1–2 seconds to prime the system. If you hear the click but the pump doesn’t run, the relay contacts may be burnt.
  3. Use a test light to check for power at the yellow wire. If no power, check the fusible link at the starter relay.
  4. Jump the relay contacts by connecting the yellow wire to the pink/black wire with a fused jumper wire. If the pump runs, the relay is faulty.

Common issue: The relay socket pins can corrode or lose tension. Remove the relay and inspect the female terminals. Use a small screwdriver to gently bend them tighter if needed.

Step 3: Reset the Inertia Switch

The inertia switch acts as a safety cutoff that stops the fuel pump in a collision. It is located inside the cab on the passenger side, near the bottom of the heater box. The switch has a reset button on top.

To check the inertia switch:

  1. Locate the switch on the passenger side floorboard, behind the kick panel.
  2. Press the reset button firmly downward. If the button is already in the down position, the switch is not tripped.
  3. Test for power at the switch. The pink/black wire from the relay should have 12V with the key on. If you have power to the switch but no power to the pump, the switch may be faulty.

Pro tip: Many owners have accidentally tripped the inertia switch by kicking it while getting in and out of the truck. Always check this first before replacing expensive parts.

Step 4: Check the Fusible Links

Fusible links are short sections of wire designed to burn out if a short circuit occurs. They are located near the starter relay on the fenderwell. The 1986 Ford F150 has several fusible links that feed the fuel pump circuit.

To check the fusible links:

  1. Look for a yellow wire coming from the starter relay battery terminal. This wire feeds the fuel pump relay.
  2. Inspect the wire visually for any melted or burned insulation.
  3. Use a test light to check for power at the relay end of the yellow wire. If no power, the fusible link is likely burned out.
  4. Replace any burned fusible links with the correct gauge wire. Do not use a standard fuse—fusible links are designed to handle specific current loads.

Important: Fusible links can appear intact but have an internal break. Always test for voltage at both ends of the wire.

Step 5: Use the EEC Self-Test Connector

The EEC self-test connector provides a quick way to test the fuel pump circuit. This connector is located near the diagnostic connector under the hood. Pin #6 is the fuel pump test pin.

To test the pump circuit:

  1. Turn the key to the ON position.
  2. Ground pin #6 of the self-test connector to the battery negative terminal.
  3. Listen for the fuel pump to run. If the pump runs, the relay, wiring, and pump are good. The problem is likely in the computer ground circuit or the ignition module.
  4. If the pump does not run when grounding pin #6, the issue is in the relay, wiring, or pump itself.

Note: This test bypasses the computer control. If the pump runs with this test but not when you turn the key, the computer is not grounding the relay coil.

Step 6: Test the Computer Ground Circuit

If the pump runs when you ground pin #6 but not when you turn the key, the computer is not sending the ground signal to the relay. This can be caused by:

  • A faulty ignition module (TFI module) – This is a common failure point on 1986 F150s.
  • A bad ground at the computer – Check the black wire with a green stripe coming from the negative battery post.
  • A faulty computer – If all other checks pass, the EEC computer may be defective.

To test the computer ground circuit:

  1. Turn the key to the ON position.
  2. Use a test light to check for power at the red wire of the fuel pump relay. This wire should have 12V with the key on.
  3. Check the tan/light green wire at the relay. With the key on, this wire should have 12V. If you ground this wire, the relay should click and the pump should run.
  4. If the relay clicks when you ground the tan/light green wire, but does not click when the key is turned, the computer is not grounding the circuit.

Troubleshooting tip: Pull the computer diagnostic codes. A code 87 indicates a fuel pump circuit failure. This confirms the computer is not detecting the relay closure.

Step 7: Inspect the Wiring and Connectors

After sitting for an extended period, wiring can corrode and connectors can fail. The 1986 F150 is known for issues at the fuel pump connector on the frame rail.

Check these areas:

  1. The fuel pump connector on the frame near the tank. Look for green corrosion or burnt pins.
  2. The ground strap from the battery to the engine block. A poor ground can cause intermittent power loss.
  3. The wire splice where the fuel pump power wire connects to the main harness. This is often located near the starter relay.

If you find corrosion, clean the connectors with a wire brush and apply dielectric grease. If the wires are damaged, cut back to clean wire and splice in new sections.

Recommended Solution: Upgrade to a KEMSO Fuel Pump

If your 1986 Ford F150 fuel pump has failed, or if you want to prevent future issues, consider upgrading to a KEMSO Fuel Pump. KEMSO is a trusted brand in the automotive and powersports industry, known for high-performance, direct OEM replacement fuel pumps.

Why choose KEMSO?

  1. High Performance – KEMSO pumps deliver up to 340 LPH (liters per hour) at 43 psi, supporting up to 700-800 bhp. This is a significant upgrade over the stock pump.
  2. OEM Replacement – KEMSO pumps are designed as direct-fit replacements for stock OEM pumps. They come with complete installation kits, including fuel strainers, hoses, wiring connectors, and clamps.
  3. Lifetime Warranty – KEMSO backs all its fuel pumps with a lifetime warranty, giving you peace of mind.
  4. E85 Compatible – KEMSO pumps are designed for both gasoline and E85/ethanol fuel.
  5. Quality Control – Each pump is individually tested for flow and pressure, and KEMSO follows ISO/TSO quality control programs.

For the 1986 Ford F150, the KEMSO 340LPH pump (part number 10910) is an excellent choice. It is compatible with Ford vehicles from 1993-2003, including the F150, Crown Victoria, and Expedition. The pump is easy to install and comes with everything you need.

Visit the KEMSO website today to find the perfect fuel pump for your truck: https://www.kemsoracing.com/

Final Thoughts

Troubleshooting the fuel pump on a 1986 Ford F150 can be frustrating, but by following the steps in this guide, you can diagnose the problem quickly and accurately. Start with the fuse panel, then move to the relay, inertia switch, and fusible links. Use the EEC self-test connector to verify the pump circuit, and check the computer ground if needed.

Remember: The most common causes of no power to the fuel pump are:

  1. A tripped inertia switch
  2. A burned fusible link at the starter relay
  3. A faulty fuel pump relay
  4. A bad ground at the computer

If you need to replace the fuel pump, choose a reliable aftermarket option like KEMSO for long-lasting performance and peace of mind.

For more information and to browse KEMSO fuel pump options, visit: https://www.kemsoracing.com/


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