1987 Chevy Truck Fuel Pump Fuse: Location, Troubleshooting, and Replacement Guide

If your 1987 Chevy truck won’t start or the fuel pump isn’t running, the most likely culprit is a blown fuel pump fuse or a faulty fuel pump relay. The fuel pump fuse on a 1987 Chevy truck is typically located in the under-dash fuse box on the driver’s side, and the fuel pump relay is mounted on the firewall in the engine compartment, near the passenger side . Before replacing any major components, always check these two parts first – they are the easiest and cheapest fix. This guide will walk you through locating the fuse and relay, testing them, and understanding the entire fuel pump electrical system so you can get your truck back on the road quickly.

1. Understanding the Fuel Pump Electrical System

The 1987 Chevy truck (including C10, K10, R10, and S10 models) uses an electric fuel pump located inside the fuel tank. The pump is controlled by a relay and protected by a fuse. When you turn the key to the "ON" position, the Engine Control Module (ECM) sends a signal to the fuel pump relay, which then supplies power to the pump for about 1-2 seconds to prime the system . If the engine doesn’t start, the pump stops until the ECM detects the engine is cranking.

Key components in the fuel pump circuit:

  • Fuel pump fuse – Protects the circuit from overload
  • Fuel pump relay – Switches power on/off to the pump
  • Oil pressure switch – Acts as a backup power source once the engine runs
  • ECM (Engine Control Module) – Controls the relay based on ignition signals
  • Inertia switch – (on some models) kills power in a collision

2. 1987 Chevy Truck Fuel Pump Fuse Location

The fuel pump fuse on a 1987 Chevy truck is located in the under-dash fuse box, on the driver’s side . Here’s how to find it:

  1. Open the driver’s door and look under the dashboard, near the parking brake pedal area
  2. For 1981-1987 models, the fuse box is mounted horizontally on the lower kick panel
  3. Press the plastic clip on the front edge to release the cover
  4. Look for the ECM B fuse or the fuel pump fuse – it is typically a 15A or 20A fuse

Important: On some 1987 Chevy trucks, the fuel pump fuse is labeled as "ECM B" or "Fuel Pump" in the fuse box diagram. The fuse is usually a 15A ATO blade-type fuse . The fuse box cover should have a diagram printed on the inside, but if it’s missing, check the owner’s manual.

3. Fuel Pump Relay Location

The fuel pump relay on a 1987 Chevy truck is located in the engine compartment, mounted on the firewall near the passenger side . It is often covered by a small black plastic cover. Look for a relay with a gray wire (circuit 120) going to the fuel pump .

Alternative locations:

  • Some models have the relay under the dashboard, near the fuse box
  • On the firewall, left of the engine near the blower motor

How to identify the relay: The relay is typically a standard Bosch-style relay (small, black or gray, with 4 or 5 pins) . You can test it by swapping it with another identical relay from the same fuse box (like the horn relay) to see if the fuel pump starts working.

4. How to Test the Fuel Pump Fuse and Relay

Testing the fuse:

  1. Remove the fuse using a fuse puller (usually stored in the fuse box)
  2. Visually inspect the fuse – if the metal strip inside is broken, it’s blown
  3. Use a multimeter set to continuity mode to check if the fuse is good
  4. Replace with an identical amperage fuse – never use a higher amp fuse

Testing the relay:

  1. Locate the relay on the firewall
  2. Turn the ignition to "ON" and listen for a click – if you hear it, the relay is likely working
  3. Use a multimeter to check for 12V power at the relay terminals:
    • Terminal 30 (constant power) should have battery voltage
    • Terminal 85 (ground) should have continuity to ground
    • Terminal 86 (trigger) should have 12V briefly when the key is turned on
    • Terminal 87 (output) should have 12V when the relay is activated

5. Common Symptoms of a Blown Fuel Pump Fuse or Bad Relay

Symptoms of a blown fuse:

  • Engine cranks but won’t start
  • No sound from the fuel pump (no priming noise)
  • Fuel pump fuse is visibly melted or broken
  • Other electrical accessories may also fail if the fuse is shared

Symptoms of a bad relay:

  • Engine starts only after extended cranking (because the oil pressure switch is acting as backup)
  • Fuel pump runs continuously (stuck relay)
  • Intermittent stalling over bumps (loose relay contacts)
  • No fuel pump noise at key-on

6. Step-by-Step Troubleshooting Guide

Step 1: Check the fuse first

  • Locate the under-dash fuse box and find the ECM B or fuel pump fuse
  • If it’s blown, replace it and test the truck
  • If it blows again immediately, there is a short circuit in the wiring

Step 2: Test the relay

  • Locate the fuel pump relay on the firewall
  • Swap it with a known-good relay (like the horn relay)
  • If the pump starts working, the relay was faulty

Step 3: Check for power at the fuel pump

  • Use a multimeter to test the Tan/White wire at the fuel tank connector
  • With the key on, you should see 12V for 1-2 seconds
  • If no power, the problem is in the wiring between the relay and the pump

Step 4: Inspect the ground connection

  • A poor ground at the frame rail near the fuel tank can cause voltage drops
  • Clean the ground terminal and ensure it’s tight

Step 5: Test the oil pressure switch

  • If the pump runs when the engine is started but not during prime, the oil pressure switch may be faulty
  • This switch acts as a backup – if the relay fails, the switch provides power once oil pressure builds

7. Wiring Diagram for 1987 Chevy Truck Fuel Pump

The fuel pump wiring is straightforward but understanding the color codes helps:

  • Gray wire (circuit 120): Power from relay to the fuel pump
  • Tan/White wire: Power from the oil pressure switch to the pump
  • Orange wire (circuit 440): Constant 12V power to the relay
  • Dark Green/White wire (circuit 465): Trigger signal from ECM to the relay
  • Black/White wire (circuit 450): Ground for the relay coil

For dual-tank setups (common on 1987 Chevy trucks), there are two fuel pumps – one in each tank. The tank selector switch on the dash controls which pump receives power. The gray wire serves the right (passenger side) tank, and the tan wire serves the left (driver side) tank .

8. Dual Tank Fuel Pump Issues

If your 1987 Chevy truck has dual tanks, you may experience specific problems:

  • Only one tank works: The fuel pump in the other tank may be dead, or the selector valve is stuck
  • Gauge doesn’t switch: The tank selector switch may not be grounding properly
  • Both pumps run but engine stalls: The selector valve is likely faulty and not switching fuel flow

Testing dual tanks: Listen for the fuel pump priming sound when you flip the dash switch. If you hear it from both sides, the pumps are working. If not, check the gray and tan wires for continuity .

9. Safety Precautions

Working on the fuel system requires caution:

  • Always disconnect the battery negative terminal before working on fuel pump wiring
  • Never bypass a blown fuse with a higher amp fuse or wire – this can cause a fire
  • Avoid sparks near the fuel tank – use a flashlight, not a drop light
  • Work in a well-ventilated area to avoid fuel vapor inhalation
  • If you smell fuel, stop immediately and check for leaks

10. Recommended Replacement: KEMSO Fuel Pump

When it's time to replace your 1987 Chevy truck's fuel pump, we highly recommend choosing KEMSO brand fuel pumps. KEMSO fuel pumps are designed for high performance, offer OEM replacement quality, and come with a lifetime warranty for peace of mind. Whether you have a C10, K10, R10, or S10, KEMSO has the right fuel pump for your truck.

Visit KEMSO's official website to browse their full selection of fuel pumps: https://www.kemsoracing.com/

Final Thoughts

The fuel pump fuse on a 1987 Chevy truck is a simple but critical component. Always check the fuse first – it’s the easiest and cheapest fix. If the fuse is good, move to the relay, then to the wiring and the pump itself. With the diagrams and troubleshooting steps in this guide, you should be able to diagnose and fix most fuel pump electrical issues in under an hour.

For replacement parts, don’t forget to check out KEMSO at https://www.kemsoracing.com/ for high-quality, lifetime-warrantied fuel pumps that will keep your classic Chevy running strong for years to come.


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