1987 Chevy Truck Fuel Pump Relay Location: Find it Fast & Fix It Right

The fuel pump relay on 1987 Chevrolet C/K Series pickup trucks and SUVs (like Blazers and Suburbans) is consistently located under the dashboard, mounted to a metal bracket on the driver's side kick panel, near the steering column. You access it by reaching up behind the dash near the brake pedal, feeling for a metal bracket holding several identical-looking plug-in components. The relay itself is typically a 1-inch square or rectangular black plastic cube with an electrical connector plugging into it.

Stop wasting time searching under the hood. While other vital relays and fuses reside in the engine compartment fuse box, the crucial fuel pump relay for your 1987 Chevy truck is almost exclusively found inside the cab, under the driver's side dash. Knowing this precise location is critical for diagnosing and resolving common "no fuel" issues like a truck that cranks but won't start, sputters under load, or has intermittent power loss.

Why Location Matters and Why It's Often Misunderstood

  • Engine Bay Focus: Most drivers logically start looking under the hood near the battery or firewall. The primary fuse box is there, containing fuses and relays for the headlights, horn, cooling fan, and other systems. This leads to confusion when the fuel pump relay isn't found here.
  • Variations in Layout: While placement is generally consistent within the cab ('85-'87 models share this design), minor differences exist between model years (C10 vs K10) and trim levels. Knowing the exact area saves frustration.
  • Invisibility Factor: The relay is tucked away above the parking brake pedal and behind trim panels. You typically need to locate it by feel, bending down and looking up under the dash – it's not immediately visible from the driver's seat.
  • Multiple Relays Close Together: The bracket holds several identical square relays. Mistaking the horn relay or flasher relay for the fuel pump relay is common if you don't confirm visually or test electrically. Their positions can also vary slightly.
  • Electrical System Evolution: Older models often had components grouped differently. Knowing the '87-specific location avoids confusion with information intended for earlier Silverados or later GMT400 trucks.

Preparing to Locate Your Fuel Pump Relay Safely

Taking a minute to prepare ensures safety and makes the job smoother:

  1. Park Safely & Set Brakes: Park the truck on a level surface. Engage the parking brake firmly. If using wheel chocks, place them behind the rear wheels.
  2. Disconnect Battery Negative Terminal: CRITICAL SAFETY STEP. Use a 10mm wrench to loosen the nut on the negative (-) battery terminal clamp. Slide the clamp completely off the terminal post and secure it away so it cannot accidentally make contact. This eliminates the risk of sparks or short circuits while handling the electrical relay.
  3. Clear Access: Remove any floor mats. Position yourself outside the truck, kneeling or lying on your back with your shoulders beneath the dash panel and your head near the brake pedal area. Use a work light (flashlight) to illuminate the space.
  4. Gather Tools (Minimal): You'll primarily need your hands, but have the flashlight ready. Keeping a small mirror or smartphone on-hand helps verify part numbers or wiring colors later. Have your 10mm wrench accessible for battery reconnection.

Step-by-Step Guide: Finding the Relay Location

Follow these instructions methodically:

  1. Position Yourself: Sit/kneel outside the driver's door. Lean in and place your head and shoulders below the steering wheel column. Look upward towards the firewall near the top of the brake pedal bracket.
  2. Locate the Metal Bracket: Directly above the parking brake pedal release handle, and slightly to the left towards the driver's door, you'll find a sturdy, vertical metal bracket attached to the inner structure of the dash. It faces toward the driver's seat footwell.
  3. Identify the Relay Cluster: Mounted directly onto this vertical metal bracket are typically four small square or rectangular plastic modules. These are all relays of the same basic physical type. They are plugged into sockets on the bracket. Sometimes the flasher module (larger and often metallic) is located here too.
  4. Count and Distinguish (Generally): Moving from the left (driver's door side) towards the right (steering column):
    • Position 1 (Furthest Left): Often the HORN RELAY.
    • Position 2: Often the FUEL PUMP RELAY.
    • Position 3: Often the MAIN ECM (Engine Computer) RELAY.
    • Position 4 (Furthest Right): Often the AIR CONDITIONING COMPRESSOR CLUTCH RELAY. Note: This sequence is common but variations occur. Always verify!
  5. Feel and Look: Locate the relay you believe is the fuel pump relay based on position. It will be a 1-inch square black plastic cube (sometimes slightly rectangular) with a multi-wire electrical connector plugged into its bottom. Inspect it visually with your light or by feel - wires leading down from it are normal.

Verifying You Have the Correct Relay (Test Socket Method)

Since position numbers can vary slightly, verification is essential:

  1. Locate the ALDL Test Socket: Near the same area, often attached to the same bracket or clipped nearby under the dash, find the Assembly Line Diagnostic Link (ALDL) connector. This is a rectangular plastic socket with multiple holes (12-pin standard for 1987 trucks). It's usually wrapped with a protective plastic sleeve.
  2. Identify Terminal "G": Look inside the ALDL connector. Focus on the row of pins closest to the firewall/engine side. The specific terminal labeled "G" is the key (sometimes stamped on the plastic next to the hole). It's typically the second pin from the left in this row. You can also trace its wire - it should be pale green or tan.
  3. Test the Terminal: With the ignition key turned ON (engine off), use your voltmeter or test light:
    • Ground: Clip the negative (-) lead of your meter/light to a clean metal bolt (like the parking brake bracket).
    • Probe Terminal "G": Touch the positive (+) probe to the metal terminal inside the ALDL's "G" socket hole.
    • Read Voltage: You should see Battery Voltage (12V) present for 2 seconds when the key is first turned ON. If you have a helper, they can turn the key while you watch the meter. If it holds 12V indefinitely (common test confusion point), that indicates the relay has failed stuck closed.
  4. Momentary Power Confirms: This brief 12V pulse at Terminal "G" directly signals the fuel pump relay activating momentarily when the ignition is switched on. Knowing the fuel pump relay should provide this pulse tells you the function associated with Terminal "G".

Important Tips for Identification and Access

  • Relay Labels or Stickers: Inspect the side of the relay facing you. Sometimes factory labels indicating function (like "Fuel Pump," "FP," "ECM," or "MAIN") remain intact. A clean rag wipe might reveal worn lettering. The fuel pump relay might have a slightly different top shape compared to the others.
  • Socket Shape Confusion: All relay sockets on the bracket appear identical. Rely primarily on position counting combined with the ALDL Terminal "G" test to confirm the fuel pump relay's socket function.
  • Removing the Relay: Grasp the relay body firmly (not the wires) and pull it straight out of its socket. Apply even pressure. Avoid prying tools which can break the plastic bracket. It will feel snug but should release with a firm pull.
  • Wire Harness Identification: On the wiring harness itself, the main power wire supplying the fuel pump relay socket from the fuse box is usually an Orange wire. This is constant battery power. If tracing wiring to confirm the socket's circuit, follow the orange feed wire.
  • Fuses Always Check First: If your truck shows no signs of fuel pump priming at all, always confirm you have power at the Fusible Link protecting the main electrical system near the battery, and the "ECM BATT" fuse (20A) in the engine compartment fuse box. Failure to do so can lead to unnecessary relay replacement.

Diagnosing a Faulty Fuel Pump Relay (Key Tests)

Understanding simple tests saves money:

  • The Swap Test: Swap the suspected fuel pump relay with an identical, known-good relay (like the Horn relay). If the horn still works but the fuel pump still doesn't prime, the fuel pump relay was likely the problem. If the horn doesn't work anymore, the problem lies elsewhere. Re-check all relevant fuses first.
  • Listening Test: Have a helper turn the ignition key to "ON" while you listen near the rear of the truck above the fuel tank. You should hear a distinct humming/whirring from the electric in-tank pump for 1-3 seconds. Hearing the pump confirms the relay triggered successfully. Hearing nothing points toward relay failure, fuse failure, or a completely dead pump motor.
  • Electrical Relay Bench Test:
    1. Remove the relay.
    2. Identify terminals: The socket has 4 or 5 blades/pins:
      • Terminals 85 & 86: Control Coil (wires energized by ignition switch/ECM command).
      • Terminal 30: Constant Battery Power Input (usually ORANGE wire).
      • Terminal 87: Power Output to Fuel Pump (usually light grey or grey with dark stripe).
    3. Using an ohmmeter: Measure resistance between terminals 85 and 86. A good coil shows continuity (some resistance value, not open circuit). Check Terminals 30 & 87: Normally should show NO Continuity (Open Circuit).
    4. Battery Activation Test: Apply 12V across terminals 85 (+) and 86 (-). You should hear/feel a distinct CLICK. Simultaneously, your ohmmeter should now show Continuity between terminals 30 and 87. If no click or no continuity exists when voltage is applied, the relay is faulty internally. Performing the click test verifies moving parts function.

Replacing Your 1987 Chevy Fuel Pump Relay

Replacement is straightforward once identified correctly:

  1. Purchase Correct Part: Get an exact physical replacement relay based on GM part number or auto parts store interchange (Standard Motor Products RY-100 is a common replacement equivalent). Pay attention to pin orientation.
  2. Disconnect Battery: Safety procedure repeated - disconnect negative battery terminal before work.
  3. Align and Install: Ensure the new relay has the same pin configuration as the old one. Align it with the socket and push it firmly straight in until fully seated. Listen for a soft click securing it.
  4. Reconnect Battery & Test: Reconnect the negative battery terminal. Turn the ignition key to "ON." Listen for the fuel pump priming hum for 2 seconds. Attempt to start the engine. Confirm proper operation.

Preventing Future Fuel Pump Relay Failure

Protect your new component:

  • Avoid Corrosion: Keep the under-dash area clean and dry. Minor moisture ingress in wet weather won't kill a good relay but prolonged exposure can.
  • Secure Connections: Ensure the relay is plugged in tightly. Loose connections cause arcing, heat damage, and intermittent failure.
  • Address Recurring Issues: If a relay fails repeatedly shortly after replacement, suspect other underlying electrical issues like voltage spikes, overheating at fuel pump connectors causing excessive draw, or failing wiring insulation creating a short circuit condition overload. Diagnose the root cause.
  • Temperature Management: While under-dash temps aren't as extreme as under-hood, excessively hot interior conditions can stress relays over time. Ensure cabin vents are clear.

When the Fuel Pump Relay Isn't the Problem

Important Note: Hearing the fuel pump relay click and the pump prime doesn't necessarily confirm the pump is pushing enough fuel pressure to run the engine. Other frequent causes include:

  • Clogged Fuel Filter: Restricts fuel flow severely.
  • Failing Fuel Pump Sending Unit: Pump runs but produces low pressure.
  • Severe Fuel Line Restrictions: Kinked lines, debris blockage.
  • Ignition Control Module Failure: Common issue preventing spark despite fuel being delivered.
  • ECM Failure: Loss of vital computer control commands including fuel pump trigger signals.
  • Wiring Harness Damage: Broken wires at the pump hanger unit inside the tank from vibration is very common on aging trucks. Causes open circuits. Corrosion in harness connectors under the truck exposed to road salt/grime is also prevalent.

Conclusion: Targeted Solution Saves Time and Money

Knowing definitively that the 1987 Chevy truck fuel pump relay location is under the driver's dash, mounted to a specific bracket near the steering column, eliminates the most common initial hurdle in diagnosing fuel-related no-start conditions. Remember to disconnect the battery, verify the correct relay using position and the ALDL Terminal "G" test, and perform simple electrical checks before replacing the part. This targeted approach saves significant frustration, time, and potential expense compared to random troubleshooting.

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