The Exact Location of the 1993 Chevy S10 Fuel Pump Relay

The fuel pump relay in a 1993 Chevrolet S10 pickup is located in the main electrical center (fuse box) under the hood, near the driver-side battery. It's a small cube-shaped device plugged into the fourth slot from the front left corner (positions vary slightly by model) and is labeled as "RELAY: FUEL PUMP" or "FUEL PUMP" on the box cover.

This relay acts as a critical gatekeeper: when you turn your ignition key, the relay activates the fuel pump to send gasoline to the engine. A failed relay will prevent your truck from starting. Below, we detail how to find, test, and replace it with precision, using only basic tools.

Step 1: Locating the Main Electrical Center

The primary electrical center is a black plastic enclosure, roughly 12” x 8”, positioned beside the battery on the driver’s side of the engine bay. Open the hood and look for these landmarks:

  • Battery proximity: The box sits adjacent to or slightly behind the battery, secured with clips or bolts.
  • Cover labels: Lift the plastic cover. You’ll see a diagram mapping each fuse and relay. For 1993 S10s, the fuel pump relay is typically labeled "F/PMP" or "FUEL PUMP." Exact slot numbering varies:
    • V6 models: Relay is usually #17 (middle row, third from left).
    • 4-cylinder models: Check slots #10–#20; it’s often #12 or #14.
  • Relay appearance: Matches a standard 5-pin "ISO mini" relay (1-inch cube, silver/metallic body).

Step 2: Verifying the Correct Relay (Quick Checks)

Identify the relay with these methods:

  • Relay diagram: Match the cover’s diagram to your truck’s engine type (e.g., the "4.3L" V6 diagram may show it at position #17).
  • Swap test: Temporarily swap the fuel pump relay with an identical spare one elsewhere (e.g., horn relay). If the fuel pump activates after swapping, your original is faulty.
  • Pin confirmation: Pull the relay. Its pins should be connected to circuits marked:
    • Terminal 30: Constant 12V supply (wire from battery).
    • Terminal 87: Output to fuel pump (leads rearward).

Step 3: Testing the Relay

Use a $10 multimeter to diagnose failure:

  1. Resistance check: Set the multimeter to Ohms (Ω).
    • Pins 85 and 86 (coil terminals): Should show 50–100Ω resistance.
    • Pins 30 and 87 (power/load): Infinite resistance normally; near 0Ω when 12V is applied to 85/86.
  2. Function test:
    • Apply 12V from the battery to pins 85 and 86.
    • You’ll hear a "click" if functional.
    • Now test continuity between pins 30 and 87 with the multimeter (should be 0Ω).

Step 4: Replacing a Faulty Relay

  1. Part numbers: Use OEM AC Delco D1743A or equivalents like Bosch 332029120. Auto parts stores stock generic "ISO 280" relays.
  2. Installation: Align the relay’s pins to match the slot orientation. Press firmly until seated. Avoid forcing.
  3. Post-replacement checks:
    • Turn the key to "ON" (without starting). Listen near the fuel tank: a 2-second hum means the pump activated.
    • If no sound, recheck relay placement or test fuel pump wiring.

Troubleshooting Tips When the Relay Isn’t the Issue

If replacing the relay doesn’t fix the non-start condition, inspect:

  • Fuses: Check the 20A fuse labeled "ECM B" or "F/PUMP" in the same electrical center.
  • Inertia switch: Located behind the passenger kick panel. If tripped (after impact), press its reset button.
  • Fuel pump wiring: Examine the harness near the tank for fraying/corrosion.
  • Grounds: Clean battery terminals and chassis ground straps near the engine block.

Why the 1993 S10 Relay Fails

High temperatures under the hood degrades the relay’s internal contacts over time. Symptoms include:

  • Intermittent stalling, especially in heat.
  • Extended cranking before starting.
  • Fuel pump silent at key-on.

Replace the relay every 100,000 miles proactively to avoid stranding. This $10 part keeps your S10 reliable for work or travel—locate yours today using the cover diagram and a flashlight.

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