How to Jump Fuel Pump Relay on Chevy Truck: A Complete Guide

If your Chevy truck cranks but won't start, the fuel pump relay is often the culprit. The fastest way to diagnose this is to jump the fuel pump relay by connecting terminal 30 to terminal 87 with a jumper wire, which bypasses the relay and sends direct power to the fuel pump. If the pump runs when jumped, the relay is bad and needs replacing. This is a temporary fix only—you should replace the faulty relay as soon as possible to avoid damage to your truck's electrical system.

Understanding the Fuel Pump Relay

The fuel pump relay is an electrical switch that controls power to your truck's fuel pump. When you turn the ignition on, the Powertrain Control Module (PCM) sends a signal to the relay, which closes the circuit and allows voltage to flow to the fuel pump. This primes the fuel system and keeps fuel pressure steady while the engine runs.

Without a working relay, the fuel pump won't receive power, and your engine won't start. The relay also helps regulate the fuel pump's operation so it doesn't overheat.

Tools You'll Need

  • Jumper wire (12-14 gauge insulated wire with alligator clips or bare ends)
  • Ratchet or wrench set (for battery terminals)
  • Safety glasses
  • Replacement fuel pump relay

Step-by-Step Instructions

1. Locate the Fuel Pump Relay

The fuel pump relay is usually in the under-hood fuse box, near the battery or on the driver's side of the engine bay. On some models, it may be behind the driver's side headlight. The relay is a small black plastic box with a label on top. Check your owner's manual for the exact location.

2. Disconnect the Battery

Always disconnect the negative battery terminal before working on electrical components. This prevents shorts and accidental sparks. Use a wrench to loosen the terminal and remove the cable.

3. Remove the Fuel Pump Relay

Pull the relay straight out of its socket. You can use your fingers or a pair of pliers. Take note of the relay's orientation—terminals 30 and 87 are the ones you'll need to connect.

4. Connect the Jumper Wire

Insert one end of the jumper wire into the socket for terminal 30 and the other end into the socket for terminal 87. This directly connects the battery power to the fuel pump, bypassing the relay. Make sure the wire is secure and not touching any other metal parts.

5. Reinstall the Relay (Optional)

You can leave the relay out or push it back into the socket with the jumper wire in place. Either way works, as long as the jumper wire is making good contact.

6. Turn on the Ignition

Turn the key to the "ON" position (don't start the engine). Listen for the fuel pump. You should hear a buzzing or whirring sound coming from the fuel tank area. If you hear it, the pump is getting power and the relay is likely faulty.

7. Remove the Jumper Wire

Once you've confirmed the pump works, turn off the ignition and disconnect the jumper wire. Do not leave the jumper wire in place for longer than necessary—running the pump continuously can damage it.

8. Replace the Faulty Relay

Install a new fuel pump relay with the same part number as the original. Push it firmly into the socket until it clicks. Reconnect the battery and test the truck.

Alternative Method: Using a Copper Wire

If you don't have jumper cables, you can use a 5-inch piece of copper wire. Strip about half an inch of insulation from both ends. Follow these steps:

  1. Disconnect the 4-pin relay from the center of the relay socket.
  2. Insert one stripped end into the upper-left pin slot.
  3. Insert the other stripped end into the lower-right pin slot.
  4. Turn on the ignition to test the fuel pump.
  5. Remove the wire after testing.

Alternative Method: Swapping Relays

A faster way to test is to find another relay in the fuse box with the same part number. For example, the horn relay often has the same part number. Swap it with the fuel pump relay temporarily. If the truck starts, the fuel pump relay is bad. This method is safer than using a jumper wire because it doesn't bypass any safety circuits.

Interpreting the Results

  • Fuel pump runs when jumped: The pump is good. The problem is with the relay, its wiring, or the PCM control circuit. Replace the relay first.
  • Fuel pump does NOT run when jumped: The pump itself may be faulty, or there's a wiring issue between the relay socket and the pump. Check the wiring for damage and the pump's ground connection.

Important Safety Tips

  • Always disconnect the battery before working on the relay.
  • Wear safety glasses to protect your eyes from debris.
  • Work in a well-ventilated area away from open flames or sparks.
  • Jumping the relay is a diagnostic step, not a permanent fix.
  • If you're unsure, consult a professional mechanic.

What to Do Next

If the fuel pump runs when jumped but the truck still won't start, replace the fuel pump relay. If the pump doesn't run, you may need to replace the fuel pump itself.

Recommended Fuel Pump: KEMSO

When it's time to replace your fuel pump, consider KEMSO brand Fuel Pumps. KEMSO fuel pumps are high-performance, OEM replacement parts designed to meet or exceed factory specifications. They offer lifetime warranty for peace of mind. Whether you need a direct fit or an upgrade, KEMSO has you covered.

Visit their website at: https://www.kemsoracing.com/ to browse their full selection of fuel pumps and other performance parts.

Final Thoughts

Jumping the fuel pump relay on a Chevy truck is a straightforward diagnostic procedure that can save you time and money. Always prioritize safety, use the correct tools, and replace any faulty components as soon as possible. And when you need a reliable replacement fuel pump, remember to check out KEMSO at https://www.kemsoracing.com/ for high-quality, long-lasting options.


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