How To Jump Fuel Pump Relay On Chevy Truck
Diagnosing a fuel delivery problem on a Chevy truck can be frustrating. When the engine cranks but doesn't start, one of the prime suspects is the fuel pump. While a faulty fuel pump itself is a possibility, the problem could lie with the fuel pump relay. Jumping the fuel pump relay is a common diagnostic procedure that allows you to bypass the relay and directly power the fuel pump. This article provides a detailed guide on how to perform this test safely and effectively on your Chevy truck.
Understanding the Fuel Pump Relay and its Function
The fuel pump relay is an electrical switch that controls power to the fuel pump. It's typically activated by the truck's PCM (Powertrain Control Module). The PCM sends a signal to the relay when the ignition is turned on, allowing voltage to flow to the fuel pump, which then primes the fuel system and maintains fuel pressure while the engine is running. If the relay fails, the fuel pump won't receive power, preventing the engine from starting.
Safety Precautions Before You Begin
Before attempting any electrical work on your vehicle, always prioritize safety. These steps are crucial:
- Disconnect the Negative Battery Terminal: This prevents accidental shorts and potential electrical damage.
- Wear Safety Glasses: Protect your eyes from any debris or sparks.
- Work in a Well-Ventilated Area: Gasoline fumes are flammable and can be harmful.
- Avoid Smoking or Open Flames: Gasoline is highly flammable, so ensure there are no ignition sources nearby.
Tools and Materials Needed
To jump the fuel pump relay, you'll need the following:
- Jumper Wire: A short length of insulated wire with alligator clips or spade connectors at both ends. A 12-14 gauge wire is recommended.
- Multimeter (Optional): To verify voltage and continuity.
- Wiring Diagram (Optional): A wiring diagram for your specific Chevy truck model can be extremely helpful in identifying the correct terminals.
Step-by-Step Guide to Jumping the Fuel Pump Relay
Follow these steps to safely and effectively jump the fuel pump relay on your Chevy truck:
- Locate the Fuel Pump Relay: The location of the fuel pump relay varies depending on the year and model of your Chevy truck. It's typically found in the under-hood fuse box, but check your owner's manual or a repair manual for the precise location.
- Identify the Relay Terminals: Once you've located the relay, remove it. The relay should have a diagram on its side or top indicating the function of each terminal. You'll need to identify the following terminals:
- Power Source: This terminal receives power from the battery. Use a multimeter (set to DC voltage) to confirm that this terminal has voltage with the ignition on.
- Fuel Pump Power Output: This terminal sends power to the fuel pump.
- Relay Coil Control: These terminals are used to energize the coil within the relay. *Do not jump these terminals.*
- Insert the Jumper Wire: Using your jumper wire, connect the Power Source terminal to the Fuel Pump Power Output terminal in the relay socket. This bypasses the relay and directly sends power to the fuel pump.
- Listen for the Fuel Pump: With the jumper wire in place, turn the ignition key to the "ON" position (without starting the engine). You should hear the fuel pump running. It may be a buzzing or whirring sound coming from the fuel tank area.
Interpreting the Results
The outcome of this test will help you narrow down the source of the fuel delivery problem:
- If the fuel pump runs when jumped: This indicates that the fuel pump itself is likely functional. The problem is likely with the fuel pump relay, its control circuit (PCM, wiring, etc.), or the relay power supply circuit. Replace the fuel pump relay with a new one as a first step. If the problem persists, further diagnosis of the control circuit is required.
- If the fuel pump does NOT run when jumped: This suggests that the fuel pump is faulty or there is a wiring problem between the relay socket and the fuel pump. Check the wiring for damage, corrosion, or breaks. Also, confirm that the fuel pump has a good ground connection. If the wiring and ground are good, the fuel pump is likely the problem and needs to be replaced.
Important Considerations
Jumping the fuel pump relay is a troubleshooting step, not a permanent fix. If the fuel pump runs when jumped, you need to diagnose and repair the underlying issue with the relay or its control circuit. Running the fuel pump continuously with a jumper wire can overheat the pump and potentially cause damage. After completing the test, remove the jumper wire and re-install the fuel pump relay. Always consult a qualified mechanic if you are unsure about any aspect of this procedure.