Rajan Wilcox
Replacing the fuel cut-off relay wiring can be a tricky task, but it's an essential part of maintaining your vehicle's fuel system. The fuel cut-off relay is responsible for cutting off the fuel supply to the engine in the event of a malfunction or accident, and it's crucial that it works correctly to prevent fires and other hazards. In this guide, we'll take you through the steps of replacing and rewiring your fuel cut-off relay, including how to locate the correct wires, cut them safely, and connect them to the relay. We'll also cover the purpose of the fuel cut-off relay and how it works, so you can understand the importance of this often-overlooked component.
| Characteristics | Values |
|---|---|
| Purpose | To replace the fuel cut-off relay when the fuel pump goes out |
| Fuel pump relay | A four-prong relay with at least 14-gauge wiring |
| Fuel pump supply wire | Cut the wire from the middle, then connect the wires to the remote disconnect relay |
| Voltage | 12 volts |
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$47.78
What You'll Learn
Finding the 12v supply wire from the ECU to the fuel pump
To find the 12v supply wire from the ECU to the fuel pump, you must first access the fuel pump's wiring. Once you have located the 12v supply wire, cut it so that you have half of the wiring running to the fuel pump, and the other half running to the factory ECU.
The relay you need should be a four-prong relay with at least 14-gauge wiring. You can then run a wire from pin 87 to your factory wire that you cut that runs to the fuel pump. The relay is like a light switch. When it receives 12 volts on pin 85, it will turn on the switch and make continuity between pin 30 and pin 87 on the relay. As pin 30 is wired straight to the battery, this will send a clean voltage straight to the fuel pump with no other obstructions.
When the car is shut off, pin 85 will lose its 12 volts, causing the coil inside the relay to drop and the light switch to turn off, cutting the continuity between pins 30 and 87, which will then cut the voltage supply to the fuel pump.
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Cutting the wire
To replace the fuel cut-off relay wiring, you will need to cut the wire. First, you need to find the 12v supply wire from the ECU to the fuel pump. Once you have located this wire, use an electrician's tool to cut it in the middle. This will leave you with half of the wiring running to the fuel pump and the other half running to the factory ECU. Make sure to securely connect the two ends of the wire for safety reasons.
Next, you will need to run a wire from pin 87 to the factory wire that you cut. This wire runs to the fuel pump. The relay acts like a light switch. When it receives 12 volts on pin 85, it turns on the switch and creates continuity between pin 30 and pin 87. As pin 30 is wired straight to the battery, this sends a clean voltage to the fuel pump with no obstructions. When the car is turned off, pin 85 loses its 12 volts, causing the coil inside the relay to drop and the light switch to turn off. This cuts the continuity between pins 30 and 87 and, in turn, cuts the voltage supply to the fuel pump.
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Connecting the wires to the remote disconnect relay
To connect the wires to the remote disconnect relay, you will need to find the 12v supply wire from the ECU to the fuel pump. Once you have found this wire, use an electrician's tool to cut it from the middle. You can then connect the wires to the remote disconnect relay. Make sure to connect the two ends of the wire securely, especially if the fuel pump supply wire is thicker than usual.
The relay is like a light switch. When it receives 12 volts on pin 85, it will turn on the switch and make continuity between pin 30 and pin 87 on the relay. As pin 30 is wired straight to the battery, this will send a clean voltage straight to the fuel pump. When the car is shut off, pin 85 will lose its 12 volts, causing the coil inside the relay to drop and the light switch to turn off, cutting the continuity between pins 30 and 87 and the voltage supply to the fuel pump.
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Ensuring the wiring is correct
First, locate the fuel pump's wiring. You need to find the 12V supply wire that runs from the ECU (Engine Control Unit) to the fuel pump. This wire provides power to the fuel pump, so it's essential to identify it correctly. Once you've found the right wire, cut it carefully in the middle. This step is crucial as it will allow you to connect the relay later.
Now, you'll have two halves of the wire: one half running to the fuel pump and the other half running back to the ECU. It's important to secure these connections to prevent any safety hazards. Make sure there are no exposed wires or loose connections.
Next, you'll need to connect the relay. The relay should be a four-prong relay with at least 14-gauge wiring. Connect one end of the cut wire to pin 87 on the relay. Then, connect the other end of the wire to your factory wire that runs to the fuel pump. This step completes the circuit and ensures that power can flow to the fuel pump when the relay is activated.
Finally, test the wiring to ensure it's correct. You can use a multimeter to check for continuity between pin 30 and pin 87 on the relay. Additionally, verify that the relay is receiving 12 volts on pin 85 when the car is turned on. This voltage should turn on the switch, creating continuity between pin 30 and pin 87, which will then send power to the fuel pump. When the car is shut off, pin 85 should lose its 12 volts, causing the switch to turn off and cutting the power supply to the fuel pump.
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Running a wire from pin 87 to the factory wire
To run a wire from pin 87 to the factory wire, you must first find the 12v supply wire from the ECU to the fuel pump. Once you have found this wire, cut it, so that you have half of the wiring running to the fuel pump and the other half running to the factory ECU. Now, run a wire from pin 87 to the factory wire that you cut. This will send a clean voltage straight to the fuel pump.
The relay is like a light switch. Anytime it receives 12 volts on pin 85, it will turn on the switch and make continuity between pin 30 and pin 87 on the relay. As pin 30 is wired straight to the battery, this will send a clean voltage straight to the fuel pump. When the car is shut off, pin 85 will lose its 12 volts, causing the coil inside the relay to drop and the light switch to turn off, cutting the continuity between pins 30 and 87, and the voltage supply to the fuel pump.
Make sure to connect the two ends of the wire securely for safety reasons. You can also use the cloud platform for remote disconnection and control of the vehicle.
The relay you need should be a four-prong relay with at least 14-gauge wiring.
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Frequently asked questions
First, find the 12v supply wire from the ECU to the fuel pump. Cut this wire so that you have half of the wiring running to the fuel pump and the other half running to the factory ECU. Then, run a wire from pin 87 to the factory wire that you cut.
You need a four-prong relay with at least 14-gauge wiring.
Once you have found the wire, use an electrician's tool to cut it from the middle. Then, connect the wires to the remote disconnect relay.
