How to Hook Up a Kill Switch to a Fuel Pumpby Mike Schoonveld
There are many high-tech devices available to thwart potential car thieves from stealing your vehicle. Many of these cost hundreds of dollars and require a trained installation expert to wire into your vehicle. As an alternative, you can install a fuel pump cutoff switch in a hidden location for less than $10 and some time. While a thief might be able to get into your car and even enable the ignition, with a fuel-pump cutoff in the off position, it's not going to run long enough to get out of your driveway. You just have to remember to flip the cutoff toggle off every time you exit the car.
Find the Hot Wire
Jack up your vehicle and insert jack stands on firm support locations, such as under the rear axle or front strut supports. The vehicle needs to be high enough for you to safely crawl under from front to back.
Locate the electric fuel pump for your vehicle. The most likely location is inside your fuel tank. Remove the gas tank filler cap and put your ear close to the spout. Have someone turn the ignition key from off to the run position. The fuel pump will turn on for two or three seconds, and you can hear it click or buzz. If you are sure the pump isn't inside the tank, follow the fuel line from the tank toward the motor until you locate the pump.
Check the service manual for your auto's make, model and year of manufacture, and locate the wiring diagram, taking note of the color of the hot wire leading from the fuel pump relay to the fuel pump.
Call the service department of a dealer and tell them what you are doing if you don't have a service manual for your make, model and year of car. Most of the time, a technician can look up the information for you. Locate the hot wire yourself by testing with a 12-volt test light as a last resort.
Disconnect the wires that deliver electricity to the pump. There is a connector that plugs either directly onto a matching connector on the fuel pump or to a short pigtail of wires leading into the pump.
Ground the test light to a solid metal part of the vehicle with the alligator clip on the end of the test light's wire.
Insert the probe into each of the plug-in slots in the connection on the end of the wires coming from the vehicle's electrical system as a helper turns the ignition key from off to run when you are ready. The hot wire is the one that is energized for two or three seconds when the key is switched to run.
Install the Switch
Locate a spot for the kill switch. It can be under the dash, under the driver's seat or on the console, as long as you can reach it from the driver's seat and it's hidden from view.
Check to see that you can route the wires from this location through the floor or firewall to the outside of the vehicle, drilling a hole in the floor or firewall, if needed. Also check to see there's enough room behind the switch location for the switch mechanism and wiring.
Install the toggle switch in the location you've chosen by drilling a hole in which to fit the switch body. Insert the switch from the rear, then tighten the ring nut on the switch body on the exterior side to hold it in position. Make sure to orient the on and off position the way you want it -- such as up is on/down is off.
Connect a pair of 14-gauge wires to the two poles of the toggle switch, using the appropriate solderless connectors.
Uncoil enough of each wire to reach the location under the car where the connection between the car's electrical harness plugs into the fuel pump.
Cut the hot wire leading to the fuel pump.
Slide a shrink-wrap sleeve onto each of the wires leading to the toggle switch.
Use a butt connector to connect one of the wires from the switch to the hot wire you just cut, routing the energy flow from the electrical system, to the switch. Then connect the other wire from the switch to the remaining end of the cut-off hot wire to allow electricity to flow to the fuel pump when the kill switch is in the on position.
Slide the shrink-wrap sleeves over the butt connectors, then heat each sleeve with a butane lighter to shrink the sleeves and waterproof the connection.
Reconnect the wiring harness connection to the fuel pump connection.
Use wire ties to support the new wires from the toggle switch.
- Make it a habit to turn off the fuel pump switch each time you leave the car so it becomes second-nature. The system isn't automatic; it will protect your vehicle only when you activate it.
Things You'll Need
- 12V test light
- Service manual
- Toggle switch
- 14 gauge wire
- Solderless butt connectors
- Shrink tubing
- Jack stands
- Wire ties
- Butane lighter
Mike Schoonveld has been writing since 1989 with magazine credits including "Outdoor Life," "Fur-Fish-Game," "The Rotarian" and numerous regional publications. Schoonveld earned a Master Captain License from the Coast Guard. He holds a Bachelor of Science in wildlife science from Purdue University.