Jeep Cherokee XJ - Fuel Pump Kill-Switch

There are many ways to deter a thief from stealing a Jeep: installing an alarm, using a club, or pulling fuses and relays. If I feel so compelled, I sometimes pull the fuel pump relay from the fuse box under the hood after parking. My hope is any would-be thief would give up on starting the Jeep after several failed cranks of the engine.

A better way to achieve the same effect of pulling the relay is to interrupt the circuit for the fuel pump with a switch. This is known as a fuel pump kill-switch. Really, any circuit on the vehicle can be spliced with a kill-switch. Some owners install multiple kill-switches all over the vehicle!

A fuel pump kill-switch is really easy to install on an XJ because the wire to splice is easy to access from inside, just underneath the driver-side of the rear bench. With some extra wire, a toggle switch, and the proper tools, a kill-switch can be installed in just a couple minutes!

The Circuit

Here is a basic diagram of the circuit we're trying to create:

We splice into the existing fuel-pump wire and add our switch to kill or activate the circuit.

Prepping the Kill-Switch

These are the items I decided to use for my kill-switch:

• Round Rocker Toggle LED Switch - 12V/20A
• Electrical Wire - 12-Gauge
• Female-Disconnect Spade Terminals - 12/10-Gauge
• Insulated Wire Crimp Connectors - 12-Gauge
• ATC Fuse Holder Box w/ 20 Amp Fuse - 12-Gauge (Optional)

 

We really only need the switch, the additional wire gives us more freedom to mount the switch somewhere other than where we're splicing (under the rear bench). The fuse holder was something I threw in for extra protection. I don't even really know if it'd protect anything, there's already a fuse in the circuit...

Using the crimp connectors, we connect the fuse holder up to a couple feet of the electrical wire. To connect the wire to the toggle switch, we'll need to terminate the ends with female-disconnects.

Now, the switch is prepped and ready to connect into the fuel pump circuit.

Finding the Correct Wire to Splice

Under the hood, we can find our target wire coming out of the relay and fuse box (a black box on the passenger side). The wire on my 1998 XJ Sport is green and white.

Inside the vehicle, we can find the same wire underneath the driver-side of the rear bench. It's located in a 4-wire bundle beneath the carpet. This bundle of wires leads down to the undercarriage of the Jeep and into the top of the fuel tank. Again, it's green and white.

Finally, we can confirm we have the right wire by getting under the rear of the Jeep near the fuel tank. As expected, the wire can be found coming from out of the vehicle and into the top of the fuel tank.

Interrupting the Circuit

Before doing anything, disconnect the negative terminal of the battery!

Since we know which wire we want to splice, we simply cut it and attach the wires to the toggle switch with crimp connectors.

When everything is all connected, reconnect the battery and give it a couple of test runs. Flip the switch on and off, attempting to start the Jeep each time. If the circuit is broken, the Jeep will crank and crank, but never turn over. If the circuit is complete, the Jeep will crank and turn over.

If everything works as expected, we just need to find a place to hide our switch.

Hiding the Switch

The switch I purchased requires a 3/4-inch hole to mount. Using the proper drill-bit, we simply make a hole and slide the switch through it. To make the install easier, we can disconnect the wires first.

Once the switch is mounted in its desired location, all we have to do is reconnect the wires.

Conclusion

It isn't completely steal-proof, but a would-be thief may not feel it's worth his/her time to crank away, getting nowhere. Obviously, the harder it is to find, the more effective the kill-switch.

Good luck and happy wrenching!