2DrXJRegulatorFix

You could splice a relay with a switch in line with the fuel pump. Run a switch with the relay.

Wire the relay this way:

Pin 30 - Positive from fuse box for fuel pump
Pin 87 - Positive TO fuel pump
Pin 86 - any constant 12v with ignition on. with a switch inline to pin 86
Pin 85 - To ground

bradleyheathhays

Thanks everybody for the good advice. Glad to see a lot of discussion on this.

Unfortunately I'm not as skilled at reading electrical diagrams etc as I'd like to be. The ASD cutoff switch sounds doable, so thanks boxburn. Don't know a whole lot about finding the correct wire but I have a factory shop manual if that would help.

boxburn

I'll take a look at the 95 LHD later to see if there's any differences in colours. I don't think there will be and I'd imagine if you have the same PDC layout as I have, it'll be the same wires on a 96. I've taken pictures from a 93 loom I have just removed so I can show you a more visual way of finding the correct wire if colours don't match.

RocketMouse

THIS IS ALL YOU NEED... Anyone can get into a vehicle if they want to bad enough... but if you don't want them to take off with it short of having their own towing flatbed truck... do the following:

Watch and DO.... In the end... if someone wants a vehicle bad enough they'll find a way to get it...but something simple like this can make it less of a target for them to be successful with and they'll move on to the next vehicle....

Spencer_P

That is exactly what I had planned to do, but to my knowledge, there isn't a fuel relay wire inside the Jeep.
Now if someone could translate that video to a Jeep Cherokee that'd be great!

boxburn

That is a great place to hide a kill switch if you have a manual. It wouldn't have worked in my old Fiesta as it had a rubber gator instead of a leather one but I still like the idea.

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EDIT: The PCM has a sense for the ASD output but not the FP output. I would not imagine that manually turning the ASD off via a switch would cause any issues as it would be the equivalent of a fuse blowing or a relay failing. Being a 96 it may have ODB2 so whether or not it may throw a fault code I don't know. It may be a better idea to cut the relay control for the fuel pump to avoid any potential fault codes. The method is the same, just change the relay wire you're looking at.
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Looking at splice locations, there isn't anywhere inside the Jeep that you could hook a switch into without it affecting multiple circuits. The following should be enough for you to work with to wire in a kill switch that will kill the ASD relay or if you choose, the fuel pump relay.

Check that your PDC lid shows the same relays in the same locations.


Pick which relay you want to control, both will have the exact same effect.

When you pull the relay out of the slot, it is the left pin next to my finger that you'll need to cut the wire for your switch.


Disconnect the battery. On the front of the PDC there is a plastic cover which underneath has two 10mm nuts which give the PDC +12V. Undo those bolts taking care not to twist the stud in the PDC. Slide the PDC out of it's mounting bracket, lift out and turn over. There are 2 tabs on the sides which hold the bottom cover on. Once unclipped the bottom cover unhinges open.


Find the wire that corresponds to the relay pin, in my case and hopefully yours, it'll be dark blue. It'll be the same colour and thickness wire on both the ASD and FP relays. You may need to snip a cable tie or unwrap a bit of insulation tape but find yourself enough wire to happily work with. In my picture the wire is already cut as it was wired into an imobiliser prior to the looms removal.


Now you will want to cut that dark blue wire. If you go too far back into the loom (which I don't think you will), you could cut it before a splice which will affect other circuits. just make sure where you cut runs directly to the relay with no other wires spliced off of it. Now all you need to do is run wire to and from your hidden switch with one end connecting to one side of the cut wire, and the other to the other side of the cut wire. Although the dark blue wire is rather thick, your switch wire does not need to be as heavy. If you look at the picture above you will see below the dark blue wire is a much thinner dark blue/yellow which is a 20 gauge wire. As long as you match that 20 gauge you will have no issues. Whether you decide to solder or crimp your wires (please please don't twist and tape), make sure what you do is covered and water resistant.

The better hidden or stock looking your new wires are, the more effective they will be. You could try to run them in the main loom bundle but that would be a difficult task.

I've never thought of doing this to my own Jeep before so I think I'll do the same job this weekend so I'll post pictures if I get around to it. Hopefully this is enough information to help you have a go.

paddler

Chuckle... boxburn just made my next task easier. I'm rehabilitating a '96 to be my future retirement property's ATV. Much cheaper... and more capable and comfortable... than a Gator. It's going to get left on the property, hidden back in the woods, with doors unlocked. Already has a battery cutoff on the negative cables, but that's too easy to jump across. However, that will eliminate any battery drain in between trips to the property. My next step is to disable the vehicle. Removing relays, or substituting a dead relay doesn't look practical, as there are 3 identical relays that have to be pulled so a thief can't just swap another relay to the fuel pump position. I was thinking of removing the positive feed to the PDC and just leaving it loose inside the cover, but that requires a socket or nut driver to remove or reinstall. Getting to the bottom of the PDC and putting a switch in the fuel pump wiring under there, not visible from above, is what I'll do.

Splicing into signal-amperage wiring probably is less risky than splicing into the higher-amperage positive output wiring from a relay, and definitely less risk than starter amperage.

For me, I only expect to disable the vehicle when I'm not on the property. When I drive down (10 hours), I'll put the battery key in and connect the battery, feel under the PDC and flip the fuel pump switch, and leave everything "live" until I head back to home and job. For a daily driver, you'll want the switch accessible without going under the hood. I've heard that a switch in somewhere in the door jamb is nasty; the first thing a thief tends to do when getting access to a vehicle is get inside and close the door so they don't look like they are trying to break in. At which point they can't see the switch in the door jamb.

I wonder if a push-button switch may be less obvious and easier to hide than a toggle switch.

awg

I would personally splice the fuel pump wire between relay and pump and bring the switch up under the rear seating area, away from any damp

If you do it well, no one will ever find it, nor work out what you did

In addition, taking the rotor button with you will stop just about anyone

I really want one of those new systems that allow you to track, locate and disable the vehicle, depending on the law of the land, that could work out fun

Red1992XJ

Could not agree more with this. A switch under the rear seat when you lift it for the fuel pump would be perfect. When I lifted the rear seat on my 92, my friends were amazed that my truck did that, because so few modern vehicles do that.

Pulling the rotor off the distributor will also confuse the average burglar. I doubt they would have a spare rotor with them unless they had been casing your truck for a long time.

I'm not knocking an alarm, I am probably going to look into one myself. An alarm would work for letting you know that someone is trying to do something, the above will keep them from doing it.

boxburn

I'm going to guess that they changed the wiring route as my 93 donor and 95 main run wires differently for the fuel pump. On the 93 the fuel pump wires run under the rear seat then out next to the ABS wiring through the floor. Splicing a switch on that loom would be as easy as finding a rust free XJ, going a month without fault, cut, crimp, switch.

cpttuna

They make a master disconnect switch that uses a plastic key. Run a new wire from BAT+ to the starter and put the disconnect switch in the line somewhere. You have to lift the hood and take the key out to disable, but it's one way of fixing the problem.

bradleyheathhays

Actually my 96 is the first year OBD-II was required on all vehicles so I might better go with the fuel pump relay kill switch as opposed to risking throwing a code. Of all the advice I've gotten on kill switches, routing it to the fuel pump has probably been the most popular option offered.

boxburn

If by that you are talking about cutting the power direct to the pump instead of the relay, remember your switch and wiring needs to be suitably rated for the current draw.

bradleyheathhays

Thanks yes. I'd rather go with the lower voltage signal line. I'll basically be doing the same thing as this guy...


That seem about right for taping into the non 12v line?

boxburn

Any switch that's sold for automotive use would be suitable for triggering a relay, unless it's the cheapest, worst build quality switch imaginable.