The Coil kill switch is the most simple and possibly the most common method used..
Just run a wire from the (-) Neg. terminal of your coil to a switched ground. If the wire is grounded (switch CLOSED), then the coil will never be able to build a charge in the secondary windings and there is no spark.
If the wire is ungrounded (switch OPEN) then nothing happens and the engine runs as normal.
Problems with this:
1) If you have the coil grounded and you crank the engine for a prolonged period of time, then the coil will build up heat and will eventually be destroyed. But I am talking about minuets of cranking, which would be stupid anyways. I forget to flip my switch all the time and its perfectly fine. I'll crank it and I know right away that I forgot to flip to switch, so I'll just flip it and fire it up.
2) Remember that you are only cutting out the spark. Fuel is still being delivered, both Carb or EFI setups. So if you crank the engine for, oh lets say 5 seconds straight with the switch Closed, and then Open the switch and try to start it, then it will run extremely rich for a couple of seconds and you will dump raw unburned gas right into your catalytic converter which is life threatening to the converter. Also excessive fuel in the cylinders will eaisly seap past the piston rings and will containimate your engine oil which will shorten the life and preformance of the oil.
Again, these problems only occur if you crank the engine for prolong periods with the coil grounded. And since you wont do that, you dont have to worry about it..
For the 85+ 5spd models, the "Clutch Start Cancel" option is a great kill switch that requires less wire and is more hidden then the coil method. If your vehicle requires you to activate the clutch in order to start the engine, then this applies to you.
Look down at your clutch pedal assembly. There will be a switch that is activated only when the clutch pedal is activated, or depressed. All this switch does is just grounds a relay that controls your "Start" circuit.
So, In order to use this circuit as a kill device, simply put a switch between the relay and the clutch pedal switch.
When the switch is closed, you will have to press the clutch pedal all the way down in order to start the vehicle.
When the switch is open, no current will flow through it, so the circuit will never be grounded, which means the Starter relay will never engage, and the starter solenoid will never activate the starter. No matter if the clutch pedal is down or not, the truck simply will not start.
This is precisely what the "Clutch Start Cancel" switch does. It just grounds out the Starter Relay so that you dont have to ground it by pressing the clutch pedal down.
So when you install this switch, make sure that you wire it near the Starter Relay so that its in front of both the "Clutch Start Cancel" and the actual clutch activated switch. Otherwise a clever wood-be thief could just press the "Clutch Start Cancel" switch and actually override your clutch cancel kill switch
The Starter Relay should be in the cabin fuse box on the drivers side. Check the map on the fuse box cover or check your FSM.
The only problem with this method is that its a "Silent" kill switch. What I mean is that lets say you park your rig out side your window at night. And someone jimmies the lock and gets in side. Then lets say he is able to hot wire your ignition and he tries to start it. Then what happens? Nothing, nothing at all. No sound. So he still has plenty of time to look around and try to figure out why its not cranking.. as you lay in your bed dreaming about Rock Crawling, he has all night to run some trouble shooting before the truck actually makes a sound.
This is apposed to the Coil Kill Switch which is not a "Silent" kill switch. Get it? If he tries to start it, it will just crank and crank and crank, never fire up, but it will hopefully wake you up! That's the difference. Or at the least, someone will notice that a vehicle is cranking and not firing and they might become curious and notice that the window is broken or something...
So this Clutch Kill Switch works great, its just a silent kill switch.
And thirdly, you could put either a switch that interrupts the fuel pump and/or and OCR (Opening Circuit Relay). This is a great kill method that is the best of both worlds: You get an engine that cranks and cranks and cranks, so its noisy and will wake you up, but their are no ill effects with this method. The spark plugs will be firing thin air, which is perfectly normal, and since the fuel pump is disabled the engine will not flood over so you dont have to worry about your cat or oil..
In my opinion you should do all three of these if possible, and also search for other methods to disable your rig. If you just spend 5 mins looking at a wire diagram, you'll find all kinds of kill areas.
And about your switch, try to be as creative as possible. Use black switches instead of chrome and put them in odd locations, like behind your visor, hey, why not? If its gonna keep your rig with you why not?
In fact one of my kill switches is not even in my cabin, its some where else. Of course its inconvenient, as its only used for extended storages, if Im away for the weekend or a trip. The guy can do all he wants inside my truck, he will never ever get it started.
Another thing is that I used to try to "hide" my actions when I was activating a kill switch. I didnt want people to see what/where I am flipping a switch each time I parked my truck. But you know what, it doesnt matter. If they want your truck they will get it somehow.. Just remember that your kill switch isn't for those who are watching you park your rig every day, they will catch on to your tricks, but rather its for those punks who think they can have your ride and just go for it. They will come up short because of your 10 mins you spend installing a $2 switch that will be the best theft deterrent device you ever installed.
Don't think about installing one, just do it.
BigMike
