Kill switch to ignition / starter

[paradigm]

Looking to add a kill switch to the ignition relay on my PSI conversion harness in my LS swap.

Looking to put a switch on pin 85 to ground on the ignition relay, so when the switch is open the ground circuit is open and the starter would be killed. Thoughts on this? This should pass the least amount of current through the kill switch.

 

[Sweet_Johnny]

You might be able to but I'd probably go a different route. There are many ways to disable the ignition or starter ranging from the Cole Hersee 24200 latching relay like Painless uses in their kit to stacking relays that you wire to assorted items. The C.H. relay can even be wired to operate via key fob if so desired. I got the following diagrams from the12volt.com after seeing this post on montecarloss.com years ago:

 

[CopperNick]

If you don't have electronics under the hood that need continuous power even with the engine off, such as that for a CPU to maintain the memory, then the simplest switch would be one inserted into the positive side of the battery like they use in drag strip applications. I say Positive, or plus, as opposed to the Neg side simply because the negative terminal can have more than one lead returning back to it that could generate a complete circuit to allow the car to run. With positive, it goes right to the starter solenoid and an isolator switch would defeat any attempt to spin the key. As an example, I personally run a master disconnect that breaks the continuity in the Plus battery lead to the starter solenoid. With the switch off, everything is dead, no starter or lights or........................ Switch on, all is well.

When I still ran that miserable misbegotten lump of a FI-Tech EFI unit it needed power even with the key off to keep the memory happy. So all I did was to add a lead to the battery in side of the switch so even with it "Off", the cpu still got its jones for power fed. MPITA because if the unit sat for any length of time it had to have a charger put on the battery or the draw by the CPU would drain the battery.

The only other upgrade to the PLUS side that I included was to go a gauge or two heavier on the cable to account for the longer distance in the power run and the added resistance that the longer cable would possess.


Nick

 

[jcelk]

i put a push button switch thats normally open in the neutral safety switch wire and hide it under the carpet alongside the seat it can;t be seen now i just push that spot to start it

 

[Ugly1]

You could just put a plow relay on the main battery feed and hide the switch similar to the Ford starter relay. Is a simple wiring and on/off. Is this for theft protection or racing ?
If theft protection you can also put shut off switch with or without a relay system to the fuel pump feed. No fuel, no go. The original LS system might have a crash safety sensor switch that shuts off the fuel pump.

 

[paradigm]

You might be able to but I'd probably go a different route. There are many ways to disable the ignition or starter ranging from the Cole Hersee 24200 latching relay like Painless uses in their kit to stacking relays that you wire to assorted items. The C.H. relay can even be wired to operate via key fob if so desired. I got the following diagrams from the12volt.com after seeing this post on montecarloss.com years ago:

That's some reading there - I will give it a look, thanks.

If you don't have electronics under the hood that need continuous power even with the engine off, such as that for a CPU to maintain the memory, then the simplest switch would be one inserted into the positive side of the battery like they use in drag strip applications. I say Positive, or plus, as opposed to the Neg side simply because the negative terminal can have more than one lead returning back to it that could generate a complete circuit to allow the car to run. With positive, it goes right to the starter solenoid and an isolator switch would defeat any attempt to spin the key. As an example, I personally run a master disconnect that breaks the continuity in the Plus battery lead to the starter solenoid. With the switch off, everything is dead, no starter or lights or........................ Switch on, all is well.

When I still ran that miserable misbegotten lump of a FI-Tech EFI unit it needed power even with the key off to keep the memory happy. So all I did was to add a lead to the battery in side of the switch so even with it "Off", the cpu still got its jones for power fed. MPITA because if the unit sat for any length of time it had to have a charger put on the battery or the draw by the CPU would drain the battery.

The only other upgrade to the PLUS side that I included was to go a gauge or two heavier on the cable to account for the longer distance in the power run and the added resistance that the longer cable would possess.


Nick

I do not want to interrupt main power, its going to need a good sized isolated switch.

You could just put a plow relay on the main battery feed and hide the switch similar to the Ford starter relay. Is a simple wiring and on/off. Is this for theft protection or racing ?
If theft protection you can also put shut off switch with or without a relay system to the fuel pump feed. No fuel, no go. The original LS system might have a crash safety sensor switch that shuts off the fuel pump.

I don't want to interrupt the main 12V line. This is for protection. I am going try to see if I can interrupt the ground on the fuel pump relay signal side (pin 86 I believe, however I tried the same with the ignition relay and the car didn't react favorably.

 

[paradigm]

The PSI harness has a relay center, one has been wired for a fuel pump and the other for ignition.

I wanted to interrupt the ignition to kill the starter via a switch. I put a switch on pin 86 of the ignition relay (black wire into PSI engine harness which I thought was ground), but when I opened it didn’t do nothing and when I closed it the fuel pump wouldn’t kick on and the electrical was under some sort of additional load. Car cranked, but it wouldn’t get fuel. Then when I removed the switch on pin 86 and wired it as original, the car got fuel and turned on, but wouldn’t turn back off until I pulled the fuel relay. I suspect the ignition relay stayed latched, and so I changed the ignition relay to another one and the car shut off when I cycled the car on and back off again.


Ignition Relay:

Pin 85 – Red wire into Monte Carlo harness (key on and cranking power?)
Pin 86 – Black wire into PSI engine harness (ground?)
Pin 87 – Red into bus bar on PSI fuse block, terminal connects to one side of 15A fuse which across from 1 pink wire (fuel injector?)
Pin 30 – Red from PSI engine harness (12V+ ?)

Fuel Pump Relay:
Pin 85 – Green from PSI engine harness (12V from??)
Pin 86 – Black into PSI engine harness (ground?)
Pin 87 – Red into Monte Carlo harness (to fuel pump or?)
Pin 30 – Yellow into Monte Carlo harness (to fuel pump or?)

What pin and on what relay would you guys suggest putting kill switch on to prevent the car from starting? I am trying to interrupt the least amount of current and effectively prevent the car from starting.

Thanks,
Phil

 

[Sweet_Johnny]

You can utilize the diagrams above to simply add a relay to the existing system, and that relay receiving power would initiate whichever line you choose to interrupt. As in a low voltage "turn on" signal. I think that would be the easiest and cleanest.

 

[doood]

Cut the power to the ECU with the kill switch. This will cut the spark and is like a 16-20 guage wire carrying ~ 1 AMP

 

[Bonnewagon]

I know two instances where a fuel cut-off worked perfectly. This was on old school mechanical fuel pumps. The car can start, but then quits 100 feet away. Now the car is stranded in the middle of the road. Both times the crooks panicked and took off. Both times the cars were recovered with only the ignition damage. This kind of cut-off gets an insurance credit.