Kill Switch

[Chris]

I ran across this and would like to know what you folks think of this setup. I already have a kill switch or two but figure another wouldn't be a bad idea.

[Patrolman]

Maybe I just don't understand one single part of it...

"Once the solenoid has closed, the relay switch if latched closed by the power feed from the relay output contactor".

That must have something to do with keeping power to the pump without having to continually press the button, but I just can't understand "how".

[Chris]

Yeah, I didn't understand that line either Jeff. I know it's common to use a momentary switch but this strikes me as a bit more complicated that need be. Isn't it as simple as breaking the fuel pump circuit? Switch off, no power to the fuel pump, switch on, power to the pump? :confused:

I think there's a 'no' to this but don't know why...

[Andrew]

http://www.autospeed.com/A_107975/cms/article.html

This thread reminded me that I still need to do this.

[scout man]

Yea, that confused me too. The relay idea is smart, but it is missing something. Pushing the button will close the relay. What it needs though is another hot wire, but one that is only hot when the vehicle is running. That wire should also run into the relay. That way pushing the button will enable you to close the solenoid and start the vehicle, then the other hot feed will keep the solenoid closed while the engine is running.
As far as the idea goes, it is great for a DD, but I dont think I would want it off road. Especially with a carburated vehicle. I think you would be far better off with a toggle switch so you can leave it on while in the vehicle. That way if you should die in a precarious position there is nothing stopping you from restarting the vehicle.

[Chris]

I've read that one Andrew but it confuses me. I don't like wiring and do like keeping it simple. Obviously, if someone wants your truck they'll get it. I'm just thinking of the punks that know the very basics.

How about a wire from the negative coil post to a toggle switch, the other side of the toggle switch goes to ground. When the toggle is open, there is no continuity from the negative to ground. When closed the ground circuit is completed and prevents the car from starting.

[Andrew]

lol that one is simple to me Chris.

[scout man]

I like that one Andrew!

[Chris]

lol that one is simple to me Chris.

Ouch! :lol:

[Andrew]

well I work in IT and have screwed around with computers and electronics all my life so :p

[WINKY]

i understand it :D

the momentary button replaces the start circuit when you turn the key. once the engine is running you no longer have to hold the button as the run circuit has taken over.

without pushing the button while turning the key to start the fuel pump will not run.

[Andrew]

Nope. At least not the one I posted.

The one I posted, you push the momentary button, and the vehicle is disabled. It is not re-enabled until you swipe over the hidden reed switch with a magnet. You can hide the reed switch anywhere behind any plastics, etc. so it's not visible at all. And the wiring can be confused enough that I'd say just about any theif would leave rather than try to figure it out. You can pull the relay that the momentary switch is hooked up to and rip all the wires off and it still won't work. It can be figured out - just takes too long.

[WINKY]

i was talkin bout the diagram chris posted :)

[Brody]

A good idea.. Someone posted up a lot of information on kill switches about 1-1 1/2 years ago, including this diagram and the link to the one showing how to build one using a swipe card. I have no idea where they ended up. Good to see this information back again.

I actually got as far in the diagram to where it says 'mount in trunk' and started thinking about how much work I would have to do to make a trunk to mount it in....:lol:

[4Runninfun]

why not just install a toggle switch on the neg side of the fuel pump and hide the switch?

[Patrolman]

I understand it now... It just took a day and some fresh eyes for me to get it. I will do a "write-up" on how it works when I have some time. Really pretty genius!

[Patrolman]

why not just install a toggle switch on the neg side of the fuel pump and hide the switch?

Because you have to remember to toggle it off where with this setup you don't. Also, the toggle is visible. If this is under the carpet, it won't be visible.

[Patrolman]

Ok, so I decided to take a stab at an explanation.

For those who don't know what a relay is, it is a switch that is activated by power. When power is applied to one side, the other side closes the gate and activates the pump in this case.

The 1st stage is obvious. When the "button" isn't pressed, there is no power to the pump since the button breaks the connection to the side and the relay breaks the connection down the middle.

2nd stage is when the button is pressed. It supplies power to the pump, allowing the vehicle to run. One option is to continue to hold your finger on the button while driving around. That would be silly. That leads to...

3rd stage is part of stage 2 really. When the button is pressed, power follows the ground through the pump to ground. It ALSO goes to ground via the relay. This triggers the relay to close, which then continues to supply power. The power continues to split between the relay (to keep it closed) and the pump.

4th stage is when the key is cut off. Then power through the pump circuit is cut out, which means the pump stops as it would from the factory. Engine shuts off. But also, the relay lost its power supply and will open again. The only way it will close is for someone to push the button and turn the key to start the vehicle again. :) No need to remember to flick the kill switch to the off position.

[Patrolman]

SO, my only concern with this "design" is that the power circuit for the EFI pump might not be able to handle the load for the pump and the relay both. Also, electricity takes the path of least resistance. Too much power might go right to ground through the relay and too little through the actual pump...

[Andrew]

why not just install a toggle switch on the neg side of the fuel pump and hide the switch?

Because that's easier to find and defeat.

[Chris]

why not just install a toggle switch on the neg side of the fuel pump and hide the switch?

I like this Jon, I don't think it has to be too sophisticated to work. Hiding a switch will deter a casual thief. Nothing's going to stop a determined one.

[sunk]

Yeah, I didn't understand that line either Jeff. I know it's common to use a momentary switch but this strikes me as a bit more complicated that need be. Isn't it as simple as breaking the fuel pump circuit? Switch off, no power to the fuel pump, switch on, power to the pump? :confused:

I think there's a 'no' to this but don't know why...
I would not use a momentary switch on the fuel pump. the pump needs power to run...to wire that up you would need the relay to be attached to the ignition. the way I wire up kill switches is to the battery lead to the starter. you need a high amp relay in line and a momentary switch...the starter only needs power when cranking.