start/stop button in injected car, where to start?

[lunarhighway]

startbutton revisited


in my previous car a had a start button and initially i had planned a stop button as well but never got round to completeing it.

i notice that i have developed the good habbit of shutting off the engine at every stop light and the button that was located in front of the shifter was a great help. i recently disconnected the button as it used the power for the 12v socket wich i needed for a GPS, and i notic reaching fot the key at every stop is quite a distraction

my next car obviously doensn't come with such handy features, so i'm going to try to refit it. problem is that electronicly this car is a great deal more complex than what i had,

the kadett was a 1987 carbed model while the vectra is from 1995 throttle body injected model. still not very advanced by todays standards but i'm not going to start cutting wires without knowing where they go and than have all sorts of lights come on etc...

the start button shouldn't be to hard, as it's just a parallel switch to the ignition key
but the stop button had and has me scratiching my head. i want to shut of the engine but nothing else. on the old car stopping the ignition was enough , but on this one i have the injectors and he chip to worry about.

can anyone give me some pointers to how all these systems depend on eachother and what i should be looking for to stop the engine.. can i somehow shut of the power going to the ignition or would that make the car mad?

ultimately i'd want a single button switch that with the key is in the ignition and turned to on, will stat the engine when pressed and will stop it when pressed again.
however initially a basic two button system would be fine.