G`day guys
 
I want to run a push start button on my esky but here in SA it must not operate when the engine is running. So what i need is a power feed that is live ONLY when the engine is running so i can power a relay to power the starter relay.
It has to be only when the engine is running, not when it is cranking or the ignition is on. This has me stumped so i hope one of the resident electrical guru`s can help.
Cheers all
Troppo

A rough way to do this is to use a tachiometric relay and a normal relay.  When the tachiometric relay sees a siognal from the coil (ie engine running) it outputs +12v into connection 87a on the normal relay.  The normal relay works such that when a signal is seen on 87a it closes the relay.  When the engine stops running the tachiometric relay stops sending +12v to the 87a causing that normal relay to open allowing +12v to flow from connector 30 into the starter solenoid thus starting the car.
 
Cannot work out how to delete files once added so the first two these attachments are wrong.
 
Hope this helps

You might be able to trigger a relay off the alternator light. Geminis use this to power the electric fuel pump.

Great stuff guys, thanks for the help. I reckon i should be able to sort it now.
Cheers
Troppo

could you use the alternator light/circuit, for cranking only?