engine start button

Hi guys, I would like to install an Engine start button as a complement to my existing key start by the use of a momentary button and a relay to control the starter wire while the key is in and on "Ignition". The only problem I'm having is that the starter button remains active after i've started the car, making it really dangerous if it's accidentaly pushed while the car is already running. Is there a way to turn off the button after the engine starts without the need for another switch to turn off the button (for convenience's sake?). Thanks guys

Matt

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Tune your cars, one day at a time

DEI Pulse Timer, 528T wired to turn on for 15 seconds after the ignition is turned on?

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Installer, IT support, and FFL. I need less hobbies.

You can wire the + side to your brake light signal that way the starter will only crank when the brake is pushed.

You can also use a frequency switch tapped to a fuel injector to disable the button once the motor has started. You could even get creative with the frequency switch and make the push button a "push and release auto crank" button instead of a "push and hold down for as long as it takes to start the car" button.

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Kevin Pierson

POST EDIT - In retrospect, this has become an FYI thread only....

The brake-switch activated starter needs to be disabled after use (if the button is latching - ie, press & forget).    

Hence a frequency switch that cuts the starter once RPM exceeds a threshold RPM (ie, just below idle) is a great idea.
At first I thought not as frequency switches are usually a backup to simpler alternator signals or airflap switches etc - eg, for fuel pump or load control.

Other than the alternator - spark, injectors, and airflaps output before the engine has started, so they aren't any good as a starter cut-out - except where a properly set frequency switch is used from the spark signal (RPM).
Injectors depend on the system - many open at timed intervals (ie, 12mS) until the ECU syncs with the engine or after it starts. (12ms can equate to 1250 RPM for 8 cylinders; and faster for less cylinders). Batch, bank or sequential injection then determines injector frequency. (Injectors are ok as a go/no go signal, but not where a certain RPM is required UNLESS you know the system never changes the number of injection per engine cycle.)

Some alternator charge lamps may go out during cranking, though usually they won't until the engine has started. (A 1-3 second off timer could be added if there are a few false starts....)


I can't see why the starter should latch on but that assumes a mere momentary button in parallel with the starter switch, else between IGN +12V and the starter relay (not solenoid unless you want a welded switch!).
If it is a press & forget button system, then yes - it isn't sensing that the engine is running.

i like the idea of a timer controlled relay, is there any way to construct this from scratch using for example a 555 timer which lets me push the button for say 10secs and then deactivates it?

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Tune your cars, one day at a time

Do you mean you want the starter to crank for 10 seconds irrespective of whether it starts, and the not retry if needed?

There are lots of timer circuits - just search.

I did read something about a timer relay somewhere just recently...

depending on the type of car here is one possibility using a 2 wire momentary pushbutton, wire one side of button to ground, other side to pin 85 of relay, pin 86 to cold side of brake switch( only gets 12 volts when brake pedal is pushed)pin 87 to ignition wire and pin 30 to starter wire in car this would enable that the only way for pushbutton to engage crank cycle is when it sees push from button while brake pedal is engaged and ign is on