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could some of the outputs be used to turn of starter when engine starts

In 12P yes you could use a flex output that is only active below a certain RPM - or use the flag to enable an output only during engine run and use the output invert option (basically becomes active only when the engine is not running then).

The later holdens that have computer controlled starter have a timer that will abort the start to control runaway cars. Worth having some similar logic. Probably a 3d table of rpm vs runtime if it counts while cranking so it disables the starter after 5 seconds. Or just have start button on a relay so it disengages when you lift your finger.

have tried with kalmaker using ac output but couldn't get it to work as kalmaker wouldnt let me have enough control

Is there a reason you need computer control on it? On my track car I just press and hold the start button then lift my finger when it fires. Its simple, and unlikely to fail and keep the starter engaged unintentionally.

yeah I use the same on mine, all I did was ran the starter through a relay and the push buttons activates the relay, only so it wasn't putting heaps of load through the button.

I want to be able to have a push button that stays in. so push the button, it turns on ignition and activates starter .Then ecu turns off starter when engine running, and push button again to turn off ignition

I think your going to need a few more smarts behind it to do that!

A standard feature that was removed in 12P would have been very handy in this case! The original code included a cranking timer that was never used for anything, could have mapped it against RPM to use it to engage the starter, but disable it after X time or when engine is running.

This was re-purposed as recording the analog input (the wire that is connected to the starter circuit on V6s), there is very limited RAM so the same byte that was a timer became the analog/digital reading. Can possibly add this back in with some code changes where if the backfire inhibit mode is enabled it stores the cranking time instead of the analog reading.

This keeps the original cranking input available as an analog input on V8s without wasted spark.

EDIT: Scrap all that. You will need more logic to get it to work properly with a timeout. Using the above it will crank, stop after X time, then start cranking again shortly after. Maybe use a 555 timer as a one shot driving the high side of a relay, triggered to start via the push button. And then use a flex output so its active below say 400RPM to provide the ground for the relay.

Some of the old cars used to start by hitting the accelerator once the ignition was switched on, that would be cool