The engines that I spoke of, on which my Dad "reversed the cams" were indeed started by air. I remember this because he told a story of an officer on the bridge that was bringing the ship into port and had no clue about what he was doing. He kept calling from the bridge for reverse, forward, reverse, forward at a very rapid rate. My Dad kept trying to warn him that he would run out of air at this fast cycling rate, and finally did. The ship ran into something as a result, I don't remember what it was.

I don't know if the compressed air pressurized a cylinder or ran an air operated starter motor, but I think it pressurized a cylinder.

This thread has become very convoluted. It seems to me it can be simplified by the fact that the ignition is "timed" BTDC, so that it has time to truly begin the ignition process. The confusion is because there is more than one answer and none of them are simple yes or no.

Have a great day,