How does the W123 shutoff system work

[psaboic]

Hi folks,

I know that when you turn off the ignition key on a gasoline powered MB it cuts the spark, thus turning off the motor. On our W123's, what does turning off the key cut off to stop combustion? Fuel flow, or air flow? Also, I'm assuming whatever gets cut off it is vacuum operated, correct?

Just trying to better understand the ignition system and engine stop system of the car, and wondering if there is something in that circuit that if it ever broke, would it prevent the car from starting.


Glenn