Switching off diesel engines

[Old Amos]

With petrol engines, turning off the ignition switch presumably cuts electricity off from the spark plugs and so the engine stops ? If this is so what happens when the ignition switch is turned off to stop a diesel engine which has no spark plugs ?

[wagolynn]

On a petrol engine today, turning the engine off will remove power from the ignition and I think, on most, the injection system, with the ignition switch fully off the ECU and fuel pump also. Old cars with carburettors had mechanical or electrical fuel pumps. Removing the power to the ignition was the main way of stopping them and removing the power from an electrical fuel pump was a secondary action.
To stop a diesel, stopping the fuel is what is required. Older diesels had a fuel shut off solenoid valve, power on to hold it open with spring loading to shut it. On the latest, I am not sure, as removing power from the injection system would also stop the engine, after that as for the petrol. I don't know if that helps.

[Old Amos]

Thanks Wagolynn.