[Piwoslaw]

Originally Posted by ecomodded

Piwoslaw i am going to look for the crankshaft position sensor. What does the motor think happened when the switch is opened ? it sounds unconventional but effective. I like it.

Here is the long answer.

The short answer is that a diesel will run as long as you supply fuel, no spark plug is needed, so in order to stop it you have to cut the fuel. You could just kill the injectors, but the newer TDs might now like that, so the ECU has its own stopping procedure. There are a few ways to invoke this safe procedure, for example when the ignition key is turned to OFF, the engine starts to stall, etc. If you cut the signal from the camshaft or crankshaft sensor, then the ECU might(*) not know the engine speed, so it'll go into shutdown mode.

*) Some ECUs calibrate the two sensors at startup, so if one is lost during operation the engine can still turn. In my case unplugging the camshaft position sensor wouldn't allow the engine to start, but wouldn't stop it once it got turning. The crankshaft sensor, on the other hand, is needed both for starting and operation.