My engine stops but why?

Why does my engine stop when I turn off the ignition... At first it is a dumb question but bear with me.

I am looking for a way to switch off the engine of my 200 tdi disco. I want to switch it off using a relay but I am told that I have a mechanical fuel pump. As I understand it as long as there is fuel and compression and the engine is turning over the engine will run.

What is the actual process that takes place when I turn off the ignition then?

There is a really good reason for asking... honest

There's an electrical solenoid valve in the fuel feed to the injection pump. Removing it's 12V supply, so that it closes, is what stops the injun. It is easy to add a relay to this circuit.

Wot Trewy sed^^^^

you have a solenoid on rear off pump it has one wire to it ,it stops fuel flow in pump switching engine off,people often put switch in the line ,but its easy by passed by any live been put on solenoid ,and screw driver across starter

Excellent! Many thanks Trewy and you others you have saved me some time! Just about to fit and Engine Off relay to the motor and hook it into my tracking system. Should be able to switch the engine off from phone or web site. Up until now I have only been doing this with petrol vehicles so thanks folks.

im sure ive read that in the uk its illegal to remotely turn off the fuel on a moving vehicle..... given the state of our "justice" system youll be the one prosecuted whilst the scroats driving will be let off scott free

Actually it was probably me that made the comment about the legality... In actual fact it is quite legal for me to fit the facility... it is even legal for me to use it... until someone gets hurt. Then causal responsibility (I think that's what its called) comes into play. There is a compromise solution, however. That would be to trigger the fuel cutoff... but only allow it to take place when the speed is under 1 to 5 mph. Hence the danger of injury to others is minimal.

I generally just classify the action as legally dubious when I am asked to include this function... after all... if a client is nicked then they can't pay me can they