How diesel engines are switched off?

[ales]

Hi, guys. I have a quesion here. Diesel engines rely on compression to ignite the fuel mixture, so no spark-plugs are needed. So here's the question - how are they made to stop? Now I know that on some trucks there are systems that mechanically stop the engine when you turn the key and/or special valve mode when the exhaust valve(s) stay open and the fuel leaves the cylinders unignited thus making the engine stop. On modern(ish) diesel passenger cars there's probably a fuel-shutoff system, quite easy to switch off the electric fuel pump (just making a guess here, although I can see that it could be potentially harmful to the engine - correct me if I'm wrong). But what about older diesels with mechanical fuel pumps? Or is it so that there is no such thing as a diesel engine with a mechanical pump? Just wanted to know

Alex

[Moppie]

It depends on the engine.

Some as you corrently thought shut off the fuel supply, either by stopping the pump, or with a shut off valve.
But most, use either a manualy activated or remotly activated solonoid to competly close the throttle body which then straves the engine of Air.

Remember you need air and fuel for it to run, and removing the air supply is normally the easiest option.

[ales]

Good point. Thanks

[SaabJohan]

Diesel passenger cars uses a mechanical pump just like truck engine. The engines are shut down by a fuel cut off, which can be a solenoid valve or a mechanical operated valve. Passenger cars uses a solenoid since the valve is operated by the key.

Dieselengines doesn't have a throttle (most of them).

[taranaki]

Older diesel equipment,particularly heavy plant,compressors,bulldozers trucks etc,generally has one of two stop mechanisms.One is the pull-type pressure relief valve,a cable runnig from inside the vehicle that cuts the pressure to the injectors,the other is a simple sliding throttle similar to a lawnmower,which allows the fuel mix to be shut off totally by cable.I've never seen the latter in road vehicles,but many of the early light commercial had pull stops.Almost all of the latest diesel motors have a fuel solenoid which disables the injector supply pump.