my l200 starts but cuts out striaght away and has lots of black smoke coming out of the exhaust, next question is there a sensor behind the crank shaft pulley

You had any work done to it recently?...could just be lack of fuel pressure........is primer pump staying hard?

Oh...and what year is it...may help with diagnosis.

Sam, what year is the truck mate...
Will admit that Crank Position Sensor usually makes them a pig to start in the first place, but if this is kicking straght into life then I would discount that.
Sounds more like fuel drop, try to pump the primer ( on top of the filter) about 30 times and then start the engine, see if it runs for longer, this will help to start to get to the bottom of the problem..

check cam belt has not jumped a couple of teeth