UK Car Repair: Rover 75 not starting, rover 75 cdt, deisel

Question
Rover 75,CDT(Deisel 2L)2001. The problem i have is when i start the ignition the fuel pump cuts off, but when i turn off the ignition the fuel pump starts running.
Thanks in advance.

Answer
MOST CARS HAVE TWO CIRCUITS, ONE FOR STARTING AND ONE FOR RUNNING, THE RUNNING FEED USUALLY COMES FROM AN ENGINE SENSOR OF SOME SORT ENSURING THE FUEL SUPPLY IS ON ONLY WHEN THE ENGINE IS RUNNING,-THIS IS A SAFETY DEVICE-.  HAVE SOMEONE CHECK THE CRANKSHAFT OR/AND THE CAMSHAFT  SENSORS.