What is the main problem of bmw car 5 series diesel engine the engine wont start but have cranking?can anyone have an idea?give some advice thanx

run the fault codes
check that the immobilizer is operational ( fob key battery)
check for broken timing belt/chain
check crank/cam position sensors
check the ignition control module

When were your spark plug wires last changed? And have you checked your ignition module? Crank shaft position sensor is another item to have checked.

If you've checked the fuel system, then check the "spark" end of things

fuel pump low in volume, or even a failed crank sensor,

If it fires only occasionally, my first suspect would be the crank position sensor (aka pulse generator). Should be on the front of the engine mounted very near the toothed wheel on the crankshaft,
You should check for fuel pressure at the fuel rail while you are cranking to see if it is a fuel delivery problem.

check for a spark if no spark and engine cranks ok then renew the ignition module

YOU MIGHT HAVE TO INSTALL A BLOCK HEATER TO OVERCOME THIS PROBLEM

Hi we have a similar fault on a 2002 X5 diesel with 140k.km
scan test on 'Autologic' says > low fuel pressure in rail under starting< we have done leak off test at diesel specialist and they say it needs #4 and #2 injector renewing, the low pressure from tank is at spec at approx.3.4bar whereas the rail press at crank is only between 102bar to 140bar on 6 diff scans, where i believe it should be at around 390bar, hope this helps, we still have not fixed this yet,

you may need to get a mechanic to cheak the crank angle sensor as if it is faulty if it gets into a certain position it wont let the car start

2002 530i radio i cant turn on
i press the botton and nothing hapen i look the fuses on the trunk and the are fine is other suses some place else please advice