To solve this mystery ...
at the end the cable from the cranksahft position sensor was unplugged :-)
The week before I was replacing the shaky plastic what separates the pedalbox from the drive train, by an aluminium metal sheet.
I'm afraid I unplugged this cable while doing this.
Found the problem using the ProTune Gauges and found that no revs where displayed when trying to start the engine.
Thanks a lot to everyone !
Thorsten
