My 2007 E 320 CDI (W211) struggled to start this morning. I turned the ignition on for what seemed the normal time and then tried to start it, although it eventually timed out without starting. On the second attempt it started although the engine management light came on and a message on the dash saying something like "ESP Problem etc". After a 30 mile driver I arranged for the AA to plug in their diagnostic machine and it reported two faults - firstly "glow plug control circuit open" and secondly "crankshaft position sensor". The AA cleared the faults and when I tried to start the engine everything is fine and no fault codes are appearing. The engine has been warm ever since is started this morning. I'm expecting it not to start correctly tomorrow. All 6 glow plugs were changed about 20 months ago (after one failed). On balance I suspect the problem lies with the glow plug control system. Does this seem logical? Is there anything I can do to validate this, such as checking the system control unit etc? Does it need to go to a workshop with Star Diagnostics or is it something I can sort out myself? Hopefully you can help.