E320 Crank but won't start.
 

I own a 2000 E320 SW and on five occasions when I have attempted to start the car, it would crank over but would not start. After letting the car sit for a few days it started. I've taken the car to the nearest Mercedes dealer, 200 mile round trip, but they couldn't diagnose the problem. Please email me, georgereddish@nehalemtel.net, if you have any suggestions. Thank you.

I had something similar to this happen. My guess is that something has gone awry in the fuel system - in particular, either the fuel pump itself or the fuel pump relay. If the relay goes bad, the pumps do not operate and fuel does not travel to the engine, thus resulting in the no-start. Have you checked the pumps to ensure that they are indeed functioning?

Aside from fuel delivery problems the common won't start problem with 112/113 motors are bad crank sensors.