ECU (Electronic Control Unit) computer issues
 

My 1994 E320 wagon will start, turn over the engine but will not run. I had been using the HfmScan for diagnosis. The Hfmscan is not able to communicate with the ECU (Electronic Control Unit) computer. I suspected the Crank Position Sensor is the problem. I am debating whether I need a used or new Crank Position Sensor. In addition, I checked the OVP relay, Fuel Pump Relay, Fuel pressure sensor, two brand new fuel pumps, new fuel filter, the fuel pressure regulator, all works fine. I was told that the ECU computer rarely fails, other than high and/or low voltage spikes. Does the ECU need to be replace or can the ECU be repairable? If replacing the ECU computer, does that involves additional configuration software/hardware to make the ECU computer to work on my Mercedes? Does anybody have this kind of problem involving ECU issues? Any comments, feedback, advice is greatly appreciated.