2003 C240 4matic turning off...please help!

[docbeck80]

I have a 2003 C240 4matic. I recently had a tune up/fuel filter/all other filters changed with indie. Woke up one morning, cranked but didnt start. towed to dealer. crankshaft position sensor was bad, replaced, car ran fine. Then while driving the car turned off (had 100miles left on gas gauge). Put in a gallon of gas just to try it and voila it worked. Filled it up and took it back to the dealer. ran codes no problems couldnt figure it out but said fuel sending unit probably needs to be replaced...quoted $1400.

I decided to drive it and see if it would happen again. 1 week later gastank half full, stopped at light and car turned off. cranks but doesnt start. got a gallon of gas and added it and wouldnt you know it the darned thing worked. So...what could this be o great mercedes minds? fuel filter problem? fuel sending unit problem? should i add some Techron and see what happens? I hate the dealers policy of just replacing everything without thought when something goes bad...of course it may need it in this case...thoughts please? thanks!

[Two560Two]

well is there a flight recorder the dealer can send you off with for a few days. At the Ford dealer I work at, we send out problem cars with flight recorder and have the customer come back when the problem happens. This will record all parameters of the PCM when the problem does happen. Never let anyone even a dealer just replace parts unless that is the most last outcome of their diagnosis. Trace back to what has been done. Tune up/Filters, etc.. Correct plugs? Filters etc.. Any loose connectors, grounds or damaged wiring? Let us know what happens and what the fix is