Weirdo starting problem

I've a 2001 C240. From the past week, I've experienced something weird. The engine starts up on cranking and immediately shuts off. After 3 such attempts or so, everything goes eerily blank and I can do nothing
but retract the key and wait. Some 3 min or so later, I hear the same sound as the one I get upon initial key insertion. Usually, at this stage, when I reinsert the key and try, the engine ignites and runs as if nothing ever happened.
I called the dealer since it's only a few days since my car returned from a B service. He took it, serviced the fuel injectors and said that the problem should now be fixed but it isn't. Yesterday when I called him, he was saying that the electronic throttle may be the culprit.
Since he doesn't seem to have much clue in what he's doing, thought I'd ask a more informed set of people :) Have anyone of you had to experience what I currently am, and how was the problem solved?
Oh and one last thing - the dealer confirmed that this isn't either a problem of the key itself, or the battery.
Ramapriya
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Try using another key, if only to exclude the key as a possibility. Then suspect the ignition switch.
I'd look at the battery and its connections. My car's battery leaked and the acid corroded the fuel pump cables right off their shunt - motor cranked but no fuel pump, no start.
Describe events to dealer's shop foreman, not a service writer.
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D Ramapriya : Have see this problem before I agree with T.G use your other key for diagnostic purposes. See if it has the same problem. There is a Diagnostic Technical Bulletin for this problem. (What dealership are you going to) There is a communication problem with the key and (EIS) Electronic Ignition Switch. Resolved by ordering new updated remote keys...//// 2nd possible repair ( how many miles) crank sensor may be faulty as well. if this problem happens when the engine is hot and has history of stalling and or cranking but not starting after driving and sitting for approx 10 minutes then this may be the problem too.....
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WRENCHER wrote:

1. I go to Gargash Enterprises, authorized UAE MB dealer. 2. The car has done nearly 53,000 miles. 3. There is just one key; dunno what 'other' key you guys are referring to (most other MB owners here confirm that they have only one key too!) :(
Thanks so much for your time, guys. Much appreciated.
Ramapriya
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New cars are delivered with TWO keys.
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