I've got a 1998 C280. Over the past few months I've noticed my fuel economy has dropped. I was consistently getting around 530km/tank but now lucky to reach 500km.
But over the past couple of weeks I have a much bigger problem (possibly related to the economy above). About 50% of the time when I try to start it (always when cold so far) the engine fires but then immediately dies. It takes another 6 -8 attempts at starting after that before it will fine fire up and run.
Does anyone have any idea what might cause this?

 

I have the exact same problem once warm its fine but cold start is a problem. Does anyone have any ideas. I have read alot about mas and temperture sensors but not sure what causes this?

 

I found the problem. It's caused by a weak battery. I had teh battery tested and it was stuffed (only 22% function remaining). A new battery yesterday and all has been good since. The guy at the battery shop told me that even though there was enough power to crank the engine over there wasn't enough left in the battery to also enable the fuel pump to come up to max pressure immedaitely after starting the engine (or at least something like that)
However while teh new battery has sorted the starting problem since installing the new battery I have to hold the button down on electric windows to wind them up or down. ie the xpress function isn't working so if anyone has any tips on how to fix that I would appreciate it.