My W203 2001 has been having this problem of switching off even if the fuel gauge is at half. I just have to add as little as 5 litres and it starts then and runs normally. The gauge isn't really faulty as indeed there is fuel in the car as all I normally need to top up to fill the tank completely is about 30 litres and I know that the tank capacity is almost twice that amount. Has anyone else had this problem? Reading on these forums, the CPS seems to be the most likely problem but no one has described similar symptoms as above.