Just changed both the main and pre fuel filters on my 210 and wanted to pass along something I learned in the process. When changing the fuel prefilter, you MUST remove the gasket from the old one or buy a new gasket which is a separate purchase from the fuel prefilter. Failure to do this will result in the engine burning the fuel already in the main filter (I filled it prior to installing it) and then stalling. Repeated attempts to restart will be unsuccessful because air is entering the system.
I don't know why they excluded the gasket from the prefilter itself but they did and it's not readily apparent. The good news is the old prefilter's gasket looked OK so I installed it, bled the fuel system and she's running great again.
I hope this keeps someone else from uttering a few choice words that would make a sailor blush when they 're doing some fuel system maintenance on their W210 diesel.

__________________
99 E300 133K
98 ML320 99K
87 Saab 900 Turbo Conv 123K