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.

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

Ockman,

Thanks for the helpful hint. I have yet to try this routine bit of maintenance on my car, with about ten thousand miles on the one presently installed. Now, if I can just remember the hint for that long.....

Thanks again, Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Been there, done that!

This is actually an O-ring. There is no need to buy a new one unless the old one is getting stiff or is flattening out.

I went through this during my first fuel filters change back in '96 when I had a new E300d. I almost emptied the battery before figuring out what I had done.

Good luck,