I had the same problem at 10k on a 98 C230. The dealer repaired under warranty. I think it was caused, according to the dealer, by fuel and the type of sensing materials used in the fuel sensor. Good Luck!

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Roger
1983 300CD 246k sold
1998 C230 52k
1980 450SL 75k needs AC
1999 Subaru Outback Ltd 43k