Thanks. Valves were adjusted in December 2011 by my trusted MB mechanic. I have considered the biocide thing. Do you have a recommendation for a good product for that? I have also considered the fuel tank inlet strainer as the cause of my problems. Is there a method to test that without completely removing the tank and all?

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Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"