Likely you have "algae" in the tank, and this may or may not be related
to biodiesel use -- the biodiesel tends to clean the tank (it's a
better solvent than regular diesel), but the problem is pretty common
on that age Benz.
You will need to run the tank as low as you can (the screen will plug
again as it gets really low), then drain completely and remove the tank
and have it cleaned. Install a new screen, and you will be home free.
In the mean time, carry several pre-filters and a new main filter, you
are likely to have plugging problems until you get the tank cleaned.
Black crud collecting in the prefilter is a sure sign of algae in the
tank....
One of the stations in Mt. Vernon has biodiesel, I think I'll get some
next fillup. I also have some old gasoline contaminated with diesel
fuel that needs to be fed to one of the diesels to get rid of it.
Peter
