I think what happened was that your starter was sucking current but it wasn't actually turning. It is probably related to what happened last week. You will probably need to replace the starter. What happens is that a minimal draw via the small starter wire activates an electro-magnet (solenoid) which moves. At the end of its travel it connects the heavy positive battery wire to the starter motor wire and the starter turns. I think the solenoid activated, the connections were made but the starter motor didn't turn for some reason hence the huge draw on the battery. Maybe a fluke occurrence, probably not.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13