This is a very common problem with lots of threads on it. Search on it to find the possible problems and various solutions. There is a 90% chance that jumping terminals 1 and 3 in the plastic junction box on top of the right front fender in front of the battery will start it every time.

Road trip rule #1: If your starter fails on a roadtrip and you don't know why, don't shut off your engine until you get home.

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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