Personally, I'd check the compression before adjusting the valves to get a sense of what you are working with. But then again, I'd just pump more WD-40 in there and keep trying. Part of the reason WD-40 works is that it uses propane as a propellant. I'd be half inclined to take a propane bottle and give it a shot of propane when attempting to start it.

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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