There are a couple of threads on here indicating that the upgraded glow plugs wont work with certain early relays. Yours may be an example of this. Can't recall the exact reason why they won't work but one guy troubleshot for a long time before reaching that conclusion.

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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