Been looking over a few things quickly this evening and found that the rear carb accelerator pump injection pipe (the little calibrated 90 degree bend pipe that squirts fuel) had fallen out of the hole in the carb and was just lying in the barrel.

Replaced it and ran car for 20-20 minutes without problem. Not sure it explains my problems...

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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE