Thanks for following up on this one Frank.

Um, the 450SEL I have is an American version from 1975 with a 350 rear subframe and a K-Jet. Learnt all that the hard way through replacing parts through the years, sometimes more "miss" than "hit".

But, anyway, definately got the "star" type ignition trigger system, and, having Googled a little, think I am beginning to see the light.....

...... if I've got this right .....

The negative poll on the coil on the K-Jet is not grounded by default.

When running the "igniter" sends a positive charge to the bottom half of the distributor, the distributer sends a pulse back, causing the igniter to work something like a relay, grounding the coil.

Typing this at 4 a.m. on a phone, hope that made sense.

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306D 1975 (camper) - rusting away
W116 450 SEL 1975 - sold
W114 long wheelbase ambulance, 3 litre diesel 1974

VW Golf 1 convertable - midlife crisis item
VW T4 van - support vehicle