Gillybenztech,

Sounds like you are describing a CIS injection system on a gasoline engine


PeterG,

Perhaps this is some sort of supplemental protection system. I'm under the impression that all Benz diesels (excl the newer ones) use a vacuum operated fuel shutoff and that there is no fuel shutoff solenoid.

Perhaps you heard the overboost solenoid clicking... perhaps this cancels fuel enrichment if the engine exceeds a certain speed. There is a mechanical centrifugal "rev-limiter" in the injection pump. It is possible that this electronic circuit is a backup system in case the mechanical system fails. Does anyone know for sure?

-Joe