The short story is that on my 1985 745 Wagon, it starts right up if I run a jumper cable from the battery negative post directly to the head. If I clip on anywhere else (chassis, various bolts in the engine compartment that are brushed clean and shiny) it will give a single tick but not turn over.


Once the car gets running, I can disconnect the battery completely and it will run fine.

It seems like the starter must not be sufficiently grounded - though it is well connected to the engine block - so the engine block itself isn't grounded.

How is that grounding normally done?