My 90 740 T has been a slow cranking beast since I got it 4 years ago. Recently changed the battery and it was still slow.

There are two ground points, one on the engine and the other is supposed to go the frame. Apparently the factory fit the one ground to a stand off bracket which was then attatched to the frame. Bad connections. Checked my wifes 940 T and it is grounded directly to the frame. So, I did the same and now it cranks as it should.

Live and learn,

dick

Had the exact same symptoms on my 86 740. Drove me batty for a while. Guess what? It was the same problem, mine broke at the engine ground. Replaced the lug now it's fine.

Great comment. I recommend to anyone with cranking problems to use a voltmeter to measure voltage drop from the engine block to the battery negative terminal. It has been several years since I repaired a German car with a cranking problem, but I remember that I had about 2 volts drop across one crimped fitting on a braided ground strap. Once I repaired that connection, the car started great until it was destroyed when rear ended. I can't remember the figure for acceptable voltage drop, but the lower the better. For reference, check a car which cranks well.