Hi Will,

Is this the same car that you suspected had water in the gas?
Did you abandon that thread? Any OBD codes?

Re the alternator ground
I looked in my 89 740 book and the case is Blue wire to an unknown ground.
In the 93 940 book it shows that case ground "D-" a Blue wire going
to ground 31/26 That's the good news.
The bad news is that they don't show where 31/26 is.

The battery ground goes to the front of the block just above the corner of the oil pan. That alternator ground should go to the block.

I'll look later if nobody chimes in.

Bill