total power loss while starting car
 

I tried to start my 83 300sd turbo yesterday and after three cranks I lost all power. Nothing works. I think the battery is fine and I never noticed a loss.
Even if the battery was low the windows and lights would still work
Since the power loss is total is there a bad connection between the battery and what?? ground wire?? how do I check
It's a greasecar system that has been running great 11,000 plus miles and I have never had an electric problem before.

Any ideas???
beerman