Turn The Key and Nothing--Sometimes

[sublettd]

Scratching my head over this one. I've replaced the starter, neutral safety switch and ignition--in that order--while trying to figure out why the '81 300D (non-turbo) doesn't start sometimes. Talked with my son and he seemed to think there was a loose wire or a bad ground. So, I went out and looked things over.

I noticed that where the negative battery cable connects to the chassis that there was rust all around the bolt. So, pulled it out and cleaned the area, as well as the bolt, as good as I could and screwed the bolt back in. Don't know if this fixed it or not, but can't think of any other options.

Anyone have any other good ideas in the event this didn't fix the problem?