I finally got my Audi to start! I see there are a lot of new people here on oppo, so to catch you up, this is my '91 Audi 90 Quattro 20V. It's had a long string of problems ever since I bought it back in late 2010, but I'm finally starting to get it close to being properly roadworthy again.
Part of the repairs I've recently done involved replacing the following: timing belt, water pump, power steering pump, front CV axles, front right wheel bearing, and a new starter. But after I finished with the repairs, it wouldn't start. Figured out that I had my starter's spade connector on the wrong connection. Switched that and now it starts, but makes an awful noise. You can check that out here:
I jacked the car up today and pulled things apart just enough to get a look at the smooth side of the timing belt to see if it had any marks on it from rubbing, and it looks exactly like it did when I put it on. What I can see of the teeth look unmarked as well, but I can't see much. There is, I suppose, the possibility that the tooth side is rubbing. That would at least explain why the noise is so loud.
Another theory is that the starter is not disengaging. It would help to have a helper to get that off though because of where the exhaust is positioned, so maybe I'll tackle that tomorrow if I can find some help. Then I can bench-test the starter and see if it's working properly, and if it is, I can look into the possibility of it needing shims.
Failing that, I'll need to pull stuff apart to get a good look at the timing belt and all of the related components and see if something is wrong with them. I'm really not sure what it might be yet.