Starter engages but KA24DE won't turn over

[imGreek]

I found out that the KA24DE I had dropped in had a bad starter. I picked up another starter from a local guy and bench tested both of them. The one that came on the motor would engage, but the starter motor wouldn't turn. The one I picked up engaged and the motor worked fine.

So, I put it on the engine and tried to turn over the motor. I heard the starter engage (click noise) but it wouldn't turn the motor over. Tried it several times but nothing. Tried manually cranking the engine, but it only went a little bit and was at the point of compression. Called up the guy I got the engine from and he said that it was sitting for a while. Also, when I changed the oil there wasn't much and it was quite black.

What could the problem be? Is it because the motor was sitting for a while? I'm pretty sure it isn't the starter anymore. Is there anything else I should consider?Thanks!