2000 montana , turn over very very slow.

A mechanic at work told me it might have jumped time.so I replaced timing set . It didn't jump. Then he said maybe the starter went bad so I replaced that. No change. Also i replaced the battery first with a new one. Nothing has helped. I drove it to the store no problems. Come out and it wouldn't start. That's how this began. I can't figure this out. No it don't start at all. Always cranks very very slow. I can turn the engine by hand no binding