2001 chevrolet tracker jump will try to turn over

I took out my 2001 Chevrolet tracker j20a engine to repair my lower crank case seal and when I reinstalled my 2001 Chevrolet tracker j20a engine, my engine jump when it try turn over and I have no I idea what would make it jump the way it do, it jumps jumps. I even use my repair manual book for Chevrolet tracker and did everything it said to do. and I believe it may have to do timing chain but everything was at (TDC). and I cant figure it out I been trying to work n for five months now.