I have a 1999 chevy suburban won't turn over I have replaced battery, starter, alternator, positive and negative wire and the wire that goes from the fuse box to the positive side of the battery it acts like it wants to start but acts like there is not enough juice in the battery but it the battery is only 3 weeks old and I had it tested twice I don't know what to do.

 

When you say it "acts" like it wants to start do you mean its trying to turn over or ?????

If your starter is indeed engaging (you hear it) then my first route would be to hook some cables up to someone else and jump it.

Try that