when putting a new belt or pump on what you need to do is loosen the bolt that holds the tensioner in place, then press it as far down as it will go (which will loosen the belt,) and then tighten it in that position. then remove and replace the old stuff. once you got the new items on, loosen that bolt again and double check your timing marks. then turn the crank counterclockwise, just about a quarter of a turn is fine, but dont release tension on the crank. that will let the tensioner take up all the slack in the belt. tighten the bolt, then recheck timing.