I am replacing my vacuum pump got the pump and the pulley off with no problem but can''t get the pulley back on at all. I have the tool and i tighten the bolt on then center nut down and when i hold the bolt and tighten the nut all it does is loosen the the bolt and it doesn't budge the pulley...What am I doing wrong?

thanks

 

https://www.ford-trucks.com/forums/9...cuum-pump.html Have a read here.
Unfortunately you don`t say what you are working on so I assumed it is a serp belt pulley.

 

I figured it out... the installer I had has small threads at the bottom and the thick threads and it wasn't getting enough bite so I rented a bigger one and it went on with no problem. thanks!!!

yeah it is a 97 powerstroke