I think I have a bad vacuum unit on my distributor. When I attach a vacuum pump the advance does not move and there is no vacuum build up. Normally this would indicate a bad vacuum unit but I wanted to see if there was something different about this unit that would cause that.

Also on the back on the vacuum advance unit there is another hose port. The PO had this blocked. Does anyone know what this is for or where the previously attached hose would go?

Thanks,
-Ed