Why does my new power steering pump have a knocking sound?

I just replaced the power steering pump on my 2001 ford focus and now it has a knocking sound. I tried aligning the pulley with the belt the best I could but there's no room to stick a level or straight edge in to see how aligned it is. How do I align the pulley? What's making the sound? Any other advice?

If the belt is running smoothly and not bouncing around, it's probably NOT the belt that's making the sound. Was this a USED pump from a salvage yard? Or maybe a rebuilt one? If so, then take it back and get a different pump.

You obviously know a lot about cars but when I had the knocking sound it was because it had run out of oil and damaging the pistons?

Sounds like you got a faulty part.

Was it new or used? Alignment shouldn't make it knock.