Did you prime the pump?
You have to fill the pump with oil first. If the pump is installed, remove the input line and loosen the output line. Then inject oil into the input port until oil starts to run out of the output port. Tighten output line and fill pump.
Re-install the input line.
Try this. Your valve should not be the problem.
If the were good before.
The knocking was caused by the pump being dry.
Hope this helps