Question
Rain Dial Controller- Grunfos Model H91340616 P10738 Model Pump - Pope1010321 Solenoid Valves
 Could this knocking be caused by the valves need servicing or replacing or what? Previously been working without knock.

Answer
I cant really tell from your question whether it is the pump or the valves that are knocking.  If it is the pump, you may have serious problems.  It could be cavitation, or something could be loose inside the pump like the impeller or even the suction line has become loose or the spacers that keep it from banging against the casing are damaged.  If it is the valves, they may need to have the flow control adjusted (probably increased).