Flotec Corrosion Resistant Shallow Well Jet Pump 1/2HP, 8GPM "causes loose prime" Questions

loose prime. Make sure the foot valve in the well is good and the ejecter is cause I have replaced some with a pin hole in them or a rock get in foot valve and not let it hold pressure right. Pressure

Grundfos JPF4A pump. takes a long time to get up to prime then once it kicks in after running water it gets to 50 shuts of but drop pressure instantaneously and kicks back in again. The constant on ...