If I understand how those tanks and valves work, it sounds like your valve is not sealing properly and letting the air out. IF I've got this right, it will cause the pump to short cycle. Don't know if the valve is separately replaceable, but if it is, suggest replacing it. The high pressure limit should cause the pump to shut off before water reaches the height in the tank of the valve. If the air is leaking out, then it will fill up with water, rapidly max out the pressure, and shut the pump off. Normally, the pressure would gradulally increase as it compresses the trapped air. If yours spikes, that would be consistent with my understanding. Note, I'm not a pro.