Well pump will not build up pressure and then it will not cut off

Are you saying the pump runs for long periods but still does not build up pressure?

This could be a faulty check/foot valve allowing the pressure to bleed back down into the well or a impeller that's broke in the pump housing. How much pressure does the gage read when the pump's running? Let me know, Tom

Tom my mother has the same issue. Changed the foot value, all new pipe, new 30/50 pressure switch, and checked the air charge of the tank which is at 28psi. Got it primed and now it will not reach the cut off 40,45-50 and stays running.If we turn on the water the pressure which when running stays at about 30 drops as needed for water to flow, then after turning water off it gos back too about 30 psi. she has been without water now for 3 days. I really need some help with this the pump 1/2 HP is about 12 years old tops, it's 68ft deep and can see water down the pipe without a flashlight. The end of the foot value was rusted off. Never touched bottom. Help!!