my well pump, JHU05 1/2 hp, open pressure, the pump running is about 20lb, when I shut the value off to let to hold pressure the pump motor is on and off, like 3 times a second, the pressure jumps from about 20 to 50 back n forth, back n forth, like 3 to 4 times a second, no, there are no leaks, I tried 2 different pressure switches, I don't think it's that, any ideals... thank you, Richard
it it hooked up to a bladder, I call it the tank that holds about 30 lb psi, that feeds to the house, but its not hooked up now, but I do have a on n off value to shut off to emulate it going to the tank

If I'm understanding you correctly, you are saying that when the pump can "get to" the tank, the system pressure will not get over 20#, and I assume from that that the pump does not cut off. Correct? If that is the case, then your problem is the pump is not getting up to cut off pressure.

A few questions:

1.With the cut-off valve turned off, is the switch still able to read pressure, or is it "behind" the valve? Is not able to "read" pressure. Is that right?
2. How old is the well pipe? Is it plastic or galvanized?

You have a deep well pump with two pipes in the well. I am leaning in the direction that you might have a leak in a well pipe. That would prevent the pump from getting up to pressure and could also cause the rapid cycling you described. A leaking foot valve would cause the cycling, but it would not keep the pump from getting above 20 psi.

one feed pipe, 1 inch, with the pump running it reads 20 lb, I hooked up a on n off value to emulate that the water has reached pressure in the bladder, so when I turn the valve off, as if the bladder is full, the pump goes on n off, on n off like 3 times a second n the pleasure goes from about 20 to 50, back n forth, back n forth, thanks

one feed pipe, 1 inch, with the pump running it reads 20 lb, I hooked up a on n off value to emulate that the water has reached pressure in the bladder, so when I turn the valve off, as if the bladder is full, the pump goes on n off, on n off like 3 times a second n the pleasure goes from about 20 to 50, back n forth, back n forth, thanks

You have no check/foot valve. The water just runs out the pipe every time the pump cuts off. It sounds like the pump is probably working pretty well.

I'm not sure you are getting my replies to your private messages, so let me just reply here. Be sure you read what I posted about a check valve. Your pump is going to short cycle until you: 1. Add a pressure tank 2. Add a check valve.

If your tank is bad, then just make sure you completely drain it of water so it can fill with air. That will at least give you an idea of whether the pump can get up to cut off pressure of 50 psi or whatever it is. That's not a long term answer, but it will work in the short run.