Jet water pump runs forever and water tank never fills
Sounds like there is too much air in the tank. Or he bladder is actually broken in the tank.  

Depending on where the valve stem is you can check by removing the valve core and seeing if water come out of where the air should be.  Meaning you have to replace the tank. Or add air to the tank with a nearby faucet open and if possible close all valves leading to the house in order to shorten up and isolate the tank. If air comes out of the open tap. Bad tank.   Also the tank could be flat.  In which case add air and start draining the tank.  Don't add too much air this could rupture the bladder 

If you get the tank drained you want to set the air at around 2-3 psi lower than your low pressure switch setting