Pump mystery

Maybe crud. But; it may have got 'waterlogged. That is completerly full of water with no air pressure reserve in the tank/reservoir? If waterlogged (a descriptive term IMHO), was/is it running frequently and very soon each time you open a tap? Check to see if it has a "Snifter Valve" and that it is adding air each time it runs. Draining down the system will often restore the air reserve that pressures the system, for while. But best to check cos you could damage the pump. Our typical pressures were; cut in at 20 lbs/sq.inch, cut out at 40 lbs. Is your pressure working OK and within those sort of limits? A 'farm' system might run higher? Say 40 to 60 lbs. Good luck. If in a rural area there is most likely someone (a neighbour?) around really familiar with those systems and perhaps the quirks of a particular type of pump. Oh, btw, check the foot valve in th well while you're messing around with it. Since it is a piston pump you must be using a shallow well, prob. less than 20 feet?