My Fresh Water pump was cycling frequently without any known faucets open, leading me to believe I had a leak somewhere downstream of the pump.  I searched past threads about what the causes may be and where to look first.  An internal leak within the pump was a potential cause, but I did not want to go to the trouble of removing and diss-assemblying the pump if the problem was elsewhere.  That lead me to try this simple test.  Right after the pump finished a cycle of pressuring up the system, I closed the valve to the water tank supplying the water to the pump, which prevented any water from going back into a supply tank.  The cycling stopped indicating that internal leaks in the pump was the likely cause.  If the pump would have come on with the supply tank valve closed, then most likely there was a leak somewhere downstream of the pump.

Diss-assembly of the pump indicated a couple of problems and I have repair parts on the way.