Originally Posted by Skip12
Did you purge all the air out of the water heater? If not, open the relief valve until water comes out of it. How full is the fresh water tank? Be sure no air is getting from the fw tank to the pump. Seems that you may have air in the system somewhere.
Even with air in the system a properly adjusted pump will shut off when the air is compressed to set pressure.
Sounds like OP's pump is a bypass type pump and is improperly adjusted. There are TWO settings on this type of pump and if improperly adjusted the pump won't shut off.