Bill,
A lot of potable pumps used in Rv and marine service air bind very easily. The air in the pump just does not push hard enough to close the check valves. If you can get to the pump and disconnect the discharge long enough to get water in the pump, the problem will probably go away. I have a by-pass fill that lets my put city water from the pressure feed back in the tank, and it works very well for this purpose as well.
Good Luck
Matt
Matt & Mary Colie
A sailor, his bride and their black dogs (one dear dog is waiting for us at the bridge) going to see some dry places that have Geocaches in a coach made the year we married.