I agree with GPWayne. Make sure there is water through out the system first (including the water heater, which takes forever to fill).
When our check valve failed (at the hose inlet), turning on the water pump forced water out of the hose hook up and the water pump could not get up to pressure. If that is your problem, a temporary solution is to block the hole so the water pump can get up to pressure. We were in the middle of no-where when it happened to us. A sharpie and duct tape solved our problem until we could find the right fitting.