I just replaced the pump that runs water features -- 2 spillways & a 3 jet water spout. I can't get the darn thing to prime. Changes all bearings/gaskets with the pump. All o-rings and seals seem fine. I've run a home to the pump feed and it gives some action so I think the outflow is good. If I close the 3 outflow valves and try to build pressure it tries, but just won't suck water. Best I can get is a trickle from the spillways. Any ideas??