I am trying to winterize but I cannot get the pump to suck, I have a bypass valve inline to suck antifreeze out of a jug near the pump. Worked fine last year. The pump runs but no suction. I even too the fitting off directly at the pump and I feel no suction, Its on a 2011 keystone sprinter which has not been used much, once this year, is there any valves or anything I can try to repair the flojet pump? Or is there another way to drain the lines which are pex? I have no air pressure near me to blow the lines out and no rv dealer within an hour/?