Prime the pump. The most common issue with getting water pumps to move water from where you have it to where you want it is air. If there is an air gap either at the piston or around the impeller, the pump will probably not be able to start a vacuum or generate a flow that can overcome gravity or other impedance. As in the olden days, you can fix this by adding water where it can do most good, either pouring right into the top of the old handle pump, removing a cap and adding water in the priming reservoir of newer pumps, or pouring water down the outlet of a sump pump. There are self-priming style pumps that usually make this a non-issue.