Abstract: A liquid pumping apparatus and pump method is provided in which a reciprocal drive piston is carried in a pump body and is reciprocated back and forth by a mechanical power source such as a crankshaft. The pump body has a pump chamber which receives the liquid to be pumped. A pump piston which is separate from the drive piston is operatively connected to the pump chamber to expand and contract the volume of the pump chamber to first fill the pump chamber with liquid and then expel the liquid from the pump chamber in a pumping action. The pump piston is coupled to the drive piston for movement therewith during a portion of a pump cycle such that the drive piston is effective to move the pump piston in its volume expanding direction relative to the pump chamber at a first speed. Then, the connection between the pump piston and drive piston is broken and the pump piston is accelerated in its volume contracting direction to a second substantially faster speed to pump the liquid out of the pump chamber.