A pump for pumping viscous liquid. The pump includes a body, an elongate core, and a tube surrounding the core. A stepper or servo motor mounted on the body has a selectively rotatable output shaft. A transmission operatively connecting the motor output shaft and the elongate tube reciprocates the tube between a raised position and a lowered position. An inlet check valve defining an expansible lower chamber is oriented to open during each downward pumping stroke so liquid enters the lower chamber. The pump includes a pump chamber and a feed passage connecting the lower chamber to the pump chamber. The passage has a check valve oriented to open during each upward stroke to deliver liquid from the lower chamber to the pump chamber. An outlet passage connected to the pump chamber permits liquid to flow from the pump chamber to an outlet on each upward and downward stroke.