Illustrative embodiments of pump systems and methods are disclosed. In at least one embodiment, an apparatus comprises a piston pump including a motor and a plunger, where the motor is configured to drive linear reciprocating motion of the plunger in response to being supplied with a flow of compressed fluid, a metering valve fluidly coupled to the motor, the metering valve being configured to control the flow of compressed fluid to the motor, a purge valve fluidly coupled between the metering valve and the motor, a linear encoder coupled to the piston pump, the linear encoder configured to generate sensor data indicative of a position of the plunger, and an electronic controller operatively coupled to the metering valve, the purge valve, and the linear encoder, where the electronic controller is configured to receive sensor data from the linear encoder and to control the metering valve and the purge valve.