Electronic metering pumps consists of a pump unit, a drive unit, and a control unit. The drive unit is an electromagnetic solenoid. When the control unit the armature shaft energizes the solenoid coil moves forward due to the magnetic force of the solenoid. The shaft is attached to a PTFE faced diaphragm, which is part of the pump unit. The diaphragm is forced into the pump head cavity decreasing volume and increasing pressure which forces liquid in the pump head out through the discharge check valves. When the solenoid coil is de-energized, a spring returns the armature to its starting position. This action pulls the diaphragm out of the head cavity increasing volume and decreasing pressure. Atmospheric pressure then pushes liquid from the supply tank through the suction check valves to refill the pump head.