Abstract: A flow control system for metering fluid flow in various amounts to a desired discharge point includes electrical signal responsive valves correspondingly mounted in a series of flow lines and switchable between open and close positions. An electrical control means is disclosed for selectively opening the valves individually or simultaneously in groups having relay switch means for operating each of the valves and a triggering means for selectively activating the valve relay switch means as a function of the step positions of a flow regulator device. The invention is especially useful for metering diluent fluid to an emulsification apparatus in the desired proportion as a result of the diesel engine fuel flow set by a locomotive throttle.