Abstract: A fuel management system that separates the three-dimensional functions of fuel injection pressure, volume and timing and thus eliminates co-dimensional dependencies. The system of the invention utilizes volumetric injection control and is based on displacement of a predetermined volume rather than volume generated by flow due to pressure with respect to time, as in prior art systems. In one of its simplest configurations, the fuel management system combines a pair of "sister" injectors and a volumetric injection control assembly comprised of a simple displacement piston which free floats a given distance to deliver fuel alternately to each injector. When one injector's solenoid valve operates to activate it's main injection, it simultaneously loads the adjacent injector with a predetermined volume of fuel for the adjacent injector's main volume injection. Throttling fuel volume is controlled by controlling the length of the cylinder's barrel containing the free floating piston.