In this article, an adaptive width/phase differential modulated controller is designed for an Active electro-hydraulic Pump (AehP) system consisting of a single straight cylinder. This controller adjusts the duty cycle and relative phase between the incoming and outgoing valve. The adjustment relies on the maximization of a cost function that characterizes the net outflow rate. The developed model relies on Computational Fluid Dynamics (CFD. Transient CFD analysis shows that the pressure propagation causes the pump performance to be highly dependent to the overall dimensions of the hydraulic system, the fluid used and the operating conditions, thus constraining and complicating the controller design process. The controller's adaptation mechanism relies on the cyclic coordinate method, which adjusts each parameter in a periodic manner. Simulation studies are used to investigate the efficiency of the proposed controller with respect to the pump-chamber's length, the piston's pulsating frequency, and the fluid properties.