We investigate by numerical simulation a highly unsteady cavitating flow of ISO 4113 test fuel in the valve chamber of a Diesel common rail injection system. Two-phase modeling is based on a single-fluid approach and a homogeneous mixture model. A fully compressible flow solver, taking into account the compressibility of liquid and liquid-vapor mixture, is employed. Computational results for two similar designs are presented. We discuss the cavity dynamics and reverse flow development in the discharge throttles for a pressure drop of approximately 2000 bar and choked flow conditions. The focus of this study is placed on inertia-driven effects and formation of collapse-induced pressure peaks, which allows us to apply an inviscid flow model. Our contribution assesses the erosion risk by monitoring maximum instantaneous wall pressures and employing a collapse detector algorithm for the identification of implosions of isolated vapor clouds. High-speed liquid jet discharging from the throttle, accompanied by supercavitation and reverse motion in the throttle, is predicted by the numerical simulation. Collapse pressures higher than 1 GPa are observed near material surfaces, resulting in high surface loads which can eventually lead to material erosion.