This paper reviews past and current efforts to develop a prototype direct injection fuel system (injector) intended for dynamometer research on the next generation advanced hydrogen Internal Combustion Engines (ICEs).  Practical experience accumulated from specialized material testing, bench testing and engine operation have helped direct research efforts on the fuel injection system. The highly developed and reliable internal combustion engine technology continues to get more sophisticated. Adapting such ICEs to utilize hydrogen can result in cost effective power plants that can serve the needs of a long term hydrogen roadmap.  Hydrogen direct injection provides many benefits including improved volumetric efficiency, combustion robustness (avoidance of pre-ignition and backfire) and yields significant power density advantages relative to port-injected approaches in hydrogen ICEs. Early, mid or late-cycle direct injection timing approaches allow engine developers maximum flexibility to optimize higher power density, efficiency and low emissions. A comprehensive development methodology was adopted to address various technical challenges encountered during the development process. Specific hydrogen-related issues with injector sub-components are described. As will be seen, hydrogen has presented unique materials related challenges and opportunities.  Technical discussion looks at the effect of hydrogen’s low mass / energy density, high sonic velocity and low viscosity.  These physical attributes directly affect component size, material choice, wear rates and diffusion effects. Chemical effects due to hydrogen must also be considered as they directly affect component life. Current efforts and plans to address these technical hurdles through are also briefly discussed. Successful resolution of these issues will bring the technology significantly closer towards the ultimate goal of commercialization.