It is believed that use of pure hydrogen, as a fuel in compression ignition engines, is not feasible since there is a high risk of knocking and high temperature that makes hydrogen combustion improbable in metallurgical aspect. For this reason, the hydrogen fraction is added to diesel in most of the reported literature. The current work is an attempt to propose water injection as a practical scheme, which can suppress knocking and intensive heating led to high thermal NOx. A multi-component computational code is used to calculate the flow field, combustion, and engine efficiency quantities as affected by fuel and water injection separately. In this investigation, water is injected in three portions of 5%, 10%, and 15% of total mixture fraction by volume represented by WI (water injection) 5%, WI 10%, WI 15% in two levels of water temperature of 27 degrees C (room temperature) and 60 degrees C. In addition, the impact of WI timing (i.e. 711 CA, 717 CA, and 723 CA) is surveyed on emissions and engine efficiency of diesel-fueled and hydrogen-fueled engine. The results show that fuel + WI 15%-W60 degrees C scenario among different cases (when WI involved) gives the highest pressure peak, indicated torque, indicated thermal efficiency and engine power, while the lowest emissions are established at fuel + WI 5%-W 27 degrees C. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.