In the design development of fuel injection equipment, computer simulation of the fuel injection process can be a powerful tool. This paper brings out the development of an extended computer simulation for the fuel injection process, including the cavitation effects. For the solution of equations in the finite difference form, Newton Raphson method has been used. The program has been validated by capturing on line data using the high speed data acquisition system. The validated simulation model has been used to carry out an exhaustive parametric study of the fuel injection system of a large medium speed diesel engine to bring out the injection system parameters which significantly influence the fuel injection system performance.