Optimization of diesel injection system using computer aided design involves complex high speed, high pressure hydraulic transient process calculation. To find the fuel discharge characteristic from injector, the fuel pumping process is first computed based on the design parameters of the injection pump. Then, knowing the forward propagating pressure wave, the dynamic response of the injector is calculated resulting in the fuel discharge process. However, if the forward pressure wave could be precisely measured instead of being calculated, and then substituted into the computer program the total calculation procedure would be substantially reduced. In this paper, a computer controlled data acquisition system with high sampling rate was used to record the fuel pumping process in a specially made long pipe to avoid distortion by the reflected pressure wave. This method is convenient, quite accurate and can save the time of computer simulation.