Two types of high pressure injection equipment, which can produce a pressure of 250MPa, have been developed. One is a hydraulic pressure intensified type, having a “GRADUAL RISE AND SHARP CUT” injection rate pattern. The other is a pressure accumulator type, having a “SQUARE” injection rate pattern. These equipments have been evaluated with a high pressure vessel for analyzing the effect of injection pressure and injection rate upon the characteristics of non-evaporating fuel spray. High speed photography, shadow photography, holography and image analysis techniques were used for these studies. It was found that the fuel injected under high pressure forms finer droplets and produces a leaner mixture. It was also found that several differences exist in the structure of fuel spray between the accumulator type and the pressure intensified type. The reasons for these differences are discussed herein. One of these injection equipments was installed on a glass piston engine for observing combustion phenomena. The combustion with high pressure injection showed quite superior characteristics.