In diesel engines, high-pressure fuel injection is very effective to reduce emissions of particulates and oxides of nitrogen. For this reason, all efforts have been directed to develop suitable high-pressure injection systems. However, high-pressure injection often increases internal leakage of the working fluid, increases power for pumping, and is sometimes still short of injection pressures at lower engine speeds. To remove these faults, the present authors developed a fuel injection system named KD-3 that relies on a novel principle using oil hammering in a convergent pipeline. The dynamic behavior of the proposed system was analyzed by the method of characteristics and computer simulations. A prototype injection system was designed and tested with success. Using a source pressure of 20 MPa, this system boosts pressure well to higher than 120 MPa at the inlet of injection nozzle. The injection timing and fuel quantity are fully controllable by timing the opening of the electromagnetic valve for starting the moving bodies and by setting the limiter of the plunger stroke, respectively.