The lowest fuel consumption in the road vehicles and the most intensive saving of natural resources are achieved with DI Diesel engines.The pollution requirements for vehicles equipped with internal combustion engines continuously increase. Low emissions, combined with a minimal maintenance requirement, are essential during the entire life cycle of vehicles.The fuel system (Fig. 1) is the most influencing part for the consumption specific emissions and the fuel consumption of the DI Diesel engine. High injection pressure capability, EGR control, injection time control and injection rate control are very important factors. Electronic engine management and engine monitoring are necessary to maintain the required accuracy and fulfill the future legal requirements. The reliability and the durability of the mechanical and electronical components should be increased so much, that a replacement of the components is not needed during entire vehicle life. At the same time the production and service cost have to be as low as possible.