With an efficiency of up to 45%, diesel engines using pump-nozzle injection technology rank as the most efficient internal combustion engines. In a pump-nozzle injection system, each cylinder in the engine is fitted with a pump-nozzle unit which generates a high injection pressure of up to 2,400 bar and injects the fuel in the correct amount and at the right moment. Mounting the units in the cylinder head dispenses with the high pressure lines which are needed in the case of conventional distributor injection pumps. The pressure increase is achieved mechanically. A small plunger is operated by an additional cam on the valve camshaft. The cam is shaped so that it provides the high speed necessary to build up to the desired high pressure rapidly. The injection timing is controlled by a solenoid valve. The pressure cannot increase until the solenoid valve is closed (electrically). The fast closing action of the solenoid valve provides a sharp cut-off to the injection, which is very important for clean and complete combustion. The benefits of pump-nozzle injection technology are lower emissions of harmful substances as well as lower fuel consumption with higher power output.