Although regarded as a whole new system the actual principle of this injection system began with the American engine builders, Cummins. The Cummins PT systems was fitted to many trucks and became a legend (at that time) due to it's reliability and economy. This injection system also has no
injection pump and injection pressures (up to 2000 bar) are achieved via the cam shaft acting upon the pump units.

Again, this system is highly sensitive to contamination and the price of replacement parts is very high. Common manufacturers of these systems are BOSCH and DELPHI.

The common rail injection system does not have an injection pump but instead uses a high pressure pump, fuel rail and electronically controlled injectors. All of which rely on the ECU and a multitude of sensors. When released this system first appeared to be bullet proof but now the systems have had a few years of service this is most certainly been proven not to be the case.

Due to the higher than normal working temperatures and ultra fine tolerances of the components many problems occur. This system can only operate on 100% pure diesel fuel, even petrol or the slightest amount of water will cause severe problems. Common makers of common rail systems are BOCSH, SIEMENS, DELPHI, ZEXEL.