Modern diesel engines need to generate up to 2000+ bar of fuel pressure to run efficiently. Any air in the fuel delivery system will affect the running of the engine. When the fuel system is being serviced and a new fuel filter is fitted air will be introduced into the system. Most modern systems are either self bleeding or have a hand pump permanently fitted to the vehicle, however many can still take some time to purge the system of any air. With two basic types of fuel delivery used on modern diesel engines - Pressure fed (using an electric fuel pump mounted in the tank to push the fuel up to the high pressure pump) and vacuum fed (using an engine driven lift pump to generate a vacuum that pulls the fuel up to the high pressure pump), this kit has been developed to allow the user to connect into as many diesel fuel systems as possible using the correct style connector coupling. For bleeding or priming diesel systems.For connection in-line with the vehicle's low pressure delivery system. The clear pipes allow any air bubbles in the system to be seen. There are a total of six different connection types included in the kit covering: Ford, PSA, GM, Fiat, Rover, Land Rover, Renault & Mercedes-Benz.