Abstract: A method and apparatus for cleaning and testing the fuel injection system of a vehicle without disassembling the fuel injectors from the vehicle engine. The cleaning apparatus comprises a mechanism for feeding a solvent-fuel cleaning mixture into the fuel supplying system of the engine, a control system for the feeding mechanism and a series of connectors between the fuel injection system and both the feeding mechanism and the control system. The method includes connecting the feeding mechanism and the control system to the engine fuel injection system and running the apparatus to clean the fuel injectors on site without disassembling the fuel injectors from the vehicle engine. The testing apparatus may be performed statically or dynamically with the cleaning apparatus. The static testing mechanism involves disassembly of the fuel injectors from the engine.