A multi-sensing fuel injection system for internal combustion engines. The system includes a fuel injector for injecting fuel into the internal combustion chamber. The fuel injector is electrically insulated from an engine body of the internal combustion engine by way of a first electrically insulated member. A second electrically insulated member is provided for fixedly disposing the fuel injector within the combustion chamber. The electrical insulation of the fuel injector, in conjunction with the integration of an ion sensing circuit including a resistor and a power source for supplying voltage to the fuel injector, allows for a full measurement of the ionization current.