Abstract: The present invention is directed to an on-board diagnostic system for detecting malfunctioning fuel injectors in an internal combustion engine during engine operation. A fuel injector control means is provided for individually actuating fuel injectors operatively connected to a fuel rail. Pressure sensor means are mounted to the fuel rail for sensing transient fuel pressure waves resulting from actuation of the individual fuel injectors and for generating a pressure signal in response thereto. Signal processing means are provided for processing pressure signals from the pressure sensor means and for generating an output signal upon detecting delayed opening or delayed closing of one or more injectors.

Abstract: The present invention is directed to an on-board diagnostic system for detecting a malfunctioning fuel pump in an internal combustion engine during engine operation. Pressure sensor means are provided for sensing fuel pressure in the fuel supply line and for generating corresponding pressure signals. Signal processing means receive and process the pressure signals from the pressure sensor means. An output signal is generated by the signal processing means if pressure signals are determined to correspond to a defective fuel pump Such output signal can be stored, used to alert an engine operator to an impaired fuel pump and/or provided to a fuel injector control means for adjusting fuel flow.

Abstract: The present invention is directed to an on-board diagnostic system for detecting a defective fuel line pressure regulator in an internal combustion engine during engine operation. Pressure sensor means are provided for sensing fuel pressure in the fuel supply line and for generating corresponding pressure signals. Signal processing means receive and process the pressure signals from the pressure sensor means. An output signal is generated by the signal processing means in the event pressure signals are determined to indicate a malfunctioning pressure regulator. Such output signal can be stored, used to alert an engine operator to an impaired regulator and/or provided to a fuel injector control means for adjusting the duration of injector actuation to better achieve a desired fuel flow quantity per individual actuation.

Abstract: The present invention is directed to an on-board diagnostic system for detecting impaired fuel injectors in an internal combustion engine during engine operation. A fuel injector control means is provided for individually actuating fuel injectors Operatively connected to a fuel rail. Pressure sensor means are mounted to the fuel rail for sensing transient fuel pressure waves resulting from actuation of the individual fuel injectors. Signal processing means are provided for processing pressure signals from the pressure sensor means. The output signal from the signal processing means corresponds to the fuel flow rate through the fuel injectors. Such output signal can be used to alert an engine operator to an impaired fuel injector and/or can be provided to the fuel injector control means for adjusting the duration of injector actuation to achieve a desired fuel flow quantity per individual actuation.

Abstract: An on-board diagnostic system is provided for determining the presence of vapor in a fuel supply line of an internal combustion engine during engine operation. Sensing means are operatively mounted to the fuel supply line for sensing transient fuel pressure waves resulting from actuation of one or more fuel injectors. The sensing means generates a pressure signal corresponding to the transient fuel pressure waves at least over a selected test interval. Signal processing means receives the pressure signal and determines its resonance frequency over at least a selected frequency range. The test interval resonance frequency is compared to a stored resonance frequency corresponding to an acceptable vapor level in the fuel supply line. The signal processing means generates an output signal upon detecting a value difference greater than a preselected amount (e.g., greater than zero) between the test interval resonance frequency and the stored resonance frequency.