Internal combustion engine with on-board diagnostic system for detecting impaired fuel injectors

An internal combustion engine comprising:

• fuel supply means for supplying liquid fuel under pressure to combustion cylinders of the engine, comprising at least one fuel injector operatively connected to a fuel rail;
• fuel injector control means for individually actuating said at least one fuel injector to pass fuel from the fuel rail during a controlled actuation period;
• and
• an on-board diagnostic system for detecting impaired fuel injectors during engine operation, said on-board diagnostic system comprising:
• pressure sensor means for sensing transient fuel pressure waves in the fuel rail resulting from actuation of at least one the fuel injector and for generating pressure signals based thereon corresponding to fuel quantity passed by the fuel injector during attuation;
• and
• signal processing means for processing pressure signals from the pressure sensor meads and for generating an output signal in response thereto, wherein the signal processing means is responsive to a timing signal from the fuel injection control means, averaging multiple values of the pressure signal taken during an actuation sampling period initiated after a predetermined pressure wave propagation delay period following the timing signal to yield an actuation value, averaging multiple values of the pressure signal taken during a non-actuation sampling period to yield a non-actuation value, and generating the output signal to the fuel injection control means based on the difference between the actuation value and the non-actuation value.

A method of detecting impaired fuel injectors in an internal combustion engine, said internal combustion engine comprising:

• a plurality of said fuel injectors;
• fuel supply means for supplying liquid fuel under pressure to the combustion cylinders of the engine, said fuel supply means comprising a plurality of fuel injectors operatively connected to a fuel rail;
• fuel injector control means for individually actuating the fuel injectors to pass fuel from the fuel rail during a controlled actuation period;
• pressure sensor means for sensing transient fuel pressure waves in the fuel rail resulting from actuation of individual fuel injectors and for generating pressure signals based thereon corresponding to fuel quantity passed by the fuel injectors during actuation;
• and
• signal processing means for processing pressure signals from the pressure sensor means and for generating an output signal in response thereto;
• said method comprising the steps of:
• actuating the fuel injectors during a fuel injector test period
• in a standard mode wherein the fuel injectors are actuated in turn in a standard engine cycle sequence, and in a test mode wherein actuation of each of the fuel injectors is deleted in turn from a corresponding one of a series of otherwise standard engine cycle sequences to provide for each fuel injector a corresponding test cycle sequence in which it was not actuated;
• generating a standard pressure signal in response to the standard engine cycle sequence and a test pressure signal for each fuel injector in response to the corresponding test cycle sequence;
• determining a fuel flow value for each fuel injector, individually, corresponding to fuel quantity passed during its actuation period by comparing the standard pressure signal and the test pressure signal to each other;
• and
• passing the output signal for each fuel injector to the fuel injector control means and adjusting the actuation period of the fuel injector based thereon.