Abstract:
A method of diagnosing a fuel injector of an engine system as contaminated is provided. The method comprises: recording a first fuel injection quantity; commanding a fuel rail pressure high; recording a second fuel injection quantity while the fuel rail pressure is high; and diagnosing the fuel injector as contaminated if the first fuel injection quantity is greater than the second fuel injection quantity.

Description:
FIELD OF THE INVENTION 
     The present invention relates to methods and systems for diagnosing contaminated fuel injectors. 
     BACKGROUND OF THE INVENTION 
     Fuel and air injection quantities supplied to an engine are controlled to meet fuel economy requirements and emission standards. Closed loop control systems sense oxygen levels in exhaust flowing from the engine in order to control air and fuel quantities flowing into the engine. If engine components such as fuel injectors malfunction fuel and air injection quantities may not be accurate. Inaccuracies in injection quantities may increase emissions and/or decrease fuel economy. 
     If a fuel injector malfunctions, it is commonly due to contaminates in the fuel injector. Sediment within the fuel or fuel tank may contaminate a fuel injector. Contaminated fuel injectors can increase emissions, smoke, and/or engine noise. Conventional methods of diagnosing a contaminated fuel injector require removal of the fuel injector from the engine in order to test the fuel injector on a flow bench. Disassembly of an engine can be both time consuming and costly. Furthermore, an operator of the vehicle receives no indication of the malfunction until the vehicle has been brought to a service station. 
     SUMMARY OF THE INVENTION 
     Accordingly a method of diagnosing a fuel injector of an engine system as contaminated is provided. The method comprises, recording a first fuel injection quantity; commanding a fuel rail pressure high; recording a second fuel injection quantity while the fuel rail pressure is high; and diagnosing the fuel injector as contaminated if the first fuel injection quantity is greater than the second fuel injection quantity. 
     In other features, the method comprises adjusting airflow and commanding the adjusted airflow if the fuel injector is diagnosed as contaminated. 
     In still other features, the method comprises sending a notification signal if the fuel injector is diagnosed as contaminated. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings wherein: 
         FIG. 1  is a functional block diagram of a diesel fuel injection system; 
         FIG. 2  is a diagram illustrating a contaminated fuel injector; 
         FIGS. 3A and 3B  are graphs illustrating the characteristics of injection quantity; 
         FIG. 4  is a graph illustrating an indicated fuel injection quantity when rail pressure is adjusted; and 
         FIG. 5  is a flowchart illustrating an embodiment of the method for diagnosing a contaminated fuel injector. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the inventions its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs; a combinational logic circuit, and/or other suitable components that provide the described functionality. 
     Referring now to  FIG. 1 , an engine system  10  includes an engine  12  that combusts an air and fuel mixture to produce drive torque. Air is drawn into an intake manifold  14  through a compressor  16 . Air within the intake manifold  14  is distributed into cylinders  18 . Although four cylinders  18  are illustrated, it can be appreciated that the engine system can be implemented in diesel engines having a plurality of cylinders including, but not limited to, 2, 3, 5, 6, 8, 10, 12 and 16 cylinders. 
     Air is drawn into the cylinder  18  through an intake port. A fuel rail  20  supplies fuel to fuel injectors  22 . The fuel injector  22  directly injects fuel into the cylinder  18 . An intake valve  24  selectively opens and closes to enable air to enter the cylinder  18 . A piston (not shown) compresses the air/fuel mixture within the cylinder  18 . Heat from the compressed mixture ignites the fuel. Forces from the combustion drive the piston. The piston drives a crankshaft (not shown) to produce drive torque. 
     Combustion exhaust within the cylinder  18  is forced out through an exhaust manifold  26  when an exhaust valve  28  is in an open position. Exhaust is treated in an exhaust system (not shown). Although single intake and exhaust valves  24 , 28  are illustrated, it can be appreciated that the engine  12  can include multiple intake and exhaust valves  24 , 28  per cylinder  18 . 
     A control module  30  determines and controls an air and fuel injection quantity to be supplied to each cylinder  18  based on engine operating conditions. The control module  30  diagnoses contaminated fuel injectors  22  and reports the diagnosis to an operator of the system  10 . Based on the diagnosis the control module  30  adjusts a quantity of air delivered to the cylinder  18  with the contaminated injector  22  via the intake valve  24 . 
     Referring now to  FIG. 2 , a fuel injector is shown in more detail. When contaminated fuel is supplied to the engine  12 , a chemical reaction can occur which creates fuel deposits. Deposits stick to sensitive movement areas shown at  32 - 42 . The fuel deposits of the sensitive movement areas  32 - 42  increase friction thus leading to an uncontrolled injection quantity.  FIGS. 5A and 3B  illustrate the effects on fuel quantities for a contaminated injector. The uncontrolled fuel injection quantity will increase a pilot injection quantity (PIQ). The increase in PIQ will result in a reduction of indicated main injection (IF) quantity. A reduction in the indicated injection (IF) quantity will lead to a reduction of indicated air flow. Actual total injection quantity (Q) will not change but actual airflow will reduce. 
     The control module  30  can diagnose a contaminated fuel injector  22  by monitoring the indicated fuel quantity when pressure to the fuel rail  20  is adjusted.  FIG. 4  illustrates an IF quantity when rail pressure is adjusted. Indicated fuel injection quantity is represented along the y-axis at  50 . Rail pressure is indicated along the x-axis at  52 . An indicated fuel quantity for a non-contaminated fuel injector is shown at  54 . An indicated fuel quantity for a contaminated fuel injector is shown at  56 . Line A represents a point where fuel rail pressure is normal for engine operation. Line B represents a point where fuel rail pressure is increased for diagnosis purposes. When rail pressure is increased and indicated fuel injection quantity drops below normal, the fuel injector can be diagnosed as contaminated. 
       FIG. 5  illustrates an embodiment of the method for diagnosing a contaminated injector. In order to diagnose an injector, the engine system must be warmed up and load from electrical devices (e.g. air conditioner, defogger, seat heater, audio system, head lamps) must not be present. Control records an indicated fuel quantity at normal fuel rail pressure at  100 . Control adjusts fuel rail pressure higher at  110  and records the new indicated fuel quantity at  120 . If the indicated fuel quantity at normal rail pressure is less than or equal to the indicated fuel quantity at higher rail pressure at  130 , control loops back and records an indicated fuel quantity at  100 . 
     Otherwise, if the indicated fuel quantity at normal rail pressure is greater than the indicated fuel quantity at the higher rail pressure at  130 , target airflow is adjusted at  140 . Control then adjusts fuel rail pressure to normal at  150  and records an indicated fuel quantity at the normal rail pressure at  160 . Control adjusts fuel rail pressure higher at  170  and records the new indicated fuel quantity at  180 . If the indicated fuel quantity at normal rail pressure is greater than the indicated fuel quantity at higher rail pressure at  190 , control notifies the operator at  200 . Otherwise control loops back to step  100 . 
     The method illustrated in  FIG. 5  requires two consecutive incidences of diagnosing the contamination before notifying an operator. As can be appreciated, other known methods for implementing diagnostic notification requirements can be incorporated into the method. For example, an X number of diagnosis must be true within Y number of samples before notification. Alternatively, an X number of diagnosis must be true within a drive cycle of a vehicle before notification. 
     As can be appreciated, the notification can be made by sending a signal to illuminate an indicator light of a vehicle containing the system  10 , sounding a chime, or any other known means of notifying an operator. Either in addition to or alternative to notifying the operator, control can set a diagnostic code and send a wireless communication signal including the code notifying an operator located remotely from the system. 
     Referring back to  FIG. 5 , in another embodiment the method of diagnosing a contaminated fuel injector can be performed by a technician via a service tool i.e. Tech2. The technician can manipulate the service tool to request the control module to adjust rail pressure higher and report an indicated fuel quantity. If the indicated fuel quantity drops below normal, this is an indication to the service technician that the injector is contaminated and needs replacement. 
     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, specification, and the following claims.