Methods and system for diagnosing fuel injectors of an engine

Abstract

Various methods and systems are provided for diagnosing a condition of a fuel injector of an engine. In one example, a method for an engine includes injecting a first pulse of fuel as a first pilot injection into a first subset of cylinders of a plurality of engine cylinders, where the first pilot injection precedes a primary injection of fuel into the first subset of cylinders by a duration; correlating a first response in an engine operating parameter to the first pilot injection; and adjusting the primary injection of fuel into the first subset of cylinders based on the first response. In one example, the first pilot injection precedes the primary injection by a predefined short duration and the primary injection of fuel is adjusted within a predefined or preset upper limit and lower limit.

1 - 13 . (canceled) 
     
     
         14 . A method for an engine, comprising:
 injecting fuel into each cylinder of a plurality of cylinders of the engine over a single engine cycle via a plurality of fuel injectors, where each fuel injector of the plurality of fuel injectors is coupled to a different cylinder of the plurality of cylinders;   determining individual engine speed accelerations resulting from the injection of fuel into each cylinder; and   indicating degradation of one or more of the plurality of fuel injectors in response to a variation in the determined individual engine speed accelerations being greater than a threshold acceleration level.   
     
     
         15 . The method of  claim 14 , further comprising indicating which fuel injector of the plurality of fuel injectors is degraded based on the individual engine speed accelerations and a known engine cylinder firing order of the engine. 
     
     
         16 . The method of  claim 15 , wherein indicating degradation includes:
 indicating an increase in a size of one or more nozzle fuel spray holes of the indicated fuel injector in response to the individual engine speed acceleration resulting from the injection of fuel via the indicated fuel injector being greater than an expected engine speed acceleration for a non-degraded fuel injector; and   indicating one or more of a decrease in response time of a solenoid of the indicated fuel injector or mechanical degradation of the indicated fuel injector in response to the individual engine speed acceleration resulting from the injection of fuel via the indicated fuel injector being less than the expected engine speed acceleration.   
     
     
         17 . A system for an engine, comprising:
 a plurality of engine cylinders including at least a first cylinder and a second cylinder;   a first fuel injector coupled to the first cylinder;   a second fuel injector coupled to the second cylinder; and   a controller operatively coupled to the first and second fuel injectors and configured to:
 during a first engine cycle, control injection of a primary pulse of fuel into the first cylinder via the first fuel injector and the second cylinder via the second fuel injector and injection of a pilot pulse of fuel, before the primary pulse, into only the first cylinder via the first fuel injector; 
 correlate a first response in an engine operating parameter to injection of the pilot pulse of fuel into the first cylinder; and 
 during a second engine cycle, following the first engine cycle, adjust the primary pulse of fuel into the first cylinder based on the first response to the pilot pulse of fuel. 
   
     
     
         18 . The system of  claim 17 , wherein the controller is further configured to:
 during a third engine cycle, control injection of the primary pulse of fuel into the first cylinder via the first fuel injector and the second cylinder via the second fuel injector and injection of the pilot pulse of fuel, before the primary pulse, into only the second cylinder via the second fuel injector;   correlate a second response in the engine operating parameter to injection of the pilot pulse of fuel; and   during a fourth engine cycle, following the third engine cycle, adjust the primary pulse of fuel into the second cylinder based on the second response to the pilot pulse of fuel.   
     
     
         19 . The system of  claim 17 , further comprising a real-time engine torque output sensor coupled to a crankshaft of the engine, wherein the engine operating parameter is a torque signal output by the torque output sensor, and wherein the controller is configured to diagnose a condition of the first injector in response to a change in the torque output over a number of engine cycles when the pilot pulse of fuel is injected into the first cylinder via the first fuel injector. 
     
     
         20 . The system of  claim 17 , further comprising a knock sensor coupled to the first cylinder, wherein the engine operating parameter is a knock signal output by the knock sensor, and wherein the controller is configured to diagnose a condition of the first injector in response to a change in the knock signal over a number of engine cycles when the pilot pulse of fuel is injected into the first cylinder via the first fuel injector. 
     
     
         21 . The method of  claim 14 , wherein the threshold acceleration levels are based on a commanded amount of the injection of fuel. 
     
     
         22 . The method of  claim 21 , wherein the determined individual engine speed accelerations are used to determine an effective amount of fuel injected. 
     
     
         23 . The method of  claim 22 , wherein fuel is injected into the engine via a primary injection and a pilot injection. 
     
     
         24 . The method of  claim 21 , wherein an amount of fuel injected is adjusted based on a difference between the determined individual engine speed accelerations and the threshold acceleration level. 
     
     
         25 . The system of  claim 17 , wherein the first response to the injection of the pilot pulse occurs before the primary injection into the first cylinder. 
     
     
         26 . The system of  claim 17 , wherein the controller is further configured to, during a third engine cycle, control an injection of a pilot pulse of fuel of the third engine cycle, before a primary pulse of the third engine cycle, into only the first cylinder via the first fuel injector. 
     
     
         27 . The system of  claim 26 , wherein the controller is further configured to correlate a response of the third engine cycle in an engine operating parameter to the injection of the pilot pulse of the third engine cycle fuel; and
 determine a difference between the first response to the injection of the pilot pulse of fuel and the response of the third engine cycle.   
     
     
         28 . The system of  claim 27 , wherein the controller is further configured to correlate a response of a further subsequent engine cycle in an engine operating parameter to an injection of a pilot pulse of the further subsequent engine cycle into the first cylinder; and
 compare the first response to the injection of the pilot pulse of fuel, the response of the third engine cycle and the further subsequent engine cycle.   
     
     
         29 . The system of  claim 28 , wherein the controller is further configured to adjust injections of primary pulses into the first cylinder based on the comparison of the first response to the injection of the pilot pulse of fuel, the response of the third engine cycle and the further subsequent engine cycle. 
     
     
         30 . The system of  claim 28 , wherein the controller is further configured to indicate degradation when the comparison determines that responses to pilot injections deviate farther from a threshold with time.