Title of Invention	DIAGNOSTIC SYSTEMS AND METHODS FOR THE HIGH PRESSURE SIDE OF FUEL SYSTEMS IN COMMON FUEL RAIL ENGINES
Abstract	A fuel system diagnostic module comprises a pressure module and a fault diagnostic module. The pressure module determines first and second pressures of a fuel rail of a fuel system at first and second times, respectively. The second time is after shutdown of an engine. The fault diagnostic module selectively diagnoses a fault in the fuel system based upon a comparison of a predetermined period with a period between the engine shutdown and the second time.

Title of Invention

DIAGNOSTIC SYSTEMS AND METHODS FOR THE HIGH PRESSURE SIDE OF FUEL SYSTEMS IN COMMON FUEL RAIL ENGINES

Abstract

A fuel system diagnostic module comprises a pressure module and a fault diagnostic module. The pressure module determines first and second pressures of a fuel rail of a fuel system at first and second times, respectively. The second time is after shutdown of an engine. The fault diagnostic module selectively diagnoses a fault in the fuel system based upon a comparison of a predetermined period with a period between the engine shutdown and the second time.

Full Text	DIAGNOSTIC SYSTEMS AND METHODS FOR THE HIGH PRESSURE SIDE OF FUEL SYSTEMS IN COMMON FUEL RAIL ENGINES CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of U.S. Provisional Application No. 60/965, 9 , filed on August 20, 2007. The disclosure of the above application is incorporated herein by reference in its entirety. FIELD [0002] The present disclosure relates to internal combustion engines and more particularly to diagnostic systems for the high pressure side of a fuel system in a common fuel rail engine. BACKGROUND [000 ] The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. [0004] Referring now to FIG. 1, a functional block diagram of an engine system 100 is presented. Air is drawn into an engine 102 through an intake manifold 104. A throttle valve 106 is actuated by an electronic throttle control (ETC) motor 108 to vary the volume of air drawn into the engine 102. The air mixes with fuel from one or more fuel injectors 110 to form an air-fuel mixture. The air-fuel mixture is combusted within one or more cylinders 112 of the engine 102. Resulting exhaust gas is expelled from the cylinders to an exhaust system 11 . [0005] Fuel is supplied to the engine 102 by a fuel system. For example only, the fuel system may include the fuel injectors 110, a fuel tank 114, a low pressure pump 115, a high pressure pump 116, and a fuel rail 118. Fuel is stored within the fuel tank 114. A low pressure pump 115 draws fuel from the fuel tank 114 and provides fuel to the high pressure pump 116. The high pressure pump 116 provides pressurized fuel to the fuel injectors 110 via the fuel rail 118. The fuel injectors 110, the high pressure pump 116, and the fuel rail 118 will be collectively referred to as the high pressure side of the fuel system. [0006] An engine control module (ECM) 120 receives a rail pressure signal from a rail pressure sensor 122. The rail pressure signal indicates the pressure of the fuel within the fuel rail 118 (i.e., rail pressure). The ECM 120 controls the amount and the timing of the fuel injected by the fuel injectors 110. The rail pressure decreases each time fuel is injected by one or more of the fuel injectors 110. The ECM 120 maintains the rail pressure via the high pressure pump 116. SUMMARY [0007] A fuel system diagnostic module comprises a pressure module and a fault diagnostic module. The pressure module determines first and second pressures of a fuel rail of a fuel system at first and second times, respectively. The second time is after shutdown of an engine. The fault diagnostic module selectively diagnoses a fault in the fuel system based upon a comparison of a predetermined period with a period between the engine shutdown and the second time. [0008] In further features, the fuel system diagnostic module further comprises a decay calculation module that determines a decay rate based upon the first rail pressure, the second rail pressure, and the period. The fault diagnostic module diagnoses the fault when the decay rate is greater than a predetermined value. [0009] In still further features, the first time occurs at the engine shutdown. In other features, the first time occurs before the engine shutdown. The second time occurs when the second rail pressure is equal to a predetermined pressure. The fault diagnostic module diagnoses the fault when the period is less than the predetermined period. The fuel system comprises the fuel rail, a fuel injector, and a fuel pump. [0010] A fuel system diagnostic module comprises a pressure module and a fault diagnostic module. The pressure module determines first and second pressures of a fuel rail of a fuel system at first and second times, respectively. The second time is after engine shutdown. The fault diagnostic module selectively diagnoses a fault in the fuel system based upon a comparison of the second pressure with a predetermined pressure. [0011] In further features, the fuel system diagnostic module further comprises a decay calculation module that determines a decay rate based upon the first rail pressure, the second rail pressure, and a period between the engine shutdown and the second time. The fault diagnostic module diagnoses the fault when the decay rate is greater than a predetermined value. [0012] In still further features, the first rail pressure is determined at the engine shutdown. In other features, the first rail pressure is determined before the engine shutdown. The second rail pressure is determined at a predetermined time after the engine shutdown. The fuel system comprises the fuel rail, a fuel injector, and a fuel pump. [001 ] A method comprises determining first and second pressures of a fuel rail of a fuel system at first and second times, respectively; comparing a predetermined period with a period between the engine shutdown and the second time; and selectively diagnosing a fault in the fuel system based upon the comparison. The second time is after shutdown of an engine. [0014] In further features, the method further comprises determining a decay rate based upon the first rail pressure, the second rail pressure, and the period; and diagnosing the fault when the decay rate is greater than a predetermined value. [0015] In still further features, the first time occurs at the engine shutdown. In other features, the first time occurs before the engine shutdown. The second time occurs when the second rail pressure is equal to a predetermined pressure. The method further comprises diagnosing the fault when the period is less than the predetermined period. The fuel system comprises the fuel rail, a fuel injector, and a fuel pump. [0016] A method comprises determining first and second pressures of a fuel rail of a fuel system at first and second times, respectively; comparing the second pressure with a predetermined pressure; and selectively diagnosing a fault in the fuel system based upon the comparison. The second time is after engine shutdown. [0017] In further features, the method further comprises determining a decay rate based upon the first rail pressure, the second rail pressure, and a period between the engine shutdown and the second time; and diagnosing the fault when the decay rate is greater than a predetermined value. [0018] In still further features, the first rail pressure is determined at the engine shutdown. In other features, the first rail pressure is determined before the engine shutdown. The second rail pressure is determined at a predetermined time after the engine shutdown. The fuel system comprises the fuel rail, a fuel injector, and a fuel pump. [0019] Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS [0020] The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: [0021] FIG. 1 is a functional block diagram of an engine system according to the prior art; [0022] FIG. 2 is a functional block diagram of an exemplary engine system according to the principles of the present disclosure; [002 ] FIG. is a functional block diagram of an exemplary implementation of a high pressure side diagnostic module according to the principles of the present disclosure; [0024] FIG. 4 is an exemplary plot of rail pressure versus time after engine shutdown; [0025] FIG. 5 is an exemplary graph depicting measured decay rates of the high pressure side of various fuel systems according to the principles of the present disclosure; and [0026] FIGs. 6A-6D are flowcharts depicting exemplary steps performed by high pressure side diagnostic modules according to the principles of the present disclosure. DETAILED DESCRIPTION [0027] The following description is merely exemplary in nature and is in no way intended to limit the disclosure, 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 phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical or. It should be understood that steps within a method may be executed in different order without altering the principles of the present disclosure. [0028] 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 execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. [0029] Faulty fuel injectors may be a common cause of fuel system problems in a vehicle. A service technician who suspects a fuel system problem may attempt to resolve the suspected problem by first replacing the fuel injectors, without knowing whether the fuel injectors are faulty. This may lead to the replacement of functional fuel injectors. If the high pressure side of the fuel system could be tested, a passing test result could eliminate the high pressure side as the source of the problem. As part of the high pressure side, the fuel injectors are likely reliable, and the service technician may then avoid replacing them. [00 0] When an engine shuts down, the high pressure pump also shuts down. For example, the high pressure pump may be driven from a crankshaft or camshaft, and therefore slows as the engine comes to a stop. Fuel at high pressure in the fuel rail may then leak back through the inactive pump. In addition, one or more valves may be opened to release the high pressure fuel. A faulty fuel injector may allow fuel to escape, such as into the cylinder, and therefore the rail pressure will decrease at a faster rate than normal. Fault in the high pressure side of the fuel system may be detected based upon the rate at which the rail pressure decreases after engine shutdown. Accordingly, fault in the fuel injectors, as a part of the high pressure side of the fuel system, may be ruled out when fault has not been detected in the high pressure side. [00 1] Referring now to FIG. 2, a functional block diagram of an exemplary engine system 200 is presented. The engine 102 may be any type of internal combustion engine, such as a spark ignition type engine or a compression ignition type engine. Although three fuel injectors and cylinders are shown, the engine 102 may include more or fewer fuel injectors and cylinders. For example only, one fuel injector 110 may be provided for each cylinder 112. [00 2] The fuel system supplies fuel to the engine 102. For example only, the fuel system may include the fuel injectors 110, the fuel tank 114, the low pressure pump 115, the high pressure pump 116, and the fuel rail 118. The high pressure pump 116 provides pressurized fuel to the fuel injectors 110 via the fuel rail 118. The fuel injectors 110, the high pressure pump 116, and the fuel rail 118 are collectively referred to as the high pressure side of the fuel system. [00 ] An engine control module (ECM) 220 receives the rail pressure signal from the rail pressure sensor 122. During engine operation, the ECM 220 maintains the rail pressure via the high pressure pump 116. For example only, the ECM 220 may maintain the rail pressure at approximately an operating pressure, such as 5 MPa. Upon engine shutdown, the high pressure pump 116 stops pumping. In various implementations, engine shutdown may correspond to a time when the engine 102 comes to a stop. Alternatively, engine shutdown may correspond to a time when a driver "keys off the engine. [00 4] A high pressure side diagnostic module 2 0 diagnoses faults in the high pressure side of the fuel system based upon how fast the rail pressure decays after shutdown. The high pressure side diagnostic module 2 0 may diagnose fault in the high pressure side (e.g., the fuel injectors 110, the high pressure pump 116, and/or the fuel rail 118) when, for example, the rail pressure decays too fast. The fuel rail 118, however, is unlikely to fail, and its failure would likely be detected by other diagnostics. The fuel injectors 110 may be more likely to fail than the high pressure pump 116, and therefore the fuel injectors 110 may be the most likely cause of faults in the high pressure side. [00 5] The high pressure side diagnostic module 2 0 generates a fault signal, which indicates whether fault has been detected in the high pressure side. In various implementations, the high pressure side diagnostic module 2 0 may detect fault in the high pressure side when a calculated decay rate is greater than a threshold. [00 6] In various other implementations, the high pressure side diagnostic module 2 0 may diagnose fault in the high pressure side of the fuel system without actually calculating the decay rate. For example only, the high pressure side diagnostic module 2 0 may detect fault in the high pressure side when the rail pressure measured at a predetermined period after engine shutdown is less than a pressure threshold. Alternatively, the high pressure side diagnostic module 2 0 may detect fault in the high pressure side when the period of time between engine shutdown and a time at which the rail pressure falls below the predetermined pressure is less than a predetermined period. [00 7] The ECM 220 receives the fault signal and may signal an error when fault has been detected in the high pressure side. For example only, the ECM 220 may set an error code when fault has been detected. A service technician may then determine whether to replace the fuel injectors 110 based upon whether the error code is set. The ECM 220 may also illuminate a light, such as a "check engine light," when fault has been detected in the high pressure side. [00 8] Referring now to FIG. , a functional block diagram of an exemplary implementation of the high pressure side diagnostic module 2 0 is presented. The high pressure side diagnostic module 2 0 includes a timer 02, a pressure module 04, a decay calculation module 06, and a fault diagnostic module 08. The timer 02 tracks the time elapsed after engine shutdown. In various implementations, the timer 02 may be started from a predetermined reset value, such as zero. [00 9] The pressure module 04 receives the rail pressure signal from the rail pressure sensor 122 and may, for example, filter, buffer, and/or digitize the rail pressure signal. For example only, the pressure module 04 may sample the rail pressure signal at a predetermined sampling rate, such as one sample every 0.1 seconds. The pressure module 04 provides a rail pressure to the decay calculation module 06. Additionally, the pressure module 04 may provide the rail pressure to the fault diagnostic module 08. [0040] The decay calculation module 06 calculates the decay rate based upon the rail pressure. In various implementations, the decay rate may be an average rate of change of the rail pressure over a predetermined period, an instantaneous rate of change at a predetermined time or sample, or any other suitable analysis of rail pressure. [0041] For example only, the decay calculation module 06 may calculate the decay rate using the equation: P1 - P2 Decay Rate = — - t where P1 is a first rail pressure, P2 is a second rail pressure, and t is a period of time between engine shutdown and P2. For example only, the first rail pressure may be measured when the engine 102 is shut down. Alternatively, the decay calculation module 06 may assume that the first rail pressure is the rail pressure maintained by the ECM 220 during normal engine operation. [0042] The decay calculation module 06 may calculate the decay rate by measuring the period of time between engine shutdown and a time at which the rail pressure falls below a predetermined pressure. This measured period and predetermined pressure may be t and P2, respectively, in the above equation. Alternatively, the decay calculation module 06 may calculate the decay rate by measuring the rail pressure after a predetermined period has passed after engine shutdown. This measured pressure and predetermined period may be P2 and t, respectively, in the above equation. [004 ] The fault diagnostic module 08 diagnoses faults in the high pressure side of the fuel system and generates the fault signal accordingly. For example only, the fault diagnostic module 08 may detect fault in the high pressure side of the fuel system when the decay rate exceeds a fault threshold. The fault threshold may be calibratable and may be set to a minimum decay rate at which the high pressure side is known to be faulty. For example only, the fault threshold may be set to 8 MPa/s. [0044] Alternatively, the fault diagnostic module 08 may diagnose faults in the high pressure side without actually calculating the decay rate. In various implementations, the fault diagnostic module 08 may detect fault in the high pressure side when the measured rail pressure after a predetermined period is less than a pressure threshold. In various other implementations, the fault diagnostic module 08 may detect fault in the high pressure side when the period of time between engine shutdown and a time at which the rail pressure falls below the predetermined pressure is less than a predetermined period. [0045] Referring now to FIG. 4, exemplary plots 402 and 404 both depict rail pressure versus time after engine shutdown for the high pressure side of various vehicles. Upon engine shutdown, the rail pressure begins decreasing from an operating pressure, such as 5.0 MPa. The decay rate of rail pressure may be calculated after measuring the period between engine shutdown and a time at which the rail pressure falls below a predetermined pressure (e.g., plot 402) or after measuring the rail pressure at a predetermined period after engine shutdown (e.g., plot 404). The high pressure side of the fuel system may be faulty when the decay rate is greater than the fault threshold, which may be, for example, 8 MPa/s. [0046] Plot 402 depicts measuring the period between engine shutdown and a time at which the rail pressure falls below a predetermined pressure. For example only, the predetermined pressure may be .0 MPa, as represented by dashed line 406. The decay rate may then be calculated using, for example, the above equation, and faults in the high pressure side may be detected accordingly. [0047] Alternatively, faults in the high pressure side may be detected by comparing this measured period a predetermined period. For example only, when the fault threshold is 8 MPa/s and the operating pressure (Pi) is 5 MPa, the predetermined period may be approximately 4 seconds [i.e., ( 5 MPa - MPa) / 8 MPa/s]. Accordingly, the high pressure side may be faulty when the rail pressure falls below .0 MPa within 4 seconds after engine shutdown. Using these values, high pressure side diagnostic modules may detect fault in the high pressure side of the fuel systems indicated by reference numeral 408. High pressure side diagnostic modules may determine that the high pressure side of the fuel systems indicated by reference numeral 410 are likely reliable. [0048] Plot 404 depicts measuring the rail pressure after a predetermined period. For example only, the predetermined period may be 4 seconds, as depicted by dashed line 412. The decay rate may then be calculated using, for example, the above equation, and faults may be diagnosed in the high pressure side accordingly. [0049] Alternatively, faults in the high pressure side may be diagnosed based upon a comparison of the measured rail pressure (after the predetermined period) with a pressure threshold. For the case where the fault threshold is 8 MPa/s and the operating pressure is 5 MPa, the pressure threshold may be MPa [i.e., 5 MPa - (8 MPa/s * 4 s)]. Accordingly, fault may be detected in the high pressure side when the rail pressure measured 4 seconds after engine shutdown is less than MPa. For example only, fault may be detected in the high pressure side of the fuel systems indicated by reference numeral 408, while it is unlikely that fault will be detected in those indicated by reference numeral 410. [0050] Referring now to FIG. 5, an exemplary graph depicts measured decay rates of the high pressure side of various fuel systems 500A-500J. Dashed line 502 indicates an exemplary fault threshold, which is 8.0 MPa/s in FIG. 5. Fault may be detected in the high pressure side of each of the fuel systems 500A-500J when its respective decay rate is greater than the fault threshold. As depicted, the high pressure side diagnostic modules corresponding to the fuel systems 500C, 500D, and 500H may detect fault in their respective high pressure sides. [0051] Referring now to FIG. 6A, a flowchart depicts exemplary steps performed by the high pressure side diagnostic module 2 0. Control begins in step 602 upon engine shutdown. In step 602, control starts the timer 02. In various implementations, control starts the timer 02 from a reset value, such as zero. Control continues in step 604, where control measures the rail pressure. [0052] In step 606, control determines whether the rail pressure is less than or equal to a predetermined pressure. If so, control continues in step 608; otherwise, control returns to step 604. For example only, the predetermined pressure may be .0 MPa. Control continues in step 608, where control measures the period. For example, control may measure the period by reading the timer 02, and calculating the difference between the reset value and the timer value. [005 ] In step 610, control calculates the decay rate, for example, using the equation: P1 -P2 Decay Rate = — - t where P1 is the first rail pressure, P2 is a second rail pressure, and t is the period. For example only, the predetermined pressure and the period may be used as P2 and t, respectively. The first pressure measured in step 604 may be used as P1- Alternatively, control may assume that Pi is the operating pressure maintained by the ECM 220. [0054] Control then determines whether the decay rate is greater than the fault threshold in step 612. If so, control continues in step 614; otherwise, control transfers to step 616. In step 614, control indicates that no fault has been detected in the high pressure side of the fuel system, and control ends. In step 616, control indicates fault in the high pressure side of the fuel system, and control ends. Control may indicate fault in the high pressure side of the fuel system by, for example, setting the error code and/or illuminating the "check engine light." [0055] Referring now to FIG. 6B, a second flowchart depicting exemplary steps performed the high pressure side diagnostic module 2 0 is presented. Control performs steps 602 to 608 as in FIG. 6A above. Instead of calculating the decay rate, control then continues in step 620 where control determines whether the period is greater than a threshold (i.e., a predetermined period). If so, control continues in step 622; otherwise, control transfers to step 624. in step 622, control that no fault has been detected in the high pressure and control ends. In step 624, control indicates fault in the high pressure side and control ends. [0056] Referring now to FIG. 6C, a third flowchart depicts exemplary steps performed by the high pressure side diagnostic module 2 0. Control starts the timer 02 in step 602. In step 6 0, control determines a first rail pressure. Control may measure the first rail pressure upon engine shutdown or assume that the first rail pressure is the rail pressure maintained by the ECM 220 during normal engine operation. In step 6 2, control determines whether the period since engine shutdown (i.e., starting the timer) is greater than or equal to a predetermined period. If so, control continues in step 6 4; otherwise, control remains in step 6 2. [0057] In step 6 4, control measures a second rail pressure. Control then continues in step 6 6, where control calculates the decay rate based upon the first rail pressure, the second rail pressure, and the predetermined period. In step 6 8, control determines whether the decay rate is greater than the fault threshold. If so, control continues in step 640; otherwise, control transfers to step 642. In step 640, control indicates that fault has not been detected in the high pressure side of the fuel system, and control ends. In step 642, control indicates fault in the high pressure side of the fuel system, and control ends. [0058] Referring now to FIG. 6D, a fourth flowchart depicting exemplary steps performed by the high pressure side diagnostic module 2 0 is presented. Control performs steps 602 and 6 0- 4 as in FIG. 6C. Instead of calculating the decay rate, control then continues in step 650 where control determines whether the second rail pressure is greater than a pressure threshold. If so, control continues in step 652; otherwise, control transfers to step 654. In step 652, control indicates that no fault has been detected in the high pressure side and control ends. In step 654, control indicates fault in the high pressure side and control ends. [0059] Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification, and the following claims. CLAIMS What is claimed is: 1. A fuel system diagnostic module comprising: a pressure module that determines first and second pressures of a fuel rail of a fuel system at first and second times, respectively, wherein said second time is after shutdown of an engine; and a fault diagnostic module that selectively diagnoses a fault in said fuel system based upon a comparison of a predetermined period with a period between said engine shutdown and said second time. 2. The fuel system diagnostic module of claim 1 further comprising a decay calculation module that determines a decay rate based upon said first rail pressure, said second rail pressure, and said period, wherein said fault diagnostic module diagnoses said fault when said decay rate is greater than a predetermined value. 3. The fuel system diagnostic module of claim 2 wherein said first time occurs at said engine shutdown. 4. The fuel system diagnostic module of claim 2 wherein said first time occurs before said engine shutdown. 5. The fuel system diagnostic module of claim 1 wherein said second time occurs when said second rail pressure is equal to a predetermined pressure. 6. The fuel system diagnostic module of claim 1 wherein said fault diagnostic module diagnoses said fault when said period is less than said predetermined period. 7. The fuel system diagnostic module of claim 1 wherein said fuel system comprises said fuel rail, a fuel injector, and a fuel pump. 8. A fuel system diagnostic module comprising: a pressure module that determines first and second pressures of a fuel rail of a fuel system at first and second times, respectively, wherein said second time is after engine shutdown; and a fault diagnostic module that selectively diagnoses a fault in said fuel system based upon a comparison of a said second pressure with a predetermined pressure. 9. The fuel system diagnostic module of claim 8 further comprising a decay calculation module that determines a decay rate based upon said first rail pressure, said second rail pressure, and a period between said engine shutdown and said second time, wherein said fault diagnostic module diagnoses said fault when said decay rate is greater than a predetermined value. 10. The fuel system diagnostic module of claim 9 wherein said first rail pressure is determined at said engine shutdown. 11. The fuel system diagnostic module of claim 9 wherein said first rail pressure is determined before said engine shutdown. 12. The fuel system diagnostic module of claim 8 wherein said second rail pressure is determined at a predetermined time after said engine shutdown. 13. The fuel system diagnostic module of claim 8 wherein said fuel system comprises said fuel rail, a fuel injector, and a fuel pump. 14. A method comprising: determining first and second pressures of a fuel rail of a fuel system at first and second times, respectively, wherein said second time is after shutdown of an engine; comparing a predetermined period with a period between said engine shutdown and said second time; and selectively diagnosing a fault in said fuel system based upon said comparison. 15. The method of claim 14 further comprising: determining a decay rate based upon said first rail pressure, said second rail pressure, and said period; and diagnosing said fault when said decay rate is greater than a predetermined value. 16. The method of claim 15 wherein said first time occurs at said engine shutdown. 17. The method of claim 15 wherein said first time occurs before said engine shutdown. 18. The method of claim 14 wherein said second time occurs when said second rail pressure is equal to a predetermined pressure. 19. The method of claim 14 further comprising diagnosing said fault when said period is less than said predetermined period. 20. The method of claim 14 wherein said fuel system comprises said fuel rail, a fuel injector, and a fuel pump. 21. A method comprising: determining first and second pressures of a fuel rail of a fuel system at first and second times, respectively, wherein said second time is after engine shutdown; comparing said second pressure with a predetermined pressure; and selectively diagnosing a fault in said fuel system based upon said comparison. 22. The method of claim 21 further comprising: determining a decay rate based upon said first rail pressure, said second rail pressure, and a period between said engine shutdown and said second time; and diagnosing said fault when said decay rate is greater than a predetermined value. 2 . The method of claim 22 wherein said first rail pressure is determined at said engine shutdown. 24. The method of claim 22 wherein said first rail pressure is determined before said engine shutdown. 25. The method of claim 21 wherein said second rail pressure is determined at a predetermined time after said engine shutdown. 26. The method of claim 21 wherein said fuel system comprises said fuel rail, a fuel injector, and a fuel pump. A fuel system diagnostic module comprises a pressure module and a fault diagnostic module. The pressure module determines first and second pressures of a fuel rail of a fuel system at first and second times, respectively. The second time is after shutdown of an engine. The fault diagnostic module selectively diagnoses a fault in the fuel system based upon a comparison of a predetermined period with a period between the engine shutdown and the second time.

Full Text

DIAGNOSTIC SYSTEMS AND METHODS FOR THE HIGH PRESSURE SIDE OF FUEL SYSTEMS IN COMMON FUEL RAIL ENGINES
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/965, 9 , filed on August 20, 2007. The disclosure of the
above application is incorporated herein by reference in its entirety.
FIELD
[0002] The present disclosure relates to internal combustion engines
and more particularly to diagnostic systems for the high pressure side of a fuel
system in a common fuel rail engine.
BACKGROUND
[000 ] The background description provided herein is for the purpose
of generally presenting the context of the disclosure. Work of the presently
named inventors, to the extent it is described in this background section, as well
as aspects of the description that may not otherwise qualify as prior art at the
time of filing, are neither expressly nor impliedly admitted as prior art against the
present disclosure.
[0004] Referring now to FIG. 1, a functional block diagram of an engine
system 100 is presented. Air is drawn into an engine 102 through an intake
manifold 104. A throttle valve 106 is actuated by an electronic throttle control
(ETC) motor 108 to vary the volume of air drawn into the engine 102. The air

mixes with fuel from one or more fuel injectors 110 to form an air-fuel mixture.
The air-fuel mixture is combusted within one or more cylinders 112 of the engine
102. Resulting exhaust gas is expelled from the cylinders to an exhaust system
11 .
[0005] Fuel is supplied to the engine 102 by a fuel system. For
example only, the fuel system may include the fuel injectors 110, a fuel tank 114,
a low pressure pump 115, a high pressure pump 116, and a fuel rail 118. Fuel is
stored within the fuel tank 114. A low pressure pump 115 draws fuel from the
fuel tank 114 and provides fuel to the high pressure pump 116. The high
pressure pump 116 provides pressurized fuel to the fuel injectors 110 via the fuel
rail 118. The fuel injectors 110, the high pressure pump 116, and the fuel rail
118 will be collectively referred to as the high pressure side of the fuel system.
[0006] An engine control module (ECM) 120 receives a rail pressure
signal from a rail pressure sensor 122. The rail pressure signal indicates the
pressure of the fuel within the fuel rail 118 (i.e., rail pressure). The ECM 120
controls the amount and the timing of the fuel injected by the fuel injectors 110.
The rail pressure decreases each time fuel is injected by one or more of the fuel
injectors 110. The ECM 120 maintains the rail pressure via the high pressure
pump 116.
SUMMARY
[0007] A fuel system diagnostic module comprises a pressure module
and a fault diagnostic module. The pressure module determines first and second
pressures of a fuel rail of a fuel system at first and second times, respectively.

The second time is after shutdown of an engine. The fault diagnostic module
selectively diagnoses a fault in the fuel system based upon a comparison of a
predetermined period with a period between the engine shutdown and the
second time.
[0008] In further features, the fuel system diagnostic module further
comprises a decay calculation module that determines a decay rate based upon
the first rail pressure, the second rail pressure, and the period. The fault
diagnostic module diagnoses the fault when the decay rate is greater than a
predetermined value.
[0009] In still further features, the first time occurs at the engine
shutdown. In other features, the first time occurs before the engine shutdown.
The second time occurs when the second rail pressure is equal to a
predetermined pressure. The fault diagnostic module diagnoses the fault when
the period is less than the predetermined period. The fuel system comprises the
fuel rail, a fuel injector, and a fuel pump.
[0010] A fuel system diagnostic module comprises a pressure module
and a fault diagnostic module. The pressure module determines first and second
pressures of a fuel rail of a fuel system at first and second times, respectively.
The second time is after engine shutdown. The fault diagnostic module
selectively diagnoses a fault in the fuel system based upon a comparison of the
second pressure with a predetermined pressure.
[0011] In further features, the fuel system diagnostic module further
comprises a decay calculation module that determines a decay rate based upon

the first rail pressure, the second rail pressure, and a period between the engine
shutdown and the second time. The fault diagnostic module diagnoses the fault
when the decay rate is greater than a predetermined value.
[0012] In still further features, the first rail pressure is determined at the
engine shutdown. In other features, the first rail pressure is determined before
the engine shutdown. The second rail pressure is determined at a
predetermined time after the engine shutdown. The fuel system comprises the
fuel rail, a fuel injector, and a fuel pump.
[001 ] A method comprises determining first and second pressures of
a fuel rail of a fuel system at first and second times, respectively; comparing a
predetermined period with a period between the engine shutdown and the
second time; and selectively diagnosing a fault in the fuel system based upon the
comparison. The second time is after shutdown of an engine.
[0014] In further features, the method further comprises determining a
decay rate based upon the first rail pressure, the second rail pressure, and the
period; and diagnosing the fault when the decay rate is greater than a
predetermined value.
[0015] In still further features, the first time occurs at the engine
shutdown. In other features, the first time occurs before the engine shutdown.
The second time occurs when the second rail pressure is equal to a
predetermined pressure. The method further comprises diagnosing the fault
when the period is less than the predetermined period. The fuel system
comprises the fuel rail, a fuel injector, and a fuel pump.

[0016] A method comprises determining first and second pressures of
a fuel rail of a fuel system at first and second times, respectively; comparing the
second pressure with a predetermined pressure; and selectively diagnosing a
fault in the fuel system based upon the comparison. The second time is after
engine shutdown.
[0017] In further features, the method further comprises determining a
decay rate based upon the first rail pressure, the second rail pressure, and a
period between the engine shutdown and the second time; and diagnosing the
fault when the decay rate is greater than a predetermined value.
[0018] In still further features, the first rail pressure is determined at the
engine shutdown. In other features, the first rail pressure is determined before
the engine shutdown. The second rail pressure is determined at a
predetermined time after the engine shutdown. The fuel system comprises the
fuel rail, a fuel injector, and a fuel pump.
[0019] Further areas of applicability of the present disclosure will
become apparent from the detailed description provided hereinafter. It should be
understood that the detailed description and specific examples are intended for
purposes of illustration only and are not intended to limit the scope of the
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The present disclosure will become more fully understood from
the detailed description and the accompanying drawings, wherein:

[0021] FIG. 1 is a functional block diagram of an engine system
according to the prior art;
[0022] FIG. 2 is a functional block diagram of an exemplary engine
system according to the principles of the present disclosure;
[002 ] FIG. is a functional block diagram of an exemplary
implementation of a high pressure side diagnostic module according to the
principles of the present disclosure;
[0024] FIG. 4 is an exemplary plot of rail pressure versus time after
engine shutdown;
[0025] FIG. 5 is an exemplary graph depicting measured decay rates of
the high pressure side of various fuel systems according to the principles of the
present disclosure; and
[0026] FIGs. 6A-6D are flowcharts depicting exemplary steps
performed by high pressure side diagnostic modules according to the principles
of the present disclosure.
DETAILED DESCRIPTION
[0027] The following description is merely exemplary in nature and is in
no way intended to limit the disclosure, 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 phrase at least one of A, B, and C should
be construed to mean a logical (A or B or C), using a non-exclusive logical or. It
should be understood that steps within a method may be executed in different
order without altering the principles of the present disclosure.

[0028] 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 execute one or more software or firmware
programs, a combinational logic circuit, and/or other suitable components that
provide the described functionality.
[0029] Faulty fuel injectors may be a common cause of fuel system
problems in a vehicle. A service technician who suspects a fuel system problem
may attempt to resolve the suspected problem by first replacing the fuel injectors,
without knowing whether the fuel injectors are faulty. This may lead to the
replacement of functional fuel injectors. If the high pressure side of the fuel
system could be tested, a passing test result could eliminate the high pressure
side as the source of the problem. As part of the high pressure side, the fuel
injectors are likely reliable, and the service technician may then avoid replacing
them.
[00 0] When an engine shuts down, the high pressure pump also shuts
down. For example, the high pressure pump may be driven from a crankshaft or
camshaft, and therefore slows as the engine comes to a stop. Fuel at high
pressure in the fuel rail may then leak back through the inactive pump. In
addition, one or more valves may be opened to release the high pressure fuel. A
faulty fuel injector may allow fuel to escape, such as into the cylinder, and
therefore the rail pressure will decrease at a faster rate than normal. Fault in the
high pressure side of the fuel system may be detected based upon the rate at
which the rail pressure decreases after engine shutdown. Accordingly, fault in

the fuel injectors, as a part of the high pressure side of the fuel system, may be
ruled out when fault has not been detected in the high pressure side.
[00 1] Referring now to FIG. 2, a functional block diagram of an
exemplary engine system 200 is presented. The engine 102 may be any type of
internal combustion engine, such as a spark ignition type engine or a
compression ignition type engine. Although three fuel injectors and cylinders are
shown, the engine 102 may include more or fewer fuel injectors and cylinders.
For example only, one fuel injector 110 may be provided for each cylinder 112.
[00 2] The fuel system supplies fuel to the engine 102. For example
only, the fuel system may include the fuel injectors 110, the fuel tank 114, the low
pressure pump 115, the high pressure pump 116, and the fuel rail 118. The high
pressure pump 116 provides pressurized fuel to the fuel injectors 110 via the fuel
rail 118. The fuel injectors 110, the high pressure pump 116, and the fuel rail
118 are collectively referred to as the high pressure side of the fuel system.
[00 ] An engine control module (ECM) 220 receives the rail pressure
signal from the rail pressure sensor 122. During engine operation, the ECM 220
maintains the rail pressure via the high pressure pump 116. For example only,
the ECM 220 may maintain the rail pressure at approximately an operating
pressure, such as 5 MPa. Upon engine shutdown, the high pressure pump 116
stops pumping. In various implementations, engine shutdown may correspond to
a time when the engine 102 comes to a stop. Alternatively, engine shutdown
may correspond to a time when a driver "keys off the engine.

[00 4] A high pressure side diagnostic module 2 0 diagnoses faults in
the high pressure side of the fuel system based upon how fast the rail pressure
decays after shutdown. The high pressure side diagnostic module 2 0 may
diagnose fault in the high pressure side (e.g., the fuel injectors 110, the high
pressure pump 116, and/or the fuel rail 118) when, for example, the rail pressure
decays too fast. The fuel rail 118, however, is unlikely to fail, and its failure
would likely be detected by other diagnostics. The fuel injectors 110 may be
more likely to fail than the high pressure pump 116, and therefore the fuel
injectors 110 may be the most likely cause of faults in the high pressure side.
[00 5] The high pressure side diagnostic module 2 0 generates a fault
signal, which indicates whether fault has been detected in the high pressure side.
In various implementations, the high pressure side diagnostic module 2 0 may
detect fault in the high pressure side when a calculated decay rate is greater than
a threshold.
[00 6] In various other implementations, the high pressure side
diagnostic module 2 0 may diagnose fault in the high pressure side of the fuel
system without actually calculating the decay rate. For example only, the high
pressure side diagnostic module 2 0 may detect fault in the high pressure side
when the rail pressure measured at a predetermined period after engine
shutdown is less than a pressure threshold. Alternatively, the high pressure side
diagnostic module 2 0 may detect fault in the high pressure side when the period
of time between engine shutdown and a time at which the rail pressure falls
below the predetermined pressure is less than a predetermined period.

[00 7] The ECM 220 receives the fault signal and may signal an error
when fault has been detected in the high pressure side. For example only, the
ECM 220 may set an error code when fault has been detected. A service
technician may then determine whether to replace the fuel injectors 110 based
upon whether the error code is set. The ECM 220 may also illuminate a light,
such as a "check engine light," when fault has been detected in the high pressure
side.
[00 8] Referring now to FIG. , a functional block diagram of an
exemplary implementation of the high pressure side diagnostic module 2 0 is
presented. The high pressure side diagnostic module 2 0 includes a timer 02,
a pressure module 04, a decay calculation module 06, and a fault diagnostic
module 08. The timer 02 tracks the time elapsed after engine shutdown. In
various implementations, the timer 02 may be started from a predetermined
reset value, such as zero.
[00 9] The pressure module 04 receives the rail pressure signal from
the rail pressure sensor 122 and may, for example, filter, buffer, and/or digitize
the rail pressure signal. For example only, the pressure module 04 may sample
the rail pressure signal at a predetermined sampling rate, such as one sample
every 0.1 seconds. The pressure module 04 provides a rail pressure to the
decay calculation module 06. Additionally, the pressure module 04 may
provide the rail pressure to the fault diagnostic module 08.
[0040] The decay calculation module 06 calculates the decay rate
based upon the rail pressure. In various implementations, the decay rate may be

an average rate of change of the rail pressure over a predetermined period, an
instantaneous rate of change at a predetermined time or sample, or any other
suitable analysis of rail pressure.
[0041] For example only, the decay calculation module 06 may
calculate the decay rate using the equation:
P1 - P2
Decay Rate = — -
t
where P1 is a first rail pressure, P2 is a second rail pressure, and t is a period of
time between engine shutdown and P2. For example only, the first rail pressure
may be measured when the engine 102 is shut down. Alternatively, the decay
calculation module 06 may assume that the first rail pressure is the rail pressure
maintained by the ECM 220 during normal engine operation.
[0042] The decay calculation module 06 may calculate the decay rate
by measuring the period of time between engine shutdown and a time at which
the rail pressure falls below a predetermined pressure. This measured period
and predetermined pressure may be t and P2, respectively, in the above
equation. Alternatively, the decay calculation module 06 may calculate the
decay rate by measuring the rail pressure after a predetermined period has
passed after engine shutdown. This measured pressure and predetermined
period may be P2 and t, respectively, in the above equation.
[004 ] The fault diagnostic module 08 diagnoses faults in the high
pressure side of the fuel system and generates the fault signal accordingly. For
example only, the fault diagnostic module 08 may detect fault in the high
pressure side of the fuel system when the decay rate exceeds a fault threshold.

The fault threshold may be calibratable and may be set to a minimum decay rate
at which the high pressure side is known to be faulty. For example only, the fault
threshold may be set to 8 MPa/s.
[0044] Alternatively, the fault diagnostic module 08 may diagnose
faults in the high pressure side without actually calculating the decay rate. In
various implementations, the fault diagnostic module 08 may detect fault in the
high pressure side when the measured rail pressure after a predetermined period
is less than a pressure threshold. In various other implementations, the fault
diagnostic module 08 may detect fault in the high pressure side when the period
of time between engine shutdown and a time at which the rail pressure falls
below the predetermined pressure is less than a predetermined period.
[0045] Referring now to FIG. 4, exemplary plots 402 and 404 both
depict rail pressure versus time after engine shutdown for the high pressure side
of various vehicles. Upon engine shutdown, the rail pressure begins decreasing
from an operating pressure, such as 5.0 MPa. The decay rate of rail pressure
may be calculated after measuring the period between engine shutdown and a
time at which the rail pressure falls below a predetermined pressure (e.g., plot
402) or after measuring the rail pressure at a predetermined period after engine
shutdown (e.g., plot 404). The high pressure side of the fuel system may be
faulty when the decay rate is greater than the fault threshold, which may be, for
example, 8 MPa/s.
[0046] Plot 402 depicts measuring the period between engine
shutdown and a time at which the rail pressure falls below a predetermined

pressure. For example only, the predetermined pressure may be .0 MPa, as
represented by dashed line 406. The decay rate may then be calculated using,
for example, the above equation, and faults in the high pressure side may be
detected accordingly.
[0047] Alternatively, faults in the high pressure side may be detected
by comparing this measured period a predetermined period. For example only,
when the fault threshold is 8 MPa/s and the operating pressure (Pi) is 5 MPa,
the predetermined period may be approximately 4 seconds [i.e., ( 5 MPa -
MPa) / 8 MPa/s]. Accordingly, the high pressure side may be faulty when the rail
pressure falls below .0 MPa within 4 seconds after engine shutdown. Using
these values, high pressure side diagnostic modules may detect fault in the high
pressure side of the fuel systems indicated by reference numeral 408. High
pressure side diagnostic modules may determine that the high pressure side of
the fuel systems indicated by reference numeral 410 are likely reliable.
[0048] Plot 404 depicts measuring the rail pressure after a
predetermined period. For example only, the predetermined period may be 4
seconds, as depicted by dashed line 412. The decay rate may then be
calculated using, for example, the above equation, and faults may be diagnosed
in the high pressure side accordingly.
[0049] Alternatively, faults in the high pressure side may be diagnosed
based upon a comparison of the measured rail pressure (after the predetermined
period) with a pressure threshold. For the case where the fault threshold is 8
MPa/s and the operating pressure is 5 MPa, the pressure threshold may be

MPa [i.e., 5 MPa - (8 MPa/s * 4 s)]. Accordingly, fault may be detected in the
high pressure side when the rail pressure measured 4 seconds after engine
shutdown is less than MPa. For example only, fault may be detected in the
high pressure side of the fuel systems indicated by reference numeral 408, while
it is unlikely that fault will be detected in those indicated by reference numeral
410.
[0050] Referring now to FIG. 5, an exemplary graph depicts measured
decay rates of the high pressure side of various fuel systems 500A-500J.
Dashed line 502 indicates an exemplary fault threshold, which is 8.0 MPa/s in
FIG. 5. Fault may be detected in the high pressure side of each of the fuel
systems 500A-500J when its respective decay rate is greater than the fault
threshold. As depicted, the high pressure side diagnostic modules
corresponding to the fuel systems 500C, 500D, and 500H may detect fault in
their respective high pressure sides.
[0051] Referring now to FIG. 6A, a flowchart depicts exemplary steps
performed by the high pressure side diagnostic module 2 0. Control begins in
step 602 upon engine shutdown. In step 602, control starts the timer 02. In
various implementations, control starts the timer 02 from a reset value, such as
zero. Control continues in step 604, where control measures the rail pressure.
[0052] In step 606, control determines whether the rail pressure is less
than or equal to a predetermined pressure. If so, control continues in step 608;
otherwise, control returns to step 604. For example only, the predetermined
pressure may be .0 MPa. Control continues in step 608, where control

measures the period. For example, control may measure the period by reading
the timer 02, and calculating the difference between the reset value and the
timer value.
[005 ] In step 610, control calculates the decay rate, for example,
using the equation:
P1 -P2
Decay Rate = — -
t
where P1 is the first rail pressure, P2 is a second rail pressure, and t is the period.
For example only, the predetermined pressure and the period may be used as P2
and t, respectively. The first pressure measured in step 604 may be used as P1-
Alternatively, control may assume that Pi is the operating pressure maintained by
the ECM 220.
[0054] Control then determines whether the decay rate is greater than
the fault threshold in step 612. If so, control continues in step 614; otherwise,
control transfers to step 616. In step 614, control indicates that no fault has been
detected in the high pressure side of the fuel system, and control ends. In step
616, control indicates fault in the high pressure side of the fuel system, and
control ends. Control may indicate fault in the high pressure side of the fuel
system by, for example, setting the error code and/or illuminating the "check
engine light."
[0055] Referring now to FIG. 6B, a second flowchart depicting
exemplary steps performed the high pressure side diagnostic module 2 0 is
presented. Control performs steps 602 to 608 as in FIG. 6A above. Instead of
calculating the decay rate, control then continues in step 620 where control

determines whether the period is greater than a threshold (i.e., a predetermined
period). If so, control continues in step 622; otherwise, control transfers to step
624. in step 622, control that no fault has been detected in the high pressure
and control ends. In step 624, control indicates fault in the high pressure side
and control ends.
[0056] Referring now to FIG. 6C, a third flowchart depicts exemplary
steps performed by the high pressure side diagnostic module 2 0. Control starts
the timer 02 in step 602. In step 6 0, control determines a first rail pressure.
Control may measure the first rail pressure upon engine shutdown or assume
that the first rail pressure is the rail pressure maintained by the ECM 220 during
normal engine operation. In step 6 2, control determines whether the period
since engine shutdown (i.e., starting the timer) is greater than or equal to a
predetermined period. If so, control continues in step 6 4; otherwise, control
remains in step 6 2.
[0057] In step 6 4, control measures a second rail pressure. Control
then continues in step 6 6, where control calculates the decay rate based upon
the first rail pressure, the second rail pressure, and the predetermined period. In
step 6 8, control determines whether the decay rate is greater than the fault
threshold. If so, control continues in step 640; otherwise, control transfers to step
642. In step 640, control indicates that fault has not been detected in the high
pressure side of the fuel system, and control ends. In step 642, control indicates
fault in the high pressure side of the fuel system, and control ends.

[0058] Referring now to FIG. 6D, a fourth flowchart depicting
exemplary steps performed by the high pressure side diagnostic module 2 0 is
presented. Control performs steps 602 and 6 0- 4 as in FIG. 6C. Instead of
calculating the decay rate, control then continues in step 650 where control
determines whether the second rail pressure is greater than a pressure
threshold. If so, control continues in step 652; otherwise, control transfers to step
654. In step 652, control indicates that no fault has been detected in the high
pressure side and control ends. In step 654, control indicates fault in the high
pressure side and control ends.
[0059] Those skilled in the art can now appreciate from the foregoing
description that the broad teachings of the disclosure can be implemented in a
variety of forms. Therefore, while this disclosure includes particular examples,
the true scope of the disclosure should not be so limited since other modifications
will become apparent to the skilled practitioner upon a study of the drawings, the
specification, and the following claims.

CLAIMS
What is claimed is:
1. A fuel system diagnostic module comprising:
a pressure module that determines first and second pressures of a
fuel rail of a fuel system at first and second times, respectively, wherein said
second time is after shutdown of an engine; and
a fault diagnostic module that selectively diagnoses a fault in said
fuel system based upon a comparison of a predetermined period with a period
between said engine shutdown and said second time.
2. The fuel system diagnostic module of claim 1 further comprising a
decay calculation module that determines a decay rate based upon said first rail
pressure, said second rail pressure, and said period,
wherein said fault diagnostic module diagnoses said fault when
said decay rate is greater than a predetermined value.
3. The fuel system diagnostic module of claim 2 wherein said first time
occurs at said engine shutdown.
4. The fuel system diagnostic module of claim 2 wherein said first time
occurs before said engine shutdown.

5. The fuel system diagnostic module of claim 1 wherein said second
time occurs when said second rail pressure is equal to a predetermined
pressure.
6. The fuel system diagnostic module of claim 1 wherein said fault
diagnostic module diagnoses said fault when said period is less than said
predetermined period.
7. The fuel system diagnostic module of claim 1 wherein said fuel
system comprises said fuel rail, a fuel injector, and a fuel pump.
8. A fuel system diagnostic module comprising:
a pressure module that determines first and second pressures of a
fuel rail of a fuel system at first and second times, respectively, wherein said
second time is after engine shutdown; and
a fault diagnostic module that selectively diagnoses a fault in said
fuel system based upon a comparison of a said second pressure with a
predetermined pressure.
9. The fuel system diagnostic module of claim 8 further comprising a
decay calculation module that determines a decay rate based upon said first rail
pressure, said second rail pressure, and a period between said engine shutdown
and said second time,

wherein said fault diagnostic module diagnoses said fault when
said decay rate is greater than a predetermined value.
10. The fuel system diagnostic module of claim 9 wherein said first rail
pressure is determined at said engine shutdown.
11. The fuel system diagnostic module of claim 9 wherein said first rail
pressure is determined before said engine shutdown.
12. The fuel system diagnostic module of claim 8 wherein said second
rail pressure is determined at a predetermined time after said engine shutdown.
13. The fuel system diagnostic module of claim 8 wherein said fuel
system comprises said fuel rail, a fuel injector, and a fuel pump.

14. A method comprising:
determining first and second pressures of a fuel rail of a fuel system
at first and second times, respectively, wherein said second time is after
shutdown of an engine;
comparing a predetermined period with a period between said
engine shutdown and said second time; and
selectively diagnosing a fault in said fuel system based upon said
comparison.
15. The method of claim 14 further comprising:
determining a decay rate based upon said first rail pressure, said
second rail pressure, and said period; and
diagnosing said fault when said decay rate is greater than a
predetermined value.
16. The method of claim 15 wherein said first time occurs at said
engine shutdown.
17. The method of claim 15 wherein said first time occurs before said
engine shutdown.
18. The method of claim 14 wherein said second time occurs when
said second rail pressure is equal to a predetermined pressure.

19. The method of claim 14 further comprising diagnosing said fault
when said period is less than said predetermined period.
20. The method of claim 14 wherein said fuel system comprises said
fuel rail, a fuel injector, and a fuel pump.
21. A method comprising:
determining first and second pressures of a fuel rail of a fuel system
at first and second times, respectively, wherein said second time is after engine
shutdown;
comparing said second pressure with a predetermined pressure;
and
selectively diagnosing a fault in said fuel system based upon said
comparison.
22. The method of claim 21 further comprising:
determining a decay rate based upon said first rail pressure, said
second rail pressure, and a period between said engine shutdown and said
second time; and
diagnosing said fault when said decay rate is greater than a
predetermined value.
2 . The method of claim 22 wherein said first rail pressure is
determined at said engine shutdown.

24. The method of claim 22 wherein said first rail pressure is
determined before said engine shutdown.
25. The method of claim 21 wherein said second rail pressure is
determined at a predetermined time after said engine shutdown.
26. The method of claim 21 wherein said fuel system comprises said
fuel rail, a fuel injector, and a fuel pump.

A fuel system diagnostic module comprises a pressure module and a fault
diagnostic module. The pressure module determines first and second pressures
of a fuel rail of a fuel system at first and second times, respectively. The second
time is after shutdown of an engine. The fault diagnostic module selectively
diagnoses a fault in the fuel system based upon a comparison of a
predetermined period with a period between the engine shutdown and the
second time.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=nr4da29KlYGvQkjY2gdYFw==&loc=wDBSZCsAt7zoiVrqcFJsRw==

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Patent Number

270377

Indian Patent Application Number

1992/KOL/2008

PG Journal Number

51/2015

Publication Date

18-Dec-2015

Grant Date

16-Dec-2015

Date of Filing

12-Nov-2008

Name of Patentee

GM GLOBAL TECHNOLOGY OPERATIONS, INC.

Applicant Address

300 GM RENAISSANCE CENTER DETRIOT, MICHIGAN

Inventors:

#	Inventor's Name	Inventor's Address
1	OMAR ELKOLALY	3939 WARREN CT. ANN ARBOR, MI 48105

PCT International Classification Number

F02M37/00;F02D41/30

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	12/194,074	2008-08-18	U.S.A.