Diagnostic systems and methods for the high pressure side of fuel systems in common fuel rail engines
View Patent ↗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.
1. A fuel system diagnostic module comprising:
a pressure module that monitors a rail pressure in a fuel rail of a fuel system of an engine;
a timer module that determines a period between shutdown of the engine and a time after the engine shutdown when the rail pressure transitions from a first rail pressure that is greater than a predetermined rail pressure to a second rail pressure that is less than the predetermined rail pressure; and
a fault diagnostic module that selectively diagnoses a fault in the fuel system based upon a comparison of the period and a predetermined period.
2. The fuel system diagnostic module of claim 1 further comprising a decay calculation module that determines a decay rate based upon the second rail pressure, a third rail pressure before the second rail pressure, and the period,
wherein the fault diagnostic module diagnoses the fault when the decay rate is greater than a predetermined value.
3. The fuel system diagnostic module of claim 2 wherein the third rail pressure is measured at the engine shutdown.
4. The fuel system diagnostic module of claim 2 wherein the third rail pressure is measured before the engine shutdown.
5. The fuel system diagnostic module of claim 1 wherein the fault diagnostic module diagnoses the fault when the period is less than the predetermined period.
6. The fuel system diagnostic module of claim 1 wherein the fuel system comprises the fuel rail, a fuel injector, and a fuel pump.
7. A method comprising:
monitoring a rail pressure in a fuel rail of a fuel system of an engine;
determining a period between shutdown of the engine and a time after the engine shutdown when the rail pressure transitions from a first rail pressure that is greater than a predetermined rail pressure to a second rail pressure that is less than the predetermined rail pressure; and
selectively diagnosing a fault in the fuel system based upon a comparison of the period and a predetermined period.
8. The method of claim 7 further comprising:
determining a decay rate based upon the second rail pressure, a third rail pressure measured before the second rail pressure, and the period; and
diagnosing the fault when the decay rate is greater than a predetermined value.
9. The method of claim 8 further comprising measuring the third rail pressure before the engine shutdown.
10. The method of claim 8 further comprising measuring the third rail pressure at the engine shutdown.
11. The method of claim 7 further comprising diagnosing the fault when the period is less than the predetermined period.
12. The method of claim 7 wherein the fuel system comprises the fuel rail, a fuel injector, and a fuel pump.
13. A method comprising:
monitoring a rail pressure in a fuel rail that receives fuel from an engine driven fuel pump and that provides the fuel to one or more fuel injectors of an engine;
determining a period between shutdown of the engine and a time after the engine shutdown when the rail pressure transitions from a first rail pressure that is greater than a predetermined rail pressure to a second rail pressure that is less than the predetermined rail pressure; and
selectively indicating that the one or more fuel injectors are reliable based on a comparison of the period and a predetermined period.
14. The method of claim 13 further comprising selectively indicating that the one or more fuel injectors are reliable when the period is greater than the predetermined period.
15. The method of claim 13 further comprising:
determining a decay rate of the rail pressure based on the second rail pressure, the period, and a third rail pressure that is measured one of before and at the engine shutdown; and
indicating that the one or more fuel injectors are reliable when the decay rate is less than a predetermined value.
16. The method of claim 13 wherein the engine driven fuel pump receives the fuel from a low pressure fuel pump at a first predetermined pressure and pressurizes the fuel within the fuel rail based on a second predetermined pressure,
wherein the second predetermined pressure is greater than the first predetermined pressure.