Methods for detecting high pressure pump bore wear
Methods are provided for detecting high pressure pump bore wear, wherein wear between a piston and bore of a pump may cause an excessive amount of fuel to leak out of a compression chamber of the pump. A reliable method is needed that involves a pump performance model that incorporates a number of physical effects and is verified by real high pressure pump test data. A method is proposed that involves comparing a target pump rate based on the pump performance model to a real fuel injection rate in order to determine if an abnormal amount of fuel may be leaking from the high pressure pump.
1. A method, comprising:
while an engine is at an idling speed:
increasing pressure in a direct injection fuel rail of the engine to a threshold fuel rail pressure;
computing a target pump rate of a high pressure fuel pump based on a pump performance model;
computing a fuel injection rate;
comparing the target pump rate and the fuel injection rate; and
issuing a piston-bore interface leak result based on the comparison.
2. The method of claim 1 , wherein the piston-bore interface leak result is abnormal if the comparison determines that the target pump rate is higher than the fuel injection rate by more than a margin.
3. The method of claim 2 , wherein the margin includes a value of uncertainty.
4. The method of claim 1 , wherein the piston-bore interface leak result is normal if the comparison determines that the target pump rate is equal to or lower than the fuel injection rate plus a margin.
5. The method of claim 4 , wherein the margin includes a value of uncertainty.
6. The method of claim 1 , wherein the pump performance model is calculated based on fuel loss due to bulk modulus of the fuel and a dead volume of a compression chamber of the high pressure fuel pump, normal leak through the piston-bore interface, and a miscellaneous cause.
7. The method of claim 1 , wherein the pump performance model is calculated by a controller with computer readable instructions stored in non-transitory memory, the controller located on-board a vehicle with the engine.
8. The method of claim 1 , wherein the fuel injection rate is computed based on measurements from one or more sensors of the engine.
9. A method, comprising:
upon completion of an initiation condition and while an engine is at an idling speed:
increasing pressure in a direct injection fuel rail of the engine to a threshold fuel rail pressure;
computing a target pump rate of a high pressure fuel pump based on a pump performance model;
computing a fuel injection rate;
comparing the target pump rate and the fuel injection rate; and
diagnosing a piston-bore interface as abnormally leaking if the target pump rate is higher than the fuel injection rate by more than a margin.
10. The method of claim 9 , wherein the margin includes a value of uncertainty.
11. The method of claim 9 , wherein the pump performance model is calculated based on fuel loss due to bulk modulus of the fuel and a dead volume of a compression chamber of the high pressure fuel pump, normal leak through the piston-bore interface, and a miscellaneous cause.
12. The method of claim 9 , wherein the pump performance model is calculated by a controller with computer readable instructions stored in non-transitory memory, the controller located on-board a vehicle with the engine.
13. The method of claim 9 , wherein the fuel injection rate is computed based on measurements from one or more sensors of the engine.
14. The method of claim 9 , wherein the initiation condition includes a starting command by a person, an automatic starting command by an engine controller, or a starting command issued every time the engine enters the idling condition.
15. A fuel system, comprising:
one or more direct fuel injectors configured to inject fuel into one or more cylinders of an engine;
a fuel rail fluidly coupled to the one or more direct fuel injectors;
a high pressure fuel pump fluidly coupled to the fuel rail; and
a controller with computer readable instructions stored in non-transitory memory for:
while an engine is at an idling speed, increasing pressure in the fuel rail, computing a target pump rate of the high pressure fuel pump based on a pump performance model, computing a fuel injection rate, comparing the target pump rate and the fuel injection rate, and issuing a piston-bore interface leak result based on the comparison.
16. The fuel system of claim 15 , wherein the piston-bore interface leak result is abnormal if the comparison determines that the target pump rate is higher than the fuel injection rate by more than a margin.
17. The fuel system of claim 16 , wherein the margin includes a value of uncertainty.
18. The fuel system of claim 15 , wherein the piston-bore interface leak result is normal if the comparison determines that the target pump rate is lower than the fuel injection rate plus a margin.
19. The fuel system of claim 18 , wherein the margin includes a value of uncertainty.
20. The fuel system of claim 18 , wherein an amount of fuel leakage corresponding to the normal piston-bore interface leak result lubricates the high pressure fuel pump.