FUEL SYSTEM DIAGNOSTICS

• US 20140060160A1
• Filed: 09/05/2012
• Published: 03/06/2014
• Est. Priority Date: 09/05/2012
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Pursifull, Ross Dykstra
• Granted Patent: US 9,322,366 B2
• Time in Patent Office: Days
• US Class Current: 73/40
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system
• CPC Class Codes: G01M 15/09 by monitoring pressure in fluid ducts, e.g. in lubrication or cooling parts
• CPC Class Codes: G01M 3/28 for pipes, cables or tubes; for pipe joints or seals; for valves ; for welds

Abstract

Methods and systems are provided for detecting a fuel system leak. While a system vacuum pump is operated to supply vacuum to a vacuum consumption device, air exhausted from the vacuum pump is routed to a fuel system to apply positive pressure thereon. A fuel system leak is identified based on a rate of decay of the pressure applied from the vacuum pump.

Claims

1. A method for an engine, comprising:

indicating fuel system degradation in response to a change in fuel system pressure following application of a positive pressure generated at an electrically-driven vacuum pump.

2. The method of claim 1, wherein the application of a positive pressure generated at an electrically-driven vacuum pump includes routing air exhausted from an electrically-driven vacuum pump to a canister of the fuel system.

3. The method of claim 2, wherein the electrically-driven vacuum pump is coupled to a vacuum consumption device.

4. The method of claim 3, wherein the vacuum consumption device is a brake booster.

5. The method of claim 4, wherein routing air exhausted from the electrically-driven vacuum pump includes routing air exhausted from the electrically-driven vacuum pump during pump actuation, the electrically-driven vacuum pump actuated responsive to brake application.

6. The method of claim 2, further comprising, indicating fuel system degradation in response to a change in fuel system pressure following application of a negative pressure generated at the electrically-driven vacuum pump.

7. The method of claim 6, wherein the indicating includes, indicating fuel system degradation in response to the change in fuel system pressure following application of the positive or negative pressure being faster than a threshold rate.

8. A method for an engine, comprising:

during a first condition, applying positive pressure generated at the electrically-driven vacuum pump on the fuel system;

during a second condition, applying negative pressure generated at an electrically-driven vacuum pump on a fuel system; and

during both the first and second conditions, indicating fuel system degradation in response to a change in fuel system pressure following application of pressure generated at the vacuum pump.

9. The method of claim 8, wherein during the second condition, applying negative pressure generated at an electrically-driven vacuum pump includes operating the vacuum pump and routing vacuum from a first outlet of the pump to the fuel system while routing air exhausted from a second, different outlet of the pump to an engine intake manifold.

10. The method of claim 9, wherein during the first condition, applying positive pressure generated at the electrically-driven vacuum pump includes operating the vacuum pump and routing air exhausted from the second outlet of the vacuum pump to the fuel system.

11. The method of claim 10, wherein the electrically-driven vacuum pump is coupled to a vacuum consumption device, the vacuum consumption device including a brake booster.

12. The method of claim 11, wherein during the first condition, vacuum is routed from the first outlet of the vacuum pump to the vacuum consumption device.

13. The method of claim 8, wherein indicating fuel system degradation in response to a change in fuel system pressure following application of pressure includes indicating a fuel system leak based on an absolute rate of change in the fuel system pressure being higher than a threshold rate.

14. The method of claim 13, wherein an orifice size of the fuel system leak is based on a difference between the absolute rate of change in the fuel system pressure and the threshold rate.

15. The method of claim 8, wherein the fuel system pressure is a fuel tank pressure estimated by a pressure sensor coupled between a fuel tank and a canister of the fuel system.

16. The method of claim 8, wherein during the first condition, while applying positive pressure, adjusting an intake throttle position in a first direction, and during the second condition, while applying negative pressure, adjusting the intake throttle position in a second, opposite direction.

17. A hybrid vehicle system, comprising:

an engine including an intake manifold;

a fuel system including a fuel tank coupled to a canister, the canister coupled to the intake manifold via a canister purge valve;

a vacuum consumption device;

an electrically driven vacuum pump including a first outlet for delivering vacuum and a second outlet for exhausting air, wherein the first outlet is selectively couplable to the vacuum consumption device or the intake manifold, and wherein the second outlet is selectively couplable to the fuel system or the intake manifold;

a pressure sensor coupled to the fuel system for estimating a fuel system pressure; and

a controller with computer readable instructions for,

while routing vacuum from the first outlet of the vacuum pump to the vacuum consumption device, exhausting air from the second outlet of the vacuum pump to the canister to apply a positive pressure on the fuel system; and

indicating a fuel system leak based on a rate of pressure decay from the fuel system following the application of positive pressure.

18. The system of claim 17, wherein the controller includes further instructions for,

routing vacuum from the first outlet of the pump to the canister while exhausting air from the second outlet to the intake manifold to apply a negative pressure on the fuel system;

and

indicating a fuel system leak based on a rate of vacuum decay from the fuel system following the application of negative pressure.

19. The system of claim 18, wherein the fuel system pressure is a fuel tank pressure, and wherein the pressure sensor is coupled between the fuel tank and the canister.

20. The system of claim 19, wherein routing vacuum from the first outlet of the vacuum pump to the vacuum consumption device and exhausting air from the second outlet of the vacuum pump to the canister to apply a positive pressure on the fuel system includes opening the canister purge valve and closing each of a first solenoid valve coupled between the first outlet and the fuel system and a second solenoid valve coupled between the second outlet and the intake manifold, and wherein routing vacuum from the first outlet of the vacuum pump to the canister and exhausting air from the second outlet of the vacuum pump to the intake manifold to apply a negative pressure on the fuel system includes closing the canister purge valve and opening each of the first solenoid valve coupled between the first outlet and the fuel system and the second solenoid valve coupled between the second outlet and the intake manifold.