Fuel system diagnostics

• US 9,261,054 B2
• Filed: 03/23/2012
• Issued: 02/16/2016
• Est. Priority Date: 03/23/2012
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Peters, Mark W., Jentz, Robert Roy, Dudar, Aed M.
• Primary Examiner(s): Vo, Hieu T
• Assistant Examiner(s): Castro, Arnold
• Application Number:
  US13/429,120
• Publication Number:
  US 20130253799A1
• Time in Patent Office: 1,425 Days
• Field of Search: 123/516, 123/518, 123/519, 123/520, 123/515, 123/16
• US Class Current: 1/1
• CPC Class Codes: F02M 25/0818 having means for pressurising the evaporative emission space
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

Methods and systems are provided for detecting a fuel system leak. One or more of a boost pressure from a compressor and vacuum from an intake manifold is sequentially applied on a fuel tank. A leak is detected based on a subsequent change in fuel tank pressure.

Claims

1. A method for a boosted engine, comprising:

indicating fuel vapor system degradation in response to a change in fuel vapor system pressure following application of each of a positive pressure generated at a turbocharger and a negative pressure generated at an engine intake.

2. The method of claim 1, wherein each of the positive and negative pressures are applied through a canister to a fuel tank of the fuel vapor system.

3. The method of claim 2, wherein application of positive pressure on the fuel vapor system includes drawing boosted intake air from downstream of a compressor charge air cooler to the fuel tank via a regulator and a first check valve.

4. The method of claim 3, wherein application of negative pressure on the fuel vapor system includes drawing vacuum from an engine intake manifold, downstream of an intake throttle, to the fuel tank via a second check valve.

5. The method of claim 4, wherein the canister is coupled to the intake manifold via a canister purge valve, and wherein a positive pressure intake line of the fuel vapor system merges with a negative pressure intake line of the fuel vapor system upstream of the canister purge valve.

6. The method of claim 5, wherein during application of each of the positive pressure and the negative pressure, the canister purge valve is maintained open.

7. The method of claim 6, wherein indicating fuel vapor system degradation includes,

following application of the positive pressure, indicating degradation in response to a drop in fuel tank pressure being faster than a threshold;

and

following application of the negative pressure, indicating degradation in response to a drop in fuel tank vacuum being faster than a threshold.

8. The method of claim 7, wherein indicating degradation includes setting a diagnostic code.

9. The method of claim 4, further comprising, purging fuel vapors from the canister to the engine intake manifold following the application of positive or negative pressure, a duration of the purging adjusted based on whether positive or negative pressure was applied.

10. The method of claim 9, wherein the purging is continued for a shorter duration when the purging is performed after the application of negative pressure on the fuel vapor system, and wherein the purging is continued for a longer duration when the purging is performed after the application of positive pressure on the fuel vapor system.

11. The method of claim 4, further comprising,

while applying the positive pressure, adjusting an intake throttle position in a first direction;

and

while applying the negative pressure, adjusting the intake throttle position in a second, opposite direction.

12. An engine method, comprising:

sequentially applying each of a positive pressure from a turbocharger compressor and a negative pressure from an engine intake on a fuel tank; and

indicating fuel vapor system degradation based on a fuel tank pressure following application of the positive or negative pressure.

13. The method of claim 12, wherein the sequentially applying includes,

during a first condition, applying positive pressure on the fuel tank via a canister before applying negative pressure on the fuel tank via the canister, and monitoring a rate of change in fuel tank pressure following application of the positive or negative pressure;

and

during a second condition, applying negative pressure on the fuel tank via the canister before applying positive pressure on the fuel tank via the canister, and monitoring a rate of change in fuel tank pressure following application of the positive or negative pressure.

14. The method of claim 13, wherein the indicating includes, during each of the first and second conditions, indicating a fuel vapor system leak based on the rate of change in fuel tank pressure being larger than a threshold.

15. The method of claim 13, wherein applying positive pressure on the fuel tank includes drawing boosted intake air from downstream of a compressor charge air cooler to the fuel tank via a regulator and the canister, and wherein applying negative pressure on the fuel tank includes drawing vacuum from an engine intake manifold, downstream of an intake throttle, to the fuel tank via the canister.

16. An engine system, comprising:

an engine with an intake manifold and an exhaust manifold;

a turbocharger compressor coupled to a charge air cooler;

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

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

a controller with computer readable instructions for,

operating the fuel vapor system in a first mode with the canister purge valve open to draw boosted intake air from downstream of the charge air cooler into the fuel tank via the canister;

operating the fuel vapor system in a second mode with the canister purge valve open to draw intake manifold vacuum from downstream of a throttle into the fuel tank via the canister; and

during each of the first and second modes, indicating fuel vapor system degradation based on a rate of change in fuel system pressure following the drawing of intake air or vacuum.

17. The system of claim 16, wherein indicating fuel vapor system degradation includes, indicating a fuel system leak in response to an absolute rate of change in the fuel vapor system pressure being larger than a threshold.

18. The system of claim 16, wherein the fuel system pressure is a fuel tank pressure, and wherein the pressure sensor is coupled between the fuel tank and the canister.

19. The system of claim 16, wherein the controller includes further instructions for,

opening the canister purge valve to purge the canister for a first, longer duration after operating in the first mode;

and

opening the canister purge valve to purge the canister for a second, shorter duration after operating in the second mode.

20. The system of claim 16, wherein the controller includes further instructions for,

adjusting the throttle towards a more open position when operating in the first mode;

and

adjusting the throttle towards a more closed position when operating in the second mode.