VACUUM DECAY TESTING METHOD

• US 20100064774A1
• Filed: 09/02/2009
• Published: 03/18/2010
• Est. Priority Date: 09/12/2008
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Wright, Nick, Drane, Robin J.
• Granted Patent: US 8,327,691 B2
• Time in Patent Office: Days
• US Class Current: 73/40
• CPC Class Codes: F02M 25/0818 having means for pressurising the evaporative emission space
• CPC Class Codes: F02M 25/089 Layout of the fuel vapour installation

Abstract

A method and system are disclosed for determining whether a leak is present in an evaporative emission control system 10 for on-board diagnostic purposes. The method comprises predicting for a leak of predetermined size the time period required for the vacuum to fall from a predicted starting vacuum to a predetermined level of vacuum at which the state of a switch changes, checking at the end of the time period the state of the switch and using the state of the switch as an indication of whether a leak greater than the predetermined size is present in the evaporative emission control system 10.

Claims

1. A vacuum testing method for an evaporative emission control system, comprising:

applying a vacuum from an engine to an evaporative emission system during an engine stop sequence; and

indicating a leak is present in said evaporative emission system when a vacuum in the evaporative emission system is less than a threshold amount after a threshold amount of time.

2. The method of claim 1, wherein said vacuum is applied from said engine when a temperature is above a threshold temperature.

3. The method of claim 1, wherein said vacuum is applied from said engine when a temperature is below a threshold temperature.

4. The method of claim 1, wherein said vacuum is applied from said engine when of a level of a fuel tank in said evaporative emission system is above a threshold level.

5. The method of claim 1, wherein said vacuum is applied from said engine when of a level of a fuel tank in said evaporative emission system is below a threshold level.

6. The method of claim 1, wherein said vacuum is applied from said engine to a fuel tank.

7. The method of claim 1, wherein said threshold amount of time is related to an amount of fuel in a fuel tank.

8. The method of claim 1, wherein said threshold amount of time is related to said vacuum applied from said engine.

9. A vacuum testing system for a vehicle, comprising:

a vacuum control valve;

an enclosed volume for storing fuel or fuel vapor;

an engine; and

a controller for applying a vacuum from said engine to said enclosed volume by way of said vacuum control valve during an engine stop, and said controller indicating a leak is present in said enclosed volume when a vacuum in said enclosed volume is less than a threshold vacuum amount after a threshold amount of time.

10. The system of claim 9, wherein said controller varies said threshold amount of time in response to an amount of fuel stored in a fuel tank.

11. The system of claim 9, wherein said controller varies said threshold amount of time in response to said vacuum applied from said engine.

12. The system of claim 9, wherein said controller varies said threshold vacuum amount in response to a temperature.

13. The system of claim 9, wherein said controller performs a natural pressure decay leak test when a condition for applying said vacuum from said engine is not met.

14. The system of claim 13, wherein said condition is a temperature greater than a threshold level.

15. The system of claim 13, wherein said condition is a temperature less than a threshold level.

16. A vacuum testing method for an evaporative emission control system, comprising:

operating an engine to a generate vacuum;

applying said generated vacuum to a fuel system component after a request to stop said engine;

shutting down said engine;

indicating a leak of said fuel system component in response to a change of a vacuum in said fuel system component while said engine is stopped.

17. The method of claim 16, wherein said fuel system component is a fuel tank.

18. The method of claim 16, wherein said fuel system component is a canister.

19. The method of claim 16, wherein said vacuum is applied from said engine when a temperature is above a threshold temperature.