System and methods for fuel system recirculation tube diagnostic

Patent metadata

Field	Value
Publication number	US-9989018-B2
Application number	US-201614993314-A
Country	US
Kind code	B2
Filing date	Jan 12, 2016
Priority date	Jan 12, 2016
Publication date	Jun 5, 2018
Grant date	Jun 5, 2018

Abstract

Methods and systems are provided for indicating restrictions in a fuel system vapor recirculation line. In one example, a fuel tank is evacuated responsive to a fuel level below a threshold, and if the vacuum is relieved via a negative pressure relief valve in a capless fuel filler system, the negative pressure relief valve is indicated to be functional such that, responsive to a fuel level greater than a threshold, the fuel system may be evacuated and a restriction may be indicated in the vapor recirculation line responsive to the negative pressure valve not relieving the applied vacuum. In this way, restrictions in the vapor recirculation line may be rapidly diagnosed and excessive loading of a fuel vapor canister may be prevented, thus reducing the potential for evaporative emissions being released to the atmosphere and prolonging fuel vapor canister function.

First claim

The invention claimed is:

1. A method comprising:
responsive to a fuel tank fill level below a first threshold, applying vacuum to a fuel system to generate a first fuel system pressure profile;
responsive to a fuel tank fill level above a second threshold, applying vacuum to the fuel system to generate a second fuel system pressure profile; and
indicating a restriction in a vapor recirculation line based on the first and second fuel system pressure profiles, wherein:
a fuel tank is coupled in the fuel system within a vehicle, wherein the pressure profiles are pressure profiles over time, and wherein the fuel tank is coupled to a fuel filler neck via a spud valve, the fuel filler neck coupled to a negative pressure relief valve;
taking an action in response to the indicated restriction; and
wherein the first threshold comprises a fuel level below the spud valve, and wherein the second threshold comprises a fuel level above the spud valve, wherein the fuel tank fill level below the first threshold comprises a first condition and the fuel tank fill level above the second threshold comprises a second, different, condition, wherein none of the pressure profile of the first condition overlaps a duration of the pressure profile of the second condition.

2. The method of claim 1 , wherein indicating the restriction in the vapor recirculation line further comprises:
indicating the restriction responsive to both the first fuel system pressure profile including a vacuum relief inflection point during applying vacuum in the first condition, and the second fuel system pressure profile not including a vacuum relief inflection point during applying vacuum in the second condition.

3. The method of claim 1 , wherein the first condition further comprises:
routing vacuum through the fuel tank to the negative pressure relief valve via the fuel filler neck.

4. The method of claim 1 , wherein the second condition further comprises:
routing vacuum to the negative pressure relief valve via the vapor recirculation line.

5. The method of claim 2 , further comprising:
indicating the negative pressure relief valve is functional responsive to an indication of a vacuum relief inflection point during applying vacuum in the first condition; and
indicating an absence of restriction in the vapor recirculation line responsive to an indication of a vacuum relief inflection point during applying the vacuum in the second condition, wherein it was previously indicated that the negative pressure relief valve is functional.

6. The method of claim 2 , wherein, during applying vacuum during both the first condition and the second condition, a vacuum relief inflection point corresponding to the first fuel system pressure profile and a vacuum relief inflection point corresponding to the second fuel system pressure profile indicates opening of the negative pressure relief valve.

7. The method of claim 6 , wherein both the first condition and the second condition further comprise:
stopping applying vacuum and relieving fuel system vacuum to atmosphere if a threshold vacuum level is reached, the threshold vacuum level comprising a vacuum level greater than a level expected to actuate the negative pressure relief valve.

8. The method of claim 2 , further comprising:
fluidically coupling the fuel system to a fuel vapor canister configured within an evaporative emissions control system by opening a fuel tank isolation valve;
wherein applying vacuum to the fuel system includes opening the fuel tank isolation valve, and activating a vacuum pump positioned within a vent line between the fuel vapor canister and atmosphere to draw vacuum on the evaporative emissions control system and the fuel system.

9. The method of claim 8 , further comprising:
prior to applying vacuum to the fuel system,
indicating a reference vacuum level by applying vacuum via the vacuum pump to a reference orifice; and

during applying vacuum to the fuel system,
indicating undesired evaporative emissions responsive to a fuel system vacuum level less than the reference vacuum level after a predetermined time period.

10. The method of claim 9 , further comprising:
responsive to an indication of fuel system vacuum greater than or equal to the reference vacuum level after the predetermined time period:
maintaining applying vacuum to the fuel system during the first condition and the second condition.

11. A method comprising:
during evacuating an evaporative emissions control system and a fuel system to conduct an evaporative emissions test with an onboard vacuum pump;
monitoring pressure in the evaporative emissions control system and the fuel system; and
responsive to an indication of an absence of undesired evaporative emissions:
in a first condition, including a fuel level in a fuel tank below a first threshold level, maintaining evacuating the evaporative emissions control system and the fuel system and indicating a negative pressure relief valve in a capless fuel filler system is functional responsive to a vacuum relief inflection point; and
in a second condition, including the fuel level in the fuel tank above a second threshold level and an indication that the negative pressure relief valve is functional, maintaining evacuating the evaporative emissions control system and the fuel system and indicating a restriction in a fuel system vapor recirculation line responsive to an absence of a vacuum relief inflection point.

12. The method of claim 11 , further comprising:
fluidically coupling the fuel tank to the negative pressure relief valve in the capless fuel filler system via a fuel filler neck, the fuel filler neck coupled to the fuel tank via a spud valve;
wherein the first threshold level comprises a fuel level below the spud valve, and wherein the second threshold level comprises a fuel level above the spud valve.

13. The method of claim 12 , wherein the first condition includes routing vacuum to the negative pressure relief valve via the fuel filler neck through the spud valve, the fuel filler neck comprising a less restrictive path to the negative pressure relief valve than a path through the fuel system vapor recirculation line.

14. The method of claim 11 , wherein the second condition includes routing vacuum to the negative pressure relief valve via the fuel system vapor recirculation line.

15. The method of claim 11 , further comprising:
prior to evacuating the evaporative emissions control system and the fuel system to conduct the evaporative emissions test:
activating the onboard vacuum pump;
drawing a vacuum across a reference orifice; and
determining a reference vacuum level;

wherein, during evacuating the evaporative emissions control system and the fuel system, an indication of an absence of undesired evaporative emissions includes attaining a vacuum level in the evaporative emissions control system and the fuel system equal to or greater than the reference vacuum level after a predetermined time period.

16. The method of claim 11 , wherein both the first and second conditions further comprise:
stopping maintaining evacuating the evaporative emissions control system and the fuel system responsive to a vacuum level in the evaporative emissions control system and the fuel system reaching a second threshold vacuum level, wherein a vacuum relief inflection point in both the first condition and the second condition is not indicated, the vacuum relief inflection point in both the first condition and the second condition comprising opening of the negative pressure relief valve.

17. The method of

Assignees

• Ford Global Tech Llc

Inventors

• Dudar Aed M

Classifications

• F02D41/0045

  Estimating, calculating or determining the purging rate, amount, flow or concentration · CPC title

• F02M25/0836

  Arrangement of valves controlling the admission of fuel vapour to an engine, e.g. valve being disposed between fuel tank or absorption canister and intake manifold · CPC title

• F02M25/0854

  Details of the absorption canister · CPC title

• F02M25/0818 Primary

  having means for pressurising the evaporative emission space · CPC title

• F02M25/0809

  Judging failure of purge control system · CPC title