Evaporative system leak detection feature after a refueling event

• US 6,202,478 B1
• Filed: 08/17/1999
• Issued: 03/20/2001
• Est. Priority Date: 08/17/1999
• Status: Expired due to Term

• Current Assignee: FCA US LLC (Stellantis NV)
• Original Assignee: Daimler Chrysler Corporation (Mercedes-Benz Group AG)
• Inventors: Richardson, Roland T., Blomquist, William B., Dawson, Gary D.
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): CYGAN, MICHAEL T
• Application Number:
  US09/375,621
• Time in Patent Office: 581 Days
• Field of Search: 73/40, 73/405.R, 73/405.T, 73/497, 731/181, 731/15, 731/16, 701/31, 123/198.D, 123/520
• US Class Current: 73/49.7
• CPC Class Codes: F02M 25/0818 having means for pressurising the evaporative emission space

Abstract

A method is provided for testing an evaporative emission control system for a missing or loose fuel cap comprising detecting a refueling event and running a leak detection test of the evaporative emission control system to determine if a large leak is present. If a large leak is detected, the methodology sets a fault code and activates a driver warning lamp indicating a potential cap sealing problem. The leak detection test is repeatedly re-executed after the large leak is detected to determine when the large leak condition ceases. When the large leak condition ceases, the previously set fault code is removed and the driver warning lamp is deactivated. If the large leak does not cease and is detected again after the next refueling event when an opportunity for resealing the cap existed, a new fault code is set indicating that the potential cap sealing problem is a persistent problem so that the integrity of the evaporative system may need to be tested. After setting the new fault code, fuel cap specific leak detection testing is suspended until the condition is serviced and the fault code is cleared or a normal leak detection test determines that there is no longer a problem. If no large leak is detected, the fuel cap is assumed to be properly sealed.

Claims

1. A method of testing an evaporative emission control system for a fuel cap sealing problem comprising:

detecting a refueling event;

running a large leak test of said system to determine if a large leak is present;

setting a large leak fault code and activating a driver warning lamp indicating a potential cap sealing problem if said large leak is detected;

rerunning said large leak test repeatedly after said large leak is detected to determine when said large leak condition ceases;

removing said large leak fault code and deactivating said driver warning lamp when said large leak condition ceases;

detecting a next refueling event after said large leak is detected if said large leak condition has not ceased;

rerunning said large leak test after said next refueling event;

setting a persistent leak fault code indicating that said potential cap sealing problem had an opportunity to be corrected but was not if said large leak is again detected;

suspending subsequent large leak tests until said persistent leak fault code is cleared; and

suspending said large leak test from running after two consecutive normal leak tests indicate a leak is present in said system.

2. The method of claim 1 wherein said large leak test is run for an automatic transmission vehicle when said vehicle is in drive.

3. The method of claim 1 wherein said large leak test is run for a manual transmission vehicle when said vehicle changes speed from zero.

4. The method of claim 1 further comprising running a normal leak test to check said system for any leak if said large leak test does not detect said large leak.

5. The method of claim 1 further comprising suspending a running of a normal leak test to check said system for any leak if said large leak test detects said large leak.

6. The method of claim 1 further comprising disabling a purge system while said large leak test is running.

7. A method of testing an evaporative emission control system for a fuel cap sealing problem comprising:

detecting a refueling event;

running a large leak test of said system to determine if a large leak is present;

setting a large leak fault code, activating a driver warning lamp indicating a potential cap sealing problem, and suspending all normal leak tests to check said system for any leaks if said large leak is detected;

rerunning said large leak test repeatedly after said large leak is detected to determine if said large leak condition ceases and removing said large leak fault code and deactivating said driver warning lamp when said large leak condition ceases;

running said normal leak tests to check said system for any leaks if said large leak is not detected;

suspending further large leak tests from running if two consecutive normal leak tests detect a leak in said system;

detecting a next refueling event after said large leak is detected if said large leak condition has not ceased;

rerunning said large leak test after said next refueling event;

setting a persistent leak fault code indicating that said potential cap sealing problem had an opportunity to be corrected but was not if said large leak is again detected; and

suspending subsequent large leak tests until said persistent leak fault code is cleared.