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EVAP LEAK DETECTION PUMP REFERENCE ORIFICE CLEANING METHOD

IP.com Disclosure Number: IPCOM000241507D
Publication Date: 2015-May-07
Document File: 1 page(s) / 250K

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The IP.com Prior Art Database

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EVAP LEAK DETECTION PUMP REFERENCE ORIFICE CLEANING METHOD

Vehicles sold in North America are required to perform Evap leak detection. Green states are required to monitor for 0.02" leaks. Federal states are required to perform 0.04" leak check.For HEV, engine run time is limited; hence a vacuum pump is required for leak detection. One such vacuum pump is the ELCM.ELCM test sequence begins by obtaining a "reference check" by turning on the pump and evacuating a small volume where an internal 0.02" reference orifice is located. Reference vacuum value obtained becomes the pass/fail threshold. The reference orifice is used to compensate for environmental conditions.Change Over Valve(COV) is then energized and pump evacuates the entire Evap system.In absence of a leak, the pump pulls down to the reference check value.In presence of a leak, pump does NOT pull down to the reference check value. The reference orifice is critical to the capability of the ELCM. Reference orifice determines the pass/fail threshold. If reference orifice becomes contaminated by debris from the environment (dirt, salt, carbon dust from canister) the pass/fail threshold becomes artificially high and monitor sets false DTCs. Clogging the orifice effectively makes it smaller, (i.e., a 0.010" orifice due to blockages),and the OBD monitor starts to detect 0.01" leaks in the system. This is a producer risk since CARB only mandates monitoring leaks >= 0.02".

Method

This method performs onboard...