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Perform the OBD Fuel System Leak Test upon Initial Engine Cold Start

IP.com Disclosure Number: IPCOM000240879D
Publication Date: 2015-Mar-09
Document File: 1 page(s) / 129K

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The IP.com Prior Art Database

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Perform the OBD Fuel System Leak Test upon Initial Engine Cold Start

     The OBD Leak Test occurs only when certain conditions exist in which the engine has the ability to purge stored hydrocarbons from the carbon canister (see Figure 1). This generally occurs for an extended period of time during the normal drive cycle after the vehicle has been running for an unknown period of time and certain operating conditions have been met. The vehicle's hardware and engine calibration strategy is able to measure and respond to the varying hydrocarbon concentration in the purge vapors drawn from the carbon canister to maintain stable engine operation. During this time, certain environmental factors which can influence the accuracy of and the ability to perform the leak test are introduced into the fuel storage and vapor recovery system. These uncontrolled noise factors include, but are not limited to: increased fuel temperature due to operation of the engine, change in the temperature of the surrounding environment, sudden changes in the barometric pressure or elevation and naturally occurring sloshing of the fuel within the tank during the normal drive cycle.

With the existing powertrain hardware and control strategy, the engine must be running to perform the large leak check. When the OBD leak test is performed, the Canister Vent Valve (CVV) (1) is closed and the engine pulls a vacuum through the Canister Purge Valve (CPV) (2). Vapors pulled from the carbon canister contain...