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EVAP LEAK DETECTION METHOD FOR HEAVY DUTY PROGRAMS

IP.com Disclosure Number: IPCOM000243424D
Publication Date: 2015-Sep-21
Document File: 1 page(s) / 255K

Publishing Venue

The IP.com Prior Art Database

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EVAP LEAK DETECTION METHOD FOR HEAVY DUTY PROGRAMS

Vehicles sold in North America are required to perform Evap leak detection as part of OBDII requirements. Green states are required to monitor for 0.02" leaks as part of the Clean Air Act Section 177. Federal states currently require a 0.04" Evap leak check.Heavy Duty (HD) programs (> 14000 lbs GVW) only require a 0.150" Evap leak check. Evap systems, whether green, federal or HD have similar Evap hardware. Evap systems consist of a CVS valve to close and seal the system and a FTPT sensor to monitor the pressure in the Evap system when performing leak detection.There are many methods for performing the leak detection, such as engine vacuum evacuation, active pump, EONV after key off, etc. While 0.02" and the 0.04" monitor require a FTPT sensor and a CVS for better monitor robustness since noise factors such as fuel vaporization can influence the results, the 0.150" leak is a crude gross leak check (gas cap off for example) and the need for an expensive variable output sensor is not necessary.

Method

This method reduces the cost for a HD vehicle Evap system by replacing the FTPT with a pressure on/off switch and replacing the CVS with a normally open spring loaded pressure actuated check valve. Pressure switches and check valves are much cheaper than FTPT and CVS.After key off when engine comes to a rest (no spin), the starter motor is engaged in reverse and the CPV is opened to pressurize the Evap system. The...