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Temperature, vapor space and fuel volatility-compensated evaporative emissions system leak test method

  • US 6,854,321 B2
  • Filed: 06/30/2003
  • Issued: 02/15/2005
  • Est. Priority Date: 06/30/2003
  • Status: Expired due to Fees
First Claim
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1. A method for leak-testing a motor vehicle fuel tank and associated evaporative emissions control system, comprising:

  • the use of a pressure regulator system, comprised of orifices attached to a nitrogen or compressed air source, to deliver gas from such source at a specified pressure measured by a pressure transducer, to the evaporative emissions system of a gasoline-powered motor vehicle until the pressure of such system is approximately 14 inches of water (about 0.45 pounds per square inch) above atmospheric pressure;

    the use of look-up tables to determine an appropriate pass-fail decision cutpoint, based on measured drop in tank pressure over a 120-second period, such tables incorporating the estimated liquid fuel temperature, and time of year (affecting fuel volatility) into the decision cutpoint;

    the use of decision-tree logic to determine whether a vehicle has a leak sufficiently large that pressurization is impossible and the vehicle is deemed to fail the test;

    the use of an electronic interface between the pressurization device and an on-line computer system which issues commands for the effective control of the pressurization device.

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