Development and Validation of a 0.020″ Evaporative Leak Diagnostic System Utilizing Vacuum Decay Methods

This paper describes the development of a vacuum-decay based evaporative leak detection sub-system that meets the model year 2000 California Air Resources Board (CARB) requirements.¹ The diagnostic algorithm was developed and tested to create a production intent calibration. In addition, the calibration was validated during a four month test period of diagnostic and driveability performance, which included hot ambient, high volatility fuels, and altitude. It was found to detect 0.020 inch leaks reliably in-use, while being robust to misdiagnosis of smaller leaks.