Abstract: A tester and method for testing for a leak in an evaporative-emissions system of a motor vehicle comprise a/an power supply, computer, display communicating with the computer, analog-to-digital board communicating with the power supply and computer, pressure sensor communicating with the board, housing into which the power supply, board, and sensor are integrated, stationary enclosure, and test connection including a hose to the enclosure. A fuel-vapor pressure-rise rate is recorded with an engine of a motor vehicle turned “off.” A value is recorded that directly correlates with an out-gassing effect created by a volume, blend, and temperature of fuel. A “purge” cycle occurs at idling of the vehicle within a short period of time. The engine applies a vacuum to a fuel-delivery system of the vehicle. Vacuum decay is recorded. A leak rate is determined by off-setting the recorded fuel-vapor pressure-rise rate with the recorded vacuum decay.

Abstract: A tester and method for testing for a leak in an evaporative-emissions system of a motor vehicle comprise a/an power supply, computer, display communicating with the computer, analog-to-digital board communicating with the power supply and computer, pressure sensor communicating with the hoard, housing into which the power supply, board, and sensor are integrated, stationary enclosure, and test connection including a hose to the enclosure. A fuel-vapor pressure-rise rate is recorded with an engine of a motor vehicle turned “off.” A value is recorded that directly correlates with an out-gassing affect created by a volume, blend, and temperature of fuel. A “purge” cycle occurs at idling of the vehicle within a short period of time. The engine applies a vacuum to a fuel-delivery system of the vehicle. Vacuum decay is recorded. A leak rate is determined by off-setting the recorded fuel-vapor pressure-rise rate with the recorded vacuum decay.