Patent ID: 6561009
Filing Date: 2003-05-13
Classification: F02M

Abstract:
A leak test system for a motor vehicle fuel system that holds volatile liquid fuel for operating the vehicle, the leak test system comprising:a processor for establishing steps of a leak test; a pump for forcing air under pressure into vapor containment space of the fuel system during a leak test; a pump operator that operates the pump in accordance with steps established by the processor to cause the pump to create a superatmospheric target pressure in the space during an initial step of the leak test, and that after completion of the initial step and in the presence of leakage from the space, causes the pump to operate according to a repeating duty cycle wherein the duty cycle comprises forcing air into the space in successive bursts of individual air pulses, each of which bursts is delayed from an immediately prior burst by a time interval during which pressure in the space decays because of the leakage; and wherein the processor processes, according to an algorithm, data corresponding to the duty cycle and uses the result of such processing to set the number of individual air pulses in each of subsequent bursts for regulating the pressure in the space substantially to the target pressure, and upon attainment of substantial stability in regulation of the pressure in the space at the target pressure, as indicated by attainment of substantial stability of the duty cycle, the processor processes data correlated with the duty cycle to indicate leakage from the space.