Abstract: A method and system for monitoring an evaporative purge system for malfunctions and leaks. First, a plurality of predetermined entry conditions are checked for satisfaction. If the plurality of predetermined entry conditions have been met, a flow of vapor in the evaporative purge system is determined. The evaporative purge system is then sealed from atmosphere so as to pull a vacuum on the fuel tank. The vacuum is compared to a predetermined vacuum range. If the vacuum is within the predetermined vacuum range, the vacuum is allowed to stabilize to obtain a stabilized vacuum level. A decrease in the stabilized vacuum level is determined after a predetermined amount of time to obtain a vacuum bleed-up. A vacuum bleed-up acceptance threshold is then determined based on the determined flow of vapor and the vacuum bleed-up is then compared to the vacuum bleed-up acceptance threshold.

Abstract: A diaphragm-activated control valve and system for both refuel and running loss venting of a fuel tank to a vapor trap. The control valve is connected to fill control and rollover valves in the fuel tank, and defines a separate venting flow path for each valve to the vapor trap. The control valve is responsive to pressure conditions at the filler pipe inlet to alternately open and close the flow paths. During refueling the control valve vents the tank through the fuel-level responsive fill control valve. When the filler pipe inlet is closed, the control valve switches to vent the tank through the rollover valve. In a preferred form, the control valve includes a liquid fuel drain to prevent its being disabled by fuel entering from the filler pipe inlet via the signal pressure line during refueling. The drain includes a reverse flow check valve to prevent vapor venting out the drain path to the atmosphere during refueling.

Abstract: An evaporative purge flow monitoring system is provided for use in a motor vehicle having a fuel tank and an internal combustion engine having an intake manifold. The purge flow monitoring system includes an evaporation canister in fluid communication with the fuel tank and a canister purge valve in fluid communication with the fuel tank and evaporation canister. A thermistor/resistor network is further provided in fluid communication with the canister purge valve and the intake manifold. An electronic engine control (EEC) assembly is similarly provided in electrical communication with the canister purge valve and the thermistor/resistor network such that the EEC is adapted to determine the voltage difference across the thermistor/resistor network resulting from discrete measurements within the canister purge valve duty cycle during a selected window of operation and compare the determined voltage difference to a calibrated difference so as to detect malfunctions of the canister purge valve.