Abstract: A noise attenuation device for reducing resonance in a natural vacuum leak detector. The device includes a housing, a first connector connected to the housing, and a first fitting connected to the first connector. Also included is a second connector which is connected to the housing on an opposite end of the housing in relation to the first connector, and a second fitting connected to the second connector. A plurality of tubes is disposed within the housing between the first connector and the second connector such that air flows through the first fitting, the first connector, the plurality of tubes, through the second connector and the second fitting. A plurality of flow paths is created by the plurality of tubes, and the plurality of flow paths reduces the turbulence and the pulsation of air flow through the housing, reducing or eliminating resonance in the natural vacuum leak detector.

Abstract: A system and method for detecting leakage from a evaporative emission space of an automotive vehicle fuel system. A reciprocating pump is operated in a pressurizing mode to build pressure in the space toward a nominal test pressure. The pressurizing mode involves operating the pump in a repeating cycle wherein the pump operates alternately in an accelerated pumping mode and a natural frequency pumping mode. During the pressurizing mode, a characteristic of successive occurrences of the natural frequency pumping mode indicative of pressure in the space is measured. The number of times the cycle repeats is counted and compared to a predefined reference.

Abstract: In a purge mode, a purge flow path extends from atmosphere through the vent valve, through the evaporative emission space, and through the purge valve to the engine intake system. In a pre-conditioning phase of a leak verification mode, a pre-conditioning flow path extends from atmosphere through the vent valve and the purge valve to the engine intake system without passing through the evaporative emission space. In a test phase of the leak verification mode, a test path extends from the evaporative emission space through the dirty air port, through the canister medium, through the clean air port, and through the purge valve to the engine intake system.

Abstract: A module (22) for an on-board evaporative emission leak detection system that detects leakage from an evaporative emission space of a fuel system of an automotive vehicle. The module has a housing (50) that includes a first port (52) for communicating the housing to the evaporative emission space and a second port (86) for communicating the housing to atmosphere. The housing contains a particulate filter (84) through which the second port communicates with two parallel flow branches that extend within the housing to the first port. One branch contains a vacuum regulator valve (90), and the other, a solenoid-operated vent valve (88). During a leak detection test, the vent valve is operated closed, and a purge valve (20), that selectively communicates the evaporative emission space with the engine intake manifold, is operated open to cause vacuum to be drawn in the evaporative emission space. The vacuum regulator valve regulates evaporative emission space vacuum to a defined vacuum.

Abstract: A system and method for detecting leakage from a evaporative emission space of an automotive vehicle fuel system. A reciprocating pump is operated in a pressurizing mode to build pressure in the space toward a nominal test pressure. The pressurizing mode involves operating the pump in a repeating cycle wherein the pump operates alternately in an accelerated pumping mode and a natural frequency pumping mode. During the pressurizing mode, a characteristic of successive occurrences of the natural frequency pumping mode indicative of pressure in the space is measured. The number of times the cycle repeats is counted and compared to a predefined reference.

Abstract: A system and method for detecting leakage from a evaporative emission space of an automotive vehicle fuel system. A reciprocating pump is operated in a pressurizing mode to build pressure in the space toward a nominal test pressure. The pressurizing mode involves operating the pump in a repeating cycle wherein the pump operates alternately in an accelerated pumping mode and a natural frequency pumping mode. During the pressurizing mode, a characteristic of successive occurrences of the natural frequency pumping mode indicative of pressure in the space is measured. The number of times the cycle repeats is counted and compared to a predefined reference.