Abstract: An oxygen storage capacity (OSC) monitoring system for a vehicle having a catalytic converter includes an inlet oxygen sensor that generates an inlet sensor signal (ISS) based on an oxygen content of exhaust flowing into the catalytic converter. A control module receives the ISS, increases a closed loop fuel control gain during a first period and determines a fuel control factor based on the ISS during the first period. The control module determines an OSC when an average value of the fuel control factor is greater than a first value and is less than a second value during the first period.

Abstract: A fuel system pressure valve includes is interposed in a fuel line between a fuel pump and a fuel rail for controlling fuel flow from the pump to the rail and from the rail to the pump. The valve includes a valve housing having a pair of half sections to form a valve chamber. A check valve is mounted in the chamber and is operable to allow fuel flow from the pump to the fuel line upon the fuel pump delivering a predetermined fuel pressure to the fuel line. A pressure relief valve is mounted within the chamber parallel to the check valve and is operable to allow fuel in the fuel line to flow through the housing to the fuel pump upon fuel pressure in the fuel line exceeding a predetermined relief pressure. In addition, a parasitic flow orifice is mounted in fluid communication with the valve chamber and allows fuel in the valve chamber to flow through the orifice to a fuel tank when valve chamber pressure is below a predetermined valve chamber pressure.