Abstract: In a system for delivering air from an air pump to the exhaust system of an internal combustion engine, an air diverter valve assembly has a regulating control responsive to air pump discharge pressure which positions the diverter valve member to divert excess air flow away from the exhaust system when the pressure exceeds a selected value. The assembly also has a timed anti-backfire provision effective to override the regulating control and divert all air flow to the atmosphere upon a sudden decrease in induction manifold pressure.

Abstract: In a system for delivering air from an air pump to an exhaust system and accessories for an internal combustion engine, an air flow control unit has a high pressure relief valve, an outlet open to the exhaust system, a vent open to the atmosphere and an outlet open to the accessories with a check valve therein. A valve member is movable in response to an engine signal between a first position closing the exhaust system outlet and a second position closing the vent; and a low pressure relief valve is included in the vent to maintain a minimum low pressure in the unit when the valve member is in its first position.