Air By-Pass Valve

The air by-pass valve is located between the air injection pump outlet and the check valve to help prevent abnormal combustion in the exhaust system. During sudden deceleration, a high amount of unburned gases are discharged through the engine into the exhaust manifold. To prevent this condition, the air by-pass valve senses the high intake manifold vacuum and diverts air from the pump back into pump inlet hose instead of the exhaust manifold.