Air By-Pass Valve

The air by-pass valve is located between the air injection pump outlet and the check valve to 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 high intake manifold vacuum and diverts air from pump back into pump inlet hose instead of into exhaust manifold.