Air Diverter Valve: Description and Operation

OPERATION
The bypass valve used on some engines, is in the normally closed position to allow pump air to flow freely through the valve fittings and into the exhaust manifold. When the throttle is closed quickly and engine manifold vacuum rises, the sudden increase in vacuum (sensed through a vacuum connection at the carburetor base) overcomes the diaphragm spring tension and momentarily moves the valve to the open position.

When the valve is in the open position, pump air flow is bypassed to atmosphere or "dumped" through a bronze silencer pressed into the outlet opening. This action is required to prevent a backfire in the exhaust system which could occur when the throttle is closed suddenly. This valve is operating normally when no exhaust system backfire occurs during rapid throttle closure.

Fig. 7 Diverter Valve:

The diverter valve, Fig. 7, when triggered by a sharp increase in manifold vacuum, supplies the intake manifold with fresh air to lean out the fuel/air mixture and prevent backfire.