E 250 Van L6-300 4.9L VIN E 1-bbl (1982)
Air Injection Bypass Valve: Description and Operation
Normally closed timed air bypass valve.
Normally open timed air bypass valve with vacuum vent.
Normally open timed air bypass valve less vacuum vent.
The air bypass system serves the same purpose as earlier types, but three different types of bypass valves are used, depending on application. These
are: normally closed bypass valve, normally open bypass valve with vacuum vent and normally open bypass valve without vacuum vent. They are
mounted "inline", or on the air pump, Figs. 85, 86 and 87.
The normally closed timed bypass valve, Fig. 85, is used on vehicles with catalytic converter. During normal operation, engine manifold vacuum
applied through the vacuum differential valve (VDV) holds the valve upward, allowing thermactor air to flow to the exhaust manifolds and blocking the
vent port. When intake manifold vacuum rises or drops sharply, the VDV operates and momentarily cuts off the vacuum to the bypass valve. The spring
