Bronco L6-300 4.9L VIN Y 1-bbl (1983)
Vacuum Delay Valve: Description and Operation
Fig. 32 Vacuum delay valve--VDV
This valve, Fig. 32, used on some vehicles, further reduces emissions by delaying the spark advance during rapid acceleration and by cutting off
advance immediately upon deceleration. This is a one-way valve and will not operate if installed backwards.
On all systems which employ the dual diaphragm distributor, the line which has high vacuum at idle (normal operating temperature) is
connected to the secondary (retard) side of the distributor vacuum advance unit. This is the connection closest to the distributor cap.
