E 350 Van L6-300 4.9L VIN E 1-bbl (1982)
Vacuum Delay Valve: Description and Operation
Cold Start Spark Hold (CSSH)
This system, used on some vehicles, provides momentary spark advance hold during acceleration when the engine is cold, to provide improved
cold engine acceleration.
When engine coolant temperature is less than 128~ F, the CSSH PVS is closed and the distributor vacuum signal travels through the restrictor.
When the engine is started cold, high vacuum acts on the vacuum advance unit to provide maximum advance. During acceleration, the high
vacuum in the vacuum advance unit is slowly bled down through the restrictor, providing a modified vacuum advance during the initial stage of
acceleration.
