K 30 1 Ton Pickup 4WD L6-292 4.8L VIN T 1-bbl (1982)
Vacuum Delay Valve: Description and Operation
This valve--used on some vehicles--is located in the vacuum hose to the EGR valve. Its purpose is to delay vacuum from bleeding down at the
EGR valve. The vacuum is metered through a .005 inch orifice and requires up to 4 seconds from vacuum to bleed down completely.