1982 C10 1/2 Ton Pickup 2WD L6-250 41L VIN D EGR Vacuum Delay Valve
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.