G 20 3/4 Ton Van V8-305 5.0L VIN F 4-bbl (1982)
Thermal Vacuum Valve: Testing and Inspection
EGR-TVS
WITH ENGINE HOT
1. Disconnect EGR valve vacuum hose from EGR valve and connect a vacuum gauge to hose.
2. Start engine and with transmission in Park or Neutral partially open throttle. As throttle opens, a vacuum increase should be noted on the vacuum
gauge.
3. If there is a vacuum increase, EGR-TVS is operating properly.
4. If there is no vacuum increase, disconnect carburetor to EGR-TVS hose and connect vacuum gauge to hose.
5. Open throttle, a vacuum increase should be noted on vacuum gauge. If there is no vacuum increase,repace EGR-TVS.
6. If there still is no vacuum increase, check for plugged or damaged hose or carburetor.
WITH ENGINE COLD
1. Drain coolant until coolant level is below EGR-TVS.
2. Disconnect vacuum hoses and remove switch.
3. Check switch to ensure that it is not damaged.
4. Connect a vacuum hose to the lower nipple on switch, marked "C" or "CARB". Connect a vacuum gauge to upper nipple, marked "E" or EGR".
5. Place switch in warm water(approximately 75 F) and submerge completely for 2 minutes while stirring the water.
6. Apply 12 inches Hg to hose on the lower nipple of switch. The switch should close. If switch does not close, replace EGR-TVS.
NOTE: Leakage of up to 2 inches Hg of vacuum in 2 minutes is allowable and does not mean switch is defective.
NOTE: Refer to the number stamped on the base of the switch or valve for calibrated switching or activation temperatures.
