F 150 4WD Pickup L6-300 4.9L (1983)
Bowl Vent Valve: Testing and Inspection
Vacuum/Thermostatic Bowl Vent Valve
1.
With valve temperature at or above 120°F, ensure that air flows between carburetor port and canister port when no vacuum is applied to vacuum
signal nipple.
2.
With valve temperature at or above 120°F, apply vacuum to vacuum signal nipple and ensure that air does not flow between carburetor port and
canister port.
3.
With valve temperature at or below 90°F, ensure that there is no or very little air flow between carburetor port and canister port, whether or not
vacuum is applied to vacuum signal nipple.