The bowl vent valve controls vapor in the feedback carburetor bowl. While the engine is running, the intake manifold vacuum acts on the diaphragm to close the bowl vent valve so the carburetor bowl opens the air vent. When the engine stops, the bowl vent valve opens to connect the carburetor to the canister, causing fuel vapor to be absorbed by the canister.
See Figure 1Feedback Carburetor
- Perform this test with the engine cold.
- Remove the air cleaner.
- Disconnect the bowl vapor hose from the Bowl Vent Valve (BVV).
- Apply a vacuum of 6 in. Hg to the bowl vent valve.
- With the engine OFF, the valve should not hold vacuum.
- Start the engine and reapply the vacuum. With the engine running, the valve should hold vacuum.