Thermal Vent Valve

The thermal vent valve (TVV) is an important component in the vehicle’s evaporative emission control system. Here’s a breakdown of its function and operation:

1. Location: The TVV is typically situated in the canister vent line, which is part of the vehicle’s evaporative emission control system. This system is designed to capture and store fuel vapors from the fuel tank to prevent their release into the atmosphere.
2. Temperature Sensitivity: As a temperature-sensitive valve assembly, the TVV responds to changes in ambient temperature, particularly within the engine compartment. It is designed to open and close based on temperature thresholds to regulate the flow of vapors from the fuel tank.
3. Cold Engine Operation: When the engine is cold or operating at lower temperatures, the TVV remains closed. This prevents fuel tank vapors from escaping through the canister vent line and entering the engine or carburetor fuel bowl, where they could disrupt engine operation.
4. Hot Engine Operation: As the engine heats up during operation, the TVV detects the increase in temperature. At a predetermined temperature threshold, the TVV opens to allow the release of fuel tank vapors through the canister vent line. This prevents excessive pressure buildup in the fuel tank and ensures proper venting of vapors.
5. Preventing Vapor Release: By opening when the engine is hot, the TVV helps prevent fuel tank vapors from being vented through the carburetor fuel bowl. This ensures that the engine receives only the necessary air-fuel mixture for combustion, without the addition of unwanted fuel vapors.
6. Emissions Control: The function of the TVV is crucial for maintaining compliance with emissions regulations. By controlling the venting of fuel tank vapors based on engine temperature, it helps minimize evaporative emissions and contributes to overall vehicle emissions control.

Overall, the thermal vent valve plays a vital role in the evaporative emission control system by regulating the release of fuel tank vapors based on engine temperature. Its operation helps ensure proper engine performance, fuel efficiency, and emissions control under varying operating conditions.