Component Description
Pressure control solenoid valve
PCV controls the fuel tank pressure to be equal to the atmospheric air pressure. Normally, the solenoid is set to OFF. The valve opens and closes mechanically in accordance with the pressure difference between tank and atmospheric air, or tank and canister.
The valve is forcibly opened by setting the solenoid to ON at the time of diagnosis.
Valve Operation and Air Flow
In the figure below, divided by the diaphragm, the part above X is charged with atmospheric air pressure, and the part below X is charged with tank pressure. Also, the part above Y is charged with tank pressure, and the part below Y is charged with canister pressure.
If the atmospheric air pressure port is A, tank pressure port is B, and canister pressure port is C, the air flows according to pressure difference from each port as shown in the table below.
| Condition of pressure | Flow |
|---|---|
| A < B (solenoid OFF) | B → C |
| B < C (solenoid OFF) | C → B |
| Solenoid ON | B ← → C |
When A < B (solenoid OFF)
When B < C (solenoid OFF)
When Solenoid is ON
Drain valve
Drain valve controls the ambient air to be introduced to the canister.