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. And 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.

Fig 1: Pressure Control Solenoid Valve Operation Diagram

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.

Fig 2: Pressure Control Solenoid Valve Operation And Air Flow Diagram

PRESSURE REFERENCE

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)

Fig 3: Pressure Control Solenoid Valve Operation Diagram - When A < B (Solenoid OFF)

When B < C (solenoid OFF)

Fig 4: Pressure Control Solenoid Valve Operation Diagram - When B < C (Solenoid OFF)

When Solenoid is ON

Fig 5: Pressure Control Solenoid Valve Operation Diagram - When Solenoid Is ON

Drain valve

Drain valve controls the ambient air to be introduced to the canister.

Fig 6: Drain Valve Controls Air Flow Diagram