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: Identifying Components Pressure Control Solenoid Valve

  Courtesy of SUBARU OF AMERICA, INC.
• 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 PRESSURE FLOW REFERENCE  .

  Fig 2: Showing Condition Valve Operation And Air Flow

  Courtesy of SUBARU OF AMERICA, INC.
  PRESSURE FLOW 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: Valve Operation and Air Flow

Courtesy of SUBARU OF AMERICA, INC.

When B < C (Solenoid OFF) 

Fig 4: Showing Condition When B < C (Solenoid Off)

Courtesy of SUBARU OF AMERICA, INC.

When Solenoid is ON 

Fig 5: Showing Condition When Solenoid Is On

Courtesy of SUBARU OF AMERICA, INC.

• Drain valve 

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

  Fig 6: Drain Valve Controls The Ambient Air To Canister

  Courtesy of SUBARU OF AMERICA, INC.