EVAP Components

EVAP CANISTER

EVAP Canister:

The evaporative emission (EVAP) canister is a sealed unit with 3 ports.
- Purge pipe
- Vapor pipe
- Vent pipe

The canister is filled with carbon pellets used to absorb and store fuel vapors Fuel vapor is stored in the canister until the Powertrain Control Module (PCM) determines that the vapor can be consumed in the normal combustion process.

EVAP PURGE VALVE

EVAP Purge Valve:

The EVAP purge valve controls the flow of vapors from the EVAP system to the intake manifold. This normally closed valve is Pulse Width Modulated (PWM) by the PCM to precisely control the flow of fuel vapor to the engine. The valve will also be opened during some portions of the EVAP testing, allowing engine vacuum to enter the EVAP system.

FUEL TANK PRESSURE SENSOR

Fuel Tank Pressure Sensor:

The Fuel Tank Pressure (FTP) sensor measures the difference between the pressure or vacuum in the fuel tank and outside air pressure. The FTP sensor mounts in the top of the fuel tank-sending unit. The PCM provides a 5-volt reference and a ground to the FTP sensor. The FTP sensor provides a signal voltage back to the PCM that can vary between 0.1-4.9 volts. As fuel tank pressure increases, FTP sensor voltage decreases (high pressure = low voltage). As fuel tank pressure decreases, FTP voltage increases (low pressure or vacuum = high voltage).

EVAP VENT VALVE

EVAP Vent Valve:

The EVAP vent valve (1) controls fresh airflow into the EVAP canister. The EVAP vent valve is a normally open valve. The PCM will command the valve closed during some EVAP tests, allowing the system to be tested for leaks.

EVAP SERVICE PORT

EVAP Service Port:

The EVAP service port is located in the EVAP purge pipe between the EVAP purge valve and the EVAP canister. The service port is identified by a green colored cap.