Evaporative Emissions System: Description and Operation

Evaporation Controls:

PURPOSE
When the engine is "OFF", vapor is contained in the fuel tank by means of a remote mounted Tank Pressure Control Valve (TPCV).

The TPCV has a vacuum relief function which allows the tank to vent during temperature/vacuum cycling.

With the engine running a manifold vacuum signal opens the TPCV to allow full time vapor passage.




OPERATION
The TPCV prevents vapor from entering the canister when either of the following two conditions are met:
- Engine is "OFF" whereby no vacuum is going to the TPCV vacuum port, or
- Tank pressure is below 15 inches of water pressure.

The TPCV opens, creating a vapor path to the canister when:
- The engine is operating, sending a vacuum to the TPCV, OR
- Tank pressure exceeds 20 inches of water.

LOCATION
The Tank Pressure Control Valve (TPCV) is located in-line with the fuel tank and vapor cannister.