Fuel Evaporation System: Description
Carbon canister storage is used for evaporative fuel control on all vehicles. The function of the evaporative emission control system is to store gasoline fumes from the fuel tank and float bowl (on carbureted engines) in a carbon canister until they can be drawn into the engine for burning during the combustion process.
There are 4 basic components used in the evaporative emission system:
- Activated carbon canister (may be sealed or open at top or bottom for fresh air intake).
- Vacuum operated canister control valve (may be mounted on canister or remotely).
- ECM-controlled solenoid (may be mounted on canister or remotely).
- Tank pressure control valve (may be mounted internal or external of fuel tank).
Some carbureted models may also have a thermal bowl vent valve installed in the fuel bowl vent hose. Not all components are used in every application. For specific component application and vacuum hose routing, see VACUUM DIAGRAMS article.
Some examples of the various combinations of these components are as follows:
- Ported vacuum purge. Example: J body 2.0L (VIN K). See Fig 1 .
- Ported vacuum purge through a manifold vacuum activated canister control valve. Example: J body 2.0L (VIN M) and P body 2.8L (VIN 9).
- Ported vacuum purge through an ECM-controlled solenoid. Example, C body 4.5L (VIN 5) and F body 5.7L (VIN 8).
- Manifold vacuum purge through an ECM-controlled solenoid. Example: A body 3.8L (VIN 3).
- Manifold vacuum purge regulated through an ECM-controlled solenoid and activated by a ported vacuum canister control valve. Example: Y body 5.7L (VIN 8).
- Restricted (low volume) manifold vacuum purge through a ported vacuum control valve, in conjunction with manifold vacuum purge (high volume), regulated by an ECM-controlled solenoid. Example: F body 2.8L (VIN S). See Fig 2 .