High Altitude

Evaporative Emission Control Schematic:

The evaporative emission control system used on this vehicle is the charcoal canister storage method. This method transfers fuel vapor from the fuel tank to an activated carbon storage canister to retain the vapors when the vehicle is not operating. When the engine is running the fuel vapor is purged from the carbon element by intake air flow and consumed in the normal combustion process.

Vapor Canister Altitude:

VAPOR CANISTER
Gasoline vapors from the fuel tank are purged and flow into the vapor canister tube labeled "Fuel Tank" and are absorbed by carbon. When the canister is purging, fresh air is drawn in through the air inlet, at the top of the canister. This air flows to the bottom of the canister and forces the vapors out of the purge line. The purge valve is an integral part of the canister. When the engine is running, full manifold vacuum is applied to the top tube of the purge valve (control vacuum signal) which lifts the valve diaphragm and opens the valve. The lower tube on the purge valve is connected to a timed port above the TBI throttle valve. The rate of purge is controlled through this port by throttle valve opening.

Tank Pressure Control Valve:

TANK PRESSURE CONTROL VALVE
The tank pressure control valve allows vapors to flow from the fuel tank into the system. When the fuel tank pressure exceeds the spring pressure on the valve diaphragm (4.3 kPa), the valve opens and allows vapors to enter the canister or go directly to the engine when purge is enabled. The tank pressure control valve is located in the engine compartment on the C & K models and near the fuel tank on others.