Fuel Evaporation System Chevrolet Sprint I

DESCRIPTION

The fuel evaporation system is designed to prevent fuel tank and carburetor vapors from escaping into the atmosphere. The system includes fuel tank, pressure/vacuum relief fuel filler cap, bi-metallic vacuum switching valve (BVSV), switch vent solenoid, two-way check valve, purge control valve, charcoal canister, and connecting lines and hoses.

OPERATION

When the engine is not running, purge valve opens fuel tank vapor line to canister and switch vent solenoid opens float bowl vent to canister.

When the engine is running and warmed to normal operating temperature, bi-metallic vacuum switching valve (BVSV) closes and allows carburetor vacuum signal to open purge control valve. With the purge valve open, manifold vacuum draws canister vapor into combustion chambers for burning.

The two-way check valve is used to balance vapor pressure between fuel tank and canister.

MAINTENANCE

Every 30,000 miles or every 2 years, check fuel tank, lines, and hoses for leakage. Check fuel filler cap gasket for even sealing imprint.

COMPONENT TESTING

TWO-WAY CHECK VALVE

1. Remove two-way check valve from vapor line and note color coded ports. Connect a new piece of hose to Orange valve port (canister side). Slowly blow air into hose and check that air flows out of Black port.
2. Remove hose from valve and connect hose to Black valve port (tank side). Slowly blow into hose and check that air flows out of Orange port. Replace valve if it does not operate as outlined.

CANISTER

1. Remove 4 hoses from canister and mark them for reinstallation. Blow air into canister "TANK" port and check that air flows out of bottom canister port.
2. Blow air into canister "PURGE" port and check that air does not flow out of any of the other ports.
3. Using a vacuum pump, slowly apply vacuum to canister "CARB" port while blowing air into canister "PURGE" port. When vacuum increases above 3.1 in. Hg, check that air flows out of "TANK" port, "C BOWL" port, and canister bottom port. Replace canister if it does not operate as outlined.

SWITCH VENT SOLENOID

1. Remove hose from canister "C BOWL" port and install a new hose on line leading to switch vent solenoid.
2. With ignition key in the "OFF" position, blow into hose and check that air flows into carburetor. Turn ignition key to the "ON" position without starting engine. Blow into hose and check that air flows into carburetor.
3. Start engine and run at idle. Blow air into hose. Air flow will be blocked if valve is operating properly.