Fuel Evaporation System Mazda 626 GC

DESCRIPTION

Fuel evaporation system prevents escape of raw fuel vapors to atmosphere. A fuel tank with integral vapor separator is installed on GLC and 626 models. B2000 models are equipped with a vapor valve instead of a vapor separator.

Additional components of system include a check and cut valve (except B2000), an air vent solenoid valve (except B2000), 2 purge control valves (only 1 on B2000), a charcoal canister, a fuel filler cap, a water thermo valve, and connecting lines and hoses. A vacuum controlled evaporative shutter valve is installed on B2000.

OPERATION

When engine is not running, fuel vapors from fuel tank flow to carbon canister for storage. When key is off, float bowl is vented to canister (GLC and 626). Check and cut valve (if equipped) prevents excessive pressure or vacuum from forming in system. When engine is started on B2000, manifold vacuum opens evaporative shutter valve to allow fresh air into carburetor.

On all models, when engine coolant temperature reaches approximately 122°F (50°C), water thermo valve opens and intake manifold vacuum is directed to purge control valve. When manifold vacuum opens purge control valve, fresh air is drawn through inlet hole at bottom of canister. Vapors are drawn into engine and burned.

MAINTENANCE

Check entire system for proper functioning every 15,000 miles. Check and cut valve should be tested every 25,000 miles. Replace parts as necessary.

GLC

With key off, disconnect air vent solenoid hose from canister and slowly blow into hose. Air must pass through solenoid. Turn key on and blow through hose. Air must not pass through air vent solenoid.

626

Remove the air cleaner. Press the air vent solenoid valve on the carburetor . Turn the ignition switch on and off. If there is a clicking noise, the air vent solenoid valve is working properly.

Scheme 5

1. Disconnect evaporation hose from canister. Connect detached hose to a "U" tube type pressure gauge filled with water. (Scheme 5) (Scheme 5): Testing Evaporation Line Use "U" tube pressure gauge for testing.
2. Gradually apply low air pressure into "U" tube so that difference of water level reaches 14" (356 mm).
3. Bind inlet of "U" tube and leave bound for 5 minutes. If water level drops no more than 1" (25 mm) after 5 minutes, evaporation line is in good condition.

Scheme 6

1. Remove check and cut valve from lines. Connect a pressure gauge with "T" on nipple leading to fuel tank. Hold finger over opposite nipple. (Scheme 6) (Scheme 6): Testing Check and Cut Valve (GLC) Hold valve horizontally during test.
2. Blow through open end of "T" fitting. When pressure gauge reads.78-1.0 psi (.06-.07 kg/cm 2 ), valve should open.
3. Remove "T" fitting and gauge from fuel tank nipple, and connect to nipple at bottom of valve (atmosphere vent). Hold valve horizontally.
4. Repeat test. Valve should open when pressure gauge reads.14-.71 psi (.01-.05 kg/cm 2 ). If valve does not operate as described, replace check and cut valve.

Remove check valve. Blow through the check valve from port A and make sure that the air comes out of port B. Next, block the port B. Air should come out of port C. Block port B, and suck through port A. If the air comes through from the port C, the valve is functioning properly. (Scheme 7)

Testing Check Valve (626) Check valve is located next to fuel tank. Scheme 7

Remove upper and lower hose from No. 1 purge control valve. Apply direct manifold vacuum to upper valve port. Blow through lower valve port and air will flow through valve if working properly. (Scheme 8)

Charcoal Canister (Except B2000). Scheme 8

1. Remove the air cleaner and plug the hoses of the idle compensator, thermo-sensor and reed valves. Disconnect the air vent hose from the carburetor and plug it. Warm engine to normal operating temperature and run at idle.
2. Cover the bottom of the canister. Increase the engine speed slowly and make sure air is sucked into canister. If so, No. 1 purge control valve and water thermo-valve are working properly.

Scheme 9

1. No. 2 purge control valve is an integral part of canister. Disconnect canister evaporation hose at line leading to fuel tank. Connect detached hose to a "U" tube type pressure gauge filled with water. (Scheme 9) (Scheme 9): Testing No. 2 Purge Control Valve (626) Connect "U" tube pressure gauge to evaporation hose.
2. Gradually apply low air pressure into "U" tube so that difference in water level reaches 13 1/2" (345 mm). Apply additional low air pressure and check that purge control valve opens and passes air through canister.
3. Apply vacuum to end of "U" tube until difference in water level is 7". Apply additional vacuum and check that purge control valve opens and allows air to be drawn into system through bottom of canister.

B2000

1. Remove hoses leading to carburetor and intake manifold from purge control valve. (Scheme 10) Plug hose to intake manifold and run engine at idle.
2. Connect test hose to intake manifold port on purge control valve and blow into hose. Air should not flow through valve.
3. Remove plug from intake manifold hose, and connect hose to carburetor port on purge control valve. Again blow into test hose and air will flow through valve if working properly.

Testing Purge Control Valve (B2000). Scheme 10

B2000 & 626

1. Remove water thermo valve and connect a piece of tubing to each nipple. Immerse valve in container of water. Insert thermometer and slowly heat water.
2. At temperature of 122°F (50°C) or above on B2000, or 129°F (54°C) on 626, blow into one of the hoses. Air should pass through valve. If not, replace water thermo valve.

1. Remove vacuum hose from upper port of No. 1 purge control valve at canister and run engine at 1500 RPM.
2. With engine coolant below 122°F (50°C) no vacuum should be felt at hose. With engine coolant above 122°F (50°C) vacuum should be felt at hose if valve is working properly.

1. Remove air cleaner and element. With engine cold, shutter valve should be completely closed. Start engine and run at idle. Shutter valve should be open.
2. With engine running, disconnect and reconnect vacuum hose to shutter valve diaphragm. Shutter valve should open and close smoothly. If not, replace shutter valve.