Fuel Evaporation System Mazda MX-6 V

DESCRIPTION

Fuel evaporation system prevents escape of raw fuel vapor to atmosphere. Components of system include a fuel tank with integral vapor separator, a check and cut valve (3-way valve on MX-6 and 626), an air vent solenoid valve (B2200 and B2600), 2 purge control valves (3 on 323, MX-6 and 626), a charcoal canister, a fuel filler cap, a coolant thermovalve (except 323 and 929), and connecting lines.

Additional components include, a 3-way solenoid valve on MX-6 and 626 (2 on 323 and 929), and an Emission Control Unit (ECU).

Scheme 1

OPERATION

When engine is not running, vapor from fuel tank flows to charcoal canister. When ignition is off, float bowl (carburetor only) is vented to canister. Check and cut valve (3-way valve) prevents excessive pressure or vacuum from forming in system.

When coolant reaches 131°F (55°C) on MX-6, 626 and B2600 or 129°F (54°C) on B2200, coolant thermovalve opens. On 323, ECU controls the system. When manifold vacuum opens purge control valve, fresh air enters bottom of charcoal canister. Vapor is drawn into engine.

On 929, a coolant temperature sensor signals ECU when engine is warm. When coolant 158°F (70°C) and engine is at idle, the No. one 3-way solenoid valve is energized. Fuel vapors will be drawn through restrictor orifice "A". With engine warm and engine speed above 1500 RPM, No. 2 3-way solenoid valve is energized by ECU. Additional fuel vapors will now by-pass restrictor orifice "A".

Scheme 2

MAINTENANCE

Check entire system for proper functioning every 5 years or 60,000 miles. Replace all hoses and tubes every 5 years or 60,000 miles. Replace parts as necessary.

B2200 & B2600

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

B2200, B2600, MX-6 & 626

1. Remove coolant thermovalve. Connect a piece of tubing to each nipple. Immerse valve in container of water. Insert thermometer and slowly heat water.
2. At temperature greater than 129°F (55°C) on B2200 or 131°F (55°C) on 626 and B2600, blow into one of the hoses. Air should pass through valve. If not, replace coolant thermovalve.

Scheme 3

1. Remove check and cut valve. Connect a pressure gauge with "T" fitting on nipple leading to fuel tank. Cap opposite nipple. (Scheme 3) Valve must be held horizontally to prevent valve from closing passage.
2. Blow through open end of "T" fitting. When pressure gauge reads.14-.71 psi (.01-.05 kg/cm 2 ), valve should open. If it does not open, replace check and cut valve.
3. Remove "T" fitting and gauge from fuel tank nipple. Connect to nipple at bottom of valve. Blow through open end of "T" fitting. Valve should open when pressure gauge reads.78-1.0 psi (.06-.07 kg/cm 2 ). If it does not open, replace check and cut valve.

MX-6 & 626

Remove 3-way valve. Blow through valve from fuel tank port. Make sure air comes out of canister port. Block canister port. Air should exit vent port. Block canister port. Blow through vent port. If air exits fuel tank port, valve is functioning properly. (Scheme 4)

Scheme 4

Scheme 5

Scheme 6

1. To check No. 1 purge control valve, remove hoses from charcoal canister. Attempt to blow through intake manifold port. Air should not pass. Attach vacuum pump/gauge to top port of purge control valve. Apply 4.3 in. Hg vacuum. Blow through intake manifold port. Air should flow through port. (Scheme 5) If not, replace valve.
2. The No. 2 purge control valve is an integral part of charcoal canister. Disconnect canister evaporation hose at line leading to fuel tank. Air should pass through valve under pressure and under vacuum, if valve is operating properly. (Scheme 6)
3. To test No. 3 purge control valve (all except 323), disconnect hoses. Remove No. 3 purge control valve from vehicle. Connect vacuum pump/gauge to single port. Blow into port "A". Ensure air does not flow from port "B". (Scheme 7)
4. Apply about 3 in. Hg on 626 or 2.6-4.2 in. Hg on B2200 and B2600, to port. Blow into port "A". Air should flow through port "B". If air does not flow, replace purge control valve.

Scheme 7

MX-6, 323, 626 & 929

1. Disconnect hoses and electrical connector from 3-way solenoid valve. Remove valve from vehicle. Turn valve so that air filter end of valve faces down. Connect hose to port "A". Blow into hose. Ensure air passes from filter. (Scheme 8)
2. Using jumper wire, apply battery voltage to solenoid valve. Blow into port "A". Air should pass from port "B". If air does not exit port "B", replace 3-way solenoid valve(s).

Scheme 8

B2200

1. Warm engine to normal operating temperature. Connect timing light to engine. Check timing. Increase engine speed gradually. Check that ignition timing suddenly advances at 1300-1450 RPM.
2. Connect voltmeter to distributor vacuum solenoid valve connector "F" terminal "GR". Voltmeter should read zero volts when engine speed is greater than 1300 RPM. Voltage reading should be 12 volts when engine speed is less than 1300 RPM.

B2600

1. Warm engine to normal operating temperature. Connect voltmeter to terminal "YR" of the purge solenoid valve and ground. Connect tachometer to engine.
2. Gradually increase engine speed. Check that voltmeter indicates zero volts when engine speed is greater than 1400 RPM. If not, check terminal "1C" of Emission Control Unit (ECU) for proper contact and the coolant thermosensor. If wiring and thermosensor are okay, replace ECU. Retest system.
3. Disconnect vacuum hose from vacuum switch. Connect vacuum pump with gauge to switch. Apply vacuum. Voltmeter should read 12 volts when vacuum reaches 7.9 in. Hg. If not, check terminals "1E" of ECU and vacuum switch for poor connections. If wiring and vacuum switch are okay, replace ECU. Retest system.

323

1. Start and warm engine to normal operating temperature. With engine idling, connect voltmeter to the No. 1 3-way solenoid valve (Black/Yellow terminal). Voltage reading should be about 12 volts. If not, check solenoid and wiring to ECU.
2. Disconnect top hose from No. 1 purge control valve on charcoal canister. Place finger over open end of hose. Increase engine speed to 2000 RPM. Ensure vacuum is not created at hose. If vacuum is present, check No. 1 3-way solenoid valve and wiring to control unit. Remove finger from hose. Leave hose disconnected. Return engine to idle.
3. Disconnect neutral/safety switch connector on manual transaxle, or inhibitor switch connector on automatic transaxle. Voltage reading should be 1.5 volts.
4. Place finger over purge control valve hose. Increase engine speed to 2000 RPM. Vacuum should be created at hose end. If not, check No. 1 3-way solenoid valve and wiring to ECU.

Scheme 9

1. Start and warm engine to normal operating temperature. With engine idling, disconnect top hose from No. 1 purge control valve on charcoal canister. Install a vacuum gauge to hose. Increase engine speed to 2500 RPM. Ensure vacuum exceeds 5.9 in. Hg. If not, check coolant thermovalve. Remove vacuum gauge. Reconnect vacuum hose.
2. Disconnect vacuum hose from port "B" of No. 3 purge control valve. Connect vacuum gauge and hose to valve port. (Scheme 7) Accelerate engine to a speed greater than 1500 RPM. Note that vacuum is present at port. If vacuum is not present, check 3-way solenoid valve, No. 3 purge control valve, and terminal "2P" at ECU for poor connection.
3. Remove vacuum gauge and hose. Reconnect vacuum hose to purge control valve. Disconnect fuel tank hose from charcoal canister. Connect vacuum pump/gauge to hose. Try to apply vacuum to hose. Vacuum should not be held. If vacuum is held, check 3-way valve or fuel tank hose for blockage.

929

1. No. 1 and No. 2 3-way solenoid valves are tested by removing vacuum hoses and blowing through port "B". With ignition off, air should flow out air filter. (Scheme 8)
2. Disconnect electrical connector and apply battery voltage to valve terminals. Blow air in port "B", air should exit at port "A".

Scheme 10

Scheme 11