Action
This system prevents gasoline vapors from leaking into the atmosphere from the gas tank and carburetor. The device of the system is different for different models of production of different years, and also depends on the equipment of the car. Cleaning control - admission of fresh air to the fuel tank - carried out by mechanical means (temperature and vacuum control) or electrically by the engine management system (on-board computer). Note that later models, especially the Prelude, use computer controlled carburetors, but the use of computers is not limited to fuel injected cars.
Gasoline vapors accumulate in the expansion tank, in the gas tank and fuel lines. When the vapor pressure of gasoline exceeds a certain value, the one-way valve opens and releases the vapor into the carbon filter. When the engine is stopped or idling, the charcoal filter cleaning valve is closed and vapors accumulate in the filter, and at part throttle, the valve is opened by manifold vacuum. Any excessive increase or decrease in the vapor pressure of gasoline in the gas tank is leveled by a two-way valve located in the filler cap or fuel line.
Testing and servicing 1984-85 Accord and Prelude with carburetor
Thermal valve A
Cold engine
The engine must be cold. The coolant temperature must be below the temperature sensor threshold and the temperature sensor must be shorted.
1. Remove the upper hose from the carbon filter cleaning valve, connect a vacuum pump to the free end of the hose.
2. Start the engine at idle. No vacuum should be detected.
3. If vacuum is detected, replace temperature sensor A on the Accord or temperature sensor B on the Prelude.
Hot engine
1. The engine must be well warmed up (cooling fan turned on at least once). Using a hand vacuum pump, disconnect the upper hose from the carbon filter cleaning valve and connect the free end of the hose to a pressure gauge.
2. Start the engine at idle; a vacuum must develop.
3. If there is no vacuum, inspect thermal valve A on the Accord and thermal valve B on the Prelude, checking for finger suction on the air filter. If there is a vacuum in the carbon filter, reinstall the thermostatic valve. If there is no vacuum, inspect the number 19 hose to the intake manifold for possible leaks or blockage.
Carbon filter
These actions are performed with a hot engine.
1. Connect a tachometer to the engine. Start and warm up the engine (cooling fan has started at least once).
2. Remove the fuel filler cap.
3. Disconnect the carbon filter hose and attach a pressure gauge to the free end of the hose.
4. Increase the engine speed to 3500 rpm. The pressure gauge should show vacuum no later than 1 minute. If a vacuum occurs, go to step 10.
5. If vacuum does not appear, the following procedures should be performed:
- A) Disconnect the pressure gauge and install the fuel filler cap.
- 6) Remove the charcoal filter and check for defects or damage.
- V) If necessary, replace the filter.
6. Stop the engine and disconnect the PCV valve from the carbon filter.
7. Connect a hand pump to the carbon filter and create a vacuum in the filter. If the vacuum is stable, go to the next step, if not, replace the carbon filter and repeat the test.
8. Connect the PCV hose to the filter and start the engine. The vacuum in the carbon filter cleaning hose should disappear. If the vacuum does not disappear, replace the filter and repeat the test.
9. If the vacuum in the carbon filter cleaning hose disappears, connect a hand pump to the PCV system filter and create a vacuum. The vacuum must be stable. If the vacuum is stable, disconnect the pump and check the operation of thermal valve A. If the vacuum decreases, replace the filter and repeat the test.
Accord 1985 fuel injected
Carbon filter
1. Connect the tachometer to the engine, start the engine, warm it up to normal temperature. The cooling fan should turn on at least once.
2. Remove the fuel filler cap.
3. Disconnect the carbon filter hose and attach a pressure gauge to the free end.
4. Increase the engine speed to 3500 rpm. The pressure gauge should show a vacuum no later than a minute later. If the vacuum registers on time, go to step 10.
5. If vacuum does not appear, perform the following procedures:
- A) Disconnect the pressure gauge and install the fuel filler cap.
- b) Remove the charcoal filter and check for defects or damage.
- V) Replace the filter if necessary.
6. Connect a vacuum pump to the carbon filter cleaning port and apply a vacuum. The vacuum must be stable. If the vacuum decreases, replace the filter and check it.
7. Using a second hand pump, evacuate air through the PcV port on the filter. The vacuum in the carbon filter cleaning hose should disappear. If the vacuum does not disappear, change the filter and check it.
8. Disconnect the hand pump from the cleaning port. Create a vacuum in the PCV system. Vacuum should be stable, if not, replace the filter.
9. Connect a vacuum pump to a container for collecting gasoline vapors and try to create a vacuum. It should NOT occur. If this is the case, install the filler cap and testing can be considered complete. If there is a vacuum, replace the filter and repeat the test.
Two way valve
1. Remove the cap from the gas tank.
2. Raise and secure the vehicle.
3. Disconnect the gasoline vapor discharge hose from the liquid-vapor separator located on the gas tank. Connect a pressure gauge to the T-piece, as well as a hand pump that goes through a hose to the gas tank.
4. Slowly, under the control of the pressure gauge, create a vacuum. The vacuum is stabilized by a two-way valve that opens in the pressure range of 5-15 mmHg. Art. If the valve opens too soon or too late, replace and check it.
5. Move the hose of the hand pump from the pumping to the discharge branch pipe, connect the pressure gauge.
6. Slowly, under the control of the pressure gauge, raise the pressure in the gasoline vapor discharge hose. The pressure should stabilize between 25 and 55 mmHg. If so, the valve is good. If the pressure stabilizes too soon or too late, replace the valve.
Carbureted Accord 1986-89 and Prelude 1986-90
Thermal valve A or B
Engine cold
1. The engine coolant temperature must be below 55°C on an Accord or 40°C on a Prelude. Disconnect the vacuum hose from the charcoal filter cleaning valve on top of the charcoal filter. Connect a hand pump to the free end of the hose.
2. Start the engine at idle - no vacuum should appear. Otherwise, replace thermal valve A on the Accord or B on the Prelude and check them.
Engine hot
1. The engine coolant temperature must be above the temperature sensor setting. Disconnect the hose from the carbon filter cleaning valve and connect the free end of the hose to the hand pump.
2. Start the engine. When the engine is warm, the vacuum should register. If not, disconnect the vacuum hose from the thermal valve and check the hose for leaks. If the hose is tight, replace the thermal valve.
3. Disconnect the hand pump, reconnect the hose.
4. Remove the fuel filler cap.
5. Disconnect the filter cleaning air hose from the filter and connect to a pressure gauge.
6. Increase the engine speed to 3500 rpm. The vacuum must be registered with a pressure gauge within 1 min. If vacuum is not detected, turn off the engine. Install the fuel filler cap. Remove the charcoal filter and inspect it for physical damage. If necessary, replace.
7. If there is a vacuum at stage 6, turn off the engine, disconnect the hose from the PCV tank nozzle. Connect a hand pump to the filter and apply a vacuum. The vacuum must be stable. If the vacuum decreases, replace the filter.
8. Restart the engine, connect the PcV hose to the assembled filter. The vacuum at the cleaning pipe should disappear. If the vacuum is not completely gone, replace the filter.
9. If the vacuum has disappeared completely - connect the vacuum hose to the PCV system and create a vacuum. The vacuum must be stable. Otherwise, replace the filter and check it.
10. Connect a hand pump to the vapor collection port on the charcoal filter and apply a vacuum. If vacuum is registered - replace the filter.
Carburetor thermal valve - only for Accord cars
1. Start the test on a cold engine. Coolant temperature must be below 30°C.
2. Disconnect the hose from the carburetor thermal valve, connect a hand pump to the valve. Create a vacuum of 200 mmHg, it must be stable. If not, replace the thermal valve.
3. Reconnect the vacuum hose to the carburetor thermal valve. Start the engine, let it warm up to the optimum temperature. Coolant temperature must be above 40X.
4. Repeat step 2. The vacuum must not be maintained. If the vacuum is maintained, replace the carburetor thermostat.
Accord 1986-90 and Prelude 1988-94
System check
1. Start the test on a cold engine. Coolant temperature must be above 55°C. Check the vacuum lines for possible cracks, blockages, and if the hoses match the connection points.
2. Disconnect the number three vacuum hose from the carbon filter cleaning valve and connect the free end of the hose to a pressure gauge.
3. Start the engine at idle. While the engine is cold, there should be no vacuum. If it is, replace the thermal valve and check it.
4. Warm up the engine to the optimum temperature. Vacuum begins to register as the temperature of the coolant reaches 55°C. If vacuum does not register with warm engine, replace thermal valve.
5. Disconnect the pressure gauge and reattach the hose.
6. Remove the fuel filler cap.
7. Remove the air purge hose and connect the free end of the hose to a pressure gauge.
8. Increase the engine speed to 3500 rpm. The pressure gauge should register a vacuum for 1 minute. If not, turn off the engine, install the gas tank cap. Remove the charcoal filter and check for mechanical damage and incorrect connection.
9. If vacuum is detected in step 6, turn off the engine, disconnect the hose from the PCV tank fitting. Connect a hand pump to the cleaning port and apply a vacuum. The vacuum must remain stable. If the vacuum disappears, replace the carbon filter.
10. Restart the engine. Connect the PCV hose to the fitting. The vacuum in the cleaning canapes should disappear. If not, replace the filter.
11. If vacuum disappears in the purge line, connect a hand pump to the PCV fitting and apply vacuum. The vacuum must be stable. If not, replace the filter and check it.
Two way valve
1. Remove the cap from the gas tank neck.
2. Raise and secure the vehicle.
3. Disconnect the vapor collection line from the liquid vapor separator tube on the fuel tank. Connect a pressure gauge to the T-piece and a hand pump to the vapor collection hose on the gas tank.
4. Slowly build up a vacuum under the pressure gauge. The vacuum is stabilized by opening a two-way valve in the pressure range of 5-15 mmHg. If the valve opens too early or too late, replace the 2-way valve and check it.
5. Move the hand pump hose from the outlet to the outlet and connect a pressure gauge.
6. Carefully, under the control of the pressure gauge, raise the pressure in the gasoline vapor collection line. The pressure should be kept stable between 25 and 55 mmHg. If so, the valve is good. If the pressure is set too soon or too late, replace the valve.
Accord 1990-91
1. On a cold engine, disconnect the vacuum hose from the upper connection of the carbon filter cleaning valve and connect a pressure gauge to the hose. You can use the pressure gauge on the hand pump.
2. With a cold engine idling, the solenoid valve must be closed. The pressure gauge should not register vacuum at the very beginning of engine operation. As the engine warms up, the valve opens and opens the carbon filter cleaning valve.
3. If there is no vacuum by the time the cooling fan comes on, check the shutoff solenoid and wires to it. The black/yellow solenoid wire should sense 12V with the ignition on. The on-board computer is the final link in the regulation chain and also influences the operation of the valve.
4. Connect a vacuum line to the valve and connect a pressure gauge to the fresh air inlet at the base of the carbon filter. Start the engine, bringing the shaft speed to a frequency of 3500 rpm. If the vacuum does not register with the opening of the solenoid valve, then the filter is most likely damaged. Check the two-way valve and make sure the fuel filler cap is not leaking.
5. Stop the engine. To check the two-way valve, remove the cap from the gas tank neck, disconnect the gas vapor outlet hose from the gas tank, connect a hand pump to the hose and create a vacuum. The vacuum should instantly stabilize within 5-15 mmHg.
6. Now apply positive pressure to the same hose. It should instantly stabilize within 10-35 mmHg. Stabilization in both cases is performed by a two-way valve, providing proper ventilation.