Power Valve: Testing and Inspection
Fig. 14 Connecting vacuum pump to power valve.:
Fig. 15 Connecting vacuum pump to power valve.:
The power valve supplies supplementary fuel into the primary main fuel passage when the vehicle is operated in the power mode.
When the intake air temperature is below 59 deg. F, the power valve is open because the power valve control solenoid does not allow vacuum to the power valve. With the vehicle below specified speed and intake air above 59 deg. F, the power valve is open because the power valve control solenoid will not allow vacuum to the power valve.
When the vehicle exceeds specified speed, the power valve is controlled by the vacuum signal switch and barometer switch, if equipped, to the power valve control solenoid valve.
The power valve is energized below manifold vacuum to the vacuum switch. Test the power valve as follows:
1. Disconnect hose from the power valve, then connect a suitable hand held vacuum pump to the valve, Figs. 14 and 15, and apply vacuum.
2. On 1984 Civic 1300 listen for clicking noise while vacuum is being applied. If clicking noise is heard, proceed to step 4. If no noise is heard, replace carburetor.
3. On models exc. 1984 Civic 1300 vacuum should remain steady. If it does not, proceed to step 4. If vacuum decreases, replace diaphragm.
Fig. 12 Connecting hand pump gauge to vacuum hose.:
Fig. 13 Connecting hand pump gauge to vacuum hose.:
4. On all models, start engine and allow to reach normal operating temperature, then disconnect hose from power valve and connect it to a suitable vacuum gauge, Figs. 12 and 13. With engine running, vacuum should not be present.
Fig. 14 Power valve control solenoid valve location.:
Fig. 15 Power valve control solenoid valve location.:
NOTE: If vacuum is not present, check for voltage at power valve control solenoid valve in emission box, Figs. 14 and 15. If voltage is present, replace power valve control solenoid valve and retest. If voltage is not present, check fuse, wiring and speed sensor.
5. Raise and support front of vehicle. With engine still running and transaxle in 2nd gear or "D," check for vacuum at power valve above approximately 10-15 mph. Vacuum should be present.
6. If vacuum is present, proceed to step 8. If vacuum is not present, check for voltage at power valve control solenoid valve.
7. If voltage if present, replace vacuum switch and retest. If voltage is not present, replace power valve control solenoid valve and retest.
8. With vehicle still in gear and above approximately 10-15 mph, disconnect vacuum hose from vacuum pipe manifold to simulate engine load. Vacuum to power valve should not be present.
9. If vacuum is not present, system is satisfactory. If vacuum is present, check for continuity across vacuum switch with hose disconnected.
10. If continuity is present, reconnect box connector and check for voltage at power valve control solenoid. If voltage is present, replace power valve control solenoid. If continuity is not present, replace vacuum switch.
Fig. 14 Connecting vacuum pump to power valve.:
Fig. 15 Connecting vacuum pump to power valve.:
The power valve supplies supplementary fuel into the primary main fuel passage when the vehicle is operated in the power mode. In normal driving modes other than acceleration, manifold vacuum is applied on the diaphragm of the power valve, keeping the valve closed. When throttle valve is suddenly opened to accelerate, power valve opens because of decreased manifold vacuum and supplies additional fuel to primary main fuel passage through power jet, ensuring smooth acceleration.
When ambient temperature is below the set temperature of the intake air temperature sensor, power valve control solenoid valve is operated by control unit which receives the signal from intake air temperature sensor. Manifold vacuum leaks through the solenoid valve so that the power valve remains open regardless of throttle valve position.
Test power valve as follows:
1. Disconnect hose from power valve, then connect suitable hand vacuum pump to valve, Figs. 14 and 15, and apply vacuum.
2. Vacuum should remain steady. If it does, proceed to step 3. If vacuum decreases, replace diaphragm.
Fig. 12 Connecting hand pump gauge to vacuum hose.:
Fig. 13 Connecting hand pump gauge to vacuum hose.:
3. Start engine and allow to reach normal operating temperature, then disconnect hose from power valve and connect suitable vacuum gauge to hose.Figs.12 and 13. With engine running, vacuum should be present. If vacuum is present, proceed to step 5. If vacuum is not present, check for voltage at power valve control solenoid valve in the emission control box.
4. If voltage is present, check control unit. If voltage is not present, disconnect #20 hose at check valve inlet side and check for vacuum. If vacuum is present and check valve operation is satisfactory, replace power valve control solenoid valve. If vacuum is not present, check vacuum lines for disconnected hoses, leaks or blockage.
5. Ground red wire of control unit, then check for vacuum to power valve. Vacuum to power valve should not be present. If vacuum is not present, system is satisfactory. If vacuum is present, check for voltage at power valve control solenoid valve in emission control box. If voltage is not present, check control unit. If voltage is present, replace power valve control solenoid valve.