Deceleration Fuel Cut System
19771. Check vacuum hose and wiring for damage or improper routing and repair or replace as necessary.
2. If engine starts, proceed to step 5.
Fig.87 - Testing Fuel Cut Solenoid Valve:
3. If engine does not start, disconnect wiring harness connector to fuel cut solenoid and apply battery voltage to solenoid, Fig. 87. If engine now starts, replace computer.
4. If engine still does not start, check related systems.
5. If engine starts in step 2 or 4, pinch hose between vacuum switch and carburetor with engine idling.
6. Gradually increase engine speed to 2500 RPM. If engine misfires slightly between 2000 and 2500 RPM, reduce engine speed and release pinched hose. Test is complete.
7. If engine does not misfire, disconnect wiring connector from vacuum switch.
8. Gradually raise engine speed to 2500 RPM. If engine misfires between 2000 and 2500 RPM, replace vacuum switch.
9. If engine does not misfire, disconnect connector from solenoid valve. If engine idles rough, replace computer. If not, replace solenoid valve.
1978 2T-C, 20R & 3K-C Engine
1. Connect vacuum switch to intake manifold vacuum with vacuum hose.
2. Start engine and make sure it runs normally.
3. Gradually increase engine speed to 2500 RPM on 2T-C and 3K-C engine or 2890 RPM on 20R engine. Engine should misfire slightly between 2000 and 2500 RPM on 2T-C and 3K-C engine, or between 2400 and 2800 RPM on 20R engine.
4. Unplug solenoid valve wiring connector with engine idling. Engine should run rough.
5. Stop engine and reconnect vacuum hose and wiring.
6. If test results are not as described, test components (found at the end of this article) individually.
1979-80 20R, 1979 2T-C & 3K-C, 1980-82 3T-C & 1981-82 22R Engine
1. Start engine and make sure it runs normally, then pinch shut vacuum hose to vacuum switch.
2. Gradually raise engine speed to 2500 RPM for 2T-C, 3T-C, or 3K-C engines, or 3000 RPM for 20R or 22R engines. Engine should misfire slightly between 2400 and 3000 RPM on 20R engines, between 2200 and 3000 RPM for 22R engines, or between 2000 and 2500 RPM on 2T-C, 3T- C, or 3K-C engines.
3. Release pinched hose and again gradually increase engine seed to 2500 RPM for 2T-C, 3T-C, or 3K-C engines, or 3000 RPM for 20R or 22R engines. Engine operation should return to normal.
4. Unplug solenoid valve wiring connector with engine at idle. Engine should idle rough.
5. Stop engine and reconnect vacuum hose an wiring.
6. If test results are not as described, test components (found at the end of this article) individually.
1980 1A-C & 1981-82 3A-C Engine
1. Start engine, then disconnect vacuum hose from vacuum switch.
2. Check that a click can be felt from second fuel cut solenoid valve when vacuum hose is connected and disconnected at idle.
3. Stop engine and reconnect hose.
4. If test results are not as described, test components individually.
Component Testing
Fig.87 - Testing Fuel Cut Solenoid Valve:
Fuel Cut Solenoid Valve
1. Remove solenoid valve and connect terminals to battery terminals, Fig. 87.
2. Check that a click can be felt from solenoid valve when battery is connected and disconnected.
3. Check "0" ring for damage.
4. Reinstall solenoid valve and reconnect wiring connector.
Vacuum Switch
1. Using ohmmeter, check for continuity between switch terminal and switch body. There should be continuity.
2. Start engine and check that there is no continuity between switch terminal and switch body.