AMC Ignition System Electronic Spark Retard Test

Vacuum switch assembly:

This test only applies to models with electronic feedback system.
1. Allow engine to reach normal operating temperature.
2. Disconnect vacuum switch assembly wire connector, Fig. 4. Disconnectand plug distributor vacuum advance hose.
3. Disconnect knock sensor connector (located on intake manifold), thenusing a suitable jumper wire ground wire to engine block.
4. Increase engine speed to 1600 RPM, then using a suitable timing light,check timing and compare to specifications. Adjust as necessary.
5. Allow engine to return to idle speed, then connect vacuum switch connector wire connector and increase engine speed to 1600 RPM while observing timing marks. Timing should advance 6° over results found in step 4. If timing did not advance, check for vacuum switch failure. If vacuum switch is satisfactory, check continuity of wiring with a suitable ohmmeter from knock sensor to MicroComputer Unit (MCU). If wiring is satisfactory, replace MCU unit and retest.If timing did advance, proceed to step 6.
6. Allow engine to return to idle speed, then connect knock sensor connectorto knock sensor. Increase engine speed to 1600 RPM, then whileobserving timing marks with a suitable timing light, knock on intake manifoldnear the knock sensor. Timing should retard. If timing did not retard, checkfor continuity of knock sensor harness connector to J2 pin 16 of MCU connector. If satisfactory, replace knock sensor and retest. If timing did retard,the electronic spark retard is operating satisfactory. Allow engine to return toidle speed and connect vacuum hose to distributor.