Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
Is it an external coil? Do you have spark from the coil?
Ok, If no spark occurs, check for the presence of normal battery voltage of the battery (BAT) terminal in the distributor cap. The ignition switch must be in the ON position for this test. Either a voltmeter or a test light may be used for this test. Connect the test light wire to ground and probe end to the BAT terminal at the distributor. If the light comes on, you have voltage on the distributor. If the light fails to come on, this indicates an open circuit in the ignition primary wiring leading to the distributor. In this case, you will have to check wiring continuity back to the ignition switch using a test light. If there is battery voltage at the BAT terminal, but no spark at the plugs, then the problem lies within the distributor assembly.
DISTRIBUTOR COMPONENTS TESTINGFig. Fig. 3 Ohmmeter 1 shows the primary coil resistance connection (the meter should read 1 ohm or less); ohmmeter 2 shows the secondary resistance connection (the meter should read 6k-30kohms)-replace the coil if any readings are off
Fig. Fig. 4 The coil on all but the 1975-77 six-cylinder engines is accessible by removing the four attaching screws-be careful when installing the coil into the cap, as the screws can strip the plastic mounting holes if overtightened
Fig. Fig. 5 Check the condition of the arc seal under the coil
Fig. Fig. 6 Ohmmeter 1 shows the connections for testing the pickup coil; ohmmeter 2 shows the connections for testing the pickup coil continuity-move the vacuum advance arm during this test to ensure no change in the reading
If the trouble has been narrowed down to the units within the distributor, the following tests can help pinpoint the defective component. An ohmmeter with both high and low ranges should be used. These tests are made with the cap assembly removed and the battery wire disconnected. If a tachometer is connected to the TACH terminal, disconnect it before making these tests.
These resistance checks will not disclose shorted coil windings. This condition can only be detected with scope analysis or a suitably designed coil tester. If these instruments are unavailable, replace the coil with a known good coil as a final coil test.