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Throttle Advance Schedule Test (1977-79 Single Pick-Up Distributor Models)

  1. Turn ignition off. Disconnect 10-pin connector from Spark Control Computer. With ohmmeter, measure resistance between terminals No. 8 and 9 of 10-pin connector. If reading is 50-90 ohms, reconnect computer and go to step  3).
  2. If reading is incorrect, remove connector from throttle position transducer and measure resistance at transducer terminals. If transducer resistance is 50-90 ohms, an open, short or poor connection exists between terminals No. 8 and 9 and transducer. If resistance is incorrect, replace transducer and go to next step.
  3. Reconnect all wiring and turn ignition on. Connect voltmeter negative lead to ground and touch positive lead to each transducer terminal. Fully open and then close throttle. A 2 volt change should occur with throttle action.
  4. Position throttle linkage on fast idle cam and ground carburetor switch with jumper wire. Disconnect wiring harness from throttle position transducer and connect it to a known good transducer (for testing purposes).
  5. Move transducer core in until fully bottomed. Start engine, wait 90 seconds, then pull transducer core slowly out to about 1 inch. See Figure.
  6. Adjust timing light so initial timing is seen at timing plate. Meter on timing light should show additional amount of advance as indicated under specifications.
  7. If within specifications, move core back into transducer and timing should return to initial setting. If timing returns to initial setting, go to next step. If timing did not react as indicated, replace Spark Control Computer. Repeat test starting at step  3. If vehicle fails test, replace throttle position transducer.
  8. Return timing light advance meter to zero. Observe timing marks while having an assistant rapidly move core of test throttle position transducer in and out one inch (5-6 times).
  9. Timing should advance as specified for about 1 second, then return to zero. If advance is not as specified, replace Spark Control Computer. Repeat test starting at step  3, using original transducer. If test fails, replace original transducer.
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