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Warm Engine

  1. Ensure engine is warm. Disconnect vacuum hose to distributor advance diaphragm B. Connect a vacuum gauge to hose.
  2. Start engine and check for vacuum at idle. If no vacuum is present, go to step 4). If vacuum is present, check for voltage at vacuum control solenoid valve in emission control box 4P connector Blue/Black wire.
  3. If there is voltage, go to Trouble Shooting. If there is no voltage, replace vacuum control solenoid valve and retest.
  4. Disconnect both vacuum hoses from the distributor advance unit. Plug both disconnected hoses. Using a "T" fitting and vacuum hose, connect a vacuum pump to both diaphragms.
  5. Pinch hose to diaphragm B. Apply 16 in. Hg to diaphragm A. If ignition timing advances and holds steady, go to step 6). If timing will not advance or does not hold vacuum, check distributor for binding condition. If no trouble is found, replace distributor advance unit.
  6. Remove pinch from hose to diaphragm B. Apply 16 in. Hg to both diaphragms. If ignition timing advances more than step 5) and holds steady, system is okay. If ignition timing does not advance as described, replace distributor advance unit and retest.
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