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1975 Models

  1. With engine cold, disconnect vacuum hose from distributor diaphragm. See Figure and Figure Connect vacuum gauge to vacuum hose and start engine. No vacuum should exist (vacuum should exist on man. trans, equipped models).
  2. If correct vacuum reading is not obtained, check voltage at ignition solenoid valve with ignition on. If voltage is present, solenoid valve is defective or vacuum passage is plugged. Repair or replace as necessary.
  3. If no voltage is present, check thermo sensor continuity with coolant temperature below 149°F (65°C). If no continuity exists, replace thermo sensor. If continuity exists, check connections, wiring, or fuse. Repair or replace as necessary.
  4. Warm engine to normal operating temperature. Connect vacuum gauge to distributor diaphragm vacuum hose. No vacuum should exist (vacuum should exist on auto, trans, equipped models).
  5. If correct vacuum reading is not obtained, check thermo sensor continuity. If continuity exists, replace defective thermo sensor. If no continuity exists, replace defective ignition solenoid valve.
  6. Increase engine speed to 2000 RPM. Vacuum gauge should indicate vacuum. If not, clean carburetor vacuum port and inspect all vacuum hoses and connections. Repair or replace as necessary.
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