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Vacuum Test

  1. Connect a tachometer to engine. Connect a vacuum gauge to hose at point "A". See Figure. Ensure temperature sensing switch is over 65°F. Disconnect lead at point "B".
  2. Run engine at 1500 RPM, vacuum should be about 15 in. Hg. If not, check vacuum source back to carburetor spark port.
  3. Connect test lead at point "B". See Figure. There should be no or low vacuum. If vacuum is present, check vacuum valve ground and electrical source back to ignition switch.
  4. Run engine at 3000 RPM, vacuum should be about 9 in. Hg. If not, check vacuum source back to carburetor EGR port.
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