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Thermal Vacuum Spark Control Valve

  1. Disconnect vacuum hose from port "1" of the CTO valve. Connect vacuum gauge to disconnected hose. Start engine.
  2. With air cleaner intake temperature below 63°F, manifold vacuum should be indicated on gauge. Above 63°F, no vacuum should be indicated. If valve fails this test, replace valve.
    Fig 1: California 4 Cylinder Spark Control System (Federal Similar, Exc. No C-4 or Thermal Vacuum Valve)
    G09348425Courtesy of CHRYSLER GROUP, LLC
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