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1977-78 Models (Servo Diaphragm Test)

  1. Connect tachometer to engine. Start and warm engine to normal operating temperature. Stop engine and remove air cleaner. Disconnect tube between servo diaphragm and vacuum control valve at servo diaphragm.
  2. Disconnect vacuum tube at manifold, between vacuum control valve and intake manifold. Run tube directly from intake manifold to servo diaphragm in order to apply manifold vacuum to diaphragm. See Figure.
  3. Disconnect and plug distributor vacuum advance hose at distributor. Start engine. Engine speed should increase to 1300-1500 RPM. If not, turn throttle opener adjusting screw. If correct RPM cannot be reached, replace servo diaphragm.
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