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Pickup & 4Runner

  1. Warm up engine, disconnect hose from distributor sub-diaphragm and plug hose end. Check ignition timing. Timing should be 0 degrees BTDC at 950 RPM maximum. Reconnect hose to sub-diaphragm. Check that ignition timing advances to about 12 degrees BTDC.
  2. Disconnect vacuum hose from lowest port of HAC valve, and plug hose end. Disconnect vacuum hose between check valve and vacuum pipe at pipe side, and plug end of pipe.
  3. Check that ignition timing remains stationary for longer than one minute. If timing changes, replace check valve. Stop engine and reconnect hose to vacuum pipe and HAC valve.
  4. Disconnect 3 hoses from ports on top of HAC valve. Blow air into each hose and check that air flows into carburetor. Reconnect hoses to proper locations.
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