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System Tests: Tercel

  1. Disconnect 2 hoses from top of HAC valve. Blow air into each hose. Check that air flows into carburetor. Reconnect hoses.
  2. Remove check valve. Check that air flows from Orange pipe to Black pipe, but not in other direction.
  3. Remove distributor cap and rotor. Apply vacuum to diaphragm. Check that vacuum advancer moves in accordance with applied vacuum. Reinstall the rotor and distributor cap. Start engine.
  4. If at high altitude, disconnect and plug vacuum hose between sub-diaphragm and check valve. Ignition timing should be 5° BTDC. Reconnect hose. Timing should advance to 13° BTDC.
  5. Disconnect and plug hose from Black side of check valve. Timing should not change for at least 1 minute. Stop engine and reconnect hose.
  6. If at low altitude, disconnect and plug vacuum hose between HAC valve and bimetal vacuum switching valve at HAC valve side. Disconnect and plug vacuum hose between distributor sub-diaphragm and check valve at sub-diaphragm side.
  7. Ignition timing should be 5° BTDC. Reconnect hose to sub-diaphragm. Timing should advance to 13° BTDC. Disconnect and plug hose from Black side of check valve. Timing should not change for at least 1 minute. Stop engine and reconnect hose.
Fig 1: Tercel High Altitude Compensation System
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