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Home >> Honda >> 1983 >> Prelude Standard >> Repair and Diagnosis >> Engine Performance >> System >> Fuel Evaporation System >> Component Testing >> THERMOVALVE & Purge Control Diaphragm Valve

THERMOVALVE & Purge Control Diaphragm Valve

  1. With engine cold, disconnect upper hose at purge control diaphragm valve and connect vacuum gauge to hose. Start engine and run at idle speed. Check that there is no vacuum.
  2. If there is vacuum, check thermovalve B. Drain coolant until level is below distributor holder. Remove distributor holder from cylinder head, then remove thermovalve.
  3. Attach hand vacuum pump to thermovalve. Suspend thermovalve in cold water with thermometer. Draw a vacuum on valve, then heat water slowly making note of temperature.
  4. Thermovalve B should open (not hold vacuum) below 97°-111°F (36°-44°C) and close (hold vacuum) above 115°-129°F (46°-54°C). If it does not, replace valve.
  5. If there was no vacuum, warm engine to normal operating temperature. Check that there is vacuum at idle speed. If not, check thermovalve B by pinching off hose to the air filter.
  6. If vacuum is now present, replace thermovalve B. If not, check hoses 7 & 19 for leaks or blockage. See Figure . Disconnect vacuum gauge and reconnect hose.
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