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Home >> Subaru >> 1987 >> XT DL >> Repair and Diagnosis >> Engine Performance >> System >> Fuel Evaporation System >> Component Testing >> THERMO Vacuum Valve >> Carbureted Engine
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Carbureted Engine

  1. To test thermo vacuum valve, remove valve from engine and connect hoses to valve ports. Cool valve with water, being careful not to submerge valve or allow water to enter valve ports or filter.
  2. With valve temperature less than 126°F (52°C), blow air into bowl vent port. Check that air flows out of top filter port and is blocked at lower port to intake manifold.
  3. Warm valve with hot water until valve temperature is greater than 153°F (67°C). Seal port to bowl vent and blow air into manifold vacuum port. Check that air flow is blocked with port sealed and that air flows freely out of port when opened.
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