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HOMESERVICE MANUALSCHEVROLET1981FORWARD CONTROL 4.8L ENG VIN T, STANDARD TRANSREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCEENGINE CONTROL SYSTEMSEVAPORATIVE EMISSIONS SYSTEMTESTING
1981 Chevrolet Forward Control 4.8L Eng VIN T, Standard Trans

Evaporative Emissions System: Testing

1981 Chevrolet Forward Control 4.8L Eng VIN T, Standard TransSECTION Testing
  1. With engine cold, position transmission in "NEUTRAL" or "PARK" and apply parking brake. Start engine and observe movement of actuator rod and exhaust heat valve. Valve should move to its closed position.
  2. If valve does not close, disconnect hose at actuator and check for vacuum. If there is vacuum, replace actuator. If no vacuum is found, disconnect hose at TVS-to-vacuum source. If there is vacuum at hose, replace TVS. If no vacuum, check hose for leaks.
  3. When coolant temperature reaches 180°F (V8) or oil temperature reaches 150°F (6 cylinder), exhaust heat valve should move to the open position.
  4. If valve does not open, disconnect hose at actuator and check for vacuum. If there is vacuum, replace TVS. If no vacuum is present, replace actuator.
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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

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