Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Canister Control Valve
There are 2 types of canister control valves. See Figure . The first type of valve performs function as fuel bowl vent and canister purge. When engine is not running, spring tension holds valve open allowing venting of float bowl. When engine is running, manifold vacuum pulls plunger up to close valve.
The second type of valve performs function of both vapor vent valve and purge valve. When engine is running, manifold vacuum from PCV system pulls lower diaphragm upward. This turns off venting of carburetor float bowl.
When engine is running above idle speed, control vacuum pulls upper diaphragm upward. This allows purging of canister through PCV system.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.