Air Intake
Purge Valve
A purge valve controls when fuel vapors stored in the EVAP charcoal canister are drawn into the engine and burned. We carry 30 purge valves from $17 to $154 by AC Delco, Dorman, Standard Motor Products and Motorcraft, with fitments for Camaro, Ford Fusion, F150, Mustang, Mazda 3 and Hyundai Santa Fe.
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What the purge valve does
Gasoline gives off vapors that the evaporative emissions system traps in a charcoal canister instead of venting them to the air. When the engine is warm and running, the engine computer opens the purge valve so intake vacuum pulls those vapors into the engine to be burned. The valve is an electrically controlled solenoid, usually mounted in the engine bay near the intake or along the vapor line.
Signs of a bad purge valve
A check engine light with an EVAP flow or leak code is the most common sign. A valve stuck open can cause rough idle and hard starting right after refueling, since it pulls extra fuel vapor into the engine. A valve stuck closed can cause a fuel smell or a failed emissions readiness check.
Cracked vapor hoses and a loose gas cap trigger similar codes, so inspect them too.
Choosing and installing
Purge valves vary by mounting, hose size and connector. Compare your old valve's part number and shape with the listing, then check the fitment table for your engine.
Most are simple to swap: unplug the connector, release the hoses and remove the mounting bolt or bracket. Inspect the hoses for cracks and replace any that are brittle. Clear the codes after the repair and let the EVAP monitor run over normal driving.
Purge Valve questions
Can a bad purge valve cause hard starting after filling up?
Yes. If the valve sticks open, fuel vapor can flood the intake after refueling, which makes the engine hard to start and rough for a moment. This is a well known symptom of a stuck purge valve.
How do I test a purge valve?
With the engine off, the valve should normally be closed, so blowing through it should be blocked. Applying 12 volts should open it with an audible click. Check the service information for your vehicle's test steps.
Is a purge valve the same as a vent valve?
No. The purge valve sits between the canister and the engine. The vent valve sits on the canister's fresh air side and closes during leak tests. Both can set EVAP codes, so confirm which one has failed.