A purge valve or canister purge valve as it is sometimes called, is used to control emissions in a vehicle. Its part of the Evaporative Emission Control (EVAP) system. The purpose of this system is to prevent fuel vapors from leaving the fuel tank and escaping into the environment. It does this by trapping the vapors in a charcoal canister.
What is a Purge Valve?
A purge valve is an electronically operated solenoid valve that stops the fuel vapors from escaping the gas tank when closed. When the valve is opened, fuel vapors enter the intake manifold and are burned in the engine. Problems can arise in the engine if the purge valve gets stuck or opens or closes at the wrong time.
When the engine is off and the solenoid is not energized, the purge valve will be closed. When the engine is running it will be opened.
Symptoms of a Failing Purge Valve
The most common issue that purge valves have is getting stuck open or close. This problem can manifest itself in several different ways. One of the more common ways is that the Check Engine Light will appear. If the check engine light comes on and has a P0441 or P0446 code, its likely that the purge valve is stuck open. If the check engine light does not come on, but you have a faulty purge valve, yo may notice some of the following symptoms:
Poor Fuel Economy
A purge valve that is stuck open could adversely impact your fuel economy. This is because a portion of the fuel vapors from the gas tank are being bled off into the atmosphere instead of being combusted in the engine. Think of it like a small leak in your gas tank. Its bad for the environment and your wallet.
Car Won’t Start After Fueling Up
So you just got done filling up your car with $3 a gallon gas and now it won’t turn on. While this could be caused by a faulty fuel pump, it also can be caused by a leaking purge valve. When a gas tank is filled, tons fuel vapors are generated. If these vapors leak past the purge valve and into the intake manifold before the engine is running, it can throw off the air/fuel mixture. This gives your car a hard start or stops it from starting in the first place.
Rough idling is another symptom of a bad purge valve. The cause of rough idling in this case would be the purge valve being stuck open creating a vacuum leak. Vacuum leaks commonly cause rough idling, hard starting, high idle rpm, and even poor acceleration. If you notice any or all of the symptoms, the purge valve could be to blame.
Check Engine Light
A faulty purge valve can cause your car to throw a code. The most common codes are P0441 and P0446. In this case its likely that the purge valve solenoid is not completely closed or stuck open. This can throw off the air and fuel mixture in the engine causing hard starts and rough idling for the first few seconds when the engine starts. Bottom line is that it is not uncommon for a vehicle with a failing purge valve to have one or all of the symptoms on this list. Driving with a damaged purge valve is not recommended and it could leave you stranded.