The purge valve is part of the vehicle Evaporative Emission Control (EVAP) system.
The EVAP system prevents fuel vapors in the fuel tank from escaping into the atmosphere. The EVAP system traps fuel vapors from the fuel tank and temporarily stores them in the charcoal canister.
When the engine is running under certain conditions, the fuel vapors are purged from the canister and burned inside the engine. The purge valve precisely controls the amount of fuel vapor that is purged from the charcoal canister.
In modern cars, the purge valve is an electrically-operated solenoid that is controlled by the engine computer. When the engine is off, the purge valve is closed. When the engine is running and fully warmed up, the engine computer gradually opens the purge valve to allow some fuel vapors to be moved from the charcoal canister and burned in the engine.
Several sensors monitor the purge flow. If the purge flow is less or more than is expected under the conditions, the computer illuminates the “Check Engine” light.
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Purge valve problems
The most common problem with the purge valve is when it sticks or does not close fully. This may cause the “Check Engine” warning light to come on. In some cars, a stuck-open purge valve can cause difficulty starting right after refueling at a gas station: for the first few seconds, the engine may run rough and stumble.
Purge valve problems are common in many cars. In some early-2000’s Hyundai models (Elantra, Santa Fe, Tucson, Tiburon), a stuck-open purge valve is fairly common to cause the “Check Engine” light with the code P0441. Similar problems are fairly common in many European cars, including Audi and Volkswagen.
In some Mazda vehicles, the faulty purge valve can cause the code P0446 and other EVAP codes. The purge valve is not very expensive ($35-$65 for the part) and is fairly easy to replace.
How do I know if my purge valve is bad?
There are many symptoms that a malfunctioning EVAP system emits. Look out for:
Engine Light
The engine controls the purge solenoid, and if anything fails, the engine light will turn on. When higher or lower purged vapors are detected, error codes, including P0446 or P0441, are displayed. If you notice the above indicators, we recommend taking the vehicle to a repair shop.
Problems with Engine
If the purge valve has failed to close, it may negatively affect the air to fuel ratio due to vapors’ leakage into the nearby environment. The engine will react to the change, leading to difficulty in powering up or rough idling.
Lower Gas Mileage
When the EVAP system doesn’t work effectively, it will inevitably decrease the gas mileage. Instead of being stored in the purge valve, the fuel vapors will start seeping out into the environment, causing increased fuel combustion.
Poor Performance in the Emissions Test
The canister EVAP is responsible for redirecting the fuel vapors back into the engine. It helps in preventing the noxious fumes from escaping into the environment. In the case of a faulty solenoid, it wouldn’t control the fumes, and it will fail emission tests.
Ruined Gaskets
Since the vapors will not pass when the valve malfunctions, the pressure will start building up. Over time, it will become so intense that it can blow out rubber seals and gaskets. Subsequent consequences will be oil leakage, which can spill out the emission system into the main engine causing severe damage.
The most common reason for the less than ideal performance of the purge valve is the pieces of carbon or foreign materials getting stuck, which results in the mechanism remaining partially closed or open. It will require a replacement or cleaning.
3 Steps to Test the Purge Valve using Multimeter
A multimeter is an electronic measuring device that can measure electric current, resistance, and voltage. In the case of a purge valve, you will want to test the purge valve terminals’ resistance. The procedure for testing a purge valve may differ for each model vehicle, but the basic concept is the same.
Below are the three common steps for testing a car purge valve with a multimeter.
Locate the Purge Valve
Make sure your engine is turned off. Leave the engine off for 15 to 30 minutes. Locate the purge valve of your vehicle. You should find it in the back of the muffler on the top of it. This is the EVAP canister location, so you’ll find the purge valve within the canister. Check your vehicle owner’s manual to see what your purge valve looks like.
Disconnect the Harness Connector and Connect the Testing Cables
There should be a 2-pin harness connector attached to the purge valve. What you’ll want to do is to disconnect the harness connector. Take your multimeter device and a pair of adapter cables, which should have come with your multimeter testing kit. If not, then purchase those cables separately. Connect the adapter cables to the multimeter and the terminals of the purge valve.
Test the Resistance
Your goal is to measure the resistance between the terminals. You should see a resistance level of between 22.0 ohms and 30.0 ohms. If you see the resistance is lower or higher than these levels, then it means you should replace your purge valve. You can do that right now if you have a spare purge valve. Otherwise, take off the adapter cables and reconnect the harness connector.
Driving with a bad purge valve- What happens
The purge valve is a fundamental element of a vehicle’s Evaporative Emission Control System (EVAP). Driving with a bad purge valve can harm your engine’s health. It also results in environmental pollution as the toxic fumes are discharged into the environment. Furthermore, the mileage you get is also significantly lower in driving with a bad purge valve.
Can a Bad Purge Valve Cause Misfire?
A bad purge valve can lead to ser predicaments such as causing a misfire. A bad purge valve doesn’t close fully or doesn’t open in time. As a result, an excessive amount of fuel vapor starts gathering in the charcoal canister.
If things continue like this for a more extended period, the engine cylinder is engulfed with fuel vapors that get repeatedly created and burned. These burning vapors can lead to a fire break out in the engine, and the engine may choke.
The solenoid valve is an essential component of a car. If you notice any of the problems listed above, the vehicle should be immediately brought for repairs. In case you want to test out the canister yourself, you can follow the steps with the multimeter, and the device will let you know if you have a malfunctioned valve!
Since we’ve presented you with how to test a purge valve with a multimeter, you may also want to check how to test a capacitor with a multimeter. You may want to check other best multimeter and decide which one fits your testing needs.
We hope this learning article helps you. Good luck!