Purge Valve (Functions, Symptoms, Replacement, & Testing)

Are you having an issue with your car emission system? Is your car having difficulty starting? These problems could be a result of a bad purge valve. This article will explain all you need to know about the purge valve.

The purge valve is an essential component of your vehicle’s EVAP system.

The Evaporative Emission Control System (EVAP System) prevents the fuel vapors in your vehicle’s fuel tank from venting into the air and escaping into the vehicle’s cab (the area of the vehicle where the driver sits.

It collects fuel vapors from the tank and then temporarily stores them in a charcoal container. Fuel vapors are removed from the canister and burnt within the combustion engine in certain scenarios. This is where the purge valve comes into the picture.

The purge valve is an emission control component that allows the engine intake vacuum to take the exact amount of fuel vapors from EVAP charcoal canisters into the engine intake manifold.

This article will discuss everything you need to know about your vehicle’s canister purge valve, how it works, bad purge valve symptoms, purge valve replacement cost, and how you can go about purge valve replacement.

We also go in-depth to discuss how to test a purge valve, how to clean a purge valve, and lots more.

Let’s get started!

In modern cars, the purge valve is controlled by a solenoid electrically. A purge valve is open when the engine is running; when it is turned off, the purge valve will be closed. 

A purge valve allows some fuel vapors from the charcoal canister to be transferred to the engine, where they will be burned. Certain Sensors are responsible for the monitoring of the purge flow. The check engine light also assists in indicating when the purge flow is lower or higher than expected. 

What Does A Purge Valve Do?

The purge valve controls the amount of fuel vapor that is released from the charcoal canister back into the engine for combustion.

The EVAP system will slowly permit fuel vapors to be discharged into the engine, where it will burn like regular fuel. The canister purge valve will control these flows and regulate the amount of vapor that will enter the engine. 

What Are The Symptoms of a Bad Purge Valve?

Symptoms of a Bad Purge Valve

You will likely see a check engine warning light if you have a bad purge valve. The check engine light will come on if the vehicle’s computer detects an unusually high or low purge level.

The following are some bad purge valve symptoms:

1. The Check Engine Light Is On

The first sign of a bad canister purge valve is an illuminated check engine light. The purge valve is controlled by your car’s computer, permitting it to observe and manage its performance. 

When the purge level is higher than expected, your car’s computer will cause the check engine light to come on, and it also displays standard error codes like P0441 or P0446. If your check engine light turns on, immediately take your car to a certified mechanic who can help diagnose the problem and fix it.

2. Car Stating Problems

If your car won’t start, it could be due to a bad canister purge valve. Air from outside can get into the engine when there’s a leak in the vacuum caused by a bad purge valve. This can result in an inability of the combustion process to take place. 

Inadequately filtered air that is mixed with fuel inside the cylinder chamber may cause engine issues which the most noticeable one is an engine that is difficult to start.

3. Engine Problems

When the canister purge valve is not closed correctly, it can adversely affect your engine. Your car will end up taking in excess air because your car computer won’t be able to control the amount of air that comes in.

This will either increase or decrease your car’s air-fuel ratio, resulting in a rough idle where your car bounces or jumps while it is running.

It can also lead to the failure of the canister or the malfunctioning of other parts of the EVAP system. 

4. Lower Gas Mileage

Improper functioning of your car canister purge valve can also affect your car’s gas mileage.

In fact, the fuel vapors located in the combustion chamber will be directed to the EVAP container, from where they are released into the air. This results in the loss of fuel. 

Also Read: Idle Air Control Valve (IAC Valve) – Everything You Need To know

Driving with a faulty valve is possible; however, it exposes your valve to further damage as well as damaging the EVAP system. Additionally, it damages other car components. 

When driving with a bad purge valve, you will notice black smoke coming from the exhaust pipe; as soon as you observe this smoke, stop your car immediately and take it to the nearest mechanic for a quick inspection and repair. 

Not taking these signs of a faulty purge valve seriously will lead to more problems and costs. Especially damage to the catalytic converter, which can cost between $950 and $2500 to replace, depending on the model and type of car.

When you factor in the cost of other components that have been affected and the labor cost, you will realize that taking the early signs seriously would have saved you lots of cash. 

Most cars do not experience purge valve failure often, but a quick fix is essential when it does. 

How To Test Purge Valve With Multimeter

How To Test Purge Valve With Multimeter

Follow this step-by-step guide to learn how to test purge valve with a multimeter.

  1. Detach the clamps on both the outlet and inlet lines that hold the purge valve from the engine and fuel tank.
  2. Keep your car idle for at least 30 minutes.
  3. Make sure your digital multimeter settings are changed to continuity mode; your meter will produce an audible sound if you touch the probes.
  4. Connect the purge valve power connector with the probes. If you start hearing a sound, that’s proof that the purge valve is working perfectly. Many purge valve devices are solenoid in nature, which means that they have cooper and metallic coil within their casings, which link the positive and negative power terminal.
  5. If there’s no audible sound, that means the purge valve is damaged and will need an urgent replacement.

Testing The Purge Valve Ohm Meter Readings With Multimeter

  1. You can see the multimeter dial’s number in the ohm-meter setting; turn it on.
  2. Place it on the purge valve power linkage with two lead probes.
  3. Check for readings on the digital multimeter. Ideally, readings between 14 to 30 ohms indicate that the purge valve is OK. Over or below that range means something is wrong with the purge valve, and urgent replacement is needed as soon as possible.

Canister Purge Valve Replacement Procedure

Here is a step-by-step guide to show you how to carry out a canister purge valve replacement.

1. Disconnect The Vehicle’s Battery

Your car canister purge valve is connected to an electrical power terminal that provides electrical energy to the device for primary purposes like turning on and off.

For this reason, you must first disconnect the power source before replacing the purge valve. This can be done by taking out the battery’s positive and negative cables.

2. Locate The Canister purge valve

The canister purge valve is located above the engine or on the side of the fuel system, and this is the same for most vehicles. An electrical harness, as well as two vacuum lines, are attached to your canister purge valve. 

One of these lines is connected through the fuel injector rail, and the other is linked to the EVAP canister, located close to the fuel cell.

If you locate a canister purge valve, make sure that it is the same as the replacement purge valve before you remove it from the connections.

3. Disconnect The Wiring Harness

When locating the purge valve, disconnect the electrical harness connected to the canister purge valve.

4. Take Out The Vacuum Lines

A great tip that knowledgeable mechanics are aware of is to mark the position of each vacuum line to ensure you can ensure that they are not installed backward.

Note: Use either masking tape with different colors, or even two zip ties of different colors to mark the vacuum line that is secured to the various male fittings.

Once you’ve clearly marked them then take them out as per the guidelines in the vehicles manual.

5. Disconnect The Canister Purge Valve

The purge valve is usually attached to a bracket close to the fuel injection rail or the firewall by a bolt that is 10mm in size. Unbolt the bolt, and then remove the purge valve from the vehicle.

6. Install The New Canister Purge Valve

The installation of this part is the reverse of removal. Follow these general guidelines, but always consult the specific directions in your service manual for your vehicle.

Install new vacuum hoses onto the canister purge valve (if the previous ones are damaged).

Install the new purge solenoid by fixing it onto the bracket using the bolt. Connect the vacuum lines using the proper male fittings, and then reconnect the electrical harness.

Once the canister purge solenoid is fitted to your vehicle in a correct manner Make sure to check your vacuum lines one more time to ensure they were correctly installed. Improper installation can cause severe engine damage.

7. Clear Error Codes

Reconnect the battery cables on the respective positive and negative terminals. Then start your car then, use a scan tool, remove all error codes. 

8. Test Your Vehicle

As you turn on the car engine, allow it to warm up until a comfortable operating temperature is achieved. Make sure the check engine light does not appear on the dashboard; if it does, shut off the engine and perform a diagnostic test. 

After you have checked that the Check Engine light or other lights are off, turn the engine off and then remove the gas cap. This test will confirm that the vacuum is functioning properly.

If you discover a vast amount of vacuum pressure after removing the gas cap, you should determine if the vacuum lines connected to the canister purge valve are crossed. 

Here is a video guide to show you how to replace a purge valve

How to Clean Purge Solenoid Valve

you can clean Purge Solenoid valves using two methods depending on how experienced you are technically and how dirty the purge solenoid valve is.

Here is a step by step guide to show you how to clean purge solenoid valve using 2 methods

How to Clean Purge Solenoid Valve without Opening it

  1. Spray a sufficient amount of Carburetor Cleaner or Mass Air Flow Cleaner into the two tubes of the purge valve.
  2. After you spay the cleaner, use your fingertips to cover both ends of the tube and then shake thoroughly. Do this for a few minutes and the cleaner should have removed all the dirt in the tube.
  3. keep the tube closed and After a minimum of 30 minutes, open the tube ends and let the cleaner that you have sprayed completely out of the tubes. The liquid that is drained would appear dark and flecked with dirt, debris, and charcoal. Continue Steps 1 and 2 repeating the steps repeatedly. When you can see that the liquid that has been drained appears clear and clean This should indicate that the valve is free of dirt.
  4. Shut off the connector valve when you are spraying the contact cleaner. Then, let everything dry completely.

How to Clean Purge Solenoid Valve by Opening It (Deep Cleaning)

Don’t attempt to thoroughly clean your purge solenoid valve if you don’t have the right understanding of the steps. In any case, you can open a purge valve using the aid of a screwdriver or small knife.

  1. In the majority of purge valves, the two halves are bonded to each other by glue. Therefore, take out as much glue as you can before you begin. After you have removed the glue, you can break it apart to split each end of the casing in a secure manner, but take care to be extra cautious.
  2. After you have separated both halves you’ll see a small cap-like round piece on one half of the purge valve and also on the other half, you’ll find all the parts that work including the solenoid. you can then remove the valve’s body from the casing.
  3. Examine the condition of the rubber components and the O-rings. If they’re functioning and in good condition, you can attempt to lubricate them with silicone grease.
  4. Spray the Carburetor Cleaner or Mass Air Flow Cleaner onto the inner walls of the solenoid. It’s an excellent idea to rub the openings using the aid of a clean cloth for a thorough cleaning.
  5. After cleaning is completed then you need to seal the case using adhesive or rubber. When sealing your valve using rubber or sealant, make sure that you put everything back together properly as it could be difficult to open the two sides of a valve sealed. When you have sealed the valve allow the rubber or glue to dry.

Vapour Canister purge valve bypass

purge valve bypass

It is not advisable to bypass your purge valve as it can cause hap to your vehicle. if your purge valve gets bad, you can just follow our purge valve replacement steps to replace a bad purge valve yourself.

Also Read: Car Leaking Oil When Parked (Causes and Fixes)

Frequently Asked Questions

What is a purge valve?

The purge valve is an emission control component that allows the engine intake vacuum to take the exact amount of fuel vapors from EVAP charcoal canisters into the engine intake manifold.

Can I drive with a bad purge valve?

While it is possible to drive with a damaged purge valve, we do not recommend it. A bad purge valve can cause damage to the vehicle’s engine, EVAP system, and other components. You also have the risk of burning fuel or releasing more emissions than necessary.

How Much Does a purge valve cost?

On average purge valve replacement costs between $110 and $170. A Purge valve cost between $75 to $110, while labor costs range between $40 to $55. This price range does not include taxes or fees and does not consider your vehicle’s make and unique location. Other repairs might also be required.

What causes a purge valve to fail?

Causal Failure Factors
If the canister or any of its supply lines are blocked or have holes, the purge valve solenoid will not function, and it will stay closed. The purge valve solenoid’s electric portion may fail, and the valve can remain closed.

Can you fix a purge valve?

Yes, you can fix a purge valve.
On average purge valve replacement costs between $110 and $170. Parts cost between $75 to $110, while labor costs range between $40 to $55. This price range does not include taxes or fees and does not consider your vehicle’s make and unique location. Other repairs might also be required.

Will a bad purge valve cause bad gas mileage?

If a canister purge valve does not open properly, it could cause a decrease in gas mileage. Your car’s combustion vapors will be sent to the EVAP container, where they are released into the atmosphere. This allows you to burn some of the fuel your car normally uses.

Is a purge valve easy to replace?

Replacing a purge valve is an easy task that anyone can do with the right knowledge. On average purge valve replacement costs between $110 and $170. Parts cost between $75 to $110, while labor costs range between $40 to $55.

Should a purge valve tick?

The purge valve ticking sound is normal and should be ignored when the windows are open. The valve should be replaced if it becomes too loud in the cab. When you refuel, the purge valve could be leaking vapor into your engine.

What happens if the purge valve is stuck closed?

The canister purge valve that is in its closed position will stop the engine from burning evaporated fuel. This can lead to a low purge code, leading to premature failure of the charcoal container in the evaporative emission system.

How do I know if my purge valve is stuck open?

Problems with the purge valve that stick or don’t close completely are the most common. This can cause the “Check Engine” warning light to go on. A stuck-open purge valve can cause problems with your car right after refueling at a gas station. The engine might stumble and run rough for the first few seconds.

Can a bad purge valve cause smoke?

The exhaust system emits white smoke that indicates coolant (water) within it. As the purge valve solenoid gets bad, the vehicle’s EVAP system could pick up vapor from either the exhaust or the fuel vapor canister.

Where is the purge valve solenoid located?

Most often, the Canister purge valve is located in the engine bay. It can be found on a hose that runs from the intake too. You can also find it near the fuel tank.

Can a bad purge valve cause overheating?

No, a bad purge valve cannot cause overheating. Symptoms of a bad purge valve included, low gas mileage, engine problems, and car starting problems

Can a purge valve cause a misfire?

An open purge valve typically transfers fuel vapors, which contributes to 5-10% of the fuel mixture burned in the cylinders. The purge valve could be bad if your car tends to misfire or not run smoothly.

How much does it cost to replace a purge valve?

On average purge valve replacement costs between $110 and $170. Parts cost between $75 to $110, while labor costs range between $40 to $55. This price range does not include taxes or fees and does not consider your vehicle’s make and unique location. Other repairs might also be required.

Is a purge valve normally open or closed?

The Purge Solenoid, which is normally closed, is opened by PCM to allow manifold vacuum within the EVAP systems — drawing fuel vapors. The fuel vapors in the tank transfer to the canister when the switching solenoids open with the command from the PCM.

How long does it take to replace a purge valve?

The time it takes to replace the purge valve, which is located near the fuel tank, would be between 30 minutes and 2 hours. Because the vehicle must be raised, it takes longer. If there is a spare, it should be removed. The fuel filler neck should also need to be removed if it is in the way.

How often does a purge valve go bad?

The canister purge solenoid is designed to last the lifetime of your vehicle. However, it can wear down from time to time. The Check Engine light will turn on if the canister purge solenoid is not working correctly and your car won’t pass an emission test.

Conclusion

The purge valve is an emission control component that allows the engine intake vacuum to take the exact amount of fuel vapors from EVAP charcoal canisters into the engine intake manifold.

The purge valve is an essential component of your car’s EVAP system; a bad purge valve is a threat to the life of your car engine. If any of the signs are related to a bad purge valve, please ensure you take your car to an experienced mechanic for proper examination and repair. 

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