How to Replace a Vapor Canister Purge Valve
If you have ever driven or even been near a car then you’ve likely noticed the distinct, and in some cases, even overpowering, smell that occurs. This smell results from the fuel evaporating, causing pollution and health issues as it disperses out and into the open air. Manufacturers created the EVAP (Evaporative Emission Control) system to address this issue.
This system has multiple components, and if any of them fail, it can cause difficulties for your car, your health, and the environment. A malfunctioning canister purge valve can cause issues, from poor fuel economy to the check engine light flashing when it isn't supposed to.
The vapor canister purge valve is an integral part of the EVAP system, but it is also prone to malfunction over time. This article will cover how to replace one, and also explain what vapor canister purge valves do and how they affect the performance of an EVAP system.
How To Replace Your Vapor Canister Purge Valve
Step 1 - Disconnect the Vehicle’s Battery
The vapor canister purge valve is attached to a power source that provides electricity to the device, allowing it to turn the solenoid on and off. As a result, disconnecting the power supply by removing the positive and negative battery wires should be done first before replacing this part.
Step 2 - Locate the Vehicle’s Vapor Canister Purge Valve
This component is usually found on top of the engine or at the back of the fuel system on most automobiles. It will be equipped with an electrical harness and two vacuum lines, one of which connects to the fuel injector rail and the other to the EVAP canister near the fuel cell. Before removing this component, make sure it matches the replacement part.
Step 3 - Remove Both Electrical Harness and Vacuum Lines
Once you've found the right part, follow the instructions in your repair manual to separate the electrical harness from the purge valve and the vacuum lines. Mark the location of each vacuum line so that you don't install them backward, as many expert mechanics know.
To distinguish which vacuum line secures the correct fittings and where they need to be re-inserted, use colored masking tape or two distinct colored zip ties.
Step 4 - Remove the Vapor Canister Purge Valve
Once you’ve found the vapor canister purge valve and have removed the harness and vacuum lines, you can now remove the valve. 10mm diameter bolts are commonly used to secure this component to a bracket found near the fuel injector rail or the firewall. Remove the old canister purge valve from the car by removing the bolt and setting it to the side.
Step 5 - Install the New Vapor Canister Purge Valve and Replace the Vacuum Lines and Harness
The procedure for installing this component is the same as for removing it, simply put it back in reverse, then resecure the valve with the bracket and bolt. Follow these broad recommendations, but always refer to your vehicle's service manual for precise instructions.
Once the vapor canister purge valve is back in place, reinstall the vacuum hoses or install new ones if the old ones are frayed. Finally, reinstall the electrical harness.
Step Six - Clear Codes and Test Vehicle
Next, start the vehicle by reconnecting the battery cables. If you have a scanning tool, use it to remove incorrect codes. Warm up the car by starting it and letting it warm up to operating temperature and verify that the Check Engine Light no longer lit up on the dashboard.
If your check engine light is still lit, you should turn off the car and run a diagnostic scan. Turn the vehicle back off and remove the gas cap after confirming that the Check Engine or other lights have gone out.
This test will ensure that the suction is operating correctly. If there is a lot of vacuum pressure when you remove the gas cap, double-check the lines you connected to the vapor canister purge valve in case they became crossed when replacing the valve.
What Is a Vapor Canister Purge Valve and What Does It Do?
The vapor canister purge valve, also known as a canister purge solenoid or simply purge valve, is integral to a vehicle's Evaporative Emission Control, or EVAP, system. This valve is named because it prevents fuel vapors from escaping into the atmosphere by catching and keeping them in a charcoal canister.
The EVAP system permits these vapors to be discharged into the motor when it starts regularly operating, where they are burned like ordinary fuel. The canister purge valve in your vehicle regulates vapor flow, deciding when and how much vapor enters your vehicle's powertrain.
The purge valve in modern cars is an electronically powered solenoid controlled by the engine computer and is typically closed when the engine is off. When used, this purge valve may make a repetitive clicking noise under the hood.
Fuel vapors from the gas tank are kept in the canister when the engine is turned off. The activated charcoal in the canister holds fumes until the engine is operating and the conditions are suitable for a vapor purge.
The charcoal canister usually is open to the atmosphere to enable fresh air to enter. However, in modern vehicles, the engine computer, often known as the powertrain control module (PCM), seals the charcoal canister when testing the EVAP system's integrity. The PCM uses a vent valve solenoid to open and close the canister.
The PCM also determines when a canister purge should be started. When the module determines that everything is in order, it instructs a solenoid to open the purge valve. Because the solenoid is usually integrated with the valve, it's commonly referred to as a canister purge valve solenoid.
What Causes Your Vapor Canister Purge Valve to Go Bad or Be Unable to Close?
The canister purge valve can become damaged in a variety of ways. Here are a few of those causes:
A faulty canister purge valve can be caused by physical scratches, dents, or cracks. Internal engine parts such as the valve crack due to extreme weather, such as being too cold or too hot, and such physical damage necessitates the repair of the purge valve right away.
Clogged Intake Supply Lines
If there isn't enough vapor flowing through the supply lines, the sensors will alert the PCM. When the vapor is still in the clogged supply lines, the PCM will eventually order the valve to open or close. Clogged supply lines can happen due to accumulating dirt and grime, and they are more likely when interior vehicle parts are neglected.
The EVAP system's canister purge valve works in tandem with the rest of the system; its operation is essentially a reaction to the flow of pollutants into the engine intake manifold. The check engine light will light up if there is a leak in the EVAP system, suggesting that the canister purge has been compromised.
The purge valve works in combination with the vehicle's PCM and is therefore dependent on how the sensor works. Any probable digital malfunction causes the valve to become stuck in place or open and close at the incorrect times.
Can You Drive with a Bad Vapor Canister Purge Valve?
Though it is never recommended, you can, in theory, drive a car with a purge valve. A malfunctioning purge vapor canister valve can allow raw fuel to enter the intake system, causing the engine to run "rich" and emitting black smoke.
If you notice this, the car should not be driven until the maintenance is completed and the valve has been replaced, as it could cause damage to the catalytic converter of your vehicle.
The cost of replacing a catalytic converter is quite expensive, with the average repair costing between $945 and $2475 depending on the kind of vehicle and including components and labor. This repair and replacement cost is far more expensive than replacing the purge valve.
What Are Some Symptoms of a Bad or Stuck Closed Vapor Canister Purge Valve?
A vacuum can emerge if the canister purge valve is stuck open, and your car's engine may suffer. Because the air will enter the machine in an unknown quantity, the computer in your car will react, resulting in rough idling and difficult starts.
If both of these problems co-occur, the canister purge valve or another component of the EVAP system is most likely to blame.
Lowered Gas Mileage
Your gas mileage may be affected if a canister purge valve does not open, either because it is broken or blocked. The combustion vapors in your automobile will proceed to the EVAP canister, where they will be released into the environment, leading you to utilize part of the gasoline that your car would typically burn.
Check Engine Light Turns On
Perhaps one of the easiest ‘tells’ of a faulty or closed vapor canister purge valve is a check engine light that has turned on. In this situation, your car's computer monitors the performance of the canister purge valve.
If the computer detects a higher or lower level of purging from the valve, the check engine light will illuminate. P0441 or P0446 or other EVAP codes are standard error codes caused by a defective canister purge valve.
Failure of an Emissions Test
Just as the vapor canister purge valve helps return gasoline vapors into a vehicle's engine, it also helps prevent some harmful hydrocarbons from exiting your car's tailpipe/exhaust. Don't be shocked if this problem causes your vehicle to fail emission tests, putting you in serious legal jeopardy in some countries or locations with strict emission standards.
Fuel Tank Collapses
An utterly open purge valve can cause the fuel tank to collapse or distort; however, this is unlikely. When the canister vent valve is closed, new air cannot be sucked into the EVAP system, causing the problem.
When the purge valve is jammed open, and the vent valve is closed, the EVAP system creates an excessive vacuum. The scenario can result in the fuel tank being sucked in and partially collapsing in some rare cases.
How Can You Check Whether Your Vapor Canister Purge Valve Is the Issue?
The purge valve should be tested regularly for an effective vehicle maintenance regimen. While the exact technique varies depending on the vehicle's make and model, it may involve measuring the amount of voltage created using power from a battery on the purge valve.
A vacuum pump can also be used to test whether the purge valve closes properly. The valve works properly if the battery voltage creates a clicking noise and the pump instantly lowers. If the valve does not function properly, it should be replaced or repaired as soon as possible to avoid further complications.
When Should You Replace Your Vapor Canister Purge Valve?
The canister purge solenoid usually lasts the vehicle's life, but it can fail at any time.
If the canister purge solenoid fails, it is typically due to dirt and dust clogging the canister from constant driving or driving in rougher, dustier, or drier terrains.
Furthermore, the canister may shatter due to extreme climatic conditions such as excessive heat or cold. The canister purge solenoid should be changed if this occurs, as it may cause damage to other components in your car.
How Much Does It Cost to Replace a Vapor Canister Purge Valve?
Replacing a canister purge solenoid is a relatively simple task that should not cost too much money or take too much time. In total, expect to pay between $80 to $200. The part will generally cost between $30 to $120, with labor expenses ranging between $50 and $80. Then there are often fees and taxes on top of that.
Of course, you can save a few dollars on labor by replacing the purge valve yourself, especially if you have any kind of car or mechanical knowledge.
Your vehicle's engine's EVAP system and vapor canister purge valve work together to regulate the quantity and quality of fuel gas entering the engine intake manifold from the charcoal canister. If these systems or components are not working properly, they can very well cause performance issues.
The issues and symptoms of a faulty purge valve range from difficulties starting the car to low fuel mileage. As a result, canister purge valve repair is a critical maintenance duty, whether you want to hire a mechanic or do it yourself.