What’s that smell? When the smell of gasoline has become pungent in your car’s interior this can signal trouble with the canister purge valve or there may be a leak within the EVAP system. The canister purge valve is a critical component of the Evaporative Emission Control (EVAP) system. Every vehicle in the United States is mandated to be equipped with this emission control system.
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When the canister purge valve or the EVAP system fails this can lead to a host of mechanical problems. A canister purge valve is often diagnosed as EVAP system failure which can be more expensive to repair. How can you determine which one of these components needs to be repaired?
How Does the Canister Purge Valve Work?
The canister purge valve also commonly referred to as the purge valve is designed to trap fuel vapors inside the gas tank and prevents them from permeating the atmosphere by temporarily storing them in a charcoal canister.
When functioning properly, the canister purge valve regulates how much fuel is purged from the charcoal canister. When the engine is running at regular speed, the canister purge valve along with the other components of the EVAP system releases these vapors into the engine where it's burned just like fuel.
In recent years, automakers have turned the canister purge valve into an electrically operated solenoid that’s operated by a computer in the engine. In these modern cars, the canister purge valve or solenoid closes when the engine is turned off. However, when the engine is on and warmed up the computer triggers the opening of the canister purge valve. The EVAP system uses a number of sensors to monitor the purge flow.
Understanding the Evaporative Emission Control System
The Evaporative Emission Control System is complex. Not only does the system trap gasoline fumes but it also ensures that other emissions are burned in the engine. On older vehicles the EVAP system the gas tank uses a spring loaded valve while newer vehicles are equipped with a valve.
A typical EVAP system includes:
- Charcoal canister
- Vents in the fuel lines
- Hoses
- Fuel tank
What Happens When The EVAP System Is Malfunctioning?
Perhaps the most common problems that tend to pop up in the EVAP System are canister purge valve failure and an EVAP leak. While problems within your Evaporative Emission Control System are exactly hazardous they can end up damaging your vehicle. You might be able to get away with driving with a badly functioning EVAP system, it can ultimately decrease your engine’s performance.
When the EVAP system isn’t working your car won’t be able to pass an emission test. In most states, if you can’t pass a smog test you’ll be given a certain amount of time to repair the faulty components or you’ll be required by law to stop driving your car.
What Is An EVAP Leak?
A vehicle’s EVAP system should be sealed. An EVAP leak is a malfunction within the emission’s system. Therefore, when an EVAP leak code is triggered when the computer engine recognizes a leak within the emissions system, this indicates that the sealing has been compromised. When an EVAP leak is detected the computer in your engine will generate the following codes:
Code PP0442: Small Leak Detected
Code PP455: Large Leak Detected
Code PP446: Vent Solenoid Valve Control
Code PP0440: EVAP System
Code PPO411:Incorrect Purge Flow
In many instances, a small EVAP leak usually involves a simple fix. A minor EVAP leak can be a result of:
- Loose or missing gas cap
- Using a fuel cap that doesn’t fit properly on the gas nozzle
- Fuel tank may be leaking
- A leak in a hose within the fuel tank or any of the hoses in the EVAP system
When there is a leak in the EVAP system the Check Engine warning light will flash onto the dashboard. Most of the time drivers won’t know that the Check Engine was triggered by the EVAP system until they go for an emissions test.
If your Check Engine light is on you should have a diagnostic test performed at your local Auto Zone or Auto Advance. The test is free but you’ll have to have a mechanic read the diagnostic results. The codes above are generated when the EVAP System has failed.
What Is Canister Purge Valve Failure?
When the purge valve fails, toxic fuel and harmful gas, and other emissions will be released through the car’s ventilation system. As a result, the car will have to use more fuel to produce the same amount of power.
Sometimes a stuck canister is mistaken for canister purge valve failure. This is because newer vehicles use electronically controlled canister purge valves. Perhaps the biggest problem with the purge valve or solenoid is that when it sticks it can easily get stuck open or closed.
When the canister purge valve is stuck open it creates a vacuum leak that allows air to flow into the engine. This can significantly decrease your engine’s performance. Stuck canister purge valves are common in several of the early Hyundai models. In these vehicles when the canister purge valve is stuck open it produces the PP0441 Check Engine light code.
When the canister purge valve is stuck in the closed position it prevents the EVAP System from burning the evaporated fuel. A low flow code will be generated and it will cause premature failure to the charcoal canister.
What About The Charcoal Canister?
A faulty charcoal canister is similar to the malfunctioning of a canister purge valve. The charcoal canister is attached directly to the purge valve. This centerpiece is designed to store the fuel vapor and other vapors before it’s burned by the engine.
When the Charcoal canister fails, it fails to capture the fuel vapors before it’s released to the powertrain. Instead, it releases these vapors into your car and the environment. Exposure to these vapors can be harmful to your health. It can cause headaches, confusion and it can even cause you to lose consciousness.
In some instances, the charcoal canister may simply be saturated or the fuel vent line is clogged. If this is the case you’ll experience some trouble while filling up. The gas pump may shut off before the tank is full because the toxic fumes will take up volume, significantly minimizing space in the fuel tank.
However, cleaning the charcoal canister or even the canister purge valve is highly discouraged. Pouring liquids into the canisters will damage the components instead they should be replaced.
Top Signs Of Canister Purge Valve Failure
Besides the smell of gasoline permeating in your vehicle’s interior what are some additional signs of canister purge valve failure?
Check Engine Light On
Perhaps the first sign of canister purge valve failure is that the Check Engine light will be triggered. The canister purge valve is regulated by your car’s computer which also monitors its performance.
Therefore, when a malfunction occurs or the computer detects an inconsistent purge flow that is either higher or lower than normal it will trigger the Check Engine sensor. If your Check Engine light is on you should have a diagnostic test conducted to confirm that it’s a canister purge valve problem.
Decreased Fuel Economy
If the canister purge valve is stuck in the closed position it will cause your vehicle to consume fuel at a much faster rate. This is because the vapors that are burned in the combustion process are transported to the EVAP canister where they will be released into the atmosphere instead of being burned along with fuel by the engine. As a result, you’ll notice that you have to make frequent trips to the gas station to fill up.
Rough Idling
A canister purge valve stuck in the open position creates a disastrous vacuum leak that over time will decrease the engine’s power. This drastically changes the engine’s air to fuel ratio. You’ll notice that your car is slow to accelerate. When your car is running it will even feel rough and it may be accompanied by vibrations. If you drive on a bad canister purge valve for too long the engine will eventually lose all of its power and you’ll be forced to purchase a new one.
Smoke Machine -Testing the Canister Purge Valve or Solenoid
Testing the canister purge valve or solenoid in a car can be different across different make and models. It’s important to follow the procedures outlined in your vehicle’s service manual when testing the canister purge valve. In most vehicles, the canister purge valve is designed to stay closed. Therefore, when it is stuck open, no voltage shall be applied to close it however voltage can be applied to open it. A multimeter that measures voltage is one of the tools used to test a canister purge valve.
A smoke test is an effective way to check for leaks or problems within your Evaporative Emissions Control System. Performed by an experienced technician all of the vacuum systems under the hood will be tested with the smoke machine to reveal potential leaks.
A smoke test is a relatively simple concept that involves blowing smoke directly into the vehicle’s EVAP system. The technician will infuse smoke from a smoke machine into the vacuum systems. Most shops use gray smoke or smoke tinted with a different color to increase the visibility of leaks within the EVAP system. If smoke is billowing through one of the vacuum systems in the EVAP system, then there is a leak.
Yes, a smoke test will reveal a compromised valve, seals, hose, or tube. This is one of the best ways to detect a crack or leak within the EVAP system. It can also help determine whether the canister purge valve or the charcoal canister is functioning properly.
Can I Repair A Canister Purge Valve Myself?
Fortunately, repairing a canister purge valve isn’t an expensive job that will burn a hole in your pockets. The labor for such a job is between $50-$60 because it’s a straightforward process that can be completed within an hour. In fact, the average cost of a canister purge valve replacement is approximately between $120 -170, depending on the type of vehicle you own and where you have your car serviced.
If you have to replace the canister purge valve or even the charcoal canister you should also replace the vent valves and seals if your budget allows. This can help further prevent leaks within the EVAP System which will only improve your engine’s performance.
However, if you are looking for a simple project you can do in your garage, a canister purge valve replacement could be a great DIY project. The canister purge valve is located near the fuel injector rail in most vehicles which is easy to spot when you pop the hood. All you have to do is remove the canister purge valve or solenoid and replace it with the new one.
What You Should Know About Maintaining Your EVAP System
When it comes to your vehicle’s maintenance, drivers rarely give any attention to the EVAP system until the check engine light comes on. Maintaining your car’s EVAP System which also includes critical components like the charcoal canister and the canister purge valve is crucial for optimal engine performance.
Leaks and cracks in the hoses, seals, and tubes of the EVAP System often develop due to corrosion. Here are few things you can do to maintain your car’s emission systems:
- Make sure the fuel cap is tightly secured after you fill your tank with gas. If you don’t have a fuel cap you should get one immediately because fuel will escape from your car.
- During those harsh summer days, you should try to park in shaded areas because gas evaporation can really happen.
- Gasoline is volatile and can not only produce harmful emissions especially when it evaporates. So make sure you are filling up during the early morning hours or at night when the temperatures are cooler.