Last Updated: 06.04.2022

The EVAP canister is one of the most important components of a vehicle’s emission system. It prevents the release of dangerous gases while making sure that an engine works effectively and efficiently. 

Like other parts, an EVAP canister is prone to damage over time. As it degrades, it compromises overall performance. With this, you must be familiar with the bad EVAP canister symptoms and how to fix them. Read on and learn how you can best deal with the issue. 

What Is an EVAP Canister? 

An Evaporative Emission Control System (EVAP) seals a fuel system, preventing harmful vapors from escaping and damaging the environment. It has several parts, including an EVAP canister. The EVAP canister is a rectangular plastic container with activated charcoal. It’s responsible for the absorption and storage of gasoline vapors.

mechanic holding an evac canister

Because of the nature of gas, vapor will also be present in a fuel tank. The goal is to move them along the tank to minimize emissions. A vent line transports the vapor to the EVAP canister. Here, charcoal will absorb the vapor until it accumulates enough. Upon reaching such a point, the purge flow sensor opens and will equalize pressure. 

Bad EVAP Canister Symptoms 

Unsure if the EVAP canister is at fault? Below are some of the most common signs to watch out for, which will help you properly diagnose the problem. 

Check Engine Light Is On 

The check engine light is one of the most reliable indicators when there is a problem under the hood that needs your immediate attention. Some of the most common reasons why it activates include engine problems, transmission issues, defective sensors, and faulty air/fuel delivery. More so, it is also a common sign that you have an EVAP canister problem.

check engine light on indicator

An EVAP system is closed and requires a specific pressure top function properly. If there is a leak or clog, you will receive an immediate warning through the check engine light. A diagnostic scanner is essential, which will help you pinpoint the specific problem as it can be because of many issues. 

Smell of Gasoline 

Whether you are inside or outside the car, the smell of gasoline can instantly make you panic. In most instances, it is not a good sign. As a highly flammable liquid, gas can evaporate and ignite. Hence, from the first time that you sense it, act immediately. Take a look at different components that can be possibly problematic, including the EVAP canister. 

When there is damage to the EVAP canister, fuel vapor accumulates and escapes the power train. This will result in a strong gas odor. Noxious fumes may be present in the cabin, which can be dangerous. Prolonged exposure can lead to nausea, confusion, headaches, and loss of consciousness. 

A strong gas smell is often a result of the splitting of the canister. It creates a hole or gap. In turn, it loses fuel vapor instead of storing it in the canister. It is not sent to the purge valve or the vent pipe. Instead, the vapor releases into the air, which is what creates a noticeable gas smell. 

Increased Emissions 

The primary function of an EVAP canister is to minimize emissions. When it is not properly working, there will be more emissions, which will result in failing the emission test. In most places, the latter is mandatory so that you can drive your vehicle legally. If you do not meet such regulations, you are at risk of being fined or apprehended. 

The EVAP canister redirects fuel vapors to the engine. This way, your vehicle won’t generate toxic hydrocarbons that will be going out of the tailpipe. Once it fails, it won’t be able to redirect the vapors. It will not only produce gas fumes, but it can also activate the check engine light on the dashboard. 

Hissing Noise

Like other weird sounds, a hissing noise is a sign that there is a problem under the hood. Most of the time, it is because of a leak or a faulty cooling system. It can also be an indication that an oil coolant has leaked into the exhaust manifold. Another thing that is worth looking at is the EVAP canister. 

The hissing noise due to a faulty EVAP canister is most evident when you open the tank and refuel. This is especially the case after driving for a long time. It results in the failure of the EVAP canister to effectively equalize. 

Sometimes, you can even feel a gust of air when there is extreme pressure, which shows that the EVAP canister has not been purging vapors. 

Difficulty Filling a Fuel Tank

If you are having a hard time refueling, the EVAP canister might have gone bad. Clogging or saturation of the vent line is a common consequence of problems in the charcoal canister. As a result, the gas pump nozzle might shut off even before you are done refilling the tank. 

With the failure of the EVAP canister to work as it should, it won’t remove vapor in the tank. The fumes will increase volume, and hence, the tank will have lesser space that you can fill. This can also cause a problem with the safety nozzle. 

Decline in Performance 

Being a crucial component of the engine, any problem with the EVAP canister will lead to a decline in vehicle performance. It might not be easily noticeable, but in the long run, your car will become inefficient. The engine will not be able to generate enough horsepower, which will worsen if you are driving in harsh environments. 

As the engine performs badly, your vehicle will also suffer from poor mileage. The fuel vapor may end up trapped in the canister instead of undergoing combustion. This means that gas will burn. You will be wasting gasoline. 

How to Clean an EVAP Canister 

As soon as you notice the signs of a bad EVAP canister, no need to panic. It might warrant a replacement, but in some instances, cleaning it would suffice. It requires a bit of effort, but it is easy enough that you can do it on your own instead of paying a mechanic to do the job. 

Step 1. Remove the Canister

removing the evap canister

Start by taking the canister out. You might need to take it out of the bracket or from any other place where it mounts, which will depend on the brand and model of your vehicle. In most cases, the canister will have one line at the bottom and three at the top. You will need a screwdriver to take it off. 

Step 2. Pump the Vacuum Pressure

pump the vacuum pressure of evac canister

After removing the EVAP canister, lay it down on a smooth surface. Pump the vacuum pressure until it reaches 50 psi. Disconnect the vacuum pressure after reaching the latter. 

Step 3. Grab the Upper Pipe

grab the upper pipe

Once you have pumped sufficient air into the EVAP canister, hold the upper vent, which you will find at the top. Take note that this is different from the outlet and inlet valves. 

Step 4. Turn the Vacuum Pump On

turn vacuum on for pressure

Use your finger for blocking the valves. Release air from the vacuum pump at 50 psi. Put your finger on the open side of the canister and release it slowly. Make sure that there is air coming out of the outlet valve. As this happens, the canister will be free of clog. 

Step 5. Return the EVAP Canister

return the evap canister

Finish the task by returning the canister to its original position. Inspect it first, making sure that there is no damage. If there is, then you should have not cleaned it in the first place and opted for a replacement instead. Upon returning, see to it that it sits tightly in its position. 


  • How much does it cost to replace an EVAP canister? 

On average, replacing an EVAP canister costs $150 to $630. The specific amount, however, will differ depending on several factors. For instance, the brand and model of your vehicle can affect the price. The type of the canister also has an impact. More so, it will depend on the cost of labor. 

  • Is it safe to drive with a bad EVAP canister? 

Technically, it is safe to drive your vehicle even if it has a bad EVAP canister. It won’t have too much impact on performance. Nonetheless, your car will have more emissions than normal. As a result, you might fail an emission test. In most states, passing an emission test is a must, which is why you need a functioning EVAP canister. 

  • What are the causes of EVAP canister failure? 

Old age is the most common reason for the failure of the EVAP canister. It can have cracks and clogs as it accumulates dirt and debris over time, making it harder to work properly. Overfilling the gas tank can also contribute to the problem. more so, it can also be because of faulty valves. 


The most common symptoms of a bad EVAP canister include having the engine light on, gas odor, failed emissions test, hissing sound, difficulty refueling, and a decline in engine performance. While you can still technically drive as the EVAP canister encounters problems, it is best to fix the issue immediately to prevent having toxic fumes.