11 Signs Of A Damaged EVAP Canister

Charcoal canister (1)

The purpose of the car’s EVAP system is to prevent harmful vapors from entering the atmosphere causing smog. This canister is connected to the fuel tank and is filled with active charcoal which absorbs fuel vapors and stores them in the canister until you start the engine and the vapors are directed to the engine. However, this system is not perfect, and these are the most common symptoms of a bad EVAP canister:

  • Check engine light is on
  • Hissing noises from the gas tank
  • Issues while filling the tank
  • Failed emissions test
  • Smell of fuel 
  • Excessive smoke from the exhaust
  • Engine problems
  • Bad gas mileage
  • Difficulties starting up the engine
  • Pinging sounds
  • Damaged gasket

Check Engine Light Is On

Modern cars are equipped with many control units that constantly monitor all the car’s sensors. If the charcoal canister starts causing issues, and the pressure inside the EVAP system changes, those sensors will notify the ECU and prompt up a check engine light. 

The check engine light can point towards countless possible issues associated with both the engine and its auxiliary systems. This means that the chances of the check engine light pointing specifically towards a faulty EVAP canister are rather slim. However, if the check engine light is also accompanied by a few other symptoms from this list, then the EVAP can be the culprit more often.

Hissing Noises From The Gas Tank

As mentioned, the EVAP system is contained in order to keep a constant pressure. If the canister starts clogging up, it will create overpressure or underpressure inside the tank. One way to diagnose this is to open the fuel tank and listen for any hissing sounds of the air rapidly going in or out of the fuel tank.

Hardly any fuel tank out there enjoys a constant optimum pressure which means that eventual barely noticeable hisses are not a problem at all. However, if you hear a hissing sound coming from your fuel tank often or the hissing intensity is rather exaggerated, chances are that your EVAP canister is clogged up.

Issues While Filling The Tank

Another fairly common symptom of a bad EVAP canister is when the fuel nozzle shuts off the moment you put it inside your fuel tank. This happens because the nozzle senses that fuel fumes are unable to leave the tank. This can also cause fuel spillage from the tank itself.

Sometimes the nozzle will not shut itself off immediately but will rather be inconsistent in regards to the flow of the fuel. This usually means that your fumes are barely finding their way out of the fuel tank which is a definite symptom that a full fuel fume blockade is imminent.

Failed Emissions Test

Most states require you to do smog check testing every year or two in order to confirm that your car meets the emissions regulations. However, if your EVAP canister is bad, it can easily start misfuelling your engine which often leads to a failed emissions test. Be sure to inspect the EVAP system after you fail an emissions test.

In order for a car to be as economical as possible, it needs to have the right ratio of fuel and air within the combustion chamber. A faulty EVAP canister is going to cause unbalanced fuel and air ratios which will in turn cause engine misfuelling.

Smell Of Fuel 

If you are often noticing a strong fuel smell inside or outside the engine, it's always a good idea to start diagnosing the issue by checking the EVAP canister. The canister itself can sometimes get damaged, and if that indeed happens, the fumes will start exiting the canister uncontrollably.

Excessive Smoke From The Exhaust

As previously stated, if your engine is being misfueled, it's usually indicated by a large amount of black smoke coming from the exhaust. Even though this is rather rare, it can often lead to a faulty EVAP canister. This means that the amount of fuel that enters your exhaust system is so large that it can sometimes even cause backfires within the exhaust system.

Engine Issues

Whenever your EVAP canister starts causing issues, it usually also strains the engine. If this does happen, you are likely to experience issues starting up the car, even if you do manage to start it up, the performance is bound to suffer.

This usually means that the engine will not be able to provide sufficient power thus causing your car to accelerate in a sluggish manner. A damaged EVAP canister has a great effect on the engine combustion process which is something you want to resolve as soon as possible.

Bad Gas Mileage

A bad EVAP canister also adversely impacts your gas mileage. If the fuel vapors are unable to enter the engine, it usually means that your engine loses a significant portion of the fuel which is usually used during the burning process.

If the fuel fumes are unable to reach the combustion chamber they will be compensated for with additional fuel which will cause misfuelling this increase your fuel consumption.

Difficulties Starting Up The Engine

If your EVAP canister has any holes in it which can cause vacuum leaks it can often be difficult to even start the engine. If this does happen, unmetered air can enter the engine and cause uneven air-to-fuel mixtures that can also create a huge disbalance in your engine’s combustion process.

Even though issues such as these are not the most common reasons why your engine is not starting, but if they are left unresolved for a while they can indeed result in your engine not wanting to kick in. This is also likely to mess up your fuel consumption and prompt your check engine light because the oxygen sensors in the engine are bound to pick this up eventually.

Pinging Sounds

If the EVAP canister is not able to effectively deal with the carbon emissions, this is likely going to cause all sorts of effects on the combustion process which can even lead to unusual engine pinging sounds. Of course, there are a myriad of different reasons why an engine might cause weird noises, but if the pinging sound is backed by any other symptom for this list, chances are that your EVAP can is to blame.

However, if you are unsure about where the sounds are coming from, it's always better not to drive your car before these issues are not 100% looked after in order not to cause any additional strain to the engine.

Damaged Gasket

If the EVAP canister is working as advertised, you will have no issues associated with how the fuel vapors are stored and how effective do they reach the engine during the combustion process. However, if your EVAP canister fails to open when necessary, it is likely going to drop your fuel consumption since the vapors are trapped within the canister.

If issues such as these continue to exist for a prolonged period, they can also cause high pressure within the system that can often result in a blown gasket and destroyed rubber seals. This can often be accompanied by all sorts of oil leaks which can contaminate delicate components within the engine.

FAQ Section

How Much Does A New EVAP Canister Cost?

 A new EVAP canister usually costs between $120-$300 with labor costs. These vary depending on the car and the sophistication of the system itself. The chances of having to replace your EVAP canister are rather slim because these components are known to last a long time. However, this can be the case with a high-mileage car or if your EVAP canister is damaged.

Can I Change The EVAP Canister Myself?

Replacing the EVAP canister is a fairly easy task. All you have to do is look for a few videos online to get to grips with the replacement process. However, be sure not to mess this up as this can cause many issues down the line.

Where Is The EVAP Canister Located?

The EVAP canister is usually located underneath the car near the fuel tank. It is usually covered with various plastic components so finding it can be tricky. However, some European cars are known to place the EVAP canister closer to the engine.

How Does An EVAP Canister Look Like?

It usually looks like a rectangular black box with lots of hoses going to it. As previously mentioned, it is often covered with all sorts of plastic protective panels which can sometimes make it difficult to scout at first. EVAP canisters can even sometimes have a rounder shape so be sure to check online as to how your car’s EVAP canister looks.

Will An EVAP Leak Damage My Car?

If your EVAP system is leaking, it is not likely to damage your car. However, if you do ignore this issue, it can later cause issues such as engine misfuelling. Issues such as these can potentially result in damages such as blown gaskets, destroyed seals, or even paint damages as a result of fuel spillage. Anyhow, these issues are indeed rare, but prevalent enough to make you repair the issue as soon as possible.


 


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CarAraC Research

About the authors

The CarAraC research team is composed of seasoned auto mechanics and automotive industry professionals, including individuals with advanced degrees and certifications in their field. Our team members boast prestigious credentials, reflecting their extensive knowledge and skills. These qualifications include: IMI: Institute of the Motor Industry, ASE-Certified Master Automobile Technicians; Coventry University, Graduate of MA in Automotive Journalism; Politecnico di Torino, Italy, MS Automotive Engineering; Ss. Cyril and Methodius University in Skopje, Mechanical University in Skopje; TOC Automotive College; DHA Suffa University, Department of Mechanical Engineering

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