Charcoal Canister Function, Bad Symptoms and Replacement Cost

When you fill up your fuel tank with gasoline, there are vapors that emit from the fuel. These vapors are a form of evaporative emissions pollution. They are very bad for the environment if they were to flow outside your vehicle. Fortunately, most automobiles are built with something called a charcoal canister. This component is associated with the evaporative emission control system, which is also known as the EVAP system.

Basic Function

The main function of a charcoal canister is to absorb the fuels vapors before they have a chance to escape into the atmosphere. After the vapors are absorbed, the charcoal traps them temporarily. The vapors are eventually recycled back into the engine where they are burned like regular fuel. The purge valve is the “switch” that enables the fuel vapors to flow from the charcoal canister to the engine. The EVAP system is in constant communication with the engine control unit. That is how the EVAP system knows when to activate the purge valve appropriately.

Bad Symptoms

The charcoal canister contributes to promoting a healthy environment. It is also essential for sustaining the functionality of your engine and ensuring that it performs to the best of its ability. If the fuel vapors are not able to enter the cylinders of the engine, then it can create problems for the entire combustion process.

Charcoal canisters don’t usually malfunction or go bad, but it has been known to happen. If you don’t know which symptoms to look out for, then you might not realize that your charcoal canister is having problems. To help you out, we have compiled a list of the most common symptoms to arise from a faulty charcoal canister.

Below are the top 7 symptoms that you can expect to occur.

1) Check Engine Warning Light – You might wonder why the Check Engine warning light would illuminate on your dashboard because of a bad charcoal canister. Since the canister provides fuel vapors to the engine, your engine control unit will detect something is wrong with the engine if it doesn’t have enough vapors for combustion. As a result, it lights up the Check Engine warning light.

2) Trouble Starting Engine – When there is a vacuum leak from having a bad charcoal canister, it will be difficult to start your engine. A lot of unmetered outside air will enter the engine and cause problems for the air and fuel mixture. This will, in turn, cause problems during the internal combustion process. Therefore, every time you try to start your engine, the combustion may not be sufficient enough.

3) Rough Idle – A rough idle will probably be the first symptom you notice after the Check Engine light comes on. If you have a bad charcoal canister or a leak in one of the hoses connected to it, then it will cause a vacuum leak to occur. This will impair the engine idle speed and create a rough idle situation to occur.

4) Fuel Odor – If fuel vapors are not flowing into your engine, then they’re probably coming out of the gas tank and into the passenger cabin. As a result, you will smell a distinct fuel odor in the cabin as you’re driving. Since a bad charcoal canister cannot absorb these fuel vapors properly, then you will end up smelling the vapors instead.

5) Bad Fuel Economy – The engine burns fuel vapors to generate power. This reduces your gas mileage expense significantly because it means the engine won’t require as much direct fuel to burn in its cylinders. However, if the fuel vapors are not entering the engine like they’re supposed to, then more fuel will be used to replace them. This means a bad fuel economy and more money spent at the pump.

6) Increased Pinging – When the air and fuel mixture is not balanced in the cylinders of the engine, their combustion will cause pinging and knocking to occur. Of course, there are several other reasons for pinging besides a bad charcoal canister. But if you’re experiencing any of the other symptoms too, then chances are that the charcoal canister is to blame.

7) Weak Engine Power – When you have a bad charcoal canister with a vacuum leak, it can either make it difficult to start your engine or cause the engine to generate less power. You will know if the latter occurs because you won’t be able to accelerate as quickly when you step on the gas pedal. The more you step on the pedal, the more you might smell the fuel odor as well. With these two symptoms together, you can be sure that your charcoal canister is likely to blame.

Read also: Map Sensor Function, Bad Symptoms and Replacement Cost

Replacement Cost 

If your charcoal canister goes bad, this is not something that you can leave alone.  You will need to replace your charcoal canister if you want your emissions reduced and your engine power restored. The average replacement cost of a charcoal canister is anywhere between $190 and $560. The cost of the canister part itself is around $160 to $440. The cost of the labor job for replacing the canister is between $30 and $120.

The exact costs of each will depend on the make and model of your vehicle and the auto mechanic that you choose to perform the replacement job. In all, you can expect to pay more than a few hundred dollars for this job. Don’t forget that taxes and fees will be added to the total price as well.

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