Last Updated on June 30, 2021
You’ve probably never considered what happens when the charcoal canister in your car goes bad. That’s because it’s possibly one of the most reliable parts of your vehicle.
The charcoal canister (aka: EVAP canister) is an essential part of the Evaporative Emission Control System (often shortened to “EVAP”). This system helps ensure that dangerous fumes from your gas tank aren’t released into the environment and instead puts them to work powering the engine.
There are times when this part is damaged or becomes faulty after years of use. Because charcoal canisters rarely degrade, it’s helpful to be familiar with the symptoms, so you know what to do next, and how much this repair will set you back.
How a Charcoal Canister Works
To put it simply, the charcoal canister in your car absorbs excess gasoline fumes and vapors that accumulate in your gas tank.
The charcoal in this part is activated carbon, which is manufactured to be very porous. These pores help maximize the amount of gas and toxins that the canister can absorb.
Here’s a video showing the inside of a typical charcoal canister:
Periodically, the charcoal canister empties by pushing this excess vapor into the engine through the fuel vapor vent line and purge valve.
Without the charcoal canister, these vapors would either collect in the gas tank or be vented from the car into the atmosphere. These vapors are often toxic and dangerous for the environment.
Because the canister collects this vapor and then uses it to power the engine, the EVAP system helps cars be safer for the environment and more efficient.
The relatively simple construction of the charcoal canister means that it’s generally self-sustaining. However, there are some situations where it gets damaged or wears out. One of the most common charcoal canister problems is caused by “topping off” your gas tank, which can cause an overflow of fuel to flood the canister.
Bad Charcoal Canister Symptoms
#1 – Check Engine Light
The computer in your car will often recognize that there’s a problem with your car’s charcoal canister before you do. Because this is a relatively autonomous car part, it’s generally not the first thing mechanics look for when diagnosing a check engine light.
Keep in mind the additional symptoms of a faulty charcoal canister so you can properly identify the cause of your engine woes.
#2 – Increased Emissions (or Failed Emissions Test)
If you’ve noticed that your car’s emissions have significantly increased, your charcoal canister might be at fault. The primary job of the EVAP system is to prevent excess gasoline vapor from being released into the environment.
You might notice that your car’s engine is running richer, or a more pungent fuel smell from your exhaust. Between the check engine light and increased emissions, a faulty charcoal canister can cause your car to fail your mandatory state emissions inspection.
#3 – Reduced Vehicle Performance
Because the EVAP system connects directly to the engine through the purge valve, trouble with your charcoal canister can impact your car’s performance. If this system is faulty, the purge valve can be stuck open, affecting your engine’s air-fuel mixture.
As a result, you might see a decrease in your vehicle’s performance. You might find you get fewer miles to the gallon, trouble starting your car, or a rough idle if your charcoal canister is defective.
#4 – Issues Filling Up Gas Tank
If your charcoal canister is saturated or the fuel vapor vent line is clogged, one of the first things you might notice is trouble at the gas pump.
You might be unable to fill your tank, or that the gas pump nozzle shuts off before your tank is full. If your canister cannot remove vapor from the gas tank, those fumes take up volume, minimizing the space you can fill.
Related: 15 Causes of Poor Fuel Mileage
#5 – Fuel Smell In or Around Your Car
A faulty charcoal canister will fail to collect fuel vapors before they escape your powertrain, which will cause a strong fuel smell around your car.
Sometimes, these noxious fumes may accumulate inside the cabin, which will be problematic for most drivers. These vapors can be dangerous after prolonged exposure and can cause headaches, confusion, or even loss of consciousness.
Can a Charcoal Canister Be Cleaned?
Some owners may be able to clean their charcoal canister using an air compressor. This process can help troubleshoot whether your canister is genuinely faulty, or if some of the lines are just blocked.
Generally, the process involves removing the canister from your vehicle and using the compressor to blow air through the canister at a specific PSI to clean it without damaging internal components effectively.
Make sure to check your vehicle’s emissions manual (if one is available) for more information on how to clean your charcoal canister. Also, never pour any liquids into the canister, as they can permanently damage this piece.
In most cases, cleaning the canister is not advisable and replacement should be done instead.
Charcoal Canister Replacement Cost
The total cost for a charcoal canister replacement can range from $150-$630. Depending on your vehicle’s make and model, a new part usually costs between $100 and $500. If you hire a mechanic for the replacement, you can expect to pay an additional $50 to $130 in labor.
Charcoal canisters are generally easy to access. However, working on the EVAP system can be a bit tricky, so make sure to check your car’s manual for more information on how to do this repair.
Is it Safe to Drive With a Faulty EVAP Canister?
In most circumstances, it is safe to drive with a bad charcoal canister. The biggest concern most owners will face regarding a damaged EVAP system will be that your vehicle will release more fumes into the environment.
If you’re a driver that is concerned about your carbon footprint, this may motivate you to fix your charcoal canister as soon as possible. But even if you sit on the other side of the climate change debate, replacing the canister should be a put on your to-do list.
However, if your defective charcoal canister causes a strong fuel smell inside your vehicle, you’ll want to expedite this repair. As already mentioned, being exposed to fuel vapors can be extremely dangerous. If you must drive, roll down a couple windows to let fresh air into the vehicle.