A charcoal canister, also known as an EVAP canister, is probably something you’ve heard of before but never put much effort into understanding what it is.
It is not very common for the charcoal cylinder to fail, and it is usually hidden under the vehicle, so it is not so strange that it is sometimes forgotten.
But what really happens when this strange piece breaks down, and how much will it cost? Let’s take a look at the common signs to look for:
The most common symptom of a bad charcoal can is a check engine light on the dashboard. You may also have trouble filling your gas tank at the gas station without making a mess. You may also hear a hissing sound when you open the fuel tank cap.
Here is a more detailed list of the most common symptoms of a faulty charcoal canister:
Defective Charcoal Vapor Canister Symptoms
1. Check that the engine light is on
The engine control unit constantly monitors all of your car’s engine sensors, and if one fails, it will store a trouble code and display a check engine light on the dashboard to let you know something is not as it should be.
This is exactly what can happen if your charcoal canister breaks down. The EVAP system is a closed system that must maintain a specific pressure. If the engine control unit notices that there is a leak in the system or if it is clogged, the check engine light will come on.
To find out exactly why the check engine light is showing, you need to use a diagnostic scanner to check for fault codes.
2. Fuel tank filling problems
Fuel vapors pass through the charcoal canister, and if the canister is clogged, the vapors will have difficulty passing through, and this will create high pressure in the fuel tank.
The same thing happens when you fill up your car. Fuel enters the tank and therefore gases and air must leave.
If the charcoal canister or fuel vapor vent line is clogged, air will not be able to escape when you pour fuel, and this will cause the fuel hose nozzle to close, and may even spill fuel everywhere except on the fuel tank.
3. Whistling sound when opening the fuel tank cap
Because for the same reason we mentioned before, when the carbon cartridge is clogged, a higher-than-normal overpressure or depression will be created in the fuel tank.
This is especially noticeable when you are about to refuel your car and you hear a lot of air leaving or entering the fuel tank when you open the fuel cap, creating a hissing sound.
A little under or over-pressure in your fuel tank is fine, but if it seems much more than normal, you probably have a problem with the EVAP system.
4. Fuel Smell Odor
If your charcoal canister has a slot in the body, it can cause the canister to lose its stored fuel vapor. Instead of being stored inside the canister before being sent through the vent tube and purge valve, a damaged canister body could cause vapor to be released into the atmosphere.
This fuel vapor has a strong odor that will be noticeable when the engine is running and also when the engine is off.
If you notice a strong fuel odor in your vehicle, even when it is not running, your carbon cartridge is a good place to start the diagnostic process.
5. Emissions test failure
Many countries and states have annual emissions tests that you must pass in order for your car to be street-legal. During this test, your vehicle’s emission levels are checked to ensure that the fumes coming out of the exhaust comply with regulations.
If your fuel cartridge is defective, it could cause your engine to fail and therefore, cause your vehicle to fail its emissions test.
This can be difficult to find as the fuel canister tends to operate only passively. You can try plugging the fuel tank vent tube and see if that affects your vehicle’s emissions. If so, this would indicate a faulty fuel can that must be replaced for your vehicle to meet emissions regulations.
6. Excessive exhaust smoke
As with any fault in your vehicle that causes low engine power, your exhaust will often emit different colors of smoke, depending on the nature of the fault. If your exhaust has started to smoke excessively, it could indicate that your engine is underpowered.
This fuel error could be caused by the charcoal tank not working as expected. Although it is rare for a charcoal canister to produce excessive smoke, it would be wrong to say that it never happens!
A simple test would be to plug the charcoal canister vent tube and see if it changes the exhaust smoke. If so, this would also indicate a defect in the cartridge.
The function of a charcoal canister
The charcoal canister or steam canister works by absorbing the fumes produced by the fuel in its tank as a byproduct. Instead of these vapors being vented into the atmosphere, which is not very environmentally friendly, they are absorbed by the coal deposit. The charcoal in the canister has been designed to be highly absorbent, making it particularly effective at absorbing the vapor emitted by the fuel.
As this vapor builds up inside the cartridge over time, you will reach a point where you need to release some of it. This released vapor is pushed through the canister vent line and purge valve into the engine, where the vapor is burned.
Charcoal Bin Location
The charcoal canister or steam canister is usually located under the vehicle, often very close to the fuel tank. It is often hidden under plastic covers, so locating it can be difficult. It can sometimes also be located in the engine compartment, especially in European cars.
However, charcoal canister locations can vary greatly depending on the make or model of your vehicle.
It should be noted that I have found these cans in the wheel arches of some European brands.
If you’re having trouble finding it, your local dealer should be able to provide you with a location for the components.
Charcoal Canister Replacement Cost
The average cost to replace a charcoal canister is between $130 and $300, depending on the car model. A charcoal steamer costs between $80 and $150. Labor costs between $50 and $150.
The chances of replacing your fuel tank are very slim, but this definitely happens if you have a car with high mileage.
The charcoal canister itself is usually relatively inexpensive and you can often find it for around $100.
Replacement is usually quite easy and you can sometimes do it with some basic knowledge in an hour. It is very poorly located in some cars, so you should check it before replacing it.