If your car is exhibiting any of the following symptoms, it might be time to replace the EVAP canister: decreased gas mileage, poor acceleration, stalling, or a strong gasoline smell.
The EVAP (evaporative emission control) canister is an important part of your car’s emissions control system. It helps to prevent fuel vapors from escaping into the atmosphere.
In this blog post, we will discuss what an EVAP canister is, how it works, and how to replace it if necessary.
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What is an Evaporative Emission Control System? How Does it Work?
An evaporative emission control system helps to prevent the release of harmful vapors from a vehicle’s fuel system. The system works by trapping the vapors in a canister filled with activated charcoal.
When the engine is running, the canister is vented to allow fresh air to flow through it and keep the gas fumes from being drawn into the engine. When the engine is turned off, a purge valve in the canister closes so that the vapors are trapped inside.
A pressure differential switch turns on the EVAP canister purge solenoid when it senses a low pressure in the EVAP system. This allows fresh air to enter the charcoal canister, which forces the stored vapors out through the purge solenoid and into the engine, where they are burned.
The EVAP canister is connected to the engine by a series of hoses and valves. These allow the vapors to be drawn into the canister when the engine is not and then released back into the engine when it is started.
What is an EVAP Canister?
An EVAP canister is a device designed to capture and store fuel vapors from the vehicle’s gas tank. The vapors are then drawn into the engine, where they are burned off, preventing them from being released into the atmosphere.
The EVAP canister is typically located near the fuel tank and is connected to the engine via a series of hoses and pipes.
To function properly, the EVAP canister must be filled with a special absorbent material that allows it to trap and hold the fuel vapors. Over time, this material will become saturated and need to be replaced.
Symptoms of a Bad EVAP Canister
If the EVAP canister becomes damaged or fails, it can cause several problems with the vehicle. The most common symptoms of a bad EVAP canister include:
- Check Engine Light
- Difficulty Starting
- Fuel Smell From Cabin
- Can’t Fill the Fuel Tank
- Rough Idle
- Poor Engine Performance
- Poor Fuel Economy
- Excessive Exhaust Smoke
- Failed Emission Test
Let us dig deeper into each one of these symptoms:
1. Check Engine Light:
One of the first signs that something is wrong with the EVAP canister is that the check engine light will come on. This is because the system is designed to capture and store fuel vapors, and if it is not working properly, those vapors will escape into the atmosphere.
There are various sensors in cars that monitor the composition of exhaust gases, like the oxygen sensor. When it senses too many hydrocarbons in the exhaust, it will trigger the check engine light.
Not only that, but the ECU also monitors the output signals from the EVAP system itself. The check engine light will come on if it sees an abnormal behavior.
The check engine light will come on as a way of alerting the driver that there is a problem that needs to be addressed.
2. Difficulty Starting:
If the EVAP canister is not working properly, it can cause difficulty starting the car. The car starts and then dies after that. This is because a bad EVAP canister will make it impossible for the engine to maintain the perfect vacuum. And when there is no vacuum, the engine will struggle to start.
Another way a bad EVAP canister can make it difficult to start a car is if it doesn’t allow fuel vapors to be properly vented. This can cause fuel vapors to build up in the engine, making it hard to start.
3. Fuel Smell From Cabin:
Another symptom of a bad EVAP canister is a fuel smell from the cabin. This is because the canister is designed to capture and store fuel vapors, and if it is not working properly, those vapors will escape into the cabin.
The fuel smell will be most noticeable when the car is first started, but it can also be present when the vehicle is running. If you notice a fuel smell from the cabin, it is important to have the EVAP system checked as soon as possible.
4. Can’t Fill the Fuel Tank:
One of the most common symptoms of a bad EVAP canister is that you will be unable to fill the fuel tank all the way. The gas pump will click off before the tank is full, even if you are using a higher-octane gas.
The reason behind this is that if the EVAP canister is clogged, the fuel vapors will not be able to escape the fuel tank. Hence, the pressure will build up inside the tank and prevent more fuel from being added.
If you notice that you cannot fill the fuel tank all the way, it is important to have the EVAP system checked as soon as possible.
5. Rough Idle:
Another symptom of a bad EVAP canister is a rough idle. This is because the canister is designed to capture and store fuel vapors, and if it is not working properly, those vapors will escape into the atmosphere.
As the fuel vapors escape, a fuel deficiency will occur in the engine. This will cause the engine to run rough and stall.
A vacuum leak can also cause rough idle. A bad EVAP canister can cause a vacuum leak, leading to a rough idle.
6. Poor Engine Performance:
Another symptom of a bad EVAP canister is poor engine performance. This is because if the canister is not venting properly, it can cause the fuel tank to pressurize, which can restrict fuel flow to the engine.
Additionally, if the canister is leaking, enough fuel would not be drawn into the engine. As a result, the engine would run lean and could potentially stall.
7. Poor Fuel Economy:
If the EVAP canister is not working properly, it can also lead to poor fuel economy. A bad evap canister can cause poor fuel economy for a couple of reasons.
One reason is that it can allow fuel vapors to escape into the atmosphere, which means that your combustion chamber is not getting as much fuel as it should.
Another reason is that a bad evap canister can cause your engine to run less efficiently, reducing fuel economy.
8. Excessive Exhaust Smoke:
Another symptom of a bad EVAP canister is excessive exhaust smoke. One potential reason for this is that the canister is not venting properly, causing a build-up of pressure in the exhaust system.
This can lead to excess smoke being emitted from the exhaust pipe and exhaust manifold leak. Additionally, a bad evap canister can also cause engine misfires, leading to excess smoke coming from the exhaust.
9. Failed Emission Test:
One of the most obvious symptoms of a bad EVAP canister is that your car will fail an emission test. The EVAP system is designed to capture and store fuel vapors, and if it is not working properly, those vapors will escape into the atmosphere.
As a result, your car will emit more pollutants than it should, and it will fail an emission test. The emission test is a mandatory test for all vehicles in some states, so if your car fails, you will not be able to register it until the EVAP system is fixed.
Causes of a Bad EVAP Canister
Now that we have gone over some of the symptoms of a bad EVAP canister let’s look at some potential causes.
One of the most common causes of a bad EVAP canister is simply aging. Over time, the seals and gaskets in the EVAP system can degrade and fail.
A failing canister purge valve can also be caused by a problem with one of the other components in the system. If there is a problem with the vent valves, fuel pump relay, or purge valve, it can cause the canister to fail.
Additionally, the plastic components in the system can become brittle and crack. If your car is older, it is more likely that the EVAP system will need to be replaced.
Another common cause of a bad EVAP canister is moisture. Moisture can enter the system through cracks and holes.
Once inside, the moisture will corrode metal components and degrade rubber seals. If you live in an area with high humidity, it is important to have your EVAP system checked on a regular basis.
A common cause of a bad EVAP canister is contamination. Contamination can come from dirt, dust, and other debris that enters the system through cracks and holes. Once inside, the contamination will clog up the vent valves and restrict airflow.
How to Replace a Faulty EVAP Canister?
Replacing a faulty EVAP canister is not a difficult task, but it does require some basic mechanical skills. Here’s how to do it:
- Disconnect the negative battery terminal to prevent any electrical shorts.
- Locate the EVAP canister under the hood of the vehicle. It is usually mounted near the fuel tank or on the frame rail.
- Detach the chassis harness connector from the canister. By slightly depressing the locking tab, you should be able to pull the connector off.
- Next, remove the air hose that is connected to the canister. This is usually a simple matter of unscrewing a couple of hose clamps.
- Now, remove the solenoid wiring connector. This is the electrical connection that controls the canister’s purge valve.
- The solenoid is held by a bracket, which is attached to the canister with two bolts. Remove these bolts and set the solenoid aside.
- Next, there is a clip that the chassis harness passes through. Remove this clip so you can pull the harness away and reach the canister.
- There is a fuel tank vent hose connected to the canister. Pull this hose off and set it aside.
- Plus, there is also a purge hose connected to the canister. This hose goes to the engine’s intake manifold. Disconnect it and set it aside.
- The EVAP canister is now free. You can remove it from its mounting bracket and set it aside.
- To install the new canister, place it in the bracket and reattach the purge hose. Make sure that the hose is properly seated and secured with a clamp.
- Then, connect the chassis harness valve connector to the solenoid valve.
- Place the solenoid valve in its cover now.
- The bracket attachments of the valve should go through the rubber grommets of the cover.
- Replace the bolts to secure the bracket and canister purge valve in place.
- Connect the canister air hose to the inlet of the new canister.
- Attach the air hose clips to secure the hose.
- Wrap the extra chassis harness wire and secure it with the provided clip.
- Now, reconnect the fuel vapor vent line to the inlet of the new canister.
- Finally, reconnect the negative battery terminal.
- Start the engine and check for any leaks.
- The EVAP system test will need to be performed to ensure that the canister is functioning properly.
EVAP Canister Replacement Cost
The EVAP canister is relatively simple and inexpensive, so the charcoal canister replacement cost is usually not very high. The EVAP canister itself typically costs between $50 and $100.
However, the total cost of replacement will also depend on labor costs and other factors such as the make and model of your car.
In most cases, you can expect to pay between $200 and $400 for a complete EVAP canister replacement.
A bad EVAP canister can cause a variety of problems for your car. If you notice any of the symptoms listed above, it is important to have your vehicle checked by a mechanic as soon as possible.
If the EVAP system is not working properly, it can lead to engine damage, poor fuel economy, and failed emission tests. Thankfully, the EVAP canister is a relatively simple and inexpensive part to replace.
Thank you for reading! We hope this article has been helpful. If you have any further questions or comments, please feel free to leave them below. Happy driving!
Frequently Asked Questions
What happens when the EVAP canister goes bad?
If the EVAP canister goes bad, it can cause a variety of problems for your car. The most common symptoms include excess smoke from the exhaust, engine misfires, and failed emission tests. Additionally, a bad EVAP canister can also lead to engine damage, poor fuel economy, and increased pollutants in the atmosphere.
Can you drive without an EVAP canister? Is it legal?
Yes, you can drive without an EVAP canister. However, it is not legal to do so. The EVAP system is required by law in some states, and if your car does not have one, you will not be able to register it. Additionally, driving without an EVAP canister can lead to engine damage, poor fuel economy, and failed emission tests.
Where is the EVAP canister located?
The EVAP canister is located under the vehicle, near the fuel tank. It is usually made of plastic or metal and has a hose connected to it. The EVAP canister stores fuel vapors from the fuel tank so that they can be burned instead of released into the atmosphere.
How long does an EVAP canister last?
An EVAP canister should last the lifetime of the vehicle. However, in some cases, it may need to be replaced sooner. The most common reasons for replacement are simply aging and contamination. Additionally, if you live in an area with high humidity, it is important to have your EVAP system checked on a regular basis.
Can you drive with a bad vapor canister?
A bad vapor canister will not necessarily prevent you from driving, but it can cause your vehicle to run less efficiently. Additionally, a damaged or leaking vapor canister can release harmful chemicals into the environment. If you have a bad vapor canister, it is best to have it repaired or replaced as soon as possible.
What is the difference between a charcoal canister and an EVAP canister?
None, in terms of function. Both are designed to store vapors from the fuel tank and prevent them from entering the atmosphere.
How to clean a bad EVAP canister?
If your EVAP canister is filled with dirt and debris, it can cause your vehicle to run improperly.
- To clean a bad EVAP canister, you’ll need to remove it from your vehicle and disassemble it.
- Then, use a metal brush to clean the inside of the canister and remove any buildup.
- You can also use an air pressure hose to blow out any debris stuck inside the canister.
- But remember not to use any fluids or chemicals to clean the canister, as this could damage it.
- Once you’ve cleaned the canister, reassemble it and put it back in your vehicle.
What is the importance of an EVAP system in a car?
The EVAP system is important because it prevents fuel vapors from being released into the atmosphere. Fuel vapors are harmful to the environment and contribute to air pollution.
The main purpose of an evaporative emission control system is to reduce air pollution. By trapping the vapors before they are released into the atmosphere, the system helps to reduce smog and other air pollutants.
In some areas, such as California, vehicles must have an evaporative emission control system in order to be registered.