How to fix EVAP Canister Problems

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You have probably had an interaction with the evaporative emission control (EVAP) system if you've ever left the gas cap loose on a modern car.

The EVAP system captures and prevents smog-forming gasoline vapours from entering the atmosphere. Your car's principal computer (also known as the powertrain control module) will turn on the check engine light if there's a problem somewhere in the system, such as a leaking gas cap. The module also saves an EVAP-related diagnostic trouble code (DTC) in its memory at the same time.

If EVAP system faults did not cause the check engine light to illuminate, you may not be aware that the system exists. If the purge valve is leaking, an EVAP problem rarely affects vehicle performance or driver comfort.

However, this does not mean you should disregard an EVAP system problem; in fact, an EVAP failure almost always prevents your automobile from passing a state emissions test. Furthermore, if there is a problem with the system, the harmful emissions produced by your car will grow.

It's a good idea to get to know the EVAP system and how it operates. That way, if any problems emerge, you'll have a fundamental understanding of the system.

Table Of Content

  1. What is the purpose of the EVAP canister?
  2. What happens when the EVAP canister goes bad?
  3. Is driving with a faulty EVAP canister dangerous?
  4. Troubleshooting EVAP canister
  5. Cleaning an EVAP charcoal canister
  6. Conclusion

1. What Is The Purpose Of The EVAP Canister?

The EVAP canister is connected to your gasoline tank via the tank vent line. The canister holds around 2 pounds of activated charcoal, which is utilized to store and trap gasoline vapours until your purge valves open, allowing the engine's suction to absorb some of the fuel vapours from the charcoal and into the intake manifold. This is done to lower your vehicle's gas emissions.

How the EVAP works

When your car is in good form and running efficiently, your EVAP canister may hold a lot of fuel vapour. The fuel vapour is drawn into your engine and burned. This is known as 'purging,' and it requires the help of the purge valve.

The burning process begins when your vehicle's Powertrain Control Module opens your purge valve. Outside air will be drawn in over the charcoal by the valve opening, forcing gasoline vapours into your engine. The fumes are used up in the engine through the normal combustion process.

But, you might be wondering, if I don't have a vapour canister, would my car operate poorly? Yes, it certainly would. A faulty canister can wreak havoc on the engine's performance, slowing down the vehicle's acceleration.

How the EVAP works

2. What Happens When The EVAP Canister Goes Bad?

When your EVAP canister fails, it causes problems with your Evaporative Emission Control System, lowering your vehicle's emission output. These highlighted symptoms are often caused by a defective EVAP canister, alerting the driver to a vehicle problem that needs to be addressed.

Gas Mileage Becomes Poor

Low gas mileage implies that your car is not performing at its best. It also means that your vehicle's gas system is leaking or consuming a lot of gas. Low gas mileage can be caused by several issues, including a faulty EVAP canister.

EVAP canister

This occurs because the gasoline vapours that your car normally uses during combustion are burned up in the environment before reaching the combustion chamber in this scenario.

This means that some of the gas normally used during combustion will be lost, resulting in low gas mileage and an increase in the cost of buying petrol for your car. Your vapour canister may become saturated or clogged as a result of this.

Engine Performance Issues

Poor engine performance is almost often the result of a damaged EVAP canister. Your engine will start to operate inefficiently, delivering minimal power for rapid acceleration. Even if you apply pressure to the gas pedal, your car may have a sluggish movement as a result of this.

Emmission system

Your car will have sluggish acceleration due to an incomplete combustion process caused by a defective EVAP canister, which you must replace promptly to avoid any undesirable condition.

Starting The Engine Is Difficult

Difficulty starting is another sign that your vehicle's EVAP canister is malfunctioning. This is due to a vacuum leak caused by problems with your charcoal canister, and it may make starting your car difficult.

EVAP canister repair

When you have a vacuum leak, it allows unmetered air into your engine, causing the air-fuel ratio to become unbalanced, causing problems in your engine's system by disrupting the internal combustion process. If this problem is not addressed, your car may eventually stop starting.

Due to a high amount of air in the engine, an uneven air-fuel ratio during combustion might result in incorrect combustion.

Check Engine Light Illuminates

When your EVAP canister is damaged, your engine check light will illuminate. If your vehicle's computer system detects a problem with your EVAP system, the engine check light will illuminate to alert the driver to a problem with the engine system.

Clogged canister

This issue is detected by your computer system via signals from your EVAP system. However, because the engine check light might come on as a result of a variety of different issues, it's a good idea to use an OTC Leak Tanner or another Smoke machine to properly scan your car for error codes and determine the exact defect that's causing the engine check light to come on.

Vehicle Experiences Harsh Idling

A harsh idle is a common indicator of a damaged EVAP canister. Due to an unstable rpm count, the car will not be able to maintain a high speed, and you may experience a shaking sensation when driving. Typically, your vehicle's rpm rate should be around 1000.

EVAP module

If this rpm is fluctuating, you're probably dealing with an idling problem. Faulty spark plugs, carburettor issues, filthy fuel injectors, and a vacuum leak can all cause rough idling.

A damaged or malfunctioning EVAP canister or the hoses attached to it can cause a vacuum leak. If you detect this symptom, you should address it right once because it can cause serious harm to your engine system.

The Smell Of Gas

Gas odour is one of the evap leak symptoms, and it can be caused by a variety of faults or engine difficulties in your vehicle's system, but a broken EVAP canister is one of the most common causes. When a vapour canister is damaged, it might emit a strong gas odour.

EVAP testing

Emissions Test Fails

If you have a defective EVAP canister in your system, your car will fail emission testing owing to gas smells. The engine check light will also illuminate as a result of this malfunction.

It Becomes Difficult To Fill The Gas Tank

The released gas vapours are routed to the EVAP canister and other related engine components when you fill up your gasoline tank. The vapour will not be able to enter the canister if it is clogged. Instead, it will return to your petrol tank, making refuelling more difficult.

EVAP system valves

3. Is Driving With A Faulty EVAP Canister Dangerous?

If you're thinking about driving with a bad evap canister, it's technically safe. This mistake may not cause your car to perform poorly on its own, but it will prevent it from passing an emission test.

A faulty EVAP canister may cause your car to emit a large number of gas fumes, generating pollution, as well as keeping your dash engine check light illuminated. When you identify a problem with your EVAP system, however, you must address it as quickly as possible.

EVAP module

4. Troubleshooting EVAP Canister

Each gasoline-fueled vehicle on the road emits fumes as a result of combustion activities inside the engine. The Evaporative Emission Control System, or EVAP, is an interior vehicle system designed by carmakers to keep dangerous emissions contained until they are combusted.

The charcoal canister is an important part of this system. This container retains gasoline fumes until they can be burned by the engine. Charcoal canisters, on the other hand, can appear to fail, necessitating a testing procedure to locate the leak within the EVAP system.

EVAP canister

1st step

Find the charcoal canister. The canister is a black cylinder that is often mounted in one of the engine compartment's corners.

2nd Step

Examine the canister visually. Make sure there aren't any visible cracks or gaps on the outside.

3rd step

Connect a handheld vacuum pump to the purge valve on the top side of the canister.

4th step

Switch on the hand pump and look at the valve. When the hand pump is activated, a properly functioning canister and purge valve assembly will open the valve assembly.

EVAP system module

5th step

While the hand pump is turned on, listen and look at the purge valve. The valve should remain open during the procedure, but no vacuum should flow from the canister. If a vacuum leak is discovered, replace the purge valve and canister configuration.

Remove the hand pump from the purge valve and set it aside. Allow the car to idle after turning it on in the park. Keep an eye on the engine compartment. Make sure there aren't any odours coming from the canister.

EVAP installed canister

5. Cleaning An EVAP Charcoal Canister

In a car, a charcoal filter is found inside the charcoal filter canister. The main purpose of the charcoal filter and the charcoal canister when the engine is turned off is to absorb excess gas fumes from the fuel system and the gas tank.

The canister's filter works like a sponge, absorbing all of the surplus gas fumes. The surplus gas vapours return to the fuel system and into the combustion chamber once the engine is restarted. Excessive buildup over time might clog the charcoal canister, preventing gas fumes from entering or exiting.

Smoke from the exhaust

1st step

Remove the top and bottom lines from the charcoal canister with a flat-head screwdriver to remove the canister. Three lines run across the top of the canister, while one runs across the bottom. Remove the canister from the bracket with a ratchet and socket if necessary.

2nd Step

On a flat surface, place the charcoal canister. Start the air compressor and allow it to reach a pressure of at least 50 psi. Once the air pressure hits 50, turn off the compressor.

EVAP canister cleaning

3rd step

Insert the rubber tip of the airline nozzle fitting onto the top of the canister's outer vent control valve pipe. This pipe is distinct from the other two at the top. The canister's exterior control pipe is located at the very end. In addition, the outer control pipe is slightly larger than the other two pipes.

4th step

With one hand, place the tips of your fingers over the apertures of the other two pipes atop the canister. Pull the air release trigger on the airline nozzle and use the other hand to blow 50 psi of air into the canister. For around one to two minutes, keep blowing air into the charcoal canister. Remove one of your fingers from the top pipes and place it at the front entrance of the pipe on the canister's bottom.

EVAP canister replacement

Apply air to the control valve pipe's opening once more, and check with your finger to see if the air is coming out of the bottom. This will ensure that the canister is clean and that air can flow freely from the top of the canister to the bottom pipe. Remove the charcoal canister and replace it.

6. Conclusion

Because the EVAP canister is such an important component of your EVAP system, you should get familiar with the symptoms of a bad EVAP canister described above to maintain your car eco-friendly and functioning efficiently.