There are plenty of new components that have been completely upgraded in modern vehicles and one such is the EVAP system. EVAP helps reduce carbon emissions and combines several components, including the canister purge valve. When all the components in a vehicle work properly, a purge valve canister significantly reduces emissions. If it’s faulty, you will start noticing bad purge valve symptoms.
Today, we will discuss the symptoms of a faulty purge valve, how to test its performance and its significance.
Before we get into the symptoms of a failing purge valve, read on and find out what a purge valve is and its function in detail.
What is a Purge Valve Canister
The liquid fuel stored in the fuel tank has a natural tendency to evaporate easily, and the degree of evaporation increases in high-temperature conditions. For this purpose, a device was designed to prevent fuel vapours from the tank from being discharged into the environment. This device is known as a canister valve and is an essential component of a car’s Evaporative Emission Control (EVAP) system.
The EVAP has a purge valve canister that restricts the amount of fuel vapour which escapes from the carbon canister. EVAP system allows these vapours to be released into the car’s engine when it starts at the regular speed. The flow of these vapours is controlled by the purge valve. Here are some of the signs of bad evaporative emission control that can help you identify if the purge valve is worn out or the whole EVAP is damaged.
The purge valve was first controlled by vacuum, but in new car models, it is controlled by the electronic control unit (ECU). The problem arises when the purge valve starts getting stuck and doesn’t open on time.
Five Common Failing Purge Valve Symptoms
As mentioned, the purge valve is an important component of an ECU system, when it fails, it affects the vehicle’s engine performance. Here are some common faulty purge valve symptoms.
Check Engine Light Comes on
There are many reasons why a check engine light appears on your dashboard warning lights. If you have a damaged or worn purge valve, this can cause your check engine light to come on. The purge valve is controlled by a car computer which allows it to control the valve’s performance.
If your car sensor shows a car diagnostic code including P0441, P0446 or any other EVAP codes, then it will illuminate the check engine light.
Failed Emission Test
As you already know, the vapour tank flush valve is responsible for redirecting fuel vapours to the engine. This prevents toxic hydrocarbons from escaping from the tailpipe. If the valve is stuck closed instead of open, the fuel vapours will not be pushed back into the engine. Instead, they will come straight out of the car exhaust, causing much higher emission levels.
Hence, if you were to have a failing purge valve, then it wouldn’t be able to redirect those fuel vapours and prevent them from escaping your vehicle. You will find this out the hard way when you go for your emissions test and end up failing.
If this happens, have the mechanic check the exhaust valve to determine if it is the part responsible for the failed emission test. If it is worn or damaged, it should be replaced quickly.
Poor Engine Performance
When the valve is stuck open, the vehicle gets more air into its system than expected. That means every time the throttle is pressed the vehicle is not getting enough fuel into the engine. While these effects are most noticeable when driving at low RPMs.
If you can start the vehicle with a bad purge valve, don’t expect it to be a smooth ride. You will experience a weaker performance from your engine.
In other words, the engine cannot make as much power to achieve the required acceleration when the accelerator pedal is depressed. This becomes more noticeable when going uphill or trying to pass another vehicle.
Difficulty Starting an Engine
If you have a vacuum leak caused by a bad purge canister valve, your vehicle will likely be difficult to start. As a result, outside air enters the engine uncontrollably and compromises the entire combustion process.
If the valve is stuck open, it will have an excessive amount of air when you go to start the engine. Also, if you haven’t mixed the metered air with the fuel in the cylinder chamber, it will cause engine cranking but the car won’t start. In case you experience such a situation, then there is a chance of failing the canister valve, or some other part of the EVAP system.
Rough Idle
If your car’s engine has a rough idle, it will no longer run smoothly. It runs at an inconsistent rate while driving, especially when stopped at a stop sign or red light.
The longer you allow this problem to persist, the more consistently your engine runs. The worst point will be when the motor stops completely.
Try not to let it get out of hand. If the flush valve is responsible for rough idle, this usually leads to a loss of vacuum which affects idle speed.
How to Test the Canister Purge Valve
First, find the location of the purge valve in your vehicle.
Purge Valve Location
It is located at the front or centre of the vehicle, depending on vehicle design. There are two typical locations for the valve depending on the car model d The valve is usually located in the engine compartment on a hose that runs from the intake to the canister. It can also be near the fuel tank.
It looks like a small black plastic component with an electrical connector and vacuum line at each end. While it can be difficult to identify, it’s usually pretty easy to access once found.
Once you find the placement of the purge valve now you can check the performance of the canister purge valve by following the below-mentioned procedure:
- Turn off the engine and let it cool
- Disconnect the cylinder bleed valve connector and measure the resistance between the two coil connectors.
- Resistance can be between ±15 ohms and ±75 ohms (depending on valve type).
- Disconnect the exhaust valve connector and plug it in from the control unit.
- Measure continuity between exhaust valve connector terminals and ECU.
- Disconnect the exhaust valve connector from the housing.
- Start the engine and measure the voltage at the positive terminal of the connector.
- Check the supply voltage (normally it is 5V or 12V)
- If there is no supply voltage, check the relay.
- If there is voltage, check the fuse.
- You can also check the continuity of the wire between the relay and the valve to see if it is interrupted.
Importance of Purge Valve Canister
The canister valve is vital for emission control, it works in conjunction with different sensors’ speed, temperature and load. A purge valve prevents gasoline vapours from emitting into the atmosphere, generating greater fuel efficiency.
The canister purge valve is part of the emission control system. Fuel vapours from the tank that is stored in the canister are transported to the engine through this solenoid valve.
If the lambda control of the engine is working, the valve is actuated by the control unit, so that the additional fuel in the form of a vapour that is transmitted through this system to the engine is compensated.
That is all about the purge valve symptoms and how you can test its performance. Besides, if you find some major issue in your car then don’t hesitate to buy a well-maintained used car in the UAE. With this, you can enjoy a hassle-free ride and avoid frequent maintenance.
To know more about car parts and how they work, stay tuned to the UAE’s leading auto blog.
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