La vent valve The fuel tank is rarely mentioned in mechanical matters, but it is very important for the efficiency, ecology and performance of a car. It is present in engines with the simple mission of prevent vapors from the fuel tank from going into the atmosphere.
In addition to the function of reducing environmental pollution, the tank ventilation valve allows a better fuel economy. Since it returns it to the system so that it is burned correctly when it corresponds. However, it is only one of the parts of the anti-pollution system in which they also participate: a canister with activated carbon to absorb the evaporated fuel, other valves to release the gases so that they are burned in the engine and the engine itself. engine ECU it is programmed to do so under certain circumstances.
Operation
the fuel goes naturally evaporating over time. Especially if the car is exposed to high summer temperatures. Those fumes are gone accumulating in the deposit itself until they reach a certain pressure, at which point a fuel tank vent valve opens and lets them pass to the canister or boat. there, they are absorbed by an active carbon filter.
As soon as we start moving with the car, a valve opens that let the air pass through the filter to take the evaporated fuel and drive it to the car admission. There they will be burned to prevent them from being released into the atmosphere. In this way, the activated carbon is available for the next time the evaporated fuel accumulates and exceeds a certain pressure.
The valve It does not open to release the fuel vapor accumulated in the canister as long as the engine is running. It will only do so if the ECU detects the right conditions to do so. For example, it will not be done when the starter or when the combustion engine is running at idle. Normally I also don't know when to go full throttle because the engine will already be getting all the fuel it can burn.
When fuel vapor is being sent to the engine, the Lambda probe is in charge of indicating to the ECU if the air-fuel mixture is adequate. In the event that it is too rich, the ECU will send a signal so that the gas release is less so that the proportion is always the best possible.
Si en very cold times the fuel liquefies instead of evaporating the pressure inside the tank will decrease. In these cases the valve will open to restore the atmospheric pressure inside and that no component is damaged. This process is also done when the pressure decreases due to the normal consumption of fuel.
What happens if the valve fails
In the event that the fuel tank vent valve fails, the pressure inside the fuel tank will increase to the point that could damage some components or pipes. In addition, the vapors will not be recycled. However, cars can release these vapors to the outside through the exhaust system, in which case they could have problems passing the emissions test of the company. ITV.
Fault symptoms
Car fails emissions tests
As we have told you, the release of fuel vapor is done through the exhaust system. Namely, hydrocarbons are released that emissions testing machines will detect and indicate a emission control failure car.
open joints
It does not happen in all cars, but it is possible that the fuel evaporation control system builds pressure open some joints. This will make himthe fault is greater than it could be at first, because more parts will have to be replaced and more workshop hours will have to be used.
damaged spark plugs
As in the previous case, this symptom only occurs in some models. Failure of the fuel tank vent valve can cause the fuel enter the intake system not properly mixed. When this happens, the spark plugs will burn and wear out prematurely.
can't refuel
When the valve becomes clogged, the pressure inside the tank causes it to the pumps are blocked as soon as the hose trigger is squeezed. If you see this happening to you, try another gas station to rule out that the problem is with the pumps where you are.
How to clean it
When you clean the fuel tank vent valve actually other parts of the duct should be cleaned, because the problem may be outside of it. To begin with, it is worth checking the dust filter that filters the air that enters the canisters.
The next step would be to remove the valve and blow into the ducts going in and out of it to make sure the obstruction isn't there. Then you have to check that the canister is not clogged, blowing air through the inlet circuit and checking if it comes out through the outlet. If it does not come out, it means that we must clean it with a specific cleaner.
If the problem is in the valve itself you have to check if it opens and closes. If it does not receive current it will be closed, so if we blow through it the air will not pass. If we pass current through its connectors, we will notice that it opens and when we blow, the air will pass. If it does not allow air to pass through, it will be necessary to replace it with a new one.
How much does a vent valve cost?
Su price It is usually between 10 and 40 euros depending on the model. If the price of one compatible with your model is too high first hand you can also find them in a scrapyard for less than half. However, we do not recommend that you save too much money on this part because you can lose more money than you wanted to save simply with the travel and time of changing them several times.
Can the canister valve be overridden?
yes you can cancel. For which everything is due except the valve in the filler neck, which is responsible for releasing excess steam pressure out. You will notice that your car smells of gasoline with some frequency and if you keep it in a closed place and with a lot of heat, the vapors will accumulate inside. Breathing these vapors is very harmful to health.
In other words, It is not recommended for safety and, but above all for ecology. In addition, the repair is cheap and it is not worth canceling a system like this.
what happens if it is deregulated that passes more gases or less what is the problem
How do I test the fuel tank vent valve?
Where is this valve located? In a 2004 honda odyssey
Carburated cars have this valve, if not, how is it ventilated?
the gas tank.
Good information, and in the event that the valve remains open, and the intake body adsorbs without any control, what would be the scenario, what failure would it present.
Very good explanation, since I have an electromechanical workshop for a short time and this helps me a lot. Thank you
very good explanation thank you