Causes of Your Nissan Sentra Vapor Canister Failure
As part of your Nissan Sentra's evaporative emission control or EVAP system, the vapor canister is tasked to store fuel vapors coming from the fuel tank and the carburetor. As you start your engine, a vacuum pulls these vapors into the canister. And while the engine is running, they are moved into the combustion chamber for burning, which turns them into less harmful substances once they are released into the atmosphere. However, this very same function may cause your Nissan Sentra vapor canister to fail. Here are some problems that often lead to its failure:
Test your vapor canister if it is in good condition by applying nitrogen, which would create pressure. Test this pressure and observe if it drops. If the pressure drops, a defect in the canister or in a hose may be present. Cracks are very common in these parts, so you might want to consider checking them first. Repair or replace the damaged component as needed.
Usually, your vapor canister leaks as a result of overfilling or topping off your fuel tank when refueling. However, it is also possible for gas to flow out of the fuel tank due to overheating. As a result, fuel gets drawn up to the vent line until it reaches the canister. And once the liquid gas makes contact with the canister purge valve, the valve saturates. In this case, a strong fuel odor would usually start to become apparent as well. The best thing to do is to replace your old vapor canister.
You may test your vapor canister for leaks using nitrogen, too. Make sure that no amount of air gets inside your canister while doing this test. Once fuel vapors are mixed up with air, it could lead to fire or explosion.
In changing your vapor canister, you need to run the engine and allow it to run for some time until all the fuel left inside are used up. You would know that your engine has already been emptied once it stops running. This is the only time you can start your vapor canister replacement.