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Hi,
Yes, that is the evaporative canister or vapor catcher for fuel tank emissions.
There is a supply line from the fuel tank that runs to a vacuum operated valve on top of the canister.
This line allows excess vapors and pressures from the fuel tank to go to the canister.
A vacuum line runs from the throttle body down to the valve.
This line triggers the valve open under certain conditions of idle or above in most cases.
There is another line that runs up from the canister to the throttle body. This is a evacuation line.
So this makes two vacuum line ports that have to be open and clean to pull from the canister. The throttle body does get dirty around the plate too.
You will want to clean those ports connections of any carbon deposits and the tiny holes below them.
Those two vacuum lines have to be intact without splits on the ends or rub spots along their lengths to operate as a system.
This canister, filled with carbon granules, is suppose to absorb vapors into itself. They can will condense because it’s a cooler place inside there.
It can become over whelmed with excess vapors, if;
The vacuum lines are not connected and or the valve will become non operational.
Without activation, of which should not happen, the vapors build up in the can to a point of overflow.
The fuel tank should not over pressurized but vents to the canister. It is suppose to stay vented and maybe slightly pressurized. The fuel pumps like that, I bet!
You”ll notice this upon filling an excited fuel tank. You loosen the cap and it blows outward for a brief second or so.
Warnings have been issued from Volvo over the years to advise on cracking the cap open at first when ever using the fuel cap.
When this “ venting” does not happen, you can or will hear a chirping or short humming sound inside the car.
I don’t hear this often, but it’s usually during hot summers or when the fuel tank has been shaken a lot over rough terrain or sudden dips into steep driveways or alike situations.
I’m not sure where the sound comes from.
This can happen if the tanks fuel cap fails to vent to the atmosphere.
It is suppose to only let air in, but not let gases out up to a fixed point of pressure.
I surmise this is limited by the o ring on the cap or maybe the fuel cap entry valve has an upper high limit built in. I don’t know.
If you pass smog it has to be OK!
There is a roll over valve in the highest part of the evaporative system. This is above the tank, on the fuel vapor line. This valve shuts in case the car is tilted more than 45 degrees. Any More than that, your four wheeled land yacht has just capsized! (:)
Maybe its that roll over valve making the chirps? I don’t know.
Anyhow something is passing gas, isn’t that nice, that is being dealt with by dumping it!
It works with humans too! (:-)
You can test the canister valve by applying vacuum on the signaling side and applying a slight pressure or vacuum on the outlet. The valve remains closed, until it gets sucked open.
At that time, either flow event confirms the valve is or should be, evacuating the canister.
If you want to ask, why go to the bother of opening and closing the line?
Well, that has to do with a leaner mixture developing behind the AMM, when it doesn’t expect it in the ECU programming! I know, it sounds like nitpicking!
The dripping gas is not normal, unless for some reason the canister is damaged. I can only imagine a high water event might cause it to have a failure to absorb vapors.
Let us know what you find.
It builds knowledge in the forum!
Phil
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