Charcoal cannister vent valve

[King_berald]

Hi all, just diagnosing a vacuum leak on a vx ls1. I was having a look at the charcoal cannister and i was wondering if anyone knows if youre supposed to be able to blow air into the vent valve? Or is my valve stuck open? Does anyone know the way to test the vent valve? is there even a valve there? cheers

 

[krusing]

Not that I had much to do with the Charcoal Canisters,

I don't think the Charcoal canister has a check valve, I would think they are open both ways,
and all the pipes should be sealed from the atmosphere,
one to the tank, and one (vapor outlet) to the manifold I guess.
May need to look at a service manual to check the route of the plumbing.

 

[J_D 2.0]

Not that I had much to do with the Charcoal Canisters,

I don't think the Charcoal canister has a check valve, I would think they are open both ways,
and all the pipes should be sealed from the atmosphere,
one to the tank, and one (vapor outlet) to the manifold I guess.
May need to look at a service manual to check the route of the plumbing.

Most systems normally have an electronic solenoid valve to shut the vacuum on and off as required. The system can’t be fully open to vacuum otherwise it’s going to create negative pressure in the fuel tank when the engine is running.

 

[krusing]

There you go, that explains it, In the past, I have often wondered how they worked.

(not any of my cars)
that explains when I have remove a fuel cap, you hear a vacuum of air.

 

[krusing]

Maybe smoke test the the intake, and charcoal plumbing.

 

[J_D 2.0]

There you go, that explains it, In the past, I have often wondered how they worked.

(not any of my cars)
Possiblly that explains when I have remove a fuel cap, you hear a vacuum of air.

I’m not completely au fait with the Commodore systems as I’ve never had a problem with them but here’s a good video explaining how the system works.

There has to be a purge valve and a vent valve otherwise the system won’t work in the intended manner so the basic diagram shown in the video should be applicable to all vehicles with charcoal canisters.

 

[King_berald]

thanks guys. After a bit more reading overnight, i was able to work out that the purge solenoid in the engine bay is basically the check valve for the system. Air is drawn through the vent port so no valve in the cannister itself.
Definitely time for a smoke test

 

[Fu Manchu]

Manual says to check the canister. Air should pass through fine. The evap lines should be checked and compressed air is about the only way to do that. If blowing back to the tank, make sure the fuel cap is loose on so it doesn’t pressurise.

The evap solenoid (I hope I have this the right way around) should be blocked with no power and open with power.