Carbon Canister Info

Thought I would enlighten those that do not know  how the carbon canister works, it's purpose and what can happen if it is not functioning correctly.

We cut one in half the other day to see what was inside as had a problem with someone's car and found this to be the culprit
Here's a picture of two with the tops removed, one on the left is a good one and the right one has collapsed internally which you can see as the gauze type filter has dropped inside




In the second photo we cut the canister in half to see what had actually failed and basically the wadding at the top and bottom of canister deteriorates  and breaks up and once this happens the gauze type filter at the top will drop allowing carbon elements to possibly be sucked up past the diaphragm back into the vacuum chamber at rear of throttle bodies, other particles can also be pushed through outlet at bottom of canister.
Once there is a void inside the canister it then becomes a hidden vacuum leak as there's nothing seperating the top section from the bottom other than the diaphragm which after many we tested had found they had perished.

Won't go into great detail of how it works but in a nutshell it's designed to remove gases from the fuel tank then vent them to atmosphere cleanly via the carbon particles inside.
This is done by vacuum opening the diaphragm at top of canister when throttles are closed the overly pressurised gases in the tank are then allowed to enter the canister which is where they remain until the throttles are opened.
The second pipe at the top of canister then pushes the gases from the canister under positive pressure where they filter through the carbon and are expelled via the bottom pipe which vents through the chassis to atmosphere.

If any of the components fail in the canister then these are problems which you could experience
1. Irratic uneven idling
2. High idle speed
3. Over fuelling (if canister is blocked) gases will build in tank putting pressure back into fuel rail where you will get black smoke and very lumpy running especially from low to medium throttle
4. Vibrating or pulsing from fuel lines into main fuel rail.

So from the above findings you can see that it actually is important that if still fitted that it's functioning correctly or any of the issues I've stated above can occur and leave you scratching your head as to what the problem could be.

Hope that helps a few of you out who have either idling or over fuelling troubles and can't seem to find the cause as it certainly is a main contender amongst other things to be on your check list.

Is it safe to remove this and if so what would I do with the pipes that go to it? I have idle issues, I'm going to start by trying another idle control valve

I removed mine all cars I've previously owned. Normally just blocked the pipes that go the inlet plenum and the pipe from the petrol tank I just leave it to vent to atmosphere under the car. Only thing I've ever noticed getting rid of it is you hear the tank vent when you open the cap to fill up with petrol

Mine does that when I open the cap.

Nice write up Bob, Ive normally just ripped the bastard out, good info

Can this be stickied somewhere?

Also could someone definitively explain the PCV valve and what we should be doing to remove it, I think this is causing me issues as I have a catch can on the right hand side as I have an induction kit thus removing the induction side feed so it had to go to a catch can.

I think the engine is breathing heavy so I am willing to give removing the PCV valve and blocking it off a go but just wondered how people do it?

shroom wrote:Can this be stickied somewhere?

Also could someone definitively explain the PCV valve and what we should be doing to remove it, I think this is causing me issues as I have a catch can on the right hand side as I have an induction kit thus removing the induction side feed so it had to go to a catch can.
I think the engine is breathing heavy so I am willing to give removing the PCV valve and blocking it off a go but just wondered how people do it?

Tom........if the pcv valve is working correctly you should not have any issues with it, if however the valve is jammed shut you could experience a build up of pressure which would cause issues with car being under powered, excess smoke and various rubber seals leaking.
If the valve is jammed in an open state and pipework still feeds back to plenum you will have low vacuum issues as its no different to having an open pipe
Remove the pcv and check its operating correctly, more often than not they just get jammed up with carbon deposits and stick.

joetheeskimo wrote:I removed mine all cars I've previously owned. Normally just blocked the pipes that go the inlet plenum and the pipe from the petrol tank I just leave it to vent to atmosphere under the car. Only thing I've ever noticed getting rid of it is you hear the tank vent when you open the cap to fill up with petrol

Joe.....yes you can remove it no problem at all and weve seen many that have been removed with no issues but other cars do not like it once it is removed.

As said the purpose of the canister is to draw pressure from the tank under light vacuum, hold vapours in canister, then disperse it to atmosphere once its filtered through the carbon.
So in theory you need to take the small pipe from the vacuum chamber 'which is top one on canister' take that to a tee piece where the vent pipe will attach to one end, the other end should then link up to the pipe which goes to the bottom of the canister and vents to outer chassis rail (that's safe there as last thing you want are petrol vapours under your car close to sources of ignition and heat).
This way you will only need to blank off the larger top pipe from plenum to canister all others are connected via the Tee to chassis pipe outlet, bypassing the carbon / canister which would filter the vapours.

Do you reckon this could be why mine idles high? Will check it out

I always bin these also, all UK spec gtir's didn't have these fitted from factory.

Great write up bob .... so would you say its better to do away with it altogether to prevent future problems ???

Depends on what your doing with the car Leighton 
If you want a standard type car then a lot of people would be wise to keep them but if it's a highly modded car I personally think you would be better to do away with it. 
1 it creates more space 
2 the more things you do away with then there's less that can go wrong

Whytie wrote:I always bin these also, all UK spec gtir's didn't have these fitted from factory.

Just out of interest what fuel tank breather set up does the sunny have?

Well as you know 1,2,3 and 4 were all my symptoms and what a head scratch that was.
Its great to not gas yourself and better on the wallet now and not to mention the 2000 plus rpm idle pissing me off which has all gone now.

was it a carbon canister issue causing your probs then?

Yes you told me to check it and it was buggered.