How does Charcoal Canister work? (Fuel smell in-cabin)

[dorikin]

Hey all

I need to know how the charcoal canister works in an EG civic.
I've read the (US) service manual but the Evap control system seems to be a little different to Australian models. For example I dont think the AUDM model has a Purge control solenoid valve.

Reason I ask is because I'm getting a raw fuel smell inside the cabin and I suspect the Charcoal canister is venting the fuel vapours out and possibly being sucked through the air vents.

[tiksie]

Check on D-series, I'm sure there will be more info there.

I removed it on my old car so can't help much!

[trism]

http://www.google.com.au/search?q=ho...ient=firefox-a


but yes, shot answer, youre correct.

[dorikin]

I need to know specifically how it works for an EG Civic (Aus model). The service manual I'm reading describes a Purge control solenoid valve controlled by the ECU but after looking in my engine bay the vacuum line goes straight to the plenum and other one goes to the throttle body (No solenoid).

This suggests that it's not controlled by the ECU (like the US models) but rather just via vacuum and a two-way valve.

Can anyone confirm?

[TheSaint]

yes the valve is in the top of the canister it is vacuum controlled

just remove it - charcoal canister does a whole lot of stuff all

they are designed to be replaced every 10 years anyway

i removed mine, plugged the vacc lines and ran the fuel vent line down towards the bottom of the car

[dorikin]

That would be the diaphragm valve. I'd rather keep it to control emissions, it's designed to minimise the amount of fuel vapour escaping to the atmosphere.

Anyway I think I found my answer thanks to this website: http://www.controllingpollution.com/...trol-canister/

There are three control methods used to purge the vapors from the emissions control canister, the first of which is controlled by the throttles position without a valve on the canister. A throttle body system may have a vacuum connecting the canister to a ported vacuum source designed as part of the throttle body. At any level higher than idle, the throttle may be positioned in will fresh air will be pushed into the emissions control canister. When the fresh air is added to the canister, it causes the fuel vapors to be purged into the throttle body through the port at a constant rate.

The second control method is by a vacuum valve that modulates the flow, also by throttle position. A diaphragm valve on the top of the canister opens when the vacuum ported from the throttle body opens it. When this valve is opened oxygen and fuel vapors are drawn into the intake manifold normally through the same port used to control the PCV system. The valve cycle under this control cycle is considered to be slaved to the throttle. The more you open the throttle the more the emissions control canister is purged.

The last of the three control methods is when the ECM activates a solenoid valve on the emissions control canister. This control method may be used only when the following pre-determined conditions are reached: The engine is within normal operating temperature, the engine has been running for a pre-determined amount of time, the vehicle speed has exceeded a predetermined rate and the throttle is open more than a predetermined level. As the solenoid is activated, full vacuum is applied from the manifold to the diaphragm of the purge valve, opening it completely. When the diaphragm fully opens the valve, fresh air rushes into the canister at a high rate, quickly purging the fuel vapors. When this happens, the ECM solenoid valve on the emissions control canister purges the canister.

The second method above sounds right for AU Civics. The system is controlled by the throttle position. When it's above idle, the diaphragm valve opens and then vacuum from the plenum draws air and fuel vapours into the intake. Now how would I be able to test if it's faulty?

[TheSaint]

it does nothing after its life span is through anyway - either replace it or remove it

[dorikin]

Anyone else? Need to know how to test if its working or not

[TheSaint]

its a replacable item - either buy a new one or throw it away

[rotary_snail]

It is there purely for emissions. The valve operates under certain engine conditions to vent the fuel vapours in through the intake and thus through the combustion chamber. This prevents raw hydrocarbons from entering the atmosphere.

The difference between Aus and US would depend on the emissions rating it was produced for. More than likely the US had stricter laws then, thus they have an ECU controlled valve, which can be controlled more accurately than a simple vacuum diaphragm valve.

Easiest thing to do would be to replace it, because as said it is a serviceable item. The carbon inside traps fuel that passes through, so after time it gets less and less effective. Bursons or repco should be able to supply one.

I would not be removing it unless you have some purpose behind doing so. It's there for a reason, emissions. Will help to avoid a defect and secondly, your engine was designed to operate with it.

[trism]

yeah, if you ever get defected, you wont pass the inspection if you remove it, its just like removing the cat

[TheSaint]

they are VERY easy to install/remove - and it doesnt effect the way the car drives at all

so you could remove OR replace OR both - if i ever have to pass emissions it would be a 5min job to put a new one back on