Has anyone replaced all the hoses going to the charcol canister? Looked at it tonight and it looks like they have a custom molded connector on the cannister end. The larger hoses going from the carb and PCV to the canister are soft and deterriated. Dr Rebuld sells the hose kit, has anyone used this? The maintenace schedule calls for changing a filter in the canister every 5K miles or so. I don't think mine has ever been changed, has yours? How does the canister work? When do you need to replace the canister?

|UPDATED|4/30/2004 7:43:40 PM (AZT)|/UPDATED|

The canister works with the fuel vapor return. You don't replace the canister but the "filter" insert in it. Just replace the insert or element and you should be fine. Why do you think it is bad?

Looking at my records I don't know if my filter has ever been changed? How do you change it? Still not sure exactly how this thing works. I'm guessing it pulls fuel vapor from the tank and not sure what else??

You replace the little foam "thing" in the bottom and that re-charges it. Dos that help?

Got it, thanks for the response Dukman.

|UPDATED|11/25/2003 8:51:38 PM (AZT)|/UPDATED|

FLA VETTE said: Got it, thanks for the response Dukman.

No problem, that's why we are here

The charcoal cannister is a pollution device. One of the emission vapors is evaporative emission. As a fuel tank heats and cools, or is sloshed around, gas fumes are created. EPA says we cannot let these fumes out to the air. The vent from the gas tank vents through the cannister. The charcoal absorbes the gas fumes, and allows air to vent to outside air. The small filter on the bottom of the cannister is the last point before getting to outside air. The filter is not needed at this point. When air cools in the gas tank, air enters the now needed filter to fill the void in the tank from cooling contracting air. All of this is when the car is shut off. When the car is running at idle or wide open throtte, the same thing happens. Keep in mind, the charcoal is absorbing gas fumes.
With the car running above idle and less than wide open, the cannister has vacuum applied from the intake manifold. This vacuum pulls fresh air into the filter, throught the charcoal, and into the engine. This positive air flow dries out the charcoal, and the engine burns the gas fumes.

If the system fails several different thing can happen depending on the failure. The car can pull gas fumes directly from the tank while running, causing poor mileage and very rich mixtures, to the point of fouling plugs in severe cases.
It can pull too much air, causing a lean condition. It can pull air at idle, causing a very lean condition, and perhaps stalling.
It can not pull any air, which will not dry out the charcoal. This will create a fuel smell. You think you have a leak but can't find one.
It can plug and not vent the tank. This can cause flooding problems or rich conditions if the tank contents expand in hot conditions, such as filling the tank when it's cool then parking it in the sun, and flood the car by forcing fuel into the carb. (this won't happen with fuel injected cars) Granted that last one is a bit uncommon.
A plugged cannister will also not allow any air into the tank when you are using fuel. This vacuum created will cause the bladder in the tank to collaspe, making it difficult to refill. The collaspe usually only occours after driving for several hours down the highway. The thank can also have enough vacuum created that the car will starve for fuel. Removing the fuel cap, then reinstalling it, corrects the problems and the car will run fine again, until it builds vacuum again.
Most of the time the driver complaint will be fuel smell or running problems.
If you overfill the gas tank, and squeeze every last drop in, the park the car on a warm day, the fuel can expand and actually drip out of the cannister, and leave a puddle on the ground. This is why you should not over fill the tank. This quanity of liquid fuel will damage the charcoal. It may simply not function anymore, or could plug up.
The filter on the bottom of the cannister is perhaps the most overlooked maintance item in any car that uses them. All cars have cannisters, not all have changeable filters. All C3's do. The very inexpensive filter just pulls out by hand, and a new one just slides in. It is just a round fiber disc. Very easy, very cheap.

Ken Styer

Thanks for the detailed response Ken. I started looking at the canister when I was chasing a carb related vacuum leak since there is a large vac hose coming from the carb.

Can't wait 'till they have perfected hydrogen powered autos so all these problems will be eliminated!

Hey Snoop, I'm very excited about this. Stark State College of Technology where I teach automotove is building a new building for fuel cell research. It will have industery co-op doing fuel cell development. I'll be able to stick my nose in once in a while. COOL!