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'79, '81 e12, '81 e24 have no gas tank cannisters. No sign they were factory installed, or removed by a previous owner.

My question goes to the three tubes out of the gas tank next to the filler neck, then the clear plastic tubing (the same as used for the windscreen fluid, NOT fuel sensitive) that connects them to the fittings under the plastic collector tank... with the pinch clips...

What the hen for, if there is NO charcoal filter nothin' to explain the three, four in/out, air what, tubing needing all of the feeding through the holes.

The charcoal cannister is in the passenger side front fenderwell on the inside behind the headlight bucket. There's a hard line coming from the gas tank area that exits the frame rail area almost underneath the ac drier cannister which connects to the charcoal canister via a cloth braided rubber line. The foam on the bottom of the cannister deteriorates allowing bits of charcoal to fall out. The charcoal cannister is common to other models and is still available.

What happens if the charcoal is worn out or or the canister is disconnected or bypassed?

canada karl wrote:What happens if the charcoal is worn out or or the canister is disconnected or bypassed?

I don't think they wear out. Bypassing it would allow fumes from evaporation out as smog, and it doesn't really hurt anything, unlike the way things like Thermo reactors do. And to tell the truth, gas doesn't evaporate like it used to either. Still, more smog, no improvement in the way it runs.

canada karl wrote:What happens if the charcoal is worn out or or the canister is disconnected or bypassed?

My guess is that it's meant to be replaced at some point relative to an emissions requirement. I simply glued foam on the bottom to replace the foam that had deteriorated to prevent the charcoal pellets from falling out. I don't think it inhibits performance in any way and don't see the point in bypassing it unless you just want to vent tank fumes directly into the atmosphere. I wouldn't plug it as the tank needs to breath.

Charcoal does absorb until it is saturated and becomes pretty much worthless, which is after four or five years. There is no maintenance given, because bmw (or any other auto manufacturer) doesn't expect you to keep your car longer than it's effectiveness, let alone thirty-plus years. It's just a can that serves no purpose at this point.

Ahh, but it does serve a purpose. It placates BAR inspectors who don't care if it works.