Originally Posted by siberbunak
How should I make sure whether this part is okay ot not ?
It is a sealed box. It is impossible to open to have a look.
There is a filter element on the bottom that I've easily took out but nothing visible from that side either.
There is no "official" check in the GM service manual. You can not open it without ruining it.
The canister is filled with activated charcoal and used to capture fumes from the fuel tank that would otherwise be vented to the atmosphere, and route them to the carb.. They don't clog. If it's not cracked and leaking charcoal, it's good. The only maintenance they ever require is to periodically change the filter element on the bottom.
If yours has a purge valve on top, (small line to ported vacuum on the carb
) you can check the operation by using a vacuum pump and putting 15hg of vacuum to it. If it holds for 20 seconds, it's operating normally.