Carbon Canister Confusion

[Yellowoctupus]

This is my rough understanding on how EVAPorative emissions controls work:  When the gas tank heats up (while the engine is turned off), the sealed gas tank should slightly pressurize, and the escaping fumes will be captured in the carbon canister. This canister must be vented, otherwise they'd both pressurize together.  It appears that the larger line going to the air cleaner is where this vents according to the diagram below.  Is there a carbon canister purge valve I'm not seeing below?  Wouldn't the carbon get saturated at some point unless it's subjected to fresh air being pulled through by the engine vacuum?

 

 

(Disclaimer: I'm trying to mate the AMC Carbon Canister from my'87 4.0 MJ to my '02 Silverado 5.3 LS swap, so I'm trying to understand BOTH systems first.)

[Ωhm]

Charcoal Canister is vented to atmosphere on its bottom.

 

_fuel evaporation system.pdf

 

Charcoal canister servicing, what's inside + new filter     

@Airborne Janitor

[Yellowoctupus]

Ah cool, thanks for the PDF and the tear-down post.  I was searching variants of "Carbon Canister" instead of charcoal, didn't come up with that one. 

 

So, the canister is vented to the atmosphere from that bottom tube (which sounds obvious now, forgot about that open hose) so there must be an ECU controlled solenoid valve that is missing in these diagrams between the canister and the intake manifold, unless it's just drawing through the carbon canister anytime the engine is running??

 

 

 

[Ωhm]

8 minutes ago, Yellowoctupus said:

unless it's just drawing through the carbon canister anytime the engine is running??

 

True. No ECU control. Vacuum sourced at the Air Cleaner (fresh air in).

 

[Yellowoctupus]

Ok, gotta love this 80's seat of your pants style documentation!  Thanks for the explanation. 

 

I have mine tied into a solenoid operated valve on my swap engine, but the Chevy has both a Vapor Canister PURGE Solenoid Valve AND a Vapor Canister VENT Solenoid Valve.  I'll have to sort out the GM side of things as I have the canister PURGE valve hooked up, but no canister VENT solenoid valve at the moment.