Evaporative Emission Control System (Charcoal canister)

[jackjeckel757]

Is it necessary to have the EECS hooked up? When I bought my 77 c10, the charcoal canister was only connected to the fuel tank and the other hose that says "carb" on the canister was connected to nothing. I never really payed much attention to it before but I was curious if it should be connected to anything. I am not running the stock carb or intake by the way and its a 305.

[bake74]

     Depends on where you live and the laws, one way to find out without giving away your truck is go into a inspection station, not driving your truck and ask.

[gto109]

where i live the Emission laws say must be there and appear to be working.  now the next county over it has to work and they will put a sniffer test on it.  best bet check your local garages.

[79GMCChris]

Here's a 79, 350ci, hope it helps.

Chris

[jackjeckel757]

As far as getting it inspected, the truck has already passed 2 times now as is. My concern was that the Haynes book says if its not hooked up right it could cause mileage & performance loss, although I haven't noticed anything bad yet.
Thanks for the diagram Chris, my '77 doesn't have as much to it with only 2 connections on the can, no air pump, or egr.
From what I figured out the other hose should go to the carb vacuum port, I will try it out and see what difference it makes.

[Jason S]

I think if the evap system is incorrectly hooked up, fuel mileage and performance will suffer.

However, if you can pass emissions without it, you could cap off the carburetor vacuum port and be fine without the canister hooked to the carb.

The charcoal canister is intended to limit fuel vapors from being able to freely vent to the atmosphere, reducing air pollution by VOC's.

[1980c10]

I have no emissions stuff hooked up to my engine at all it runs great has good power and great mpgs. I also have no inspection to pass.