i am sure it has been asked many times, but here i go,who can tell me where the 3 lines go to, i know one goes back to the gas tank, but the other 2 are just laying there.

one of the other ones, probably the largest, gets engine vacuum.

You'll have to understand how it works first.

Obviously, the one line goes to the tank and is the line that collects the vapors and deposits them into the activated charcoal in the canister.

There will be a second line (usually the bigger one- 5/16" or 3/8") that typically gets patched into the same line as the PCV valve. Full manifold vacuum, basically.

Then there is the 3rd (usually smallest) line that is the "brains" of the operation. It controls the valve on top of the cansiter that allows the canister to purge into the PCV line and burn the vapors along with the rest of the A/F mix. When vacuum is sent to this line it opens the purge valve. When no vacuum is present the purge valve is closed.

It is important that this vacuum line sends vacuum to the valve ONLY if both of the following conditions are met:

1. Only above idle speeds. I.e. the vacuum line must start from a PORTED vacuum source on the carb that only supplies vacuum above idle speeds. Purging at idle sends the idle quality to heck in a hand basket.

2. Only on a warm engine. The control line is ALWAYS routed though a thermostatically-operated vacuum switch. This vacuum switch will be closed when the engine is cold (no vacuum allowed through) and open when the engine is warm (vacuum allowed through).

Some canisters also have an unused port on top that is designed to be open to air with no line attached to it at all. Others have the bottom of the canister open with a small, round, removable fiber filter covering the opening (make sure this filter is not too badly clogged up). Some have both.

Hope that helps.


[This message has been edited by Damon (edited September 16, 2005).]

thanks for the info, i guess i will just leave it as it sits, looking useful but not at all.

just remove the cannister get a vented gas cap, plug the line to it and call it good.

so the one that goes to the carb shoud just be plugt to?

so the one that goes to the carb shoud just be plugt to?

holy thread from the dead batman!

what is your question referring to? removing the whole thing? if so, then yes, you will have to plug the carb port.

a 73 but im sure its similar http://i255.photobucket.com/albums/hh155/stinsonz/vaporlines.jpg

just remove the cannister get a vented gas cap, plug the line to it and call it good.

Will this work o.k.?

yes i want to remove the whole thing

You'll have to understand how it works first.

Obviously, the one line goes to the tank and is the line that collects the vapors and deposits them into the activated charcoal in the canister.

There will be a second line (usually the bigger one- 5/16" or 3/8") that typically gets patched into the same line as the PCV valve. Full manifold vacuum, basically.

Then there is the 3rd (usually smallest) line that is the "brains" of the operation. It controls the valve on top of the cansiter that allows the canister to purge into the PCV line and burn the vapors along with the rest of the A/F mix. When vacuum is sent to this line it opens the purge valve. When no vacuum is present the purge valve is closed.

It is important that this vacuum line sends vacuum to the valve ONLY if both of the following conditions are met:

1. Only above idle speeds. I.e. the vacuum line must start from a PORTED vacuum source on the carb that only supplies vacuum above idle speeds. Purging at idle sends the idle quality to heck in a hand basket.

2. Only on a warm engine. The control line is ALWAYS routed though a thermostatically-operated vacuum switch. This vacuum switch will be closed when the engine is cold (no vacuum allowed through) and open when the engine is warm (vacuum allowed through).

Some canisters also have an unused port on top that is designed to be open to air with no line attached to it at all. Others have the bottom of the canister open with a small, round, removable fiber filter covering the opening (make sure this filter is not too badly clogged up). Some have both.

Hope that helps.


[This message has been edited by Damon (edited September 16, 2005).]

Thats interesting info Damon, I never knew this stuff. The cannister on my '77 (350, manual trans) is the open-bottom filtered type, with only two ports on the top. One goes to the tank, the other goes to the carb baseplate (full time vacuum)...which means its purging at idle? I have to check my pics of the original vacuum hose routing diagram, but I *think* it shows this routing as correct.

Some carbs (QJets) have a port specifically for purging the canister. It's a venturi vacuum port, believe it or not. Very little vacuum until you rev the engine up quite a bit.

Still thought there would be a thermastatic switch in there somewhere, but there's about a bezillion different emissions hose routing setups on GM cars and I'm sure there are some I haven't run across yet.

OK cool, I guess I have it right then. I'm just as puzzled as you about the lack of a thermostatic switch. Here's the '77 hose routing.

http://i472.photobucket.com/albums/rr86/V8TEC357/EvapCannister8D-1.jpg