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Old 09-27-2019, 11:19 AM
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Forgot about the charcoal canister.

So I went from a stock camaro TBI system to carb and totally forgot about the canister. I smell strong odor of gas after running a while. The canister has some solenoids that open and close controlled by the ecm. How do I properly hook up my charcoal canister to the carb.? I want those vapors burned by my engine thus giving me more fuel efficiency haha.

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Old 09-27-2019, 12:30 PM
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Quote:
Originally Posted by boneste624 View Post
So I went from a stock camaro TBI system to carb and totally forgot about the canister. I smell strong odor of gas after running a while. The canister has some solenoids that open and close controlled by the ecm. How do I properly hook up my charcoal canister to the carb.? I want those vapors burned by my engine thus giving me more fuel efficiency haha.
Unfortunately the ECM has to control your particular cannister. You might be able to fashion an old 70's carb type evap cannister to work, but I do know it uses vacuum regulated through a thermal switch and the EGR valve signal is in there too. I'm betting everything is calibrated for a particular application so it runs right while purging the cannister. Better to take it off and plug the line to it from the tank unless you area forced to retain the emissions. If you are, you are in for an interesting time. …… oops I see you are in California. Not sure what their laws are during emissions inspection, but I don't think what you have done by replacing fuel injection with a carb is legal there.
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Old 09-27-2019, 01:50 PM
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You can't plug the line to the tank. It's the vent on those cars. It's not smog legal but two options are to get an older non computer canister and vacuum operated purge valve like he said above. It doesn't really need the temperature vacuum switches. I put a canister on my 67 Ford to stop gas smells in the garage. I used the gm vacuum purge and canister from a 70s truck I think. Basically one line from tank to canister, another from canister to purge valve, then I teed it into the pcv with a vacuum restriction (a Holley jet pushed into the line so it's not just a huge vacuum leak). Then the third port on the purge valve goes to ported vacuum so it doesn't purge at idle but does when you crack the throttle. It works good and I didn't notice much change with my wide band o2 gauge either.

Another option would be to hook ignition hot 12v to one side of the solenoid and ground the other wire. That will open the purge valve with the key on. Hook the vacuum line from the purge solenoid straight to manifold vacuum (t into pcv or use a pcv with the F shaped plastic nipple on top like fords used, that's what the top leg of the f is for). Put a vacuum restriction in that line between pcv and canister. It can be a store bought restriction, or a small Holley jet, or a bolt with a small hole (1/16" or so) drilled in it. Retune the carb afterwards in case it threw the mix off a little and roll on. This is basically a constant purge system. My dad's 88 bronco used this setup factory, basically it has no purge valve at all, there's a constant small vacuum leak through the canister with the engine running to purge it out through the restriction.

Like I said it's not likely smog legal if you have to pass an inspection, but it does work and will cut the gas fumes down. Since it's not been purging the canister has become saturated so now it can't absorb fumes and you can smell them. A slight flow of air from the vacuum is all that's needed to pull the fumes from the charcoal pellets.
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Old 09-27-2019, 01:59 PM
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Quote:
Originally Posted by Tim C View Post
You can't plug the line to the tank. It's the vent on those cars. It's not smog legal but two options are to get an older non computer canister and vacuum operated purge valve like he said above. It doesn't really need the temperature vacuum switches. I put a canister on my 67 Ford to stop gas smells in the garage. I used the gm vacuum purge and canister from a 70s truck I think. Basically one line from tank to canister, another from canister to purge valve, then I teed it into the pcv with a vacuum restriction (a Holley jet pushed into the line so it's not just a huge vacuum leak). Then the third port on the purge valve goes to ported vacuum so it doesn't purge at idle but does when you crack the throttle. It works good and I didn't notice much change with my wide band o2 gauge either.

Another option would be to hook ignition hot 12v to one side of the solenoid and ground the other wire. That will open the purge valve with the key on. Hook the vacuum line from the purge solenoid straight to manifold vacuum (t into pcv or use a pcv with the F shaped plastic nipple on top like fords used, that's what the top leg of the f is for). Put a vacuum restriction in that line between pcv and canister. It can be a store bought restriction, or a small Holley jet, or a bolt with a small hole (1/16" or so) drilled in it. Retune the carb afterwards in case it threw the mix off a little and roll on. This is basically a constant purge system. My dad's 88 bronco used this setup factory, basically it has no purge valve at all, there's a constant small vacuum leak through the canister with the engine running to purge it out through the restriction.

Like I said it's not likely smog legal if you have to pass an inspection, but it does work and will cut the gas fumes down. Since it's not been purging the canister has become saturated so now it can't absorb fumes and you can smell them. A slight flow of air from the vacuum is all that's needed to pull the fumes from the charcoal pellets.

Restriction. Gotcha. Thanks for that bro.
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Old 09-27-2019, 02:00 PM
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the gas stink in the garage is a problem I hear about alot, houses are too well sealed up now, some good ideas here to fix that seemingly simple problem
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Old 09-27-2019, 02:20 PM
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I'm back at the point of how this fits into the California emissions reguations at all? That would be starting with the removal of the injection for a carburetor and on?

Bogie
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Old 09-27-2019, 03:42 PM
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the gas stink in the garage is a problem I hear about alot, houses are too well sealed up now, some good ideas here to fix that seemingly simple problem
It made a big difference. It'll still smell some with the fuel in the carb bowls but it's not nearly as strong. On my Fairlane I use an electric pump. So to stop it pretty much completely I kill the fuel pump at a certain neighbors mailbox so the carb with 4 corner idle runs dry just as I coast down the driveway. No more overpowering fumes when you open the kitchen door the next morning and I just key on and let the pump run a second before I hit the starter next time I drive.
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Old 09-27-2019, 04:46 PM
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There are no computer controls. The egr, pcv, and egr solenoid do all the emission. O2, iac, tps, map, and coolant do the fuel trim.
It is a very simple setup which is why it is copied.

The canister has a tank port, a vent port(one way check valve on the end), and a port that goes to the throttlebody.

Maybe California is different. But every 87-93 I have seen has run that setup stock.


Quick search to provide pictures:

http://www.45cui.com/45cui/tech/chev...-vacuum-system
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Old 09-28-2019, 04:53 AM
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Not trying to hijack the thread, but I think I have a related question.

Does anyone know if there was an even simpler charcoal canister system used on 70's GM vehicles? When I got my '75 truck GMC truck (with the stock 350) it had a separate port on the Quadrajet for vacuum to the charcoal canister, and there was no purge valve or other controls for the purge function. It seemed to be just constant vacuum on the canister to pull out vapor, unless something inside the Quadrajet provided control over the purge vacuum on/off.

When I swapped to an '80's vintage Quadrajet it did not have the extra port for the line to the vacuum canister, so I just tied into the PCV line. However, that screwed up AFR, based on my wideband, and it ran much leaner.

I then tapped into the body of my air cleaner and put the canister purge line on a fitting there so that there is a constant draw of fresh air on the canister purge line. However, it probably doesn't really "pull" that much out of the canister, and under certain conditions I still get a gas smell.

I don't have the original emissions diagram for my truck, but it has HD truck emissions and I don't believe it ever had an EGR. Is there a way I could use stock parts to duplicate something similar to the canister purge diagram provided in the last post, even if I don't have an EGR?

Thanks,

Bruce
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Old 09-28-2019, 02:30 PM
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Quote:
Originally Posted by 75gmck25 View Post
Not trying to hijack the thread, but I think I have a related question.



Does anyone know if there was an even simpler charcoal canister system used on 70's GM vehicles? When I got my '75 truck GMC truck (with the stock 350) it had a separate port on the Quadrajet for vacuum to the charcoal canister, and there was no purge valve or other controls for the purge function. It seemed to be just constant vacuum on the canister to pull out vapor, unless something inside the Quadrajet provided control over the purge vacuum on/off.



When I swapped to an '80's vintage Quadrajet it did not have the extra port for the line to the vacuum canister, so I just tied into the PCV line. However, that screwed up AFR, based on my wideband, and it ran much leaner.



I then tapped into the body of my air cleaner and put the canister purge line on a fitting there so that there is a constant draw of fresh air on the canister purge line. However, it probably doesn't really "pull" that much out of the canister, and under certain conditions I still get a gas smell.



I don't have the original emissions diagram for my truck, but it has HD truck emissions and I don't believe it ever had an EGR. Is there a way I could use stock parts to duplicate something similar to the canister purge diagram provided in the last post, even if I don't have an EGR?



Thanks,



Bruce
My truck (79 GMC) has the diagram on the rad support I can pm you a picture if you want

Sent from my VS996 using Tapatalk
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Old 09-28-2019, 05:28 PM
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They are all roghly the same from 72 to modern day. The early 70's systems can vary in effectiveness and over complication (Chrysler). But by mid 70's a system was found that worked well enough till the 2000's when some electronics were added to make it more emmisions effective at the cost of reliability. A pre 2000's system can run for 30 years without needing to be touched if kept sealed.

In all the setups you have 3 basic parts:

You have a FROM TANK line coming off the tank that goes to the canister. On some models there is a spring or electronic diaphragm. This is a one way check valve and when the tank exceeds a few psi it opens allowing vapor into the canister.

You have the VENT line which allows air back into your tank when adding fuel using a one way check valve(usually inside the canister) that then uses the "from tank" line to feed the tank fresh air and prevent the pump from clicking off prematurely.

You have the PURGE line. This has a diaphragm(spring or electronic) that when the engine is first started sucks that diaphragm up there by pulling the vapors out of the canister and into the intake to be burned.

Modern engines have a electronic valve that does not purge until the engine is warm. Reducing emissions slightly. Pre 2000ish cars use the pcv to do this.




Potential problems can be had if your "purge" valve gets stuck or someone just caps it off. The charcol will become saturated and quickly useless.

On the other side of this if your "purge" valve is stuck open then the gas tank is venting right into the throttlebody of the carb. The only thing stopping(lessening) the smell is the closed blades and air cleaner.

More of a offroad note. If the charcoal outlet of the canister gets coated in mud or water blocking or washing the charcol out. That can kill the effectiveness of the canister and require replacement.



The system is a sealed system. If you have a leak in any of the lines or the canister itself then it will vent gas. Usually the lined on top of the tank can become rusty or be damaged during install causing leaks. Lines can be kinked or just have the clamp cut into them and over time crack causing the vapors to leak out.
The rubber lines should be updated to new more volatile fuel standards preventing the lines form becoming "soft" and cracking.
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Old 10-03-2019, 12:43 PM
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we're talking fumes from the tank, right? I just ran the line to the air cleaner without a charcoal canister. The fumes get sucked into the engine and burned. You could of course add a canister if needed to pass inspection. We don't have inspections here in MN, so we do the sensible things, not the govt things.
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