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Venting a Charcoal Carbon Vapor Canister...

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ericbee

Full Member
Joined
Jan 27, 2012
Messages
209
Paul, I didnt mean to insult you and I appreciate all of your advice. However, I have to address each of your points because, once again I see things differently.

The photo in this very post shows a HOLE in an air cleaner. Not in a carb, not in a float bowl, in an air cleaner. Points have been made to vent to the air cleaner, the vacuum and the float bowl and all 3 are different, correct me if I am mistaken.

Second, I never, ever, in any photos or diagrams ever seen a hose connected to one of the Large Chimney vents. The only time that could even be an option is when there are no other nipples or fittings on the CC. If the CC has any nipples, either small or large, then the chimney stacks are never connected to anything. Please show me anything, anywhere to prove that to be incorrect. A photo in this very thread shows both chimneys with vented caps.

As far as the tank goes, it is a BC Broncos tank. You stated "the big vents NEVER go to the tank. Otherwise you'd have a fitting that size on your tanks. And I've never seen or heard of one that size on any of our tanks.

Please look at this link.
http://www.bcbroncos.com/store/product_info.php?cPath=131_68&products_id=2024

It is the BC Bronco's tank and the fittings are 3/8 and 5/16. The canister has 2 nipple sizes, 5/16 and 1/4. I guess I found the only tank in the world with a 5/16 fitting and the hose fits perfectly on the bigger nipple of the canister which is the exact same 5/16.

If there was a 1/4 nipple on the tank then I suppose it would be obvious to vent to the smaller nipple on the CC but, since one of the fittings is 5/16 and the same size is on the CC, I thought it was obviously supposed to go there. Now I need to find a step down barb to connect a 1/4 hose to the 5/16 hose that vents the gas tank.

My MSD EFI does have a ported/timed vacuum source so it appears that is where I will be venting, the confusion is all of the step up and step down fittings required to make nipples on all 4 ends of the hoses fit correctly.
 

DirtDonk

Contributor
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Messages
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The photo in this very post shows a HOLE in an air cleaner. Not in a carb, not in a float bowl, in an air cleaner. Points have been made to vent to the air cleaner, the vacuum and the float bowl and all 3 are different, correct me if I am mistaken.

Nope. You're correct. But each is different because each is for a different application. And it wasn't said to vent to the float bowl. You vent more fumes FROM the float bowls.
The only one that was on an EB was Doug's pic of the hole, which he said in his text, and I repeated, was supposed to have a fitting in it to fit the hose to, but it was missing.
Only missing. Still need one to make it work. But the point was that this is what Ford used to vent to the air-cleaner.

The other two are just what I said previously. Nothing gets vented to a float bowl. It gets vented from the float bowl. And I said somewhere that the carb and the air cleaner were effectively the same thing as far as EVAP is concerned. All they mean by "venting to the carb" is that the vapors are re-introduced into the air-fuel mix through the carb venturii via a hose to the air cleaner. Same things, different words.

All carbs have a float bowl vent to atmosphere inside the air cleaner, which is a potential source of pollution. So later carbs had a vent/valve to use the CC as the carb's new "vent". This would combine vapors from the carb with vapors from the tank in the canister, then burn them through the air cleaner. Just like normal.
There was a 1-way valve in that line to keep vapors going in the direction of the canister.

The vacuum is still as stated. It can work under the right circumstances. You just have to be able to control it.
Since you can't with your setup, you can't use vacuum as EVAP. Completely different system than yours.


Second, I never, ever, in any photos or diagrams ever seen a hose connected to one of the Large Chimney vents. The only time that could even be an option is when there are no other nipples or fittings on the CC. If the CC has any nipples, either small or large, then the chimney stacks are never connected to anything. Please show me anything, anywhere to prove that to be incorrect. A photo in this very thread shows both chimneys with vented caps.

You're right. I only described it verbally because that's how it was set up on a Bronco. And in 904's photo of his '77, he shows a hose laying there on top of the canister. It's not clear where it goes unless you know. Sorry, I just happened to know where it went, but describing it was not the same as seeing it.
I don't have any pics of mine, since it's now disconnected during a retrofit, but there are hopefully some here that can post one up. Your Bronco originally had one just like described though, if it was one of the years so equipped. I think from mid '69 to early '76?
The pre-'76 Broncos would have had the low-mount canister on the frame. This had one fitting for the small hose to the evap-condensing tank behind the driver's seat, and two large "chimney" fittings. One for a hose up to the firewall with a plastic "grommet" to hold the hose open (later years had the mushroom cap) and the other large hose went to the hole on the air filter that 904 showed in his pic.
The only diff was that in his pic the fitting is missing. He was only using the hole to show you where the hose and fitting are supposed to go. The hole is usually filled with a plastic hose fitting. But the concept is valid. We just need a pic of the fitting to prove it.


As far as the tank goes, it is a BC Broncos tank. You stated "the big vents NEVER go to the tank. Otherwise you'd have a fitting that size on your tanks. And I've never seen or heard of one that size on any of our tanks.

Please look at this link.
http://www.bcbroncos.com/store/product_info.php?cPath=131_68&products_id=2024

It is the BC Bronco's tank and the fittings are 3/8 and 5/16. The canister has 2 nipple sizes, 5/16 and 1/4. I guess I found the only tank in the world with a 5/16 fitting and the hose fits perfectly on the bigger nipple of the canister which is the exact same 5/16.

If there was a 1/4 nipple on the tank then I suppose it would be obvious to vent to the smaller nipple on the CC but, since one of the fittings is 5/16 and the same size is on the CC, I thought it was obviously supposed to go there. Now I need to find a step down barb to connect a 1/4 hose to the 5/16 hose that vents the gas tank.

Ok, I was referring to stock original tanks. Sorry I wasn't clear on that. I wasn't even thinking of aftermarket, which I should have been. But I was also referring to the big fittings. By that, I meant the "BIG" chimney fittings. If you meant the larger of the two "small" fittings, then I misunderstood what you were saying. I consider all four fittings on the canister in my statements. 3 different sizes, 4 distinct fittings.
Still, with a "stock" tank, it's the smallest of the hose fittings that receives vapors from all years of EB tanks. The larger of the two small ones on your specific tanks is, I believe, still for the vapors to go up to the engine via the CANP circuit.

Still, I thought the larger of those two looked like it was 3/8" instead of 5/16" like you say it is. Thanks for clearing that up. I should be more familiar with aftermarket tanks in minute detail, since I sell them, but I've only looked at the later canisters a few times. And it's been awhile.

One thing that's been consistent over the years at least, the aftermarket tanks don't match the factory hose sizes very well. My old NWMP tank's two evap vents that are in the same place as the stock ones on the main tank were not correct either. I got some to fit, but wasn't happy about how much I had to clamp down on the 5/16 hose to get them sealed tight against the factory steel and plastic lines.
But here again, you're using a non-stock EVAP canister. So an aftermarket Bronco-specific tank and a non-stock canister might not match even if the tanks did match the stock setup.


My MSD EFI does have a ported/timed vacuum source so it appears that is where I will be venting, the confusion is all of the step up and step down fittings required to make nipples on all 4 ends of the hoses fit correctly.

Stop. Don't pass go.
Just because your new throttle body has a timed vacuum port has, in no way, any bearing on your evap system. Unless MSD says to hook it there. In which case I'd actually call them to find out why myself.
Timed vacuum is usually (always?) only for a vacuum advance distributor and has nothing to do with EVAP unless it's through other specific accessories specifically designed to control that circuit.
Which it doesn't sound like it is.

I haven't read the MSD instructions lately, so I'll try to do that tomorrow to see if there is anything I can find that would help here. Probably not, as you've got them right in front of you, but it would make me feel more in touch if I re-read them again to re-familiarize myself with what's going on.
Sorry if none of that was clear for whatever reason. All of the questions you just asked seemed to me to be the same ones we've been answering.

Ok, here's my bottom line suggestion for you then. It's just a suggestion to give my angle on this whole thing though. If you think there's a better way, or if someone chimes in and has more direct knowledge of how it would work better, then do it that way.
The bottom line is that you have an EFI equipped engine that does not have a dedicated EVAP control circuit. Therefore, you should hook it up just like you would on any non-EFI Early Bronco V8 engine.
And that is:

1. Smallest fitting on the canister goes to the tank line. If that's the 1/4" one on the canister, and 5/16 on the tank, then it's just got to be adapted like you said. That's where all vapors will enter the canister.

2. The medium fitting on the canister gets plugged/capped/closed. Not used.

3. One of the large chimney types (might as well be the one farthest from the motor) gets a mushroom cap and is the atmospheric pressure equalizer, or whatever it's called.

4. The remaining large chimney fitting will get the proper fiber hose (available at most auto parts stores I would think) fitted and routed to the air cleaner housing somewhere. This is how it will get to the throttle body to be used in the engine.
Depending on your air cleaner, you can contact the manufacturer to see if they have those plastic elbow fittings that attach to knockouts in the lower plate, or drill your own for some sort of fitting that is the right size to match the chimney on the canister.

Most of the major air cleaner manufacturers include knockouts in the lower plate for just this purpose. Edelbrock, K&N, Mr Gasket, etc. should have the spot and the fitting available. If not, you need to make your own.
If you have a stock air-cleaner housing, you could use that. I know it's not as cool or as free-breathing as a nice big aftermarket filter housing is, but it's got good hood and distributor clearance and would have a nice convenient fitting (or just a hole to put one) in a nice convenient spot.
Just a thought.

5. Forget vacuum.

Paul
 
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ericbee

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Interesting. The diameter of the chimney is larger than any hose I could step down with an adapter. The only way I could think of to do what you suggest is to find a cap with a nipple on it for one of the chimneys. Never seen one, don't know how I could even fab one.

Gonna call MSD in the morning and see what they say. THX Paul.
 

DirtDonk

Contributor
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...The diameter of the chimney is larger than any hose I could step down with an adapter. The only way I could think of to do what you suggest is to find a cap with a nipple on it for one of the chimneys. Never seen one, don't know how I could even fab one.

You don't step it down, you don't adapt it, you don't need to change anything with the hose. You just add something to the filter housing instead of changing the hose or the canister.
The proper hose fits the chimney fitting.
The only thing you need to get, or fab up, is the fitting where that same large hose is going to fit up to the air cleaner housing. That's all.

What type of air cleaner are you using? Maybe knowing that, someone can suggest a source for the fittings, or a direction to proceed.
Here's what one company offers:
https://sites.google.com/a/ydfdss.pl/cat-15727151/B000CMGZWI

And here, just down from the top:
http://www.knfilters.com/filteraccess.htm


Another thing to think about, unfortunately, is after all this, if you have an open-element air filter you still might have some fumes in the garage under excessive evaporation conditions.
That's why open-element filters, or holes drilled into your stock housings, are not smog-legal in most areas. Because there is still someplace for the fumes from the engine to get out into the atmosphere.
Still though, fitting up the EVAP is better than not doing it. Even with an open filter.

Paul
 
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ericbee

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Jan 27, 2012
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Contacted Ford Motorcraft, they do not know which nipple is for gas vapor intake or which is for the air cleaner or vacuum. This is very frustrating for something so simple.

MSD also doesnt know which port to use on the throttle body or to go direct to air cleaner.

Gonna try Chuck at BC Broncos as it's his tank and maybe he knows.
 

Nellybell

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Joined
Sep 22, 2012
Messages
107
Eric,

Paul has it right.

It can be pretty simple. Run a gas tank vent line to the small nipple. Cap the Large nipple. Put a mushroom cap on one of the chimneys. Run a large line from the other chimney to a fitting on the bottom of your air cleaner.

When your running the slight negative pressure from the air cleaner will purge the canister.

If you want to use the main engine vacuum you will need to create a control system to purge the canister at the appropriate conditions or you will run with a rather large vacuum leak.

You could run as described temporarily, if you want to develop a more sophistcated system. But I think the above will be sufficient.

Best of luck,

Ted
 
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ericbee

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After all of your help (especially Paul and Nelly) I think I have it figured out, I hope this thread will help others...

The canister with 2 nipples is for a V8, the single nipple they sell is for a V6.
The small nipple is indeed the one that you connect to the fuel tank vent hose.
The large nipple, in this case needs to be capped.
One of the chimneys will get a mushroom cap, which is actually a vented cap.

Finally, and here is my only remaining question..

The last chimney shall either be mushroom capped (thus never getting purged) or shall run to the air cleaner which would provide a minimal vacuum effect possibly purging the CC during operation.

The opening of the chimney is at least an inch in diameter. I need a way to cap it with a nipple and then run it to the air cleaner. I cannot run a 1 inch diameter hose to the air cleaner.

Does such a cap with nipple exist?

Thanks again y'all.
 

Nellybell

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Sep 22, 2012
Messages
107
Cool. Glad you were able to make some headway. I would just clamp a one inch piece of hose to the canister chimney. Cut it as close to the canister as will work,probably 2-3", and then use a 1" to whatever size barb you want. You can do the same at the air cleaner end, if you need to.

good luck,

Ted
 

stevenson44

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May 17, 2010
Messages
233
Does anyone know the part number for the charcoal canister bracket? How about mushroom caps?
 

chuck

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Now that you have this all figured out I want to add a few thoughts. The stock charcoal filter that mounts to the right frame about the same height as the tanks has a 5/8" paper pipe going to the stock air filter.
The stock expansion tank is about 1 gal max. The stock tank is 13 gals max sand the Ox tank 8 max. I am told but did not look it up that fuel will expand as much as 20% from night to day on a hot day. Some one can look it up and correct me if you want but I am going with 10% for my thinking. So if both tanks were filled at say 4 AM and 45 degrees and the EB were parked out in a 100 degree day the fuel could become 2.1 gals more or a total of 23.1. Now I know that all gas tanks can not get totally full because of the air trapped in the tank. I think ford thought of this also and sized everything to work together but I as most of you have seen fuel coming out of the gas cap of a setting bronco so two things are not guess fuel expands and ford did not make the expansion tank big enough for all conditions.
Now we install a big tank and discard the expansion tank. Not so good in my opinion. Lets see, 23+8x.10= 3.1 gals that have no place to go. If you add a CC it might hold less than a qt. and all the 20' of line might hold a qt thick will = 1/2 gal. And I am thinking.. where does that other 2.6 gals go? As the air inside the tank can be compressed that could account for some, let us say 1/2 and now we are down to 1.3 gals that I don't know where goes so I am going to figure 50% error in my off the wall numbers and that leaves me with about .75 gals. For me, I don't want to connect that line to the intake or the air cleaner or anything even close. I know this is extreme case perfect conditions but you still need to think about those things. The newer CCs like the one from the Mustangs have a solenoid to allow the CC to vent but it only comes on while the engine is running. And both the big caps vent to air. That means that it can not put gas in the engine and when the valve is open it sucks air in thought the vents and purges the CC. My tank has a vent that should go to a expansion tank then the a CC. The end.
 
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ericbee

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ericbee

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BTW: Big thanks to Chuck (above) who spoke with me at length about how best to route these hoses. I am still on the fence about running one of the chimneys to the air cleaner or just putting a mushroom cap on it but, the small nipple has the fuel tank vented to it and the other nipple is now capped closed.

Open to hear opinions on mushroom capping or venting to air cleaner if you have one :)
 
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ericbee

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I mounted mine with one screw through the hole on the top of the canister, no bracket. It is mounted in my engine compartment, against the firewall, on the drivers side. It wedges between the fender well and the rear firewall. It doesnt move.
 

Rox Crusher

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Dec 13, 2008
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2,773

I have a couple of the mushroom caps in the tool box. Measure the ID of your ports and I will send you the right ones (assuming I have them, that is).

No charge of course.
 

Nellybell

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Sep 22, 2012
Messages
107
From what I can tell, the coefficient of expansion for liquid gasoline is 0.00052 /degree f. So a 23 gal tank, completely full would increase to 23.66 gal. If the temperature went from 45 to 100. You should not get much overflow if you don't burp the tank.

If you do not vent the canister to the air cleaner, the canister will hold vapor until it vents out the chimneys. Eventually, it will stink. If you seal the system up completely, you'll hear the tank creak and pop as it heats and cools. I would find a way to purge the canister.

Best regards,
Ted
 
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ericbee

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Not looking to seal the system up completely, I was considering just putting the vent caps on the chimneys and calling it a day. I do not want my garage to stink so here is the thinking:

1. If the vapor fills up in the CC It will eventually come out of the chimney's but the air coming out should not stink as it was filtered through the charcoal.

2. If it does eventually flow out of the CC, it could happen while its parked or while I am driving so, it may not stink in the garage.

3. If it vents to the air cleaner it is still venting to the open air so, it may still stink as it isnt a closed system.

4. Is the vacuum force of the air cleaner strong enough to purge the canister at all?

This is the final straw in the puzzle. Couldnt I vent the chimney to a T fitting between the PCV valve and the intake manifold on the edelbrock head that has constant vacuum for the PCV valve?
 

DirtDonk

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What's with the vacuum again? Vacuum sucks...
Forget vacuum. You can't use it. It won't work. T-ing it to your PCV would not only would not be the correct function of the CC, but would make the engine run like crap.

Eric, can I text you some images to a phone?
I'm not sure how to upload them to my computer from my I-phone (not that up-to-date yet) or if I need some program on my computer to do it or not.
I can show you how they're hooked up on a stock '76 EB that I took pictures of today, if you're interested.

It's original except for the old paper hose must've decomposed, as so many do, and was replaced by a 3/8" fuel line instead.
Interesting to see that actually. The size appears just right to go on the INSIDE of the large fittings, instead of around the outside like was original. It's not as good, but it seems to work.
Check for yourself whether a piece of 3/8 will fit inside the chimney snugly. Either that, or just go out and buy the correct hose that should still be available. You can probably find it online even.

You're correct in thinking what we talked about yesterday, that your open-element air cleaner (that's what you have I assume?) could vent some fumes to the outside. But that's the way it goes. The alternatives are worse.
And if the charcoal takes away the fumes, like you were saying, then they wouldn't be any worse from inside the air filter housing.

But I'm pretty sure that's not how the charcoal works. Could be wrong though.

If I can't get the images to you though, in a nutshell they go like this:

1. The smallest fitting to the gas tank.
2. The next largest one to the carburetor bowl vent.
3. The chimney farthest from the engine gets the vent cap (mushroom)
4. The chimney closest to the engine gets the hose to the air cleaner.

If you want to see the images, text me at 408-398-7170. At least I can figure out how to send images that way. They're not perfect, but you can at least see some detail and get the idea.

Paul
 

904Bronco

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Wow. My brain hurts after reading through this all...
$29.99 for a mushroom cap on EBay :(

Paul thanks for picking up where I left off and filling in some blanks.

Ericbee you are determined to get this right!
 
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