Venting a Charcoal Carbon Vapor Canister...

Nellybell · Oct 16, 2012

Paul,

Thanks for the welcome and all the posts that got me to thinking about how this process might work. I have really enjoyed learning more about this process.

Ted

Greg_B · Oct 16, 2012

I tried every combo everyone ever suggested on mine and the canister would still fill with fuel. I removed it and just let the vent line go to the ground but I just couldnt deal with seeing fuel dripping on the ground everyday.

When I went to EFI I still had exactly the same problem if not worse. So I went back to the junk yard and got a canister purge solenoid from a Mustang. Now it works like it is supposed to. No more fumes or fuel dripping on the ground.

I know that doesnt help with your setup but it does show the importance of having it working properly.

Greg

ericbee · Oct 16, 2012

Greg, the purge valve only works when you are using a stock Ford harness and EFI. I am using MSD and a centech harness so, it's not an option for me as there is no way to control the purge valve to tell it when to open or close. But, thank you.

Nellybell · Oct 16, 2012

Eric,

The purge valve will open when it sees 12v to the solenoid. You could use a thermal switch to open the valve only when the engine is warm or the run terminal of the ignition to open it when the ignition is on. Lots of ways to control it, if you want to go that route.

Good luck,

Ted

chuck · Oct 16, 2012

Nellybell said:
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

Your numbers most lightly right. I know that if you put 2000 gal of jet fuel in a 2500 gal. tank it will overflow in the middle of the day but will not if you put 1800 in. Funny how close the end numbers came out. Your math/knowledge =0.66 and my doodling =0.75 and like you said if you don't top off there should be no problem. I think the main problem is unless people know better they will top off but even at that it would be a rare thing to have fuel come out. But it does happen. With the CC connected to the tank and the caps installed the fuel would come out the caps and not get into the engine/intake if it did over flow that much. We have installed a lot of these CCs over the last few yours and had no complaints. No smell or leaks so they work I am just trying to see the worst case scenario.

Nellybell · Oct 16, 2012

Chuck,

I thought it was pretty cool how close you were with your estimate and I can't argue with the experience you guys have installing canisters. Personally, I've come to respect the vapor/liquid separator tank a lot more than I did. I am going to reconnect mine and go with the purge valve set up. I have a SEFI system so everything is in place except the tubing.

Best regards,

Ted

chuck · Oct 16, 2012

Nellybell said:
Chuck,

I thought it was pretty cool how close you were with your estimate and I can't argue with the experience you guys have installing canisters. Personally, I've come to respect the vapor/liquid separator tank a lot more than I did. I am going to reconnect mine and go with the purge valve set up. I have a SEFI system so everything is in place except the tubing.

Best regards,

Ted

I don't think the purge valve is needed but it is not going to hurt anything either. Kind of like giving brand to a horse

A wire from the run turminal to a toggle switch to the purge valve would assure that the engine was running when the purge was happening. PS I have been looking into expansion bottles for a while without much luck.

landshark99 · Apr 14, 2013

I know this tread is a bit old but thought i would revive it as my question very much goes along with what has been talked about in this thread.

I'm about to install a charcoal canister in my 69 so that I can run a sealed gas cap and not have to worry about fuel spilling out of the cap or the gas smell.

I'm very familiar with the standard mustang EFI setup using the purge valve as I installed on on my 76. Works great and haven't had any problems.

On my 69 Bronco I have a custom EFI setup using a Holley 950 computer and not using the ford computer. I have looked over the Holley manuals and done quite a bit of searching and have concluded without running a custom circuit there is no way to hook up a purge valve with my setup.

In digging deeper It would seem I could just vent the canister to the air cleaner on my bronco and that should take care of the majority of the fuel smell and allow me to run a sealed gas cap.

I have included a few pics below but wanted to post up to make sure I was thinking this through correctly.

Since this inlet is not on the TB/intake the vacuum should be at a minimum and hooking the canister up like this should not cause a vacuum leak as the air at this point is un-metered by the computer/EFI.

Does anyone see any problems with this?

ChrisC74 · Apr 29, 2013

Landshark99 - did you connect as you outlined above? Any problems? Did it solve some of your smell problem???

landshark99 · Apr 29, 2013

ChrisC74 said:
Landshark99 - did you connect as you outlined above? Any problems? Did it solve some of your smell problem???

Opps sorry.. forgot to update this thread.. i hate it when people do that!

Yes - I hooked it up as stated above, haven't had any fuel smell but hasn't been too hot here either, that will be the true test. Also I dont top off when I fill up anymore as I have seen a little fuel in the lines after I fill up...

One thing I'm going to modify is adding a "loop" in the vent line. I will run a length of fuel line up the inner fender from the vent on the tank to keep liquid gas out of the lines.. i think with a full (or near full) tank off road I will probably get some fuel in the lines so hopefully 3 high spots in the system will minimize fuel getting sucked into the charcoal canister. Also looking at a one way vapor valve like the 77's have...

Heres a pic...

73azbronco · Apr 29, 2013

First, to the above comment on air cleaner nipple, that is exactly where you want to connect the vent line from the charcoal canister.

Second, the charcoal canister is there to help reduce fuel odor, when it is saturated, that's when you get the fuel smell in the carport or garage, the vent line to the air cleaner helps suck some fresh air through the fuel tank into the canister and helps clean the charcoal of vapor.

Lastly, sorry Chuck,

but if your fuel is expanding from 2000 gallons and spilling, you don't have a true 2500 gallon tank, fuel is a liquid, liquids do not expand or contract except for very minor amounts. The charcoal canister was not made to hold any amount of fuel liquid, just vapor coming off the fuel. Lastly, fuel tanks do have sufficient space to account for the extra 1/2 gallon in 20 you get do to expansion.

Compressibility of liquids: http://en.wikipedia.org/wiki/Thermal_expansion

Crush · Apr 30, 2013

funny story regarding the siphon effect. when I first got my 76 it was a mess. wouldn't run for more than 15 min and had vaccume lines all over the engine bay. cured the 15 min problem by putting in a new duraspark box and while I was at it decided to clean up the vaccume lines. got them all hooked up and went for a drive. all was good. stopped to fill up and left the gas station only to have it backfire and carry on like it is flooding. got out and messed with the carb, no luck. was able to nurse it home. next day decided to trace down all the lines I rerooted and low and behold, one line I put in the vacume tree was the vent line to the tank. there was no charcoal canister or rollover valve in the line. so when I filled up, every time I accelerated the vent line acted like a straw dumping raw fuel into the back of the intake. LOL! felt like such a dumass. I quickly ziptied it to another line on the firwall and fixed the problem. ran great til the motor blew. LOL! Moral of the story is...fuel tank vents should never be hooked to vacume on carbed engines!

Gwunited2 · Aug 9, 2017

ericbee said:
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.

I know this is years old, but the thread has helped me immensely. I now know how to plum the fuel tank vent lines. Thanks to all of the contributors to this thread!

mrdrnac · Aug 9, 2017

X2]THis thread was a major help to me as well, awhile back, when I decided to do something about the fumes on my 66.

McLeod · Nov 5, 2017

landshark99 said:
Opps sorry.. forgot to update this thread.. i hate it when people do that!

Yes - I hooked it up as stated above, haven't had any fuel smell but hasn't been too hot here either, that will be the true test. Also I dont top off when I fill up anymore as I have seen a little fuel in the lines after I fill up...

One thing I'm going to modify is adding a "loop" in the vent line. I will run a length of fuel line up the inner fender from the vent on the tank to keep liquid gas out of the lines.. i think with a full (or near full) tank off road I will probably get some fuel in the lines so hopefully 3 high spots in the system will minimize fuel getting sucked into the charcoal canister. Also looking at a one way vapor valve like the 77's have...

I am getting ready to plumb up a new fuel tank and upon doing some research, saw your post.

If you run the vent line high right out of the tank and create a loop as you describe, you run the risk of condensation collecting in the low spot between your high loop and the carbon canister, which will eventually completely clog your vent line as it fills with liquid.
This would be equal to running no vent at all on the gas tank.

Your vent line should be sloped gradually back to the gas tank and have no low spots to collect liquids. Condensation will then drain back to the gas tank.
I am installing a Coyote brand roll over valve right at the tank to help keep liquid fuel out of the line and safety in an accident.

http://www.tanksinc.com/index.cfm/page/ptype=results/category_id=160/mode=cat/cat160.htm

sykanr0ng · Nov 5, 2017

One way check valve like used on the 1977 Bronco:

https://store.delorean.com/p-6703-roll-over-valve.aspx

904Bronco · Nov 5, 2017

Just to add...

Fox body Mustang CC and my 2000 Explorer motor. EFI Guy was able to add a purge valve to the harness he reworked.

One thing I noticed in cleaning up parts is that the plastic coupling between the line to the manifold and to the 90* elbow has a brass restrictor in it... Never noticed it B4 but I can see the reason behind it.

I can say everything works fine going this route.

McLeod · Nov 5, 2017

This is the one I am using. It screws into the tank.
(Cheaper too.)

I will be installing CC at same place as 904Bronco's except mine is carbed.

Not sure yet if I will use the medium size CC port (most efi uses this one) or the large 3/4 port (most carbed use this) to extend to air cleaner.

Is the construction of the canisters throughout the different years essentially the same interior wise so it wouldn't matter which one is attached to the air cleaner.

DirtDonk · Nov 6, 2017

I think they are. But I would continue to use the larger port on a carbed engine because that's what they used from the factory.
Since the air cleaner location is not high-vacuum anyway, it's just getting the vapors into the engine gently. Maybe the larger port actually helps this flow.
I don't know that the medium sized port would hurt, hamper, hinder or help, but I've never seen them used that way except when controlled by a valve.
The medium one was always an "inlet" on non-computer vehicles, or the "outlet" on those with a purge valve.
Only the large port would be used for non-vacuum setups.

Doug's (and other EFI computer controlled units) use the smaller one on full vacuum controlled by the electric valve. Probably because it's easier to fit the small holes and not waste volume with the larger ports. Might not be as efficient at pulling sufficient vapors as the valve is not open all the time like you would have with the gentle pull of the carbureted air cleaner fitting type.
Not as much suckage, but it's literally getting some pull all the time while the engine is running.

Paul

McLeod · Nov 8, 2017

Thanks guys...

I do wish there was cut away drawings of the canisters available just to confirm, but you are probably correct that they are all the same or very similar.

Venting a Charcoal Carbon Vapor Canister...

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