Mustang EFI / Charcoal Canister

[ksagis]

I'm tired of smelling gasoline in my garage and thinking of adding a charcoal canister. I've googled the forum and found these two helpful links:

https://classicbroncos.com/forums/threads/charcoal-canister-installation.261451/

https://classicbroncos.com/forums/threads/where-should-the-charcoal-canister-be-mounted.218039/

Specifics on the rig: 1972 U15 with 1992 Mustang 5.0 EFI / AOD swap, currently no charcoal canister and BCB 24 gallon tank.

General thoughts: I'm thinking of following the approach that xcntrk did on first link above and evacuating the canister prior to MAF.

Basic questions:
1. I assume one needs to use non-vented gas tank cap on this approach?
2. There are four fittings on charcoal canister. The two large ones obviously get the caps, then also is a small fitting and a medium fitting. Does small fitting or medium fitting go to MAF?
3. How does the tank get backfill of air as the gasoline is consumed? Is there another connection needed to tank. Maybe with check valve to allow air to get into tank but not allow gasoline fumes to migrate out?

Thanks in advance for advice or any links that already address the above questions.

 

[Broncobowsher]

Do not put the canister purge before the MAF. There should be a canister purge solenoid, probably going to have to add the wire back for it, ECM controls the ground, power the same as the injectors or any other computer controlled solenoid/relay. The line goes to full vacuum, preferable a port that goes to the plenum and not one that goes to a single cylinder. That way there is even distribution to the flow of fumes to all cylinders.

As for the lines. The big ones get mushroom caps. They are vented but keep junk out. I forget the medium and small lines, one goes to the gas tank, the other to the purge solenoid.

The purge solenoid and manifold vacuum are the key. The vacuum pulls the vapors out and clears the carbon for another round of fume collection. You need the vacuum port to get a proper purge of the gas fumes from the carbon. When cruising the purge solenoid opens. A little fresh air goes in the mushroom caps and airs out the carbon. The gas fumes are released in this passing air and go into the engine to be burned.

I have used charcoal canisters in the past on project trucks and it generally works great. A long term park with minimal driving can still overload the canister and you get gas fumes. That is a sign that you need to go out for a nice long drive.

 

[ared77]

Here are pics of where xcntrk (Tony Ramos) mounted it.

 

[ksagis]

@ared77, thanks for pictures, very helpful.

All, any thoughts on my question on how the tank would backfill air when the gas is being consumed?

Looking at the diagram of the 1995 Bronco, it looks like there are two vapor lines, one going to the charcoal canister and a second that maybe exits at back of vehicle.

http://www.supermotors.net/registry/media/244698_1

 

[DirtDonk]

Your 72 was originally equipped with a charcoal canister in all states as far as I know, so you’re available gas caps will all be the proper type to allow one-way venting. Allows air to come in to occupy the empty space, while theoretically not allowing vapors to escape.
Assuming a cap in good shape of course…

Unless you kept the circuitry and wiring for a CAN-P system (canister purge) Then you will not be using a computer controlled solenoid that needs a vacuum signal. So yes you will be going to the intake tract instead, as you were saying.
You can use either the medium size fitting, or one of the large size fittings on the canister. Completely up to you and what you think works best in your case. On EB‘s from 70 to 75 they used one of the large fittings and the hose entered the air filter housing outside of the filter. Where the medium fitting was for the carburetor float bowl vent. Took vapor to the canister that would otherwise have escaped into the filter housing.
A 76 or 77 may have as well but I don’t remember.

The better you seal the inlet to the intake tract, the better. Fuel vapors entering an open element air filter can still stink up the garage.
On cone shaped air filters like most of us with EF I conversion seem to be using, seems like putting a fitting into the base plastic of the air filter would be easy, but if you have some tubing between your filter and MAF then The farther away from the filter you let the vapors enter is probably a better.

The vapor canister system itself doesn’t care whether the outlet tube terminates at a point just sitting next to the air filter, or all the way back to just in front of the throttle body. And I’m not sure just how much of a difference it would make to your fuel mixture if you put it behind the MAF instead. Ultimately the O2 sensors should be able to compensate I would think.
After all, it’s unmetered perhaps, but it is still air and fuel vapor mixed together.
But I suppose even that little bit of difference could be enough to upset the balance, which is probably why in front of the MAF so that it counts as part of the incoming air is the most common practice.

 

[DirtDonk]

Ultimately ‘bowshers method would be the best of all. Just depends on whether or not you can add the electric circuit to the harness and main ECM connector.
But that method gets the most complete venting to the correct part of the engine (the combustion chamber) and the least likely to allow any into the atmosphere.

I didn’t look at your link diagram, but anything for a 95 is going to have the purge valve and computer control. And very likely any other fuel lines are just the return line rather than a second vapor line. Although I can’t vouch for that.
By then lots of evaporative emission systems were getting very complex and clever.

 

[ared77]

This is where larger hose attaches

 

[ared77]

Smaller hose runs down to frame and back to this little canister where my finger is pointing. Then hose out of the top appears to run back toward gas tank. Hope this helps!

Norm

 

[DirtDonk]

Yes that’s your standard Ford installed anti-rollover valve (edit: correction. Not original type). Part of the 76 and 77 equipment
Nice that that is still there at least. Makes plumbing up to any new charcoal canister pretty simple. Does the hard line heading to the front still go all the way to just the beginning of the engine compartment near the firewall?

 

[DirtDonk]

Not much material to work with at the base of that air filter. If it was a fully enclosed filter all you’d have to do would be to put a fitting into the air box. But since it’s just a shield and otherwise open around 3/4 of its perimeter, that wouldn’t do much for subduing fumes except when the engine is running.

Fabricating a slight extension between the filter and the MAF could be your answer for future proofing it for filter changes. But if that’s not feasible at this point then simply drilling a fitting into the plastic base of the filter there right at the MAF would be your solution I would guess.

Other than that, you could always insert a fitting into the intake tube behind the MAF and see how it runs. See if it affects how well the computer keeps the engine running.
If it works, and everything runs well, you’ve got a win. If not and it affects things like idle quality or perhaps even full throttle power, you can always seal off the fitting and go back to the air cleaner.

By the way, is that a differential breather back there on the firewall? Or is that your “charcoal canister“ replacement?

 

[ksagis]

ared77, thanks for the pics and information, do you happen to have a pic of where the hose connects to the air filter area (sorta hard to make out the details from this pic).

dirtdonk and broncobowsher, thanks for your replies as well.

Anybody know where one can source the 1976 or 1977 rollover valve?

Seems like a pretty simple solution and per a PM to ared77, he doesn't smell gas in the garage.

 

[67 Halfcab]

I don't know where you can find the 76-77 rollover valve, but the one in ared77's picture looks like the DeLorean one.

https://store.delorean.com/101402-rollover-valve.html

 

[ared77]

 

[ared77]

"By the way, is that a differential breather back there on the firewall?"

Yes, leads down to differential.

 

[ksagis]

@ared77, thanks for the additional pics.

Here's another option for a roll-over valve option that might fit in nicely on the frame hardline to CC riser hose run:
https://www.tanksinc.com/index.cfm/...t_id=811/category_id=167/mode=prod/prd811.htm

Appreciate all the input, time to start ordering parts.

 

[DirtDonk]

I don't know where you can find the 76-77 rollover valve, but the one in ared77's picture looks like the DeLorean one.

https://store.delorean.com/101402-rollover-valve.html

Thanks for pointing that out Halfcab. Definitely not an original type that would also have had a little metal rock shield around it. I glossed over that (again) in my haste to throw out an answer.

Up until a few years ago at least, the factory replacement was still listed in a Dorman catalog. Doesn’t mean it was still available at the time, and I didn’t order one unfortunately, but it was there in the book.

 

[robs68]

Thanks for pointing that out Halfcab. Definitely not an original type that would also have had a little metal rock shield around it. I glossed over that (again) in my haste to throw out an answer.

Up until a few years ago at least, the factory replacement was still listed in a Dorman catalog. Doesn’t mean it was still available at the time, and I didn’t order one unfortunately, but it was there in the book.

I am also looking to install a vapor canister the same way ared77 is. I do not have any fuel smell but when I open my gas cap I get a rush or vapor comin out. I am also getting a back fire with my engine. Would you be able to use an inline check valve? If you put it in the opposite direction between the tank and vapor canister. Would it still let the vapor out but stop any liquid from going to the canister. Is the check valve the same as a roll over valve?

 

[DirtDonk]

Is this the '68 in your username Rob? If so it might not even have a single vent tube fitting in the tank unless it's been replaced at some point. Sounds to me like your cap is going bad, or the wrong one was somehow installed and is not venting properly like it is supposed to.
And you know the air is rushing OUT and not IN for sure? Not hard to tell of course, and it sounds like you're sure, but figured I'd ask anyway.

not sure about the backfire just yet. Might need more information. But first, is it backfiring out of the exhaust or carburetor? Still carburetor, or EFI?

As far as the check valve, it would depend on how it's made and what it's intended to do. I would think there are those where the "float" or "ball" or whatever is used, would allow gasses to pass one way, but if the vehicle rolled over it would move to block the outlet from fuel leaking out. I'm sure they're out there, but not sure I remember anyone saying they found a good source.

Paul

 

[robs68]

Is this the '68 in your username Rob? If so it might not even have a single vent tube fitting in the tank unless it's been replaced at some point. Sounds to me like your cap is going bad, or the wrong one was somehow installed and is not venting properly like it is supposed to.
And you know the air is rushing OUT and not IN for sure? Not hard to tell of course, and it sounds like you're sure, but figured I'd ask anyway.

not sure about the backfire just yet. Might need more information. But first, is it backfiring out of the exhaust or carburetor? Still carburetor, or EFI?

As far as the check valve, it would depend on how it's made and what it's intended to do. I would think there are those where the "float" or "ball" or whatever is used, would allow gasses to pass one way, but if the vehicle rolled over it would move to block the outlet from fuel leaking out. I'm sure they're out there, but not sure I remember anyone saying they found a good source.

Paul

Yes it is my 68. It has a 5.0 EFI out of a 91 Mustang. It has a stock tank not original with an external fuel pump. The tank has two small vent tubes. It has a brand new cap from WH. When I replaced my pump a few weeks ago the hose between the tank and the pump had a lot of pressure when I disconnected it . It only had about a 1/4 tank of gas and had not been ran for a couple of days. So my concern is that the vapors are building up and pushing the fuel out of the tank. The filler neck is not original to the bronco as well. The later model cap fits it.

Sometimes when I drive it for the second time in the morning it will sputter and backfire from the intake. It also seems to not to have much getty up. When I take the cap off it stops the hiccup and has more getty up. It was worse before I changed the fuel pump it would do it all the time now with the new pump it only does it if I go for a drive after sitting for only 30 minutes.
I installed the a vapor cannister like ared77 did and it turned out nice. I am just wondering if I need a check valve to keep fuel from coming into the vapor canister.

 

[DirtDonk]

Vapor build up itself does not build up pressure. The most common reasons for that would be heat expansion and lack of venting. Even a return line pushing gas back in should never push more in than is being pulled out.
But it sounds like you have venting. And also the correct neck and cap.
Are both the small tubes hooked up, or just one?
One is all that’s normally needed, but I don’t know if one of them is up high and the other one extends down to the bottom. I think they’re both high, but maybe someone else who knows for sure can answer that.

You might double check to make sure that the vent lines are clear and easy flowing. No kinks or bands or some thing that would restrict easy flow of vapor and pressure.

A simple rollover valve would probably not keep liquid gas from getting to the vent system under normal low pressure conditions. It would take a sudden flow, like a splash or tilt to do it I would think. Here again it comes down to the design. And I don’t really know that much about valves and rollover valves.

Bottom line though is that it sounds like something is wrong with your venting because the cap should not make a difference when you remove it.