Vapor Canister

I have a 1971 and it has that vapor canister behind the drivers seat. Has 4 lines coming out of the bottom of it. Well a couple of the lines are deteriorated and leaking fuel. Have a few questions.....

1. Why did it fill up with fuel, I didn't think that was supposed to happen, that it was collecting vapors only.
2. Should I cap the lines? If so, how do I cap them and do I have to get vented gas caps after that?
3. Should I repair the lines? If so, how? They aren't normal lines apparently.

Shalackin said:

1. Why did it fill up with fuel, I didn't think that was supposed to happen, that it was collecting vapors only.

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It should not have, but if the drain-back line was clogged at some point, eventually the vapors condensing back to liquid "could" have added up to quite a bit of gas.
Or, there is pressure building up in the gas tank and forcing more liquid into it than it can handle.
Do you still have the steel canister on the passenger frame rail by the front wheel? What about the main gas tank? Is it stock, or aftermarket?
Maybe other reasons too, but those were the first two that popped to mind. The fact that the gas is still there is making the clogged return line scenario sound more feasible.

The four lines are: 1. vapor in from main tank. 2. vapor in from aux tank 3. vapor out to charcoal canister on the frame up front, and... 4. Condensed liquid back to the second port on the main tank.

Shalackin said:

2. Should I cap the lines? If so, how do I cap them and do I have to get vented gas caps after that?

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I would not yet. Maybe they're already capped/plugged and you need to open them up?
Follow them all to their ends and see what's going on with all of them.
And yes, you'd have to vent your caps. Correct caps with vents would not be easy to find, so most simply drill small holes in their existing caps. This isn't exactly by-the-book, but it's been done numerous times. Probably with varying degrees of success.

Shalackin said:

3. Should I repair the lines? If so, how? They aren't normal lines apparently.

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No, they aren't. I'm sure it's easy, but luckily I've never had to do it. Hopefully someone has a quick-n-easy way to do that.
Where are they leaking?

Good luck.

Paul

one of the lines had a hole in it about 4 inches down from the tank. I was going to try and use some vacuum tubing to splice it, but while doing that, one of the other lines broke off right at the steel fuel line it was attached to.

I don't think it was clogged. When I lifted the tank up (it is laying down in the bed from previous owner), the gas would empty.

One other note, when i open one gas cap there is a vacuum pressure release. When I open the other, there is no pressure release.

No pressure is OK. Pressure on main tank: there should not really be any pressure, everything vents to atmosphere. Unlike modern cars with vapor recovery systems which use a solenoid to open.

That may be the case the main tank is pushing fuel up into the vapor recovery tank cause the vent is blocked

Use fuel rated line, not vacuum line.

Nice looking rig! How long have you had it? Looks like a friend's dads Bronco that he sold not long ago, but I think that one was a '73 and it would not have been half apart I don't think.
Anyway, nice looking Bronco.

Shalackin said:

I don't think it was clogged. When I lifted the tank up (it is laying down in the bed from previous owner), the gas would empty.

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Shalackin said:

1. Why did it fill up with fuel, I didn't think that was supposed to happen, that it was collecting vapors only.

Click to expand...

Well let's revisit this question now that you've answered it yourself after giving the rest of the pertinent information.
No, it's not supposed to fill up with liquid. But when it's laying on the floor instead of being mounted upright and higher, of course it's going to fill up.
Laying on the floor it's only a couple of inches higher than the gas in the (full) tank. Laying on the floor it can't drain back.
There. Mystery solved...

It can't collect and condense vapors and return liquid when the drain-back line is at the same level as the vapor lines anyway.

Shalackin said:

One other note, when i open one gas cap there is a vacuum pressure release. When I open the other, there is no pressure release.

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Which cap? Front or rear tank?
And which is it? Vacuum, or pressure? Does it suck in when you open the cap, or does it blow out?
If it sucks in then your gas cap is defective and your vents are not doing their job.
If it blows, then your vents are not doing their job.

Since the venting system is at least partially modified (the tank laying on it's side down low with liquid in it) then perhaps the other issue is just as simple as putting it back to where it was.

Did the PO say why they took it out in the first place? Usually they start leaking around the top seam and vent fumes into the cabin after each fill up. But if it had a split seam, you would think it would have been dumping liquid gasoline out the crack at some point.

So it's a mystery still. And of course now your plastic lines are old and hard and need replacing. I would think that in a pinch you could use fuel hose of the proper size to at least splice the remaining good plastic with the metal lines? Not sure how much you have left, or if they're breaking off at the tank.
If at the tank, you might have to get creative and perhaps use some steel line that fits into the tank instead of those permanently crimped plastic doohickeys they used.

I think a better idea though (no pun intended) would be to simply get rid of the condensing tank and steel pancake style charcoal canister on the frame, and convert your system to the '76 and later style where the single charcoal canister was mounted up higher on the firewall in the engine compartment instead, and the in-cab tank was eliminated completely.
The only other thing that was changed that I know of was the addition of an anti-rollover valve (or a rollover valve?) to keep gas from going up to the canister if the vehicle rolled. Otherwise it would have a very hard time ever reaching the tank under normal circumstances. Which is the whole reason for the condensing tank in the cab in the first place.

There is a discussion that should be right here on the first page about a guy doing just that. His is now mounted on the driver's side firewall top, but the factory ones were on the passenger side. But either works, just as long as the canister is higher than the old ones were.

Good luck.

Paul

Thanks for the feed back.....

Then front gas cap has no pressure. The back gas tank has pressure. And I believe it is pressure out, not suction. PO thought it was the windshield washer tank

Here is a pic of where the line broke off. And it appears that another line was not even hooked up....

Yeah, pretty deteriorated for sure. If you can re-splice them back into the tails that come out of the tank, great. But if that's looking like a hassle (and it is to me from here) then I would update.
Many people chose door number three and eliminated the system altogether. After all, it was "just some more smog junk" to many. But while some never had trouble after that, a lot lived to regret the decision when their garage/shed/side yard always smelled like gas. Which is why the evap systems came into play in the first place. It was obvious how much fuel vapor was going into the air. And in an enclosed space, enough of that and it's more than just a minor nuisance.

Anyway, check out Canzelc's thread about it, and any others you come across. It's not difficult to source the newer style canister, mount it up high and eliminate your in-cab tank completely. This also gets rid of about half of the plumbing.

We won't know if the gas cap is bad and letting the tank pressurize until you fix the evap system. Most likely any pressure buildup is due to the condition of your gas-filled bottle and the plugged vent lines.
You can test that theory by making sure that the two small lines in the forward most positions on the driver's side of the main/rear tank are open. There should be zero pressure build up if they're open.

If you don't have a fuel return line from the carburetor or EFI, the only remaining reason that I can think of for pressure buildup in a tank is heat. As the day warms, or the gas warms due to proximity to the exhaust, pressure naturally builds up inside as the liquid expands.
The evaporative emissions system (evap) is designed to eliminate pressure buildup and keep the fumes from getting into the atmosphere. Or your garage. Whichever comes first...

Paul

If the charcoal canister has been compromised the system may not work as intended. Not very many Broncos Had the paper tubes on the canister all these years. In order for the canister to work fresh air has to go in and air with gas fumes must be able to be sucked out. Over 40 years or so the canister can be plugged with dirt and silt. This is an extremely low vacuum suction going to the air cleaner assembly. if you put a piece of hose on the canister and suck in the air must be able to flow through easily. Later model canisters have a vacuum operated check valve that only allows the air to flow through while the engine is running. I don know if the later firewall mounted canisters on 76 & 77 had this function or not.

There was nothing to protect the canister from whats outside from getting into the canister. The mushroom cap didn't have a filter just a hood to keep water out from washing under the hood and once you lost the paper hose that low mounted canister is very vulnerable to the elements. I know mine went swimming under water even very dirty water several times in my 40 + years of ownership.

I was lucky. My hoses were perfect all those years I drove it.
Of course, my helper just tore them out, thinking since I was going EFI that I wouldn't need that stuff anyway... Ugh.

Rustytruck said:

Later model canisters have a vacuum operated check valve that only allows the air to flow through while the engine is running. I don know if the later firewall mounted canisters on 76 & 77 had this function or not.

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Nope, still the same function. Just the newer style tank.
I don't know when they started using the controlled solenoid. I know that the later EFI/computer controlled units did (CANP or "canister purge") and I'm guilty of assuming that they came about during the computer controlled era. But it's possible I suppose that they used some other type of electro/mechanical/vacuum control to do that before computers were widespread.
But all EB's (that I've seen at least) used engine intake to do it through the air cleaner housing.

Paul

What is the recommended newer style canister that I can replace this with? Also, I looked and don't believe I have the charcoal portion up front.

If the old canister line is plugged due to there being no canister, that would also explain why there was more liquid in the other tank. Just nowhere else for it to go.
You'd be looking for a flattish shaped can, with a semi-circular stone shield, mounted to the passenger side frame rail at the back of the front wheel if yours had one.

The newer style will look like, or similar to, this:

In the upper left corner of the pic is the rectangular shaped black plastic canister.
They come in black or cream color, with various port and mount configurations, but all do essentially the same thing.

You can get them new from local parts stores, Summit racing and elsewhere. And you can still get them from the junkyards too, since they're on basically every car and truck from the factory. Not sure when they stopped using this design, but it was in service for more than 20 years, so there are usually plenty in the junkyards.
Picking one with a mounting tab for a screw will save a lot of trouble though.

Paul

I just ordered one of these to deal with a venting issue on my efi. quick question, do i just run a line straight from the vent hole directly to this cannister? nothing inline between the hole and cannister?

DirtDonk said:

If the old canister line is plugged due to there being no canister, that would also explain why there was more liquid in the other tank. Just nowhere else for it to go.
You'd be looking for a flattish shaped can, with a semi-circular stone shield, mounted to the passenger side frame rail at the back of the front wheel if yours had one.

The newer style will look like, or similar to, this:
View attachment 419277
In the upper left corner of the pic is the rectangular shaped black plastic canister.
They come in black or cream color, with various port and mount configurations, but all do essentially the same thing.

You can get them new from local parts stores, Summit racing and elsewhere. And you can still get them from the junkyards too, since they're on basically every car and truck from the factory. Not sure when they stopped using this design, but it was in service for more than 20 years, so there are usually plenty in the junkyards.
Picking one with a mounting tab for a screw will save a lot of trouble though.

Paul

Click to expand...

rean1mator said:

I just ordered one of these to deal with a venting issue on my efi. quick question, do i just run a line straight from the vent hole directly to this cannister? nothing inline between the hole and cannister?

Click to expand...

Canister purge valve goes between manifold port and canister, it's computer controlled

Can this be bypassed and only have the vent line connected to the vapor cannister?

also, it looks like the two evap lines were also bypassed on my tank. there is a hose connecting from one evap hole to the other.

ransil said:

Canister purge valve goes between manifold port and canister, it's computer controlled

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If the canister is mounted up high (like high in the wheel well or on the firewall) you run the vent line straight to one of the small fittings on the canister.
An anti-rollover valve is what Ford used in that line, but it's not required for the vapor capture action to function.

If your computer's CAN-P (canister purge) function is disabled, then you simply run it like the older, non-computer versions did. With a hose from one of the larger ports to the intake tract up-stream of the throttle body.
You could run it to the air filter housing itself, if you have one, or into the tubing between the filter and MAF, or between the MAF and throttle body. Personally, I believe that since the computer is not able to control it's activation, the inlet should be ahead of the MAF instead of after it.

Paul

So my shop who did the install of the efi and toms 23gal tank did not install a vapor canister, from what i can gather they plugged both the evap line holes of the tank with a hose going from one to the other, ran the vent hole on the tank with a hose to the fill vent hard line that's connected to the fill neck.

So based on this i don't think anything is going back toi the intake tract since there is no vapor canister.

So would the intake tract connection you reference in the second part of your reponse be required?

I've been having stalling issues since the install. My shop is no longer in business and i can't get a hold of the mechanic to confirm why they did it this way.

Bronco runs like top up until i drive it too long and the tank pressure builds up(i think this is the cause based on my findings).

Don't think I"m qualified to run any lines from the canister i ordered into an intake tract so need to know if this is a hard requirement or not. if so will need to find a mechanic to do this for me.

hoping i can just run the vent from tank to canister and be done with it.

DirtDonk said:

If the canister is mounted up high (like high in the wheel well or on the firewall) you run the vent line straight to one of the small fittings on the canister.
An anti-rollover valve is what Ford used in that line, but it's not required for the vapor capture action to function.

If your computer's CAN-P (canister purge) function is disabled, then you simply run it like the older, non-computer versions did. With a hose from one of the larger ports to the intake tract up-stream of the throttle body.
You could run it to the air filter housing itself, if you have one, or into the tubing between the filter and MAF, or between the MAF and throttle body. Personally, I believe that since the computer is not able to control it's activation, the inlet should be ahead of the MAF instead of after it.

Paul

Click to expand...

CAn anyone comment on this pic? it was commented that a hose needs to be run from the cannister to the intake of the engine somwhere.

this pic that dirtdonk included only has the vent hose connected and all other holes capped off. my cannister came in today and will be installing it this weekend. need to know whether i can bypass the connection to the intake since it was bypassed already, since no cannister was installed during my efi conversion by my mechanic.

DirtDonk said:

If the old canister line is plugged due to there being no canister, that would also explain why there was more liquid in the other tank. Just nowhere else for it to go.
You'd be looking for a flattish shaped can, with a semi-circular stone shield, mounted to the passenger side frame rail at the back of the front wheel if yours had one.

The newer style will look like, or similar to, this:
View attachment 419277
In the upper left corner of the pic is the rectangular shaped black plastic canister.
They come in black or cream color, with various port and mount configurations, but all do essentially the same thing.

You can get them new from local parts stores, Summit racing and elsewhere. And you can still get them from the junkyards too, since they're on basically every car and truck from the factory. Not sure when they stopped using this design, but it was in service for more than 20 years, so there are usually plenty in the junkyards.
Picking one with a mounting tab for a screw will save a lot of trouble though.

Paul

Click to expand...

The attached pic shows the mustang evap canister configuration. It shows the how the vent connects to the canister and how the line should run to the intake. The best way to do it would be to install the canp or canister purge soloniod. The way I did it was to run a tube from the canister to the air filter.

Here are some pics of how I installed my system.