Fuel Vapor Separator

[gr8scott]

Mine doesn't look like the one pictured. It only has three lines coming in at the bottom. Two come from the rear tank (no aux tank),
and the third one runs over to the passenger side and ends there. I know it should run to a charcoal canister. So how does mine
separate fuel and fuel vapor? Is there some internal baffling involved that prevents fuel from entering the vent line?

 

[DirtDonk]

No, just it's location well above the fuel level in the tanks. The only reason they used this design (that I'm aware of) was that the original charcoal canister was mounted on the frame, at or below the fuel level.
It's just there to catch any liquid gas, and evaporate, and let gravity take it back to the tank.

The one that runs across the frame member to the passenger side can be run up towards the front and attached to the small nipple on the canister.
Do you have the frame mounted canister anymore?
Where does the metal tubing end on the frame?

If you no longer have the canister, you can eliminate this tank (or just leave it in place and disconnect it) and run a modern plastic canister mounted up on the firewall higher than the tanks. This is what Ford did in '76 during the changeover when the rules no longer allowed fuel containers inside the cabin.

Paul

 

[gr8scott]

Thanks for the reply Paul. So mine is truly just an expansion tank. The picture shows where the metal line ends. And I'm guessing the vent lines are plugged because I've never seen gas dripping from that line. No frame mounted canister, so a newer style one with the mushroom cap mounted to the firewall should be okay? Along with a roll-over valve of course. Will the venturi effect from the carb be enough to pull gas all the way through? As a side note, I do have one of your 23 gallon tanks that I bought a long time ago. I has two small nipples coming out the side at the top left rear corner.

 

[DirtDonk]

This is the '74 in your signature? If so, right at that tube end there was probably a short section of curved rubber hose interfacing into another run of metal tubing that ran up the frame to where the canister would have been. No real issue here, and you can run this end to the new charcoal canister with rubber or home-bent steel tubing.

Newer style is fine and even more desirable for it's simplicity and availability. It's basically killing two birds with the one stone and just plumbs directly to the tank vents.
Depending on how yours is set up (being a carb, it probably does not have a return line?) you can use the two vent fittings on your tank either:
1. Cap one and run the hose from the other (does not matter which one).
2. You can "Y" them together for more venting efficiency. (likely unnecessary though)
3. Run a return line someday. (more work, but can relieve some pressure at the carb when bouncing around off-road)

Some basic anti-rollover valves are usually readily available through various sources.

The carburetor at the air filter is not pulling enough vacuum to suck gas into the charcoal media. Factory was outside of the filter itself, with it's own little "filter" module, but if you have a different filter setup and it's got a place to put it inside the filter, but still above the carburetor, you're good there too.
You just can't use actual vacuum from under the carb. That's when you suck liquid gas into the canister.

The canister itself will likely have four ports. Two large and two small. Or perhaps two large, one medium and one small.
The smallest one, or one of them if more than one, is attached to the tank vent.
The medium, or second small one gets capped off.
One large port gets a mushroom vent cap.
The other one gets the hose up to the air filter.
Done.

Paul

 

[MarsChariot]

Does it look like this, just without the aux line? Frankly, I am not impressed with the later style on the firewall. If the fuel caps are not correct, and few seem to be, the fuel will back all the way up to the firewall cannister. Better to have an actual liquid-fuel separator.

 

[gr8scott]

This is the '74 in your signature?

Yes

but if you have a different filter setup and it's got a place to put it inside the filter, but still above the carburetor, you're good there too.

So I can't fabricate a nipple to the bottom of my air filter housing?

Thanks again Paul

 

[gr8scott]

Does it look like this, just without the aux line? Frankly, I am not impressed with the later style on the firewall. If the fuel caps are not correct, and few seem to be, the fuel will back all the way up to the firewall cannister. Better to have an actual liquid-fuel separator.

Yes, kind of. It's more "square-ish" with three lines. So is it a separator, or just an expansion tank?

 

[gr8scott]

Okay, maybe not so square. Here's another picture.

 

[DirtDonk]

So I can't fabricate a nipple to the bottom of my air filter housing?

Sure, not a problem. By "above" the carburetor I meant just not below it where you get full intake vacuum. Does not have to be above the top of the carburetor. Just above the throttle blades.
Anywhere there is air filter, is above vacuum

Your '74 should have the correct post-smog gas caps.
Seems like anything that pushes liquid all the way up the line to the evap canister on the firewall would be a tank issue, but not sure what else (besides vacuum) would do that.

What was your experience Mars? I'm guessing we've talked about it before, but we can talk about it again as far as I'm concerned. Nothing wrong with the system as Ford did it in '74, but once the condensing tank leaks it's a pain to fix. And in this case it might be easier to find a good later model canister as being discussed, vs finding a good original.
I'm just a fan of getting the gas out of the cabin myself, and have never experienced a problem with the '76/'77 style setup.

One of my big concerns has always been whether or not the tank manufacturer's leave enough room in the tanks for normal expansion. Being able to fill a tank to the brim when cold is a recipe for liquid getting all the way up and out any vents, and even the filler necks on your nice new paint!

Did you reconfigure to a later system then? And did you have an aftermarket or factory tank? What did you find out about the issue with the cap(s)?

Thanks

Paul

 

[DirtDonk]

So is it a separator, or just an expansion tank?

It's called a condensing tank, but it can legitimately be called any of the three really. It's condensing function is basically acting as a natural "separator" (since that's what condensing is) albeit without any fancy baffling or mechanism to promote separation, and expansion tank too, if for some reason fuel expansion pushes liquid up into the lines.
But generally that is not supposed to happen.

It's also the main reason we've been told not to "top off" our tanks since the late sixties. Doing so leaves no room in the main tanks for the expected expansion and contraction gas goes through when heated and cooled.

So it's while it's not literally a separator based on some fancy baffling feature, it naturally separates by letting excess vapors condense back into liquid, where it's then gravity fed back down the drain line into the rear tank.

That last bit is why the aux tanks only had one vent hose and the main tanks always had two. Of the two, only one is a "vent" while the other is a liquid return as it drains out of the condensing tank.
It functioned pretty well too, but a split seam or leaky fitting was an entirely too common issue putting heavy fumes into the cabin. And why they got outlawed finally. Or at least self-outlawed if the government did not mandate it. But I think they did finally.
When mine split, it was fine most of the time but as soon as I filled the tank up the fumes would be hot-n-heavy in the cabin for a day or two (about 40-50 miles or so).
I managed to seal the split, but never trusted it after that and is why I'm still a big fan of the high-mounted later model stuff.

By '77 no vehicle was allowed to have extended filler necks poking out of the side (hence the doors on '77 pickup trucks and Broncos) or gas "tanks" inside the cab. That's why the condensing tank in Broncos went away in '76 and the in-cab fuel tank in pickups disappeared in mid-'77 for the Fords. GM had already gone that way by '73 I think.

Paul

 

[gr8scott]

Sure, not a problem. By "above" the carburetor I meant just not below it where you get full intake vacuum. Does not have to be above the top of the carburetor. Just above the throttle blades.
Anywhere there is air filter, is above vacuum

That's what I thought you might of meant, just wanted to clarify.

Of the two, only one is a "vent" while the other is a liquid return as it drains out of the condensing tank.

Paul

So they can't all be at the same level at the bottom of the tank, or all three would act as "drains". So maybe the vent line and canister lines have
tubes protruding inside the tank at different heights, with the drain line level with the bottom of the tank? That's the only way I can see it working as you described.
Anyone ever cut one open or peeked inside a broken one to see how it's configured?

 

[gr8scott]

Actually, after looking at it more today, when it's mounted the bottom isn't level. It sits at a slight angle, where the CC line is the highest of the three.

So I was able to blow air through the gas tank via the vent and return lines. I was also able to blow air through the condensing bottle via it's vent and return lines.
But could not for the life of me push or pull any air through the bottle's CC line. Looks like I may have to take Paul's route.

 

[DirtDonk]

That was always my assumption though I've never seen inside one either.
I do believe someone had either a picture or factory diagram that would have shown how it was laid out inside.
As far as I know then, the way you describe it is how it's made.

Shining a bright light through it would theoretically tell the tale.

Paul

 

[gr8scott]

Tried the bright light thing, it's just too darn opaque.

 

[gr8scott]

Figured out why I couldn't pass any air through the condenser bottle's CC line. The metal tube at the end of the line was completely plugged. All clear now.
Got a charcoal canister, mushroom cap, and check valve on the way.

 

[DirtDonk]

Good catch. All that stuff is just gettin' old like everything else I guess.

Paul

 

[hankjr]

Figured out why I couldn't pass any air through the condenser bottle's CC line. The metal tube at the end of the line was completely plugged. All clear now.
Got a charcoal canister, mushroom cap, and check valve on the way.

what did you find for a check valve?

Hank

 

[gr8scott]

what did you find for a check valve?

Hank

https://store.delorean.com/p-6703-rollover-check-valve.aspx

 

[hankjr]

Ah. The famous Delorean valve. I bought one and lost it. Ordered a second. Went to put away in logical location and found the first one.....

Hank

 

[gr8scott]

All ready to be mounted...

Turns out a 8mm spark plug boot fits perfectly into the "chimney" port, and 7mm spark plug boot fits nice and snug to the vent port.
I know the clamps aren't necessary, but I like overkill.