Fuel evap canister hookup

[jeffncs]

Hi all!

I wanted to reconnect a fuel evap canister onto my 70. Pic below. The tank is a 71 part number and only has 3 small ports going into it.

The FAQ write up talks about 2 small ports and a large port. Any idea how to connect this thing to the fuel tank and carb to manage the wonderful scent of raw fuel?

Also - sounds like there’s something broken inside - like a piece of plastic or charcoal - nothing damaged on the exterior. Should I just run it?

 

[DirtDonk]

You’re probably mixing up two separate items.
The charcoal canister has the different size fittings, and would normally be mounted to the outside passenger frame rail just under the firewall.
The item in your pictures is the condensing/return/recovery tank if you will.
We talked about it here, not long ago and someone had the correct term, but I’ve always been calling it a condensing tank.
This is just the first item in the line, in the EVAP system.
Looks like you have a single gas tank Bronco? Or do you have dual tanks?

Normally there are two vent fittings on the rear main gas tank. One is actual vapor going up into the plastic tank in your picture, the other is liquid fuel after it’s condensed being returned to the other fitting. The third fitting goes forward to the actual charcoal canister.

The reason it was done this way was because the Bronco, as a utility vehicle, was expected to be on awkward angles, and perhaps for extended periods of time.
At the time, the charcoal canister was mounted low on the frame, it was felt that liquid fuel might get into the charcoal media. Ruining it.
So this tank in your picture, resides higher up in the cabin and collects any liquid fuel that might otherwise work its way into the system.
Probably making it more of a “recovery“ tank than it is a “condensing“ tank.
The 77 model safety regulations dictated removing any fuel items out of the cabin. So in mid 76 Ford went to the plastic charcoal canister mounted high on the firewall in the engine compartment. Eliminating the plastic tank inside the cabin.

Sorry for the long winded dissertation. But figured you’d wanna know how it all worked.
Do you still have a charcoal canister mounted to the frame upfront?

 

[DirtDonk]

Oh, and the reason you’re showing a 71 engineering number, is that it was originally designed and intended to be used for 71 and later model trucks.
But as was common practice, the change was made when it was available to do so, or perhaps just making sure it got implemented as soon as possible, avoiding any issues between Broncos that were registered as commercial vehicles, versus passenger vehicles.
Thus making it a running change sometime in the 70 model year.

Between 70 and 71 several things changed on Broncos.
The wiring changed, moving the fuse panel to the glove box and getting rid of the finicky firewall connectors.
The air cleaner and the PCV valve hose routing changed.
The addition of the evaporative emissions system came along.
The addition of the Dana 44 front differential in mid 71 also happened.
Probably other things that I’m not thinking of as well.

 

[jeffncs]

Thanks @DirtDonk for correcting my terminology and offering guidance. I usually pull these pieces off and enjoy the gas cologne. This is my wife’s truck and she’d rather not smell the fuel.

I have several trucks and piles of parts. I’ll see if I can locate the actual charcoal canister to complete the system after installing the “recovery” tank.

My truck used to be 2-tank but I’ve never been a fan of having a gas tank under my seat so it’s a single tank truck now.

Do you know which line goes to each location on the recovery tank? I’m sure there’s a schematic hiding out there someplace.

Thanks again @DirtDonk

 

[jeffncs]

Found one of 3 in my stash!

 

[DirtDonk]

Cool. That’s one of the 76/77 models.
For that style, you don’t even have to have the recovery tank in the cab.
In fact, that might not be a bad idea. Use the later model canister under the hood, completely eliminate your in cab tank, so that your wife never has to put up with a smell.
Sometimes those plastic tanks split a seam and every time you fill up the gas tank, the truck smells like gas.
Many of us have been through that, and many have literally tossed out that tank instead of patching it up.

 

[DirtDonk]

And that way you also don’t have to worry about which line goes to which location.
And yes, there is an order, and there are charts with pictures here on the forum. I was never able to remember off the top of my head which one goes where.
The newer style is fairly simple in comparison.

 

[jeffncs]

Thanks @DirtDonk !! That makes my life a whole lot easier!

 

[Glass Pony]

This is from a Haynes manual. I used the bottom/left diagram "Canadian vehicles using leaded fuel" on my carbureted Bronco.

 

[hadams417]

Im preparing to remove the “recovery” tank from my ‘73 so that i can use the freed up space for speakers. But I dont want to screw up the venting on the fuel system.

The tank I’m going to remove is located inside the cab directly behind the driver’s seat / in front of the driver’s side rear tire well. Im not totally following the layout of the fuel vent lines from this threat. I have the Haynes manual (36054) but can’t find where it references these details. Does the vent line run from my gas tank into the recovery tank? And then to the charcoal filter? If so then would I just need to relocate the vent tank? Bottom line is that I want to ensure that I dont accidentally screw up the fuel system when I remove the recovery tank.

 

[hadams417]

I may have found some answers. I dug up some fuel line diagrams that others guys had posted here. And then i found a threat where @DirtDonk had already answered some of my questions (https://classicbroncos.com/forums/threads/vapor-canister.276706/). So it looks / sounds like I need to get myself another tank (like the one referenced in the picture) to replace the one I’m removing from behind my driver’s seat. Does that sound right?

 

[DirtDonk]

It should be relatively straightforward.
Are you going to just be street driving the Bronco? Or will it do any time at all off the road? Even to the point of parking on a steep hill?

The stock pre-'77 setup had one vent on the aux tank and two "vents" on the main rear tank. One of the rear tank fittings is for venting, the other is for liquid return when present. That's the whole point of the extra recovery tank behind the seat anyway. As a "liquid return" means.
Whether you keep the original round metal charcoal canister on the frame up front, or change out to the (slightly more desirable) later model plastic tank mounted on the firewall, you can bypass the recovery tank pretty easily.
With the simple version, not adding a roll-over valve, you simply plumb all three lines (do you have dual tanks, or just one?) into the single line running up front. Done!
The only reason I say this for both of the fittings on the main tank, is because I never remember which one is venting and which one is return. Won't matter if they're all tied together, but if you simply want to cap one off, you will need to follow the tubes to see what does what. Or someone here may remember which is which.
If you can find one of the discussions with full pictures, or diagrams of which tube has which function in the recovery tank, you can determine which is the return to the main tank. If you can do that, you can simply cap that one off at the tank nipple, and run the other one up to the charcoal canister.

If you want to do it right, you an add an anti-rollover valve to the vent line. This is to keep liquid gasoline out of the charcoal canister. It's a slight, but still very real potential problem.
If you raise the canister up, by mounting the plastic one pictured up high on the firewall (or wherever) then the risk of liquid getting into the canister charcoal media is greatly reduced. But Ford still put an anti-rollover valve in the '76 and '77 models that got the high-mount canister. So it's never really a bad idea. Just "less necessary" than with the early low-mount style canister.

Is that what you were needing?

Paul