Sealed Gas Caps Needed

[DonaldDouchebag]

I just plumbed an evaporative canister and am still getting fumes. Would like to install a couple non-vented fuel caps to see if that helps. This is for a ‘71 with the longer fuel caps. Does anyone have a part number or know who sells them? Can’t find any online. Thanks!

 

[73azbronco]

how do you have it plumbed? What year because i don't think my 73 has them for emissions

 

[DirtDonk]

Your 71 (and your 73 too az) should be sealed and non vented already.
The correct one for your year is non-vented. Or, more appropriately, vented one way. In only and not allowing fumes out.
Cause all 71 through 77 Broncos had a charcoal canister. Shouldn’t matter what state it was sold in originally for the light duty Bronco. Only heavier duty, full-size trucks avoided the charcoal canister for several more years.

Does your 71 still have the plastic condensing/recovery tank behind the driver’s left shoulder? If so, it’s very possible that the fumes are coming from there.
Where do you smell it most of the time, and under what circumstances? Right after a fill-up by any chance?

 

[73azbronco]

Bingo.

I just rebuilt mine, was trying to use the original round but far to big for landscape. Used a mustang 90's, line from tank, line to intake, two caps, I'm not using the 3/4 inch silver foil to intake.

 

[DonaldDouchebag]

Your 71 (and your 73 too az) should be sealed and non vented already.
The correct one for your year is non-vented. Or, more appropriately, vented one way. In only and not allowing fumes out.
Cause all 71 through 77 Broncos had a charcoal canister. Shouldn’t matter what state it was sold in originally for the light duty Bronco. Only heavier duty, full-size trucks avoided the charcoal canister for several more years.

Does your 71 still have the plastic condensing/recovery tank behind the driver’s left shoulder? If so, it’s very possible that the fumes are coming from there.
Where do you smell it most of the time, and under what circumstances? Right after a fill-up by any chance?

I deleted the in-cab expansion tank and it’s lines and ran lines from the rear and aux tank up to to a Mustang evap canister in the engine compartment. From there it goes to a fitting on my aftermarket air filter.

Smells every time I drive it, no matter the amount of fuel in tank. Was hoping an evap canister would cure it.

 

[DonaldDouchebag]

Bingo.

I just rebuilt mine, was trying to use the original round but far to big for landscape. Used a mustang 90's, line from tank, line to intake, two caps, I'm not using the 3/4 inch silver foil to intake

Bingo.

I just rebuilt mine, was trying to use the original round but far to big for landscape. Used a mustang 90's, line from tank, line to intake, two caps, I'm not using the 3/4 inch silver foil to intake.

I used that canister but mine has just one 1/4” inlet. I have the tanks router to the 1/4” inlet, i added a mushroom cap to one large outlet, and I have the corrugated silver tubing on the other large outlet up to the air filter.

 

[DonaldDouchebag]

Makes sense that the caps I have are one-way and should be fine. Maybe the next step is to look at the edelbrock carb and see if it’s evaporating there. Maybe a phenolic spacer to keep it cooler. Could look at rejetting as it may be running rich.

 

[DirtDonk]

Being rich can certainly make it smell of gas long after it's stopped running. But from what I've seen, it's not quite the same smell as raw gas. Does yours smell like raw gasoline?
Sounds like you don't have any vacuum lines to the canister, so that's good. Could it be an oddball type of canister, since it's only got the one small port instead of the usual two?
I would not think so, but thought I'd throw that possibility out there.

Next time you're under the hood, lean over the canister and see if it smells like it's coming out of there. If you're somehow managing to get liquid gas into the charcoal medium, maybe it's just overwhelming the canister.
How high up do you have it mounted? As high as possible, or down low by any chance?
And is your aftermarket air cleaner an open element type? If so, then at least some of the fumes are coming out of there.

Paul

 

[Broncobowsher]

Where do you have the charcoal canister mounted? The stock early location down low uses that liquid seperator behind the seat to keep liquid gas from getting into the charcoal canister. I think it was the '77 that had it mounted high enough that gravity prevented that problem.

You don't have the foil hose. So how are you purging the canister. The charcoal canister does not have in infinite storage capacity. The idea behind it is it stores a little bit of vapor while stopped and as the engine is running air flowing through the canister purges the vapors back out and into the engine where they are burned.

Along those lines, what air cleaner are you running? The stock one has a long path for fuel vaporizing out of a hot carburator to get out. A standard aftermarket open element air filter doesn't. I remember a friend didn't like the gas smell in the garage and his fix was an electric fuel pump. Learned where to turn it off on the way home so he could get it in the garage and let it idle a little bit and run the carb dry. That was enough to fix his stinky gas garage smell.

 

[fordguy]

I am experiencing gas fume smell with EFI and Mustang canister on firewall. I did not seal fuel pump like the manufacturer recommended but that has now been corrected. I did do a vapor test on line from tank to canister. The mushroom caps were rolling out the vapor, but I guess the charcoal has done its thing by then? I don’t know if I have a vented cap or not. I will post a pic so we can verify. I did put some fuel in the tank after sealing pump and did not experience spell. The last time before the fix, it was filled all the way to full.

 

[DonaldDouchebag]

I have the canister mounted to the top of the cowl as high as possible. I do have the silver corrugated hose going to my air filter. It’s a K&N open type.

It’s definitely a gassy smell. Some raw fuel scent, for sure.

I’ll drive it and then really investigate by sniffing around.

 

[73azbronco]

I used that canister but mine has just one 1/4” inlet. I have the tanks router to the 1/4” inlet, i added a mushroom cap to one large outlet, and I have the corrugated silver tubing on the other large outlet up to the air filter.

is the silver line going to the air filter outside of the filter or inside? Is it on a stock air cleaner assembly?

 

[MarsChariot]

On the original air cleaner housing the purge line (tube) was routed to the outside of the air filter, the idea being that low vacuum inside the air cleaner housing would draw vapors from the charcoal can when the engine is running. Here are a couple of images that are not Bronco specific, but illustrate the principal routings and the gas cap characteristics. The duplicate image discusses how the main vent for the charcoal can was itself on a long tube that went up into the corner of the engine compartment with a mushroom cap. Presumably to get the inlet out of the dusty wheel well environment where the early cans were mounted. This is the round version. The other later version of course was mounted on the firewall.

 

[Broncobowsher]

I am experiencing gas fume smell with EFI and Mustang canister on firewall. I did not seal fuel pump like the manufacturer recommended but that has now been corrected. I did do a vapor test on line from tank to canister. The mushroom caps were rolling out the vapor, but I guess the charcoal has done its thing by then? I don’t know if I have a vented cap or not. I will post a pic so we can verify. I did put some fuel in the tank after sealing pump and did not experience spell. The last time before the fix, it was filled all the way to full.

If you see vapor rolling out the canister, it is saturated. Do you have canister purge hooked up to the EFI? I am assuming you are using an OEM EFI with canister purge. Aftermarket EFI can be done but it gets trickier. I was looking at tricking a Sniper into doing it with an electric fan set to engine temp and aux fuel pump set to ~10% throttle. When both are triggered (warmed up and cruising) to open a purge solenoid. Never got to it, sold it before I to it.
How is your exhaust to fuel tank routing? Easy to cook some fuel, a little cooked fuel makes a lot of vapor, it has to go somewhere. Charcoal canisters are not unlimited storage. They need to be refreshed (canister purge) to suck that stored vapor out. I'm working on a non-Bronco project aux fuel tank with charcoal (and OBD-II) and just had an issue with fuel boiling into the charcoal system. Not enough heat shield and not enough expansion volume (air space before the vent).

 

[73azbronco]

The mustang charcoal cannister has 4 inlets, 2 large 3/4inch ports for the caps which vent to atmosphere, Another is a 1/4inch size and the other is a about 1/8th.

I have the line from fuel tank vent port with a sort of reverse drip line and rollover valve I placed up by the gas tank filler hose in the left rear wheel well, that routes back down and follows the right frame rail to the inlet of the 1/4inch charcoal cannister. This vents the tank. Prevents fuel from flowing up to the canister which was a problem every time I hit the brakes.

The smaller 1/8th line off the evap cannister, I have running to an as yet to be drilled fitting on a spectre air filter, it will be between the filter and carb, so there will be some small vacuum. This positively vents the cannister by drawing air into it via the two large caps, across the charcoal, and into the induction air.

 

[DonaldDouchebag]

is the silver line going to the air filter outside of the filter or inside? Is it on a stock air cleaner assembly?

It goes to a fitting on the underside, inside the filter. It’s a typical aftermarket 14” round k&n filter—had the fitting location stamped into the base.

 

[DonaldDouchebag]

The mustang charcoal cannister has 4 inlets, 2 large 3/4inch ports for the caps which vent to atmosphere, Another is a 1/4inch size and the other is a about 1/8th.

I have the line from fuel tank vent port with a sort of reverse drip line and rollover valve I placed up by the gas tank filler hose in the left rear wheel well, that routes back down and follows the right frame rail to the inlet of the 1/4inch charcoal cannister. This vents the tank. Prevents fuel from flowing up to the canister which was a problem every time I hit the brakes.

The smaller 1/8th line off the evap cannister, I have running to an as yet to be drilled fitting on a spectre air filter, it will be between the filter and carb, so there will be some small vacuum. This positively vents the cannister by drawing air into it via the two large caps, across the charcoal, and into the induction air.

My evap canister has just the single 1/8” inlet. I did install a rollover valve that is made to allow fumes to vent — installed it inline before and below the canister.

 

[DirtDonk]

Got a pic of this valve? Never seen an inline one used on a Bronco before. Well, Ford used one of course, but it was way back behind the passenger side door.
Most of the aftermarket ones are on top of the tank, or nearby.
I wonder if location has any effect? Would not think so, but wondering anyway.

Paul

 

[fordguy]

If you see vapor rolling out the canister, it is saturated. Do you have canister purge hooked up to the EFI? I am assuming you are using an OEM EFI with canister purge. Aftermarket EFI can be done but it gets trickier. I was looking at tricking a Sniper into doing it with an electric fan set to engine temp and aux fuel pump set to ~10% throttle. When both are triggered (warmed up and cruising) to open a purge solenoid. Never got to it, sold it before I to it.
How is your exhaust to fuel tank routing? Easy to cook some fuel, a little cooked fuel makes a lot of vapor, it has to go somewhere. Charcoal canisters are not unlimited storage. They need to be refreshed (canister purge) to suck that stored vapor out. I'm working on a non-Bronco project aux fuel tank with charcoal (and OBD-II) and just had an issue with fuel boiling into the charcoal system. Not enough heat shield and not enough expansion volume (air space before the vent).

Not sure how to check purge valve (done by Garry) exhaust is only close on one spot, should not be an issue. I have the canister out on a vacuum line off of explorer intake.

 

[DonaldDouchebag]

Got a pic of this valve? Never seen an inline one used on a Bronco before. Well, Ford used one of course, but it was way back behind the passenger side door.
Most of the aftermarket ones are on top of the tank, or nearby.
I wonder if location has any effect? Would not think so, but wondering anyway.

Paul

Here's the guy:


https://www.summitracing.com/parts/...2Be1NkYGI9SHG4FIQ4gopfbPh0ihsN201cySn8zuHHrtY