Leaking auxiliary fuel tank

[jacrz]

The auxiliary tank on my 1974 Bronco appears to be leaking fuel from the sending unit. I assume this just requires a replacement gasket? I can't tell if this could be my gas smell issue.

 

[Brush Hog]

I had same issue on what appeared to be an original aux tank. It was so gummed up I ended up replacing the whole tank and sending unit. My advice is don’t do that and put that money towards a 23 gallon tank. I was a diehard “must have 2 tanks because it’s a cool EB thing”. Got over that real quick when I realized how nice,convenient, leak free,etc the 23 gallon tank is. One of best upgrades I’ve done. I kept the aux tank but don’t fill it.

 

[DirtDonk]

Did you try tightening the screws by any chance?
And correct me if I’m wrong, but wasn’t the factory tank a little different? I don’t remember screws and a flange like that.
So maybe that’s an aftermarket replacement already. They were actually well known for poor sealing at that area, which made me think about it being aftermarket.
I’m still a dual tank fan as well, even though my 68 has only the 23 gallon. Still, I wouldn’t mind it being 30!

 

[Oldtimer]

Jacrz,
Your tank looks like the replacement tank sold by Tom's Offroad.
You might contact them and ask about seals/gaskets?

Auxiliary Fuel Tank, OE-Style, 66-77 Ford Bronco

Another TOMS OFFROAD Exclusive!!! This new poly fuel tank is an exact replica of the original Early Bronco front auxiliary gas tank. This OE Quality Auxiliary Fuel Tank includes the fuel sending unit o-ring and lock ring. Unlike the aftermarket poly fuel tanks, our new OE-Quality Auxiliary Gas...

tomsoffroad.com

 

[jacrz]

Super helpful, thanks all. It does seem to be a replacement. One small apparent difference from the Tom's version is that it has this metal rod that was inserted into the tank. Any idea what it is?

I'm debating just deleting the tank for now, since it appears the PO left it full of gas connected to the original Bronco fuel tank selector valve, but then routed a new rear main tank directly to the Holley Sniper EFI using steel line that doesn't utilize the selector valve at all. So it goes nowhere from what I can tell.

 

[DirtDonk]

Super helpful, thanks all. It does seem to be a replacement. One small apparent difference from the Tom's version is that it has this metal rod that was inserted into the tank. Any idea what it is?

That's for the charcoal canister (EVAP) system. Guess the new tank was not outfitted for it?
Though, when disconnecting it or leaving it off, you usually don't see the internal rod! Just the hose part.
Maybe they thought to reconnect it to the new tank, but found the fitting was not the same and could not separate the old rusty rod from the fitting, or figure out another way to connect it.

I'm debating just deleting the tank for now, since it appears the PO left it full of gas connected to the original Bronco fuel tank selector valve, but then routed a new rear main tank directly to the Holley Sniper EFI using steel line that doesn't utilize the selector valve at all.

that's pretty typical, since it's more work to run two tanks with EFI.
Where is the pump located?

So it goes nowhere from what I can tell.

The main feed hose, or this hose/line in the picture?
The vent line pictured would have gone up into the cabin ('71-'75 models only) through the grommet and into the plastic tank behind the driver's shoulder. From there it would run to the passenger side, up to the front wheel well where the metal canister was mounted to the frame.
On a '76 or '77, it would have run into a "Y" junction and from there, over to the passenger side frame rail, through an anti-rollover valve, and up to the charcoal canister on the firewall.

Paul

 

[Speedrdr]

I have a WH aux tank and don’t remember it looking like that. Guess there’s a difference in the different suppliers maybe?

Randy

 

[jacrz]

That's for the charcoal canister (EVAP) system. Guess the new tank was not outfitted for it?
Though, when disconnecting it or leaving it off, you usually don't see the internal rod! Just the hose part.
Maybe they thought to reconnect it to the new tank, but found the fitting was not the same and could not separate the old rusty rod from the fitting, or figure out another way to connect it.

that's pretty typical, since it's more work to run two tanks with EFI.
Where is the pump located?

The main feed hose, or this hose/line in the picture?
The vent line pictured would have gone up into the cabin ('71-'75 models only) through the grommet and into the plastic tank behind the driver's shoulder. From there it would run to the passenger side, up to the front wheel well where the metal canister was mounted to the frame.
On a '76 or '77, it would have run into a "Y" junction and from there, over to the passenger side frame rail, through an anti-rollover valve, and up to the charcoal canister on the firewall.

Paul

Paul this is great, thanks.

I'm having a hard time tracing it. There is a rubber hose that connects the charcoal canister (on the passenger side of the Bronco) to the tank behind the driver shoulder, and then also appears to connect to the rear tank through that driver shoulder tank. There is a whole series of lines to/from that driver shoulder tank. There is no direct connection between the rear/main tank and the charcoal canister. Does that make sense? I wish I could share a good picture of the driver shoulder tank, but it's tough to get one that's useful.

 

[jacrz]

I have a WH aux tank and don’t remember it looking like that. Guess there’s a difference in the different suppliers maybe?

Randy

Agreed, I can't even seem to confirm that my replacement tank matches the one currently available from Tom's.

 

[DirtDonk]

There is no direct connection between the rear/main tank and the charcoal canister. Does that make sense?

Yes, perfect sense.
The vent lines from the tanks went directly to the plastic recovery tank in the cabin. From there one single line went back out to the rear main tank so that any accumulated liquid gas could be recovered and reused.
Another single line went from the plastic tank in the cabin up to the charcoal canister.
That’s the single line you see in your picture coming up from the rear to the charcoal canister.

The two larger ports on the charcoal canister originally had matching hoses like you still see on the one running up into the engine compartment. One was vented to atmosphere and one was connected to the air cleaner housing.

In the early style charcoal canister system that we had from sometime in 1970 model year, up to 75, there was no direct connection between the gas tank and the charcoal canister.
Because the canister was mounted low on the frame, and this was a utility vehicle expected to work at awkward angles, they mounted a higher recovery tank up in the cabin.
This is to keep liquid gas from working its way forward to the charcoal media and ruining it.
In 77 the rule was no more gasoline in cabins of any kind. Hence, no behind the seat gas tanks in pickup trucks from mid 77 on up to today.
Ford was a little proactive for once and the Broncos got the shoulder tank removed for the 76 and 77 model years. Probably because in some markets and some registrations, Broncos were listed as passenger cars and probably had to meet the safety standards earlier.
Using a different, higher mounted, charcoal canister with a direct connection to the tanks.

 

[jacrz]

Got it. How critical do you think it is to have the hoses running to the engine compartment? It seems like, if it is functioning properly, the charcoal canister has already done its fuel vapor cleansing work once air exits from those larger ports?

 

[DirtDonk]

Not quite. The charcoal doesn't make the fumes disappear. It only holds it in suspension temporarily to let it get sucked gently into the engine over a period of time, to burn in the combustion process. Only with the in-cab recovery tank, was some of the liquid returned to the gas tank instead of into the charcoal canister.
But it's always a "sealed" or semi-sealed system.
If you let both ports vent to atmosphere, you'll still get gas smells into the air around the vehicle. Will it be reduced? Not sure. Will it be totally gone? Can't see how that would work.

With the two vent hoses, one was indeed open to atmosphere, but only to allow the gentle tug of semi-vacuum (or whatever it's called on the outside of the carburetor, rather than behind it) to pull the vapors/fumes into the air cleaner housing. The first year or three, it was just open. After '72 they changed the open tube to use what we call the "mushroom" style cap. Keeps debris and moisture out, keeps a tiny bit more of the potential fumes in.
That's why they went to sealed element air cleaners and disapproved of it when you cut holes in your air cleaner housing, or flipped the lid upside down to get more air in (or just to get that good old whoommmm/cop car sound!) or whatever reason. Once the filter area was exposed, all the fumes that were supposed to be available for sucking into the engine, could easily get out into the air of the garage or around the house.

You can certainly leave it that way and see if you get fumes, or if it doesn't put out enough to bother anybody. But if you want it complete, one of the big tubes has to go to the air cleaner housing.
By the way, it's just the housing. Definitely NOT to a vacuum source.

Paul

 

[jacrz]

Ah now I understand, many thanks. Any idea about the hose I need to replace the old (probably original) one going into the charcoal canister? It appears to be 1/2" OD, 1/4" ID. Picture below. Thanks!

 

[DirtDonk]

Never replaced one. Every Bronco I know of that did not have it's charcoal canister thrown out for being "smog crap" still has it's original!
Is that blue plastic bit in the end, just a bit of reinforcement that fits over a nipple on the canister? Or is that the nipple broken off in the hose?
Doesn't look broken, so hopefully just there for a better fit.

Paul