Gas fumes in cab

[Bolt]

New fuel system but noticed light gas smell in cab. Didn’t replace the gas caps. Could that be the culprit?

 

[Broncobowsher]

Probably not

 

[blubuckaroo]

There are only a couple sources for gas to get into the interior.
The most common is the auxiliary tank manual selector valve. It's just in front of the driver seat near the floor. There is an o-ring in there that goes bad, and soaks the carpet with gas. Easy to fix.

The other is a vapor or surge chamber in the rear quarter panel on some models. I'm not really sure what it does, but it's a nightmare of hoses with places to leak.

 

[DirtDonk]

And with a new fuel system (what exactly does that mean by the way?) it could be any of the new components not fitted or tightened properly. Or even a cut hose from rubbing on something.
And yes, the gas cap too. But if the smell is primarily inside, then it's likely to be either directly under the body, or what blu said about those two components that share space inside with the passengers.

Paul

 

[Rustytruck]

What year is your Bronco.

 

[Rustytruck]

What year is your Bronco.

 

[Bolt]

My bronco is a 1974. All new tanks, fuel lines and filler hoses. The tank selector valve is new as well. Thanks for your help.

 

[DirtDonk]

Your '74 would have had the EVAP system (charcoal canister) which includes the charcoal canister and condensing tank previously mentioned.
The charcoal canister is mounted on the passenger side frame rail just below the firewall, and the condensing tank is mounted just left of the driver's shoulder under a screwed-on panel.

It's extremely common for this condensing tank to split at it's seam and fumes will fill the cabin easily. Especially common right after a fill-up.
It could still be your gas cap of course, but you'll need to check all the other stuff as well.

Dual tanks? Make sure the single vent on the aux tank and the two vent and recovery lines on the main tank are not worn out or leaking.
Then follow the vapor line along the frame and up to the charcoal canister to see if any of it is compromised.
Then there are at least two hoses running up to the engine compartment. Possibly three on an unmolested '74. The venting lines running up near the air cleaner, and possibly a float bowl vent line from the carburetor to the canister.
So check the three or four hoses at the canister and see if any are old and cracked. Or in the case of one of the large hoses, still attached to the air filter housing.

Paul

 

[Bolt]

Thanks Paul, I don’t even recall the EVAP being replaced during the restoration. Is there a diagram on how it is connected? And yes I have duel tanks.

Thanks again for you help. I have a list to check off now.

 

[Rustytruck]

1974 has non vented gas caps so pressure and fumes have to go through the myraid of vent hoses, vapor recovery tank and on to the charcoal canister. I would check the recovery first as that is the only component inside the truck. Its behind the drivers seat on the side of the bed right in front of the wheel well. There are 3 sheet metal bolts holding the access cover on.

 

[cs_88]

With mine it was the fuel/vapor canister behind the drivers seat.
Some silicone around all the entries took care of it.

 

[DirtDonk]

Same here. But instead of the tube entry points, it was the top of the tank along the seam. About a 1" length had split the seam.
Good old Permatex Form-a-Gasket #1 around the whole seam and it was good to go.

Paul

 

[Bolt]

Thanks Paul for your help. I am running Dual tanks. I don’t recall replacing the EVAP or the condenser tank not so I remember seeing a receipt for the parts. Are either available at WH?

 

[DirtDonk]

Not yet unfortunately. I keep thinking we should at least carry the canisters, but we don't. And I'm not really certain that the condensing tank is reproduced.
Seems like I saw one recently, but can't remember if it was new or used.

But there is an upgrade that's even easier than replacing like with like. And that's going to the '76 and newer style that eliminates the tank from the interior. In '76 and '77 you see all the trucks getting rid of their in-cab tanks and going to gas doors instead of extended filler necks sticking out. Regulations that did made sense.

You can purchase the newer style at just about any parts store or Summit or wherever. You need to mount it to the firewall (higher mounting is better) over on the passenger side where Ford put it in '76, then plumb just a single line from each tank to a "Y" fitting somewhere underneath, then up to the small port on the canister.
From the canister run the large fitting to the air filter housing and you're basically done.
The second large port gets a breather cap to keep debris and water out of the canister.

Other than that, I'm not sure that the original design parts are available anymore. That would be either a junkyard junket, or someone in the classifieds selling their old ones.

Paul

 

[sprdv1]

My bronco is a 1974. All new tanks, fuel lines and filler hoses. The tank selector valve is new as well. Thanks for your help.

output of the exhaust the culprit maybe?

 

[sprdv1]

Same here. But instead of the tube entry points, it was the top of the tank along the seam. About a 1" length had split the seam.
Good old Permatex Form-a-Gasket #1 around the whole seam and it was good to go.

permatex, ahhh yeah quite useful in a lot of applications