Gas tank venting issues

[Clay Dots]

thanks for postin this diagram, where do the grommets go into? thanks CD

 

[sleepar]

I replaced my cap with a "vented anti-surge" cap by Gates, and so far it's worked fine. It was pretty hot out this weekend and I didn't notice any significant issues. For what it's worth, according to my trusted parts store guy, he verified that 66-67 Chargers list a different cap than other similar B-bodies. Even a '67 Coronet lists a different cap according to Rock Auto...

Thanks everyone!

I keep my old cap for long trips and use the new locking cap for storage because it holds a vacuum keeping the moisture out

 

[C-440-300]

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Mine has done that too . I think gas gets trapped in the u bend and any excess pressure tends to drip gas. but then you say you don't have the line in the trunk. weird.

FYI - the '66 (and guessing the '65) C-bodies had the same dual vents - one of them horseshoe like up through the trunk (first grommet) on the driver side, near the hood hinge, then, up 8 or 9 inches, u-turn back down, across the metal, pop back in through second grommet and into what appears to be a body cavity that isn't obviously visible from above the axle/pumpkin area. Any, thanks for posting the pics. I had all the troubles mentioned running through AZ a few weeks, ago, even though I have the Uncle Tony Third Nipple Fuel Vapor Lock filter and return line. I dn't have VLock. She starts right up all day long in the parking lots. It's the "small" (I say any is not small.) puddle of gas that drips when stationary. Tank pressure startled me. Anyway, taking comments to heart from here and dropping the tank and taking all vent lines down/out, blowing them out. It might be the sections in the tank that is blocking. The cap is spec'd for the car/tank. It's a regular cap like the one Mama Mopar gave her. Lastly, the new gas in older car design is totally correct. Not fully compatible. Cheers from a nosey C-Body.

 

[C-440-300]

thanks for postin this diagram, where do the grommets go into? thanks CD

Grommets are in the body of the trunk. See my message just posted. Or imagine the body metal where the grommets are in the back of your trunk (under the rear window area, over the axle).

 

[Maxrat]

FYI - the '66 (and guessing the '65) C-bodies had the same dual vents - one of them horseshoe like up through the trunk (first grommet) on the driver side, near the hood hinge, then, up 8 or 9 inches, u-turn back down, across the metal, pop back in through second grommet and into what appears to be a body cavity that isn't obviously visible from above the axle/pumpkin area. Any, thanks for posting the pics. I had all the troubles mentioned running through AZ a few weeks, ago, even though I have the Uncle Tony Third Nipple Fuel Vapor Lock filter and return line. I dn't have VLock. She starts right up all day long in the parking lots. It's the "small" (I say any is not small.) puddle of gas that drips when stationary. Tank pressure startled me. Anyway, taking comments to heart from here and dropping the tank and taking all vent lines down/out, blowing them out. It might be the sections in the tank that is blocking. The cap is spec'd for the car/tank. It's a regular cap like the one Mama Mopar gave her. Lastly, the new gas in older car design is totally correct. Not fully compatible. Cheers from a nosey C-Body.

The 66 Charger has no such fuel vent line that goes into the trunk. It's very simplistic. Gas down through the filler tube to the bottom of the tank. When full, the gas comes out to the overflow tube at the top of the tank then back up where it re-enters the top of the filler neck and re-enters the tank. There is no vent line -- period.

 

[Maxrat]

It was a small puddle, maybe 6" diameter. However, there is no loop of vent line or anything in the trunk. The only connections on the tank are the sending unit, the main fill tube, and another line that comes off the top and connects at the top of the fill tube. This is commonly referred to as the "vent line" but I can't see how anything vents with it since it just connects back up to the fill tube. I've seen other setups from 68-72 and there are a variety of them, usually with one line connecting to a canister or the engine to allow expansion and then burn the fumes. This has none of that.

Obviously you have to let air in as gas goes out- but is the tank intended to hold pressure like that if it heats up? I've been through this care front to rear and I believe the tank is setup correctly, but I have a hard time believing it should pull a vacuum or hold pressure.

You're right -- there is no vent line to depressurize. There are two tubes. The fill tube and the overflow tube (some call it a vent line) which connects back into the fill tube. That's it. No vent line with a purpose to depressurize a tank.

 

[5.7 hemi]

That’s why ya need a vented cap.

 

[Maxrat]

That’s why ya need a vented cap.

A manufactured vented cap prevents the tank from collapsing under vacuum (as the carburetor sucks fuel). A vented cap valve is a one way valve. It does not prevent a tank from expanding under pressure (usually as temperature rises). The problem posted is tank pressurization.

 

[5.7 hemi]

Fuel expands when sloshed or hot. If a cap is vented 1 way, it should work just fine. How else did thousands of cars get around with vented caps?

 

[Maxrat]

Fuel expands when sloshed or hot. If a cap is vented 1 way, it should work just fine. How else did thousands of cars get around with vented caps?

Yes, the cap is vented one way --- to suck air in -- not to let air out.

 

[dodge68charger]

Does The Long Vent Line That Runs Inside The Gas Tank From The Front To The Rear of The Tank Go To The Vent Line That Goes Across The Trunk Floor or Does It Matter?

Thanks