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Old 05/22/13, 07:36 AM   #1
Jerseydevil
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Fuel tank venting

Hey y'all, I have a fuel tank issue. It goes like this. If I fill the tank too much, gasoline leaks past the cap, while its parked, in the heat of day. Thus is not an overfill issue, as I stopped adding before there was gas up to the top of neck.
I know what is happening, I think. I believe it is the result if the fill neck being located on the side of the tank, as opposed to the top. As the gas expands or vaporises due to heat, it pushes gasoline up the neck, and past the cap. A vent on the top of the tank (check valve) would probably fix this problem, which I see others have had.
Has anyone installed one, or found any kind of safe, reliable fix? If you have a new tank, does this problem still come up? Where is the fill neck located on new tanks? Thanks
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Old 05/22/13, 07:46 AM   #2
NYLES
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stock tank? fill necks still in same place because of where the caps are located on the body.

'69, 306 EFI'ed, ZF, DANA 44, 4 WHEEL DISC'S, ASTROBOOST, 3.5"SUSPENSION LIFT, 2"BODY LIFT, GLASS BODY, 37" ON MRW, 5.13's GRZZ/GRIZZ , MOSER, STONE CRUSHER, POWER STEERING, BAILIE BILT, DURABACK, RJM
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Old 05/22/13, 07:53 AM   #3
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Yes, as far as I know. It's a 68, made up from parts from who knows what years the engine is from a 71 car.
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Old 05/22/13, 07:58 AM   #4
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Do you have a vent line running out of the tank? Maybe running up to a charcoal canister? It was my understanding (which may be wrong) that vapors and fuel upon expansion, would be pushed up this line and then through the canister. So when it expands it has a place to go other than over the side of your quarter panel.

On a bright note, if this continues to happen for the next 30+ years or so, you'll have an absolutely wonderful patina on the side of your truck. No joking, this was one of my favorites of all the ones at Super Celebration!
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Old 05/22/13, 08:06 AM   #5
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http://broncograveyard.com/bronco/i-...-tank-kit.html

See lil red capped vent tubes? If you have them use one to connect a tube as high as you can above the tank zip tie in a 4-5 inch loop....add check valve(not required) should fix ya problem BUT DONT CALL ME WHEN THE WIFE COMPLAINS ABOUT SMELLING GAS IN THE GARAGE!!! Thats what the charcoal can was for.

Anyway you lokk at it youu need some kinda vent, your tanks doing the same thing as any common gas can, you gotta relieve the pressure.

'69, 306 EFI'ed, ZF, DANA 44, 4 WHEEL DISC'S, ASTROBOOST, 3.5"SUSPENSION LIFT, 2"BODY LIFT, GLASS BODY, 37" ON MRW, 5.13's GRZZ/GRIZZ , MOSER, STONE CRUSHER, POWER STEERING, BAILIE BILT, DURABACK, RJM
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Old 05/22/13, 08:44 AM   #6
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I just stopped topping off my tank in the summer and allowed a bit more room for expansion. If i get carried away at the pump it likes to do that. Nyles advise is wise I did that and it hasnt burped out again.

1976 302 4bbl, Gateway buckshot mudders , C4, Warn M8000, 4.11 gears, Dual Batteries, ,170amp 3G alternator, Front & Rear Extended Fuel Tanks, ARB Front & Rear
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Old 05/22/13, 09:44 AM   #7
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Thanks guys. I had my tank off recently, and don't remember seeing any plugged ports. Also, don't think I have the canister. Could that have been added in later years? I took a look at the tanks on the graveyard site, and the neck is higher on the side than I was thinking. So, I guess I'll also not fill so much in the summer, which won't result in a significant drop in fuel level. I'll look into a vent as well.
Pretty funny, getting advice on gas tanks from a guy called fireball. Btw, my fender is not quite that bad, but my black primer is not original I have seen pics of cars from in the sixties with that same stain, I figured it was from over filling.
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Old 05/22/13, 10:27 PM   #8
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Even with the vents and such you can still get gas dripping. The heat can expand gas like 10% so that gas dripping out the cap has no choice as the gas expands venting wont help much at all as its the liquid that is coming out not vapors. As was said just plan your fill ups a little better either drive a little farther before parking or dont top it off during the hot months.

73 Ranger 2 1/2 lift 302 TFS heads NP435,PS,PDB, tierod over, 33x10.50x15 BFG M/T
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Old 05/22/13, 10:38 PM   #9
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Hey Jersey! Havin' fun it sounds like. Seen this many times on EB's unfortunately. Even when they were just a few years old.
I'd kind of be curious to see how much you're actually able to put in there. If it's more than 11 gallons, I could see it being overfilled. If it's not though, that would seem kind of extreme expansion, unless something was reducing the volume for expansion. Takes quite a bit to push fluid up that filler neck after all.

I'm not sure what to do to fix it, but still be interested to see how much you're getting in there when it overflows.

What's the condition of your body mounts? If they're original and crushed, the body could be kinking/smooshing the filler hose. Can't see how this would cause your issue, but it can contribute to erratic filling habits.
You didn't mention it, so I "assume" yours fills fairly well? A lot of us have experienced the old on/off pull/click/pull/click when you can only get about a half a gallon (or less) in at a time before the pump shuts off.
Yours do that, or is it fairly easy to fill?

Paul

'71 Wagon, 3.5" lift, F150 disc brakes and steering, 4.11 33x11.50 Thornbirds, Kayline soft top, Hanson bumpers.
Soon to be 5.0 w/ NV3550 and NP241 and whatever other parts are stuffed in the cab, storage room and garage, waiting to be installed.

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Old 05/22/13, 10:43 PM   #10
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Paul, he parks on a hill gas cap down!

Im LMAO right now thinkin about a place at OCBR somehow I always get stuck parking right ant the end of this taril in the same spot gas cap down pourin gas........and get five guys tell me hey ya leaking gas!!!!!!!

'69, 306 EFI'ed, ZF, DANA 44, 4 WHEEL DISC'S, ASTROBOOST, 3.5"SUSPENSION LIFT, 2"BODY LIFT, GLASS BODY, 37" ON MRW, 5.13's GRZZ/GRIZZ , MOSER, STONE CRUSHER, POWER STEERING, BAILIE BILT, DURABACK, RJM
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Old 05/23/13, 07:58 AM   #11
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Mine did that even when it was new but being a '77, it didn't hurt the paint. I do believe thought that the problem is worse now than when these cars were new because fuel vaporization temperature is lower.

'77, 2" suspension lift, 1" body lift, 32" tires. 302, 4 bbl, headers. NV3550, 4.11s, Yukon rear posi.
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Old 05/23/13, 10:54 AM   #12
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I learned about gas expansion the hard way my first day on the job driving the fuel truck at the local small airport when I was younger. Filled the truck off a tank of nice cool gas which was underground. First call went and filled a guys experimental aircraft he just pulled into his hangar. Was nice and warm from sitting in the sun after a flight he just got back from. Topped off the tanks in his wings and went to leave when I hear him yelling at me- gas just poring down his wings. D'oh! No one had told me you need to leave a good 10% room to cover expansion.

'77 Ranger, 1" BL, 2.5" WH suspension, 32" BFGs, C4, 351W, DUI, BCB Headers
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