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#1 |
Registered User
Join Date: Sep 2010
Location: Lake Tahoe, Nevada
Posts: 755
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Gas tank vent line puking fuel
I have a 72 with two lines coming from the fuel tank, routed into the engine bay. One is routed to the fuel pump, the other is just hanging out with some sort of breather cap on it. I am assuming it is a fuel vent line (perhaps that assumption is my first mistake).
Problem is, if I fill up the fuel tank beyond about 3/4 full, fuel will begin to flow out of that vent line. Coincidentally, the end of this vent line is mounted at a height I'd assume to be right around 3/4 height of the tank. SO it would appear that as soon as the fuel rises above the end of this vent line, it becomes a drain. I'm sure that's not normal. The knee-jerk reaction would be "just mount the breather end higher than the tank. Problem solved!" That's not a solution, that's a band-aid. I want to actually SOLVE the problem. So educate me. Those that have vent lines on their tanks, where are they routed to? Or am I mistaken and this ISN'T a vent line at all? If it's not, then what the heck is it?
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I know a little about cars, but if you have a question about electricity or sport quads, I'm your man!!! |
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#2 |
Registered User
Join Date: Jul 2015
Location: Sedalia Mo.
Posts: 1,131
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Re: Gas tank vent line puking fuel
You should have three lines coming from the tank on a 72. One for feeding the fuel pump, one for return from the fuel pump, and the last one would originally be hooked to a charcoal canister under the hood which would be the vent.
3/8"=Supply, 5/16"=Vent, 1/4"=Return This thread might help you out a little... http://67-72chevytrucks.com/vboard/s...d.php?t=662158
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He who is without oil shall throw the first rod. Compressions 8.7:1 1972 C10 1976 C10 (parts truck) 1985 K20 Last edited by sick472; 01-18-2019 at 04:52 PM. Reason: adding info |
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#3 |
The Older Generation
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Location: Montezuma, Iowa
Posts: 25,491
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Re: Gas tank vent line puking fuel
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If the charcoal canister is no longer there cap that line at the tank, put a vented gas cap on it, and call it a day.... LockDoc
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Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 - |
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#4 |
Registered User
Join Date: Sep 2010
Location: Lake Tahoe, Nevada
Posts: 755
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Re: Gas tank vent line puking fuel
Maybe that's the answer, it's supposed to be the return line. But I don't have a return plumbed up, because it's not the original fuel pump (because it's not the original engine). My fuel pump doesn't HAVE a return. Just two connections, an inlet and an outlet.
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I know a little about cars, but if you have a question about electricity or sport quads, I'm your man!!! |
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#5 | |
Registered User
Join Date: Aug 2016
Location: Lake Forest, CA
Posts: 2,177
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Re: Gas tank vent line puking fuel
Quote:
Im on my 4th cap in a month. I have a 70 with non vented tank. I get two results from them, either too much pressure in tank (that the cab smells like fuel and the gap about blows out of my hand when removing) or fuel spills all over side of truck when I make a hard right turn.
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"Work hard, use your vacation days." 1970 C15 GMC Long Bed 1986 C20 Scottsdale 1983 K2500 Sierra Classic Suburban 6.2 Instagram: C10sofOC |
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#6 | |
The Older Generation
![]() ![]() ![]() Join Date: Aug 2006
Location: Montezuma, Iowa
Posts: 25,491
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Re: Gas tank vent line puking fuel
Quote:
That's only because some of the new caps are really crappy. Obviously the non vented one is working good though..... What brand are you using. I have had pretty good luck with Stant caps. I have replaced the rubber seal and brass backing plate on a couple of originals with good luck. LockDoc
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Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 - |
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#7 |
Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,936
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You may want to consider a late model charcoal canister to hook to it and take care of the smell. They are cheap enough at the local yards and install it under the battery as factory out of sight. Are you could use the factory one if it's still there and go to Walmart in the fish area and buy a couple of bags of charcoal to rebuild it.
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1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 ![]() Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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#8 |
Registered User
![]() Join Date: Oct 2013
Location: CT.
Posts: 260
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Re: Gas tank vent line puking fuel
Hello, Obviously the return line to the tank is clear so if your using a mechanical pump you could change to one with a return connection.
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#9 |
Registered User
Join Date: Sep 2010
Location: Lake Tahoe, Nevada
Posts: 755
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Re: Gas tank vent line puking fuel
Looks like it's time to pull the seat and get a really good look at things.
I definitely do NOT have a charcoal canister under my battery, nor do I have the lines running a high loop up the passenger side door frame. But I could probably fabricate them if they seem to work. It sounds like the vented gas caps can be slightly problematic with a full tank of gas. Anybody have an original charcoal canister, can give me some direction (or pictures) for hose routing?
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I know a little about cars, but if you have a question about electricity or sport quads, I'm your man!!! Last edited by wilkin250r; 01-20-2019 at 12:19 AM. |
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#10 |
Registered User
Join Date: Sep 2010
Location: Lake Tahoe, Nevada
Posts: 755
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Re: Gas tank vent line puking fuel
Well, the story I heard was that some 70-71s had vent lines, but all 72s had them. Either that is not the case, or this is not the original fuel tank because I do NOT have the vent line that runs up the passenger side frame rail.
I do have two lines on my sending unit. I believe the second one is a return line? It looks like the plan is to cap that return line. Can somebody give me a link or part number to a vented gas cap?
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I know a little about cars, but if you have a question about electricity or sport quads, I'm your man!!! Last edited by wilkin250r; 01-28-2019 at 07:51 PM. |
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#11 | |
Senior Member
![]() Join Date: Nov 2018
Location: Waterford California
Posts: 2,526
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Re: Gas tank vent line puking fuel
Quote:
Just did one 2 days ago |
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#12 | |||
"I ain't nobody, dork."
Join Date: Sep 2007
Location: Whidbey Island, Washington
Posts: 8,940
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Re: Gas tank vent line puking fuel
Quote:
http://www.67-72chevytrucks.com/vboa...&postcount=313 I also have the return line capped off at the sending unit. Gary
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'cuz chicks dig scars... My 1972 GMC 1500 Super Custom (Creeping Death) "long term" build thread. The Rebuild of Creeping Death after the wreck Quote:
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#13 | |
Registered User
Join Date: Sep 2010
Location: Lake Tahoe, Nevada
Posts: 755
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Re: Gas tank vent line puking fuel
Quote:
But I'm not that brave.
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I know a little about cars, but if you have a question about electricity or sport quads, I'm your man!!! |
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