daddy, where do gas tank vent hoses go?

[edpdx]

Well I have been trying to figure out why the 73 c20 I drive wont allow a decent fill in either mid chassis tank. I don't get to pump my own gas here in Oregon, so I have to rely on the professionalism of the attendant. When the station is busy, I take what he can get in before it burps gas all over the tarmac. When they are not busy, a gut that know his way around the various problem truck and nozzles MAY use his skills to get the full tank I ask for, or he may just blow off his job and ram it, jam it, and scram it...dammit!

So... I have read in various forums that my problem is: "the nozzle I am using at the moment has been engineered to deliver gas to aggressively for yesteryears cars (they just aren't what they used to be)", "It is a GM planned obsolescence", "The sender is bad", "the inside tube fell out of the filler neck", "The vent tube is blocked or either tube is collapsed". I don't want to drop the tank yet so I am going to try a couple of things first:

I noticed when I crawled under the truck that the driver side tank has two hoses (fuel line type) routed toward the switch-over solenoid. One goes to the appropriate inlet on the switch. The other line is just looped and hung up over the driveline. I guess this is the vent tube? It definitely comes from the gas sending unit. Should this just be "open" and not attached to something. I am guessing this may be the problem. If it is a venting hose and it became clogged with dirt or insects, this could be the reason that the tank keeps burping fuel and that I seldom get more than a half tank. ?!?!

What of the idea that one fellow gave me about the original Inner rubber hose that resides in the original metal filler neck having become dislodged? He says it would have been pushed loose into the tank sometime when I was trying to force a siphon tube into the tank. Anyone hear of this on a 73?

Any help you can give is truly appreciated!

Ed

[donut]

My tank and filler hose have been replaced on my '73, but I'd check the vent line.(mud daubers or other critters can wreak havoc) I've just got a short length of fuel line with an axle vent on the end to keep critters out. It should connect to the top of the sending unit, just like the fuel line.

FWIW, We used to have a couple company welding rigs, the only way to get fuel into them was to hold the nozzle (and your tongue) just right.

[gchemist]

The hose curves too much for pump pressures. Have the attendant turn the nozzel upside or at least sideways. It will fill up faster without spilling everywhere!

[2tons of fun]

that and the pump nozzels are not the same as they were in the 70-80's.

that stupid fawking acordion neck is what is fawking you and it sucks. turning them upside down help depending on what station you are at and if it has the long or short neck.

[edpdx]

Any truth to the filler tube inside of the original metal filler neck?

What about the smaller hose that parallels the filler neck hose, could this be the problem? Collapsed maybe?

Ed

[2tons of fun]

i have many necks and tanks apart and have never seen inner filler tube

[asphaltburner]

Yo! I get a good fill when I gas up, but the new nozzles do not shut off quickly enough and my truck spits about a cup of gas on the ground before turning off.
I kid about mine being a '78 and not knowing to not waste gas!
And my twin tanks are both completely rebuilt with all new components: new rubber filler necks and vent hoses.
My tanks have outlet lines to the pump, inlet lines as overflow from the carb, and vent hoses that route to the charcoal canister for venting back to the carb.
There has never been an "inner filler tube".
Todd.

[LostMy65]

Does someone know which hose is for which?
Out of a 79 Suburban:
I'm pretty sure the second from the left goes to the fuel pump, and the fourth from the left goes up next to the filler neck.

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[LostMy65]

Originally Posted by LostMy65

Does someone know which hose is for which?
Out of a 79 Suburban:
I'm pretty sure the second from the left goes to the fuel pump, and the fourth from the left goes up next to the filler neck.

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Actually, the following post might be my answer:

Originally Posted by rfmaster

Fuel supply is 3/8" SAE30R7
Fuel return is 5/16" (if equipped)
Fuel vapor 1/4" (CCP return)
Filler neck to tank fuel inlet 1-1/4" (hard to find 90 bend)

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[tucsonjwt]

Our trucks either have a short hose with a one way vent on the end which is a vent hose at the sending unit, or the hose runs to the engine compartment for an evaporative canister. If you have an evap canister under the hood, thenthe hose should go there. If you don't have an evap canister then it should have a vent cap and that is it. There is also a vent hose at the filler neck which should help equalize pressure. I have my short hose and vent cap routed to the back of the bed near the spare tire to minimize gas smell in the cab (I have dual tanks, so I have two vent hoses.) You can see the grey vent caps in the second pic.)

[travis401]

Originally Posted by edpdx

Any truth to the filler tube inside of the original metal filler neck?

What about the smaller hose that parallels the filler neck hose, could this be the problem? Collapsed maybe?

Ed

my 91 camaro's gas tank has a metal tube inside the filler tube as well as a tank vent. some newer vehicles got the tube within a tube design to let the pressure out from the newer gas nozzles.

[LostMy65]

Thanks tucsonjwt for the detailed post.

I'll be using this tank in my 66. So I will not have an evap canister. I'll plug the lines I don't need.
I'm pretty sure I know now which one is the fuel supply line.
I think the biggest one is the vent for the filler neck.
I just need to identify which one is the one that also connects to the fuel pump as the return line. I'll then plug the one that originally went to evap canister.
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