Gas tank venting -'67 Olds C.S.
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Gas tank venting -'67 Olds C.S.
Gentlemen,
I'm soliciting some new information about my (stock) gas tank venting problem. It will spew fuel from the smaller vent tube while travelling (tank under pressure with non-vented cap, vents on rear driver side next to filler pipe).
Blowing through smaller vent tub (at filler) creates the sound of bubbles within the gas tank (tank 1/2 full and level). Obviously, the end of the small tube is below the level of the fuel.
Larger vent tube, when removed is perfectly clear, but the vent hole into the tank , about 2 " into tank is closed, blocked solid. ( What is this large tube designed to do???? Why is it larger than the other??)) Before I try to drill out whatever is blocking vent tube in the tank I'm seeking any information about that vent opening. Has anybody ever tried to a) blow through large vent and should it be a clear vent tube, or b) is there some kind of valving or material to slow the loss of fuel?? Could this material have hardened in the tube and is now causing the blockage??
Has anybody every opened up tank to see if vent is clear... ( or have an older tank lying around that you can put wire into it to indicate if opening is clear???). Why is the smaller vent tube "under" the fuel level if it is a vent??
The situation is that the tank can build pressure and with one tube blocked (by design?) and one under the fuel level, gas will spew out!
I'm presently using a VENTED cap ( only allows air INTO tank. Does not relieve pressure).
Does anybody know of a 2 waY VENTED CAP THAT WILL ALLOW TO relieve pressure ( but not allow gas to slosh out)? Yr, Make, Model of vehicle, or cap #
I've ordered the gas vent surge collector, but to my knowledge, this will collect fumes from the tank... I don't think that it will stop or collect fuel under pressure. BTW. on a trip to Tampa, I lost about 4 gallons over 80 miles!!!!
There are several older threads concerning the collection of small drips, but nothing addresses the tube functions and blockages.
Any insights will be appreciated.
Hotrodder
I'm soliciting some new information about my (stock) gas tank venting problem. It will spew fuel from the smaller vent tube while travelling (tank under pressure with non-vented cap, vents on rear driver side next to filler pipe).
Blowing through smaller vent tub (at filler) creates the sound of bubbles within the gas tank (tank 1/2 full and level). Obviously, the end of the small tube is below the level of the fuel.
Larger vent tube, when removed is perfectly clear, but the vent hole into the tank , about 2 " into tank is closed, blocked solid. ( What is this large tube designed to do???? Why is it larger than the other??)) Before I try to drill out whatever is blocking vent tube in the tank I'm seeking any information about that vent opening. Has anybody ever tried to a) blow through large vent and should it be a clear vent tube, or b) is there some kind of valving or material to slow the loss of fuel?? Could this material have hardened in the tube and is now causing the blockage??
Has anybody every opened up tank to see if vent is clear... ( or have an older tank lying around that you can put wire into it to indicate if opening is clear???). Why is the smaller vent tube "under" the fuel level if it is a vent??
The situation is that the tank can build pressure and with one tube blocked (by design?) and one under the fuel level, gas will spew out!
I'm presently using a VENTED cap ( only allows air INTO tank. Does not relieve pressure).
Does anybody know of a 2 waY VENTED CAP THAT WILL ALLOW TO relieve pressure ( but not allow gas to slosh out)? Yr, Make, Model of vehicle, or cap #
I've ordered the gas vent surge collector, but to my knowledge, this will collect fumes from the tank... I don't think that it will stop or collect fuel under pressure. BTW. on a trip to Tampa, I lost about 4 gallons over 80 miles!!!!
There are several older threads concerning the collection of small drips, but nothing addresses the tube functions and blockages.
Any insights will be appreciated.
Hotrodder
Registered User
Joined: Feb 2011
Posts: 881
From: Ironton Ohio 45638
Nope, 67 is non vented cap.
Normally if a tank has a vent to the atmosphere the cap is non vented.
And the other side of the coin, a tank with no vent to the atmosphere has a vented cap.
I cured my (Now gone) 67 convertible by replacing the vent hoses, adding clamps to the hoses, making sure there were no kinks in the new hoses. making sure they went in a continuous up direction to where they end in the area of the fill neck where there was a metal strap thing to hold them, and putting a tight fitting piece of a lawn mower air filter in the end of each hose. Problem solved. IMO the air needs to move very slowly, with little volume of air moved. This prevents any possibility of sloshing fuel out the vents because the fuel can not displace the air fast enough to slosh out.
It worked for me.
Normally if a tank has a vent to the atmosphere the cap is non vented.
And the other side of the coin, a tank with no vent to the atmosphere has a vented cap.
I cured my (Now gone) 67 convertible by replacing the vent hoses, adding clamps to the hoses, making sure there were no kinks in the new hoses. making sure they went in a continuous up direction to where they end in the area of the fill neck where there was a metal strap thing to hold them, and putting a tight fitting piece of a lawn mower air filter in the end of each hose. Problem solved. IMO the air needs to move very slowly, with little volume of air moved. This prevents any possibility of sloshing fuel out the vents because the fuel can not displace the air fast enough to slosh out.
It worked for me.
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