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non vented gas tank #79253
06/24/08 06:03 PM
06/24/08 06:03 PM
Joined: Aug 2007
Posts: 6,089
Valencia, España
NachoRT74 Offline OP
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NachoRT74  Offline OP
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Valencia, España
Can a non vented gas tank affect on carb fuel level making some bad air/fuel mixture rate ?

everytime I fill the tank, LOT of pressure is released.

Dunno if the fuel cap I have is vented or not, or maybe got damaged.

My gas tank does have apparently a venting valve linked with a 1/4" hose to a tee on top of gas tank hump ( 74 ) the valve is built in on a fuel line section bolted to the body, and does look similar to a PCV valve inside the 1/4" fuel line.

My car does not have canister or any return line ( yet ), just the line to the gas pump AND the stuff described above like a valve.

Note: when I was installing the new fuel sender unit when I hammered the lock ring to lock, fuel began to release from the line. Hose wasn't fit yet and cap was installed.

Due the high preassures, oftenly, specially on a full thottle and irregular surface street, a whistle is able to be heard

Last edited by NachoRT74; 06/24/08 06:15 PM.

With a Charger born in Chrysler assembly plant in Valencia, Venezuela
Re: non vented gas tank [Re: NachoRT74] #79254
06/24/08 07:24 PM
06/24/08 07:24 PM
Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
70Cuda383 Offline
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you need some venting from somewhere, either a vent line or the filler cap.

as gas comes out and is used by the engine, air has to get in somewhere, or you get negative pressure/vacuum inside the tank, eventually this will suck back harder than the pump can pull forward, and the fuel flow to your engine stops until the pressure is equalized.

so yes, if your tank truely is not venting, it can cause problems with your engine.


**Photobucket sucks**
Re: non vented gas tank [Re: 70Cuda383] #79255
06/25/08 02:03 PM
06/25/08 02:03 PM
Joined: Aug 2007
Posts: 6,089
Valencia, España
NachoRT74 Offline OP
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NachoRT74  Offline OP
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OK I understand that, needing replace the gas with air when gas pump is demanding the gas... but my problem ( if is a problem ) is backward... PRESSURE inside the tank, not Vacuum


With a Charger born in Chrysler assembly plant in Valencia, Venezuela
Re: non vented gas tank [Re: NachoRT74] #79256
06/25/08 02:34 PM
06/25/08 02:34 PM
Joined: Jan 2003
Posts: 1,092
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BRawls Offline
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BRawls  Offline
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The only way to get pressure in the tank is the air inside the tank expanding due to increase in temp. If you have either vacuum or pressure as the problem, the fix is the same - Tank needs to be vented. I try a vented cap first.

Re: non vented gas tank [Re: NachoRT74] #79257
06/25/08 02:37 PM
06/25/08 02:37 PM
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Posts: 3,054
USA
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b54406barrel Offline
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USA
Gas caps for non-vented tanks should only pass air in, not out. As an example, If it was vented both ways on a mopar with the behind the license plate filler, gas would spill out of the vent hole every time you took off. It's 'normal' to have some pressure build up from the fuel slosh as air can only go 'in' through the vent hole, not out, if it's working properly.

Re: non vented gas tank [Re: BRawls] #79258
06/25/08 02:55 PM
06/25/08 02:55 PM
Joined: Aug 2007
Posts: 6,089
Valencia, España
NachoRT74 Offline OP
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NachoRT74  Offline OP
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Valencia, España
Quote:

The only way to get pressure in the tank is the air inside the tank expanding due to increase in temp. If you have either vacuum or pressure as the problem, the fix is the same - Tank needs to be vented. I try a vented cap first.




Gas emission due evaporation makes pressure too... Just hitting the tank will prove that ( like a Coke ). Remove fuel sender hose and hit the gas tank and will see how gas beging to get out throught sender outlet due the gas pressure. It does happen to me this while replacing fuel sender, when hit with a screwdriver and a hammer to lock the sender lock ring. Cold enviroment.

mmm about gas cap... I got a Stant unit. Dunno remmeber the number. Is lock kind. I think I still have the box somewhere


With a Charger born in Chrysler assembly plant in Valencia, Venezuela
Re: non vented gas tank [Re: b54406barrel] #79259
06/25/08 02:59 PM
06/25/08 02:59 PM
Joined: Jan 2003
Posts: 25,200
Upper Midwest
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MoparforLife Offline
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Upper Midwest
Some of tanks were vented to the charcoal canister on cars equipped with them.
When eliminating this type of system I usually buy a vented gas cap. Most sizes are available at parts houses or if it is a unique design or that is special to the car or truck a small hole can be drilled above the cap sealing gasket into the the center (tank side of the cap). Unnoticeable but functional. All the tanks one way or another have to be vented to breath. I have seen tanks with a plugged breather literally suck the bottom of the tank up before the car stalled from lack of gas.

Re: non vented gas tank [Re: MoparforLife] #79260
06/25/08 04:51 PM
06/25/08 04:51 PM
Joined: Aug 2007
Posts: 6,089
Valencia, España
NachoRT74 Offline OP
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NachoRT74  Offline OP
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Valencia, España
Quote:

I have seen tanks with a plugged breather literally suck the bottom of the tank up before the car stalled from lack of gas.




well I'm having just right the opposite... tank BLOWED and when open the cap, beside the release of preassure I can heard the tank getting back LOL


With a Charger born in Chrysler assembly plant in Valencia, Venezuela






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