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Talkwrench
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Ted
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The fuel tank does need to be vented either by way of the original vent line or a vented cap. Not venting the tank will give symptoms of a failing fuel pump or a line sucking air.
 Lorena, Texas (South of Waco)
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jrw429
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Is it true that a "vented gas cap" means that it vents only when there is vacuum in the tank - i.e. you've pulled fuel out while operating and the vent replaces that with air? What about venting when the tank is pressurized - i.e. when it heats up sitting in the sun? I've not figured out how this is handled, if at all, in old cars. I think the carbon canisters and extra plumbing came into effect around 70/71.
Jim - Erie Colorado, 1957 Country Sedan
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Hoosier Hurricane
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Jim: The older gas caps, (pre-emission standards) had simple vented caps with no check valves, they vented unrestricted in both directions, so the tank neither saw a vacuum nor pressure.
John - "The Hoosier Hurricane"

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paul2748
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What you might want to check is the sending unit for leakage. The gasket does go bad and you would get a gas smell when the tank is full or nearly full because of the leak. Talkwrench (4/6/2012) The fuel tank in "Fanny" has been replaced and I can see the breather/overflowpipe is not connected, it just hanging there next to the opening of the fuel tank, the new tank doesn't have any way of connecting it up. Should I have a fuel cap that seals or a fuel cap that vents somehow? Would it matter?
I am getting a strong fuel smell, No leaks that I can find, and a new trunk seal. I usually get it when the tank is more than 2/3rds full and if I have people [load] in the car. if I open a window it really sucks it in. phew!
54 Victoria 312; 48 Ford Conv 302, 56 Bird 312 Forever Ford Midland Park, NJ
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marvh
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Paul's correct on the sender unit leaking.
If the screw holes in the gasket are too large it will also leak along the screw threads even though the surface between the tank and sender unit is leak tight. The gasket screw holes have to be tight on the threads to prevent the leaking. I have seen this when people have made their own gasket.
marv
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Talkwrench
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oldcarmark
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Be very careful working around gas tank.Any spark from a power tool etc can have bad results.

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Talkwrench
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