Just a curiosity. What is the purpose of that little side-hose in a gas tank filler tube? Before the invention of modern evap systems I can see its purpose, to allow the air in the gas tank to escape when refilling. But wouldn’t the evap’s venting system preclude the use of that side-tube in modern vehicles? The air in the tank gets pushed into the charcoal canister during refiling. Yet the side-tube remains??? Any theories?
I’ve come up w/a theory to explain the need for the side-tube. There’s air in the filler tube before beginning refilling. Some of the air gets pushed back into the tank by the fuel as refilling starts, but the side-tube gives the rest of the air another way to escape, back down the side tube to the tank’s airspace. So the purpose is to make it easier to refill the gas tank without the pump shutting off automatically from air pressure building up during refueling. None of the fuel-polluted air escapes to the atmosphere, it still gets pushed to the charcoal canister.
Simple terms air behind water…You would get a lot of splash back or the handle would keep clicking off…
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That sounds correct. I got to thinking that part of the reason must be b/c on modern-evap equipped cars the main filler tube’s far end is usually near the tank’s bottom & therefore submerged. So it is going to be hard for the air in the filler tube to move to the fuel tank’s airspace above the gasoline level. The little tube must provide an easy path for the air in the filler tube to move directly to the fuel tank’s airspace, doesn’t have to be pushed to the bottom of the tank and bubble up.