Overfilling The Gas Tank - Good Or Bad Idea

[navylife59]

Have you ever been told by someone, "Don't do this or you will damage your car", "If that ever breaks, your motor will be destroyed", or "Use this to get better gas mileage"? I am willing to wager that you have. While these sages of wisdom are correct, for the most part, there is some advice out there that just aren't correct for your Scion and modern cars in general. One of these "truths" that does not directly correlate to the modern Toyota Brands is that of overfilling your fuel tank.

This has been a matter of debate since the first canister emission systems were developed in the late 60's to early 70's. Many a person will warn you not to overfill your fuel tank or you will end up with liquid gasoline in your charcoal canister. This fuel clogged canister would then cause venting issues in the fuel tank making the fuel pump work harder or eventually vapor lock and fail emissions testing resulting in a costly repair and possible fines. While this held true for a vast majority of cars in the past, modern evaporative emission systems have been redesigned to counter act these problems when overfilling the gas tank. Although car Owner's Manuals clearly state not to overfill the gas tank, people are fallible creatures and gas station fuel pumps don't always click off.

For complete detail on this topic and how it applies to your tC, please follow this link to the exposé in our Tech Article Knowledgebase.
http://www.club-tc.com/forums/tc-kno...html#post41005

[mtnbk]

attached you'll find the Toyota documentation on the system
http://tijil.org/Scion_Docs/Scion_06...r/2azfeemi.pdf

It clearly shows that the canister vents at the fill pipe opening.

[navylife59]

attached you'll find the Toyota documentation on the system
http://tijil.org/Scion_Docs/Scion_06...r/2azfeemi.pdf

It clearly shows that the canister vents at the fill pipe opening.

It actually integrated to the top, outside of the fill pipe at the end. When refueling, the pressure in the tank is equalized by venting to atmosphere via the charcoal canister and the air filter in this line. Further, this escaping air from the tank is considered clean air. The atmosphere, therefore, can not capture liquid fuel even if the tank was full and gasoline was pouring out of the filler neck. There is a notch on the lower edge of the boot that will drain excess liquids (fuel or water) over the side. There is a small notch just below the filler neck in the rubber surround. This just drains any fuel captured in the accordion surround, such as, from an overfill or excess fuel in the gas station pump hose when it is removed from the filler neck.

NOTE: You would not want to direct pressurized water from the car wash or pressure washer into the upper area of the refueling compartment for too much time as it could force water down into the fresh air line contaminating the air filter and charcoal canister. Just a quick spray should be enough to clean the area and not cause worry of contamination.


NOTE: This information was added to the Tech Article as it provided a somewhat clearer picture to the entire Evaporated Process.

[andwat13]

good knowledge!