How many MPB (miles per bar)?

[Krusher]

MIL (Malfunction Indicator Light) = CEL (Check Engine Light) I know it's hard to believe... but it's true. Why do I call it a CEL? Because that's what the domestic industry calls it... that's what I'm used to... oh well, get over it.

Take a charcoal canister and soak it in fuel... it will get.... soaked... Why can the canister get soaked? Ok... I'm going to go a little bit into the system:

For the evap system self-test: Using the engine's vacuum, via the intake, the tank will be brought to a vacuum. If it is unable to pull a vacuum a code will set off the CEL. (Either small or large leak, depending on if the tank can pull a vacuum but not hold it, or not pull a vacuum at all... this can happen by the purge/vacuum valve sticking open/closed (checked by either forcing PIDs and/or plugging the vent per pinpoint tests), the gas cap o-ring not sealing the fill pipe(checking the condition of the cap or doing an actual pressure test on it), or an actual hole in the system(smoke testing... my favorite)) If it is able to pull a vacuum and hold it for a specified period of time it will release the vacuum into the charcoal canisters by sending a 12V signal (or completing the ground, depending on how the system is designed) to the purge valve solenoid which will open the tank to atmosphere. This line is typically vented to the fuel fill area. Now here comes the physics lesson...

Pull a vacuum and then let it go... what happens? 14.7# air will push it's way into the tank. Ever blow onto a liquid? What happens? It moves, doesn't it? Now put your face closer to the liquid and do the same thing (simulating putting more fuel into the tank)... get it close enough and your face will get a little wet... Now do this over the course of 8 years or 80,000 miles (epa mandated emissions warranty). My guess is that your face will be wetter then if you pulled your face away a little bit.

Your charcoal canister is getting the same thing... They are not designed to last forever... they do have a operational life since they are supposed to see a minimal, and engineered, amount of fuel vapor. If you put more liquid into the canister it will shorten it's life... by how much? Unknown to me, but if you're keeping your car don't you not want to spend about $300 for a canister until you really have to?

Although it seems that some people don't think that an eye dropper can fill a bucket one drop at a time...

If overfilling ruined the EVAP system then I guess there would be warnings about never parking a vehicle on a slope.

This is an engineering concern and a fuel tank, if you notice, has been designed to eliminate that concern.

Canisters get damaged while the car is running, running improperly and a faulty EVAP system, has nothing to do with topping off a fuel tank.

Guess what... when you top off the tank and you start the car... I know it's hard to believe, but the car is running... and your evap system will be conducting it's business with more fuel than was engineered to do so until you drive for a while!

Unfortunately I actually dumbed it down so that I didn't have to actually go into the operation of the system and just plainly say that overfilling the tank can cause problems... but since you found it necessary to try and "dumb it down" further by being technical I find it necessary to correct you.

Again, read the full post.

^Good write-up - It's like an episode of Mythbusters.

I find this amusing since the write up was written "Yeah, we'll dumb it way down." Mythbusters uses technical procedures to either prove or disprove a theory. They don't dumb it down...

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