Potential Evap System issues after over filling tank?

[BirdTRD]

While filling up with E85 today, the pump was running really slow so I flipped the "catch" down so I didn't have to hold it and the next thing I knew there was fuel spilling onto the ground.

Is there anything I need to do or check evap system wise, after over filling my fuel tank?

[BirdTRD]

OK, so after much research (because I really didn't know squat about it), I will try to answer my own question. Short answer...don't worry about it...despite all the doom and gloom you read about on the interweb about over filling your fuel tank and wrecking your charcoal canister with liquid fuel.

Summary: The fuel filler neck and associated vent tube both originate in the same place (or close). The vent tube comes into the filler neck at about the same area where the filling station fuel pump nozzle end would reach. The other end of both tubes, terminate in the fuel tank (well duh!) with the vent tube opening being slightly higher than the filler tube opening. Suffice it to say that the positioning of this vent tube in relation to the filler tube assists in the filling station pump auto shut off process. These 2 tubes have no direct connection to the charcoal canister so over filling the tank as I did will not cause liquid fuel to enter the charcoal canister, which was designed to handle only fuel vapors.

There is, however, another tube that runs along side the filler neck assembly that does connect to the charcoal canister by way of the canister pump module. This tube is open at the other end near the fuel filler door and is a fresh air inlet for the canister.

Maybe on some vehicles it's a different story but it appears that ours are safe...but please correct me if I'm wrong!

[RZNT4R]

The idea that the liquid and vapor side side aren't connected is a mistake, as they HAVE to be connected.

The valves that vent the fuel tank into the canister are at the top of the fuel tank and much lower than the fuel level when your's was overflowing out of the filler neck. These valves are designed to shut off once once liquid fuel reaches them, but nothing is ever perfect, they are only closed by little floaters and aren't meant to be submerged.

When filling a fuel tank, the majority of vapors that escapes to make room for liquid fuel escape through those vents, through the canister and vent valve, which is why many cars with vent valve failures are "hard to fill", very little escapes out the filler neck.

I'm not going to suggest you remove your canister to check, it's a PITA to get to, what's done is done, you'll know soon enough if you filled it up.

But I do wonder in what kind of 4th world gas station did you fill up that they had pumps so old they didn't have automatic shutoffs. Fuel nozzles are supposed to stop automatically even if you jam the trigger at full tilt, and that system has been ubiquitous for at least my lifetime.

[BirdTRD]

Gotcha. They are connected via the fuel tank (but from what I can tell, not physically/directly connected to each other)...still trying to figure it all out.

It's my understanding that during a normal fuel fill up, when the fuel level reaches the vent tube end inside the tank, the fuel then "backs up" into the filler neck which "Should" trip the sensor on the nozzle telling it to shut off.

I've used this pump on numerous occasions and never had it overflow like this so I suspect it has a problem, plus the fact that it was running VERY slowly may be another clue that there's something wrong with the pump/nozzle.

[RZNT4R]

Yes, directly connected to each other, as in, there is a hose directly connecting the top of the tank to the canister.

The only thing stopping fuel pouring into the canister are little floats that, ahem, float on fuel to close the valves.

[BirdTRD]

Originally Posted by RZNT4R

Yes, directly connected to each other, as in, there is a hose directly connecting the top of the tank to the canister.

The only thing stopping fuel pouring into the canister are little floats that, ahem, float on fuel to close the valves.

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