We began to experience the smell of raw fuel in about 2017
We did research and found that there were many similar complaints So many infact that it was very difficult to find a Pontiac cannister as they had been consumed in warranty repairs. I did find a couple but went looking for alternative sources and found other GM cars equipped with the Ecotec use basically the same canister that will fit with minor modification to one of the plastic tabs.
The factory repair involves dropping the fuel tank to access the canister and plumbing on top of the tank. This in turn requires dropping the rear suspension. Being a bunch of experienced shade tree mechanics and several engineers, this path was of course ridiculous.
So we pulled the trunk liner of the affected Sky and got out the moto tool and cut the top of the Mayan temple off. Brain surgery if you will.
Here are some pictures from later thread
Charcoal Canister... | Pontiac Solstice Forum
When we pulled the canister, it was contaminated with FUEL. When asked, the driver said that yes, they "topped off" regularly. When we cut it open it was obviously contaminated with fuel.
We replaced the canister and the valve put it back together, riveted tabs onto the Mayan temple top and screwed it back in place. It's been fine for a decade
Our conclusion based on inspection was
1) topping off will and does put fuel into the cannister
2) every instance of the same issue was associated with topping off
3) don't cut open a charcoal filter INSIDE THE GARAGE. It's very messy.
Could GM have made the fuel tank vent idiot proof? Probably but at what cost? The fix is to stop filling when the pump clicks off the first time. It is DESIGNED to operate that way. Back pressure turns off the filler. All good.
I don't view this as a defect. And I have been working with 50 club member cars and as soon as we got the word out about not topping off, NONE of those 50 cars have had an issue.
There are plenty of design tradeoffs that could have been done better. Start with them and suggest solutions.
Start with the flaps
And the buttress latches
And keeping crap out of the radiator
And the fact that if you turn the fan on HIGH for long duration you risk melting the wiring.
And the blend doors tend to fail at bad times and are a bitch to get at.
While you are at it, take a look at the passenger seat sensor. That is a real winner
I am somewhat mystified why the Charcoal canister has become the center of your focus when it is fine if operated correctly at least in my experience, and there are plenty of other "defects" to address first.
I did look up the cost of the canister and solinoid