If you pressurize a fuel tank, can it back flow into the charcoal canister?

If you pressurize a fuel tank incorrectly to empty the fuel, can it back flow into the charcoal canister?

We paid for a $500 bill. There was about 10% water in the gas of our Sentra. It took the mechanics a while to get to the car, then a few days to figure out what was wrong. We could fill the car up with no issues the night before the car stalled out and we had to have it towed to our local garage. After they pressurized the fuel tank to empty it, we could not fill the tank, the car began spitting up liquid from what turned out to be the charcoal canister.

The mechanics are now telling us that the car would have had to be in deep water for this to have happened. We pretty much never take this car out in the rain because it has issues with the mass airflow sensor (It will blow if it gets wet). The car also has a body kit on it, which would probably snap if we drove it into a flood, which is what the mechanic is telling us had to have happened.

Please help. We’re out a chunk of money that we could use back. We already know the mechanic who worked on it was inexperienced because he did hours of unnecessary labor (If he had just checked the history of the car, he would have known about the recall it had and that it’s already been taken care of).

No, it cannot. And why would anyone pressurize a fuel tank anyway? Water seperates out and sinks to the bottom of the tank and can be either drained out or pumped out using a hand pump with a tube that’s dropped to the lower surfaces of the tank through the fuel pump hole.

Honestly, this whole diagnosis sounds flakey to me.

All fuel tank ports are at the top…

Pressurizing a fuel tank is risky business…The correct way to empty a fuel tank is to open the fuel line at the filter, jump the fuel relay and let the pump empty the tank…Takes about 10 minutes. The water comes out first…

If your tank was FULL to start, then yes, they could have forced fuel into the vapor recovery system and damaged the canister by attempts to “pressurize” the tank… Ask to see the equipment they used to do this…A rag and an air-hose???

Well, you should avoid this shop in the future because they’re going about it all wrong. Like Caddyman, I can see some guy now stuffing a red shop rag and a blow gun into the tank inlet.

They’re using the deep water thing as an excuse.

I have often emptied tanks using shop pressure regulated down to 3 psi. When the tank is full and the pump has failed it seems the most practical solution. I would strongly recommend that the regulators on shop compressors not be used for that purpose. I have a regulator used for low pressure spraying that has 1 psi increments from 1 to 15 and feed the air via a 1/4 inch hose while fuel escapes through a 3/8’ hose.

And, no amount of pressure will cause a liquid to be levitated. Over pressuring the tank will swell it, possibly to the bursting point. Even at 3psi swelling can be noticed on some tanks.