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Kia Optima Fuel Tank Overfills

I have a Kia Optima, 2007. I’ve had the car since 2009 and about a year after having it, started having trouble filling the gas tank. I do NOT top off. However, if I allow the tank to fill until the pump shuts off, more often than not, gas comes overflowing back out of the car. Not only is it an environmental concern, but it’s also a waste of money because I’ve now paid for the gas that’s pooling on the ground. The amount that comes out varies, but is typically at least a few cups worth. This has happened to my husband as well when he has filled my tank. Neither of us top off. I’ve brought it to the dealership multiple times and they can find nothing wrong. Someone suggested it was more an issue with the gas pumps not shutting off when they’re supposed to, but this happens at varies stations. Plus, no one else I know has this issue, so I can’t imagine how this is a gas station issue. The car was rear-ended 6 months after I got the car and the side with the gas tank was pushed into another car, but the damage was minimal (the point of impact was the opposite side). Any ideas on what could be causing this would be greatly appreciated. Again, we do NOT top off.

I have researched your fuel tank vapor recovery system and you do have a Onboard Refill Vapor Recovery system that vents the escaping tank vapors through the vapor recovery canister during filling. When the tank is filled to the requisite level a float valve blocks the venting; the remaining vapor is compressed until the fuel starts backing up the fill pipe; and then the nozzle shuts off.

There will still be pressure above the tank fuel trying to push the fuel back out the fill pipe. There usually is an antiback flow valve at the entrance of the tank to keep the fuel from pushing back up the fill pipe. It also acts as an antispill valve incase of a roll over and breach of the fill tube.

In my research I didn’t find any reference to this antibackflow valve. So you might contact Kia and ask them if the tank has that valve. It is possible that the valve is damaged or otherwise ineffective. It is most likely that the only way to replace the valve is to install a new fuel tank ($537 plus 1.8 hours of labor). You might just put a set amount of fuel into the tank at each refueling i.e. if you are down 12 gallons only put in 10.

On further research I found reference to the valve affecting back flow. Kia calls it an ‘fuel shutoff valve’. There isn’t a callout for a replacement valve so it is part of the fuel tank. The valve could well have been damaged when the fuel collided with the side of the tank in the rear end accident. If you can convince your auto body shop or insurance company that this problem is related to the accident, you might get the repair covered under your insurance policy.

Hope this helps.

This does indeed sound like something wrong with a faulty valve or leaking or collapsed tube of some kind in the fuel tank evap system. Evap component failures is a fairly common problem reported here btw. Not just for your car, for an assortent of cars. I suspect you sustained some damage that hasn’t been corrected in the prior crash.