Strange fueling issue.

I recently bought a 2002 Sonata from my parents, V6 ,automatic transmission with 42k miles. It runs great.

Yesterday I had to make about a 350 mile round trip to pick up my daughter. I filled the fuel tank early (8:00 a.m.) ambient air temp was approx 78 degrees. Had no problem and went out on the highway. Picked her up and started the return trip. Fuel gauge was at half full but wanted to top it off because the price was good. As soon as I removed the gas cap fuel started coming back out of the filler neck and wouldn't stop until I put the cap back on. Ambient air temp now aprox 98 degrees.

Still had enough fuel to make it home so I started out, again running fine. 45 minutes later I decided to stop and try to fill up again. No fuel coming out this time but as soon as I started to fill it the gas started coming back out the filler. I got maybe .60 cents worth in. Put the cap back on and headed out again, no problems. Air temp still 98 degrees.

Got below 1/4 tank and decided to try one last time. Removed gas cap and pressed the filler flap with my finger and noted the temp in the filler neck was a lot warmer than the outside air, still at 98 degrees. Attempted to fill up and once again after .60 cents gas started coming back out the filler.

Made it home and stopped at a mechanic I use on the way and he said it was probably the fuel tank evaporative system. He said I might be able to use a funnel and a gas can and slowly add fuel that way until I could bring it in to be repaired.

No where during all of this did the check engine light come on indicating an error in the fuel venting system.

This morning I got up and headed to the nearest station to fill my gas can and try to get a little gas in the tank. Ambient air temp again cooler at approx 78 degrees. Thought why not try again and inserted the gas nozzle just a small way into the filler. Did the quick squeeze over and over and got about $2 worth in. Tried fueling slowly and had no issues. Increased to about middle velocity on filling and had no issues. Squeezed the gas nozzle and filled up the tank no problems.

Anyone have any ideas what is going on? Am I just going to have to fill up in the mornings when it is cooler? Any chance the air temp is causing some sort of vapor lock in the fuel system?

Thanks.

Did you overflow the fuel tank?

The charcoal filter for evap system might be saturated with fuel, this helps to prevent less emission, if there's a problem the system should throw a code.

I learned my expensive lesson with overfilling the fuel tank years ago with an Audi. Now I don't even round it up the the nearest nickel. When it clicks off I am through.

And I haven't gotten an error code yet. The puzzling thing is having the problem during the heat of the day but not after the car sat overnight.

Are you using the same service station fuel pump?
Maybe the fuel nozzle is set too sensitive, or not calibrated.
The heat of the day(car tank) + fuel pressure from the service station will trigger pump off.

All of the instances where I had a problem trying to fuel the car were along the trip home, different stations and pumps. I have used these stations and various pumps at them as I make this trip enough to know about when I need to fill up and the spacing works out. This is the first time I have made this trip or used these gas stations with the Sonata.

The station that I had no problems at either before this trip or the morning after I had problems is the same station near my home but it was not the same pump.

The first problem didn't even involve a gas pump. Gas started spewing from the tank filler neck as soon as the gas cap was removed before a gas nozzle was ever lifted from the pump.

I am more puzzled now than ever. I have fueled the car three times since this happened and have not had an issue. All three times have been in the relative coolness of the morning. The first time the tank was almost empty, second time was at about a half tank and the last time was at about 1/4 tank.