schotzy350

I have a 2003 350z. I recently have come to a problem that is a real puzzle First I will say that all the gauges are right,no lights have come on,it sounds right and no odd smell,I also had it hooked up to that machine and nothing was wrong BUT....when I go to the gas station and fill her with gas I can start her at the gas station,the second time is very hard and the 3rd not at all. I have to let her sit for 4 hours and then she will start. After all that, from then on until I need gas again she runs like she is suppose to. Has anyone ever had this problem.?