My 300 has failed to start twice, even after sitting for two days. The first time, it was towed to the dealer and the service advisor attempted to start and no-go; however later that same day, when the technician attempted, it started up fine. The dealer tried to duplicate the problem for several days, but no success. There was no check engine light or code. Then about three week later after fueling up at the service station, it failed to start again. I pushed to a nearby parking space and let it sit overnight until I could have it towed the next morning. The next morning, the two driver also tried to started without success; however, once it was downloaded at the dealer, the tow driver tried to start it again, and it fired up....no codes or check engine light. The dealer kept it for a week and has not been able to determine the problem, however, they suspect it maybe the fuel pressure sensor. The replacement cost is $1400, but they wont guarantee this will fix the problem. I am reluctant to spend $1400 on a hunch; is there a way to determine if the sensor is intermittent? How difficult is it to DIY the fuel pressure sensor and does anyone have a part#, as I have been unable to find the OEM number. Could it be the fuel pump or regulator? I don't suspect an electrical problem because there is not lost of cranking power and no codes or check engine light.