Hello, I have searched this issue several different places and it seems like a few people have had a similar problem but not exactly the same.

I have a 2003 350z that will crank on the first attempt then I have to turn the key back a notch, wait ~3-5 seconds for everything to reset then it'll start up (slowly) on the second try.

I've tried injector cleaner that was suggested to someone else, that didn't help the problem. A fellow who was having a similar problem replaced the spark plugs and the problem went away for a week then came back.

I think perhaps it could be something to do with the fuel pump assembly. The car has a return fuel line (which I don't think came stock, not sure) and an adjustable fuel pressure regulator. I just purchased the car a few days ago and it was set on 44 psi. I upped the pressure to 51, which I think is closer to stock, but that hasn't fixed the problem either. Has anyone had and fixed this problem or have any suggestions? Thanks in advance for any tips.

 

too many variables.... take it for proper diagnosis