Having ECU Power Issue

[Chambers]

Hi all, I've been having occasional issues with starting my car. This morning I went to start my car and nothing, the engine wouldn't even turnover. Originally I thought it had something to do with the ECU main, in the fuse panel under the hood. But after swapping through 7 ECU mains the car still didn't stat, so I had to get a ride to my back up vehicle, not a big problem. I was thinking I would go to the dealership and get another main for temporary but then I thought it might be a ground, so I check the ground from the battery to the body and engine, and they were good, I don't know where any other grounds are so I haven't check them all.

When I got home about one hour ago I went out looked at the main, and the grounds again, then tried to start it, it turned over instantly but it took about four turnovers for it to start and it was running rough, so I popped the gas pedal and it started to idol fine. I then got hit with a big cloud of exhaust that smelled like unburnt fuel, it lasted for about one minute. So now I know the ECU is getting power because it pumped fuel into the cylinders and didn't burn it until I started it later. I'm not looking for the quick fix or the answer to all my problems, just suggestions and accounts if anyone else has had this happen to them. Where should I start to check the systems, and how should I go about the checks? Thanks.