Will crank but does not start

I recently changed the fuel pump and battery because it was cranking up but it wasn't starting. It was good for about 4 days and then it did the same thing. It would just crank but it doesn't start. I started messing with the fuse box I noticed that once I unplugged and re-plugged the crank, ignition and fuel pump fuse sometimes it helps and it will start. So I was wondering if maybe it was the fuse box that's going bad or electric problems.