We have a JD 5400 that hasn't run in a while. A few hears back, someone trashed the fuel pump trying to get the solenoid off. Put a new pump on(I've heard it is the wrong one, but I don't trust the person who said do.). A couple of years later, my great-uncle(the source) filled the tank with gas, supposedly messing up the injectors. I know it didn't run right when it was parked, smoking and no real power. I'm wondering what could be wrong and how to fix it. Any advice?