car wont start and rpms clime when cars not running

[timothy shaffer II]

I have a 94 3.2 liter that won't start as part of a car fuel pump stays running when it should just Prime RPMs climb up on the car's got power to it when I first got it back wiring harness was spliced into to run amps and the person before did something with the battery cables and there's a black cord coming off of the alternator plug that I don't know where it goes and apparently when the old owner had it it would blow up batteries from the alternator back feeding