Hi mate, get your self a schematic and start with basics, fuses, live's and earth's, as for the fuel pump wired from the side lights wasn't that modification to steal one in the 90's. Anyway this is an easy repair, there a diagram knocking round on here of how to rewire it. If you have no luck finding it, pm me your email and i will send it to you.

Good luck, it will all come good in the end.