I would get a volt meter and a wiring diagram and starting at the coil check voltages with the key off and then on.
ex: with the key on and the black wire from the meter on a ground you will see either a + or – 12 Volts. If there is no voltage then check the two contacts on the key sw. With the ignition on they should both have the same voltage on them. with it off only 1 of them will have a voltage