I need some advice please! I have a 1996 suburban with a 7.4 454 and getting no spark. Changed crank sensor, cam sensor or pick up coil, coil, plugs, wires, cap and rotor. I've checked to see if if there is power to wire harness plugs to cam, crank, and coil and all fuses with ignition on and off and seem to be getting power the way it intended leads me to believe it's not the ignition switch. Any ideas? Anyone? Please help?