Friend’s truck won’t start

If you have the proper power to the coil in the run position, it's not the ballast resistor or bad wiring. If the starter cranks the engine over fine, it's not a battery problem either. Most likely the coil or ECU took a dump, has a bad ground, or, in rarer cases, the pickup coil in the distributor went bad. Verify that you don't have spark coming out of the coil......not at the spark plug. It's always possible you could have a bad rotor or cap.