no spark out of coil

I have power to the coil from the red and yellow wires. I replaced the coil, the plug, the ingnition modulator on the firewall and the modulator off the key under the steering column. I also replaced the coil wire and rotor and rotor cap yet i still don't have spark out of the coil.... I replaced the coil a second time,,, it ran ok until it cooled down the ran for about a minute, died and not spark again.... what can you advise about my problem

thank you for your help