Unknown ignition issue
My dad has a 1992 Buick LeSabre, about a month ago it started to die after running about 10 mins or so. My uncle (a mechanic) replaced the crank sensor and thought he had it. It did it again so after working on it we all figured the ECM (the pad the coils sit on) was bad so a new one was put on. It will start and run for about 5-10 mins then shut down & will not restart until it cools off. We are at a lose here, my uncle has never seen anything like this. When it dies it gives no warnings, it just shuts down like you turn the key of, no spark at the coils, acc's work, no security light comes on or even flashes the engine will crank but does not even try to start. Any help would be appreciated.