Why won't my car start sometimes?

My car a 1976 Lincoln will die randomly and refuses to start without cooling for an hour or two. The temp gauge is normal. There is no spark when it gets hot, there is when it cools. The shop said that it was the electronic ignition control module. They replaced and the problem persists. The battery, starter, starter solenoid, wires, ignition, spark plugs, spark plug wires, distributor cap and rotor are all good. Shop can't diagnose. Help!