Taunus Ghia 82

Hello, I have a Ford Taunus Ghia 82, I made a full engine and I find a problem, I manage to turn on the engine (with gasoline) but it regulates for a few minutes and then suddenly begins to lose strength and stops. At that same moment it is as if a short current is acted since it is left without a spark for a few minutes, I must wait so that it has a good spark again. Download my new battery very quickly, change coil, and yet, it continues the same. I would appreciate some of help ... thank you very much