1989 3.0L gets no spark

My 89 Caravan has a 3.0L. There is no spark from the coil. The new coils I have put in keep opening up the secondary windings. What would cause the overloading of the secondary in the coil. I have followed the troublshooting guide in the Haynes manual. I have replaced the brains, optical sensor in the distributor, the throttle position sensor, and the ground strap to the alternator. The only code stored was low/high voltage to the throttle position sensor. It has fuel, 10 volts to the coil when cranked, a good ground wire to the brains. I just want this van to make it through to the fall. Your help is greatly appreciated
Dan