Coil question

When the car is running, how many volts should be at the positive side of the coil? I believe my coil is overheating because I get around 20 miles and the car instantly shuts off, no stumble or anything. Coil is hot as can be. Give it 10 minutes, she fires right up, go about 100ft and she kills again. Once everything cools down completely, she will go another 20 miles give or take.

Thanks in advance.
Author: jake