MSD weak spark
 

In my 77 911 with MSD and blaster coil i was not able to start it. I did a search on the board on weak spark. I also have a protronix as well. The coil wire off and to ground from coil one quarter inch away is yellow and weak. They are about 7 yrs old. I cleaned the ground strap. Question is can the MSD be tested or coil to find out whats the cause?. A step by step plan would be great thanks Chuck.