This particular coil pack failed which seems to be a common problem on the GT86. I decided to see how they are constructed to see if there was any sign of why this one failed.
It sat in Dichloromethane for about two months to remove the potting compound and plastics. Occasionally i would take it out and remove some of the softened plastic and immerse it again.
Although the depotting process has caused significant damage to it we can see the major components.
A coil pack is basically a pulse transformer, there is an iron core with the high voltage secondary coil wound around and separated into sections, this is to provide isolation between the sections of the coil as the coil will generate many 10s of kilovolts. The primary winding can't really be seen but the thicker gauge wire is visible slightly at the top connected to the outer most conductors at the top.
Also visible is a diode and under the main connection terminals is the driver IC (a black rectangle) which has four connections. These connect to the external 3 contacts which provide GND, +12v and Trigger inputs, the fourth connection on the IC is the other side of the primary winding.
The spark plug connection has departed from the secondary coil as it was connected only to the fine wires of the secondary, it fell off during the depotting process.
Interestingly the driver IC does seem to be cracked, it's not clear though if this was caused by me during depotting or if it is the cause of the coil pack failure.