Could somebody tell me what this item is please. It is black, circular about 6mm diameter and 2mm thick in this case. It has two leads which are soldered to the two opposing flat sides. It is part of a solid state ignition system
It is black, circular about 6mm diameter and 2mm thick in this case.
If it looks like one of these: -
It's still a disc thermistor as per the top picture but more modern devices fully encapsulate the soldered lead to prevent corrosion.