Thanks to all who responded. I will be more attentive to grounding. I plan to make a few wires as per Mumbles photo and keep them with the compression tester.
No, they are solid brass rod which has been turned on the one end and drilled on the other for soldering the wire on. The groove was to make it snap into the spark plug terminal. A piece of solid wire, with the end bent back on itself would probably work to.
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