Couldn't get the stupid spark plug adaptor in tight. I just got one of those 20$ gauges with a rubber hose and an adapter. I guess I will try again. And I will make sure to have the engine hot and hold down the accelerator pedal.

Can I hook up the gauge, then go to the car and crank the engine, then comeback and read the gauge? Or do I need someone cranking the engine while I look at the gauge?