Ignition coil HV power supply damage?
This circuit depends on the quirks of the two-wire lighting dimmer you use. Some will will not work into the 'interesting' load, and most will not work below some minimum load.

You can modify the circuit to be more robust (and to test the dimmer!) by first wiring the dimmer in series with a suitably sized filament bulb. This provides a 'tame' load, and importantly provides a visual indication of whether it's working or not.

Now you can put your ignition coil + series capacitor combination across the dimmer terminals (or the lamp terminals, but the dimmer terminals reduce emission to the house wiring, a little).

SAFETY

Do follow the instructables' safety advice, and to Jack's in comments (use an isolation transformer). Mains voltage is made somewhat less dangerous by the fact that it won't jump through dry clothing. However, what you've built is an arc starter, the iggy-coil output will jump half an inch through air or clothing, and that arc could then connect you to mains. Several people have died in this way, with an un-isolated mains-powered high voltage generator connecting them accidentally to mains.