Coil Test to Make sure the Coil is Good.
Here's another method of testing coils, which is more "low-level". This will test if the coil itself is good, and that there is power at the coil.
Game is on and in "attract" mode, and the playfield lifted.
On games WWF Royal Rumble and later, close the coin door.
Connect an alligator clip to the grounding strap by the playfield prop rod.
Momentarily touch the other end of the alligator clip to the GROUND lug of the coil in question. This will be the coil lug with the single (thinner) wire attached. The ground coil lug is also the one with the non-banded side of the diode connected. If accidentally the alligator clip is touched to the power side of the coil, the game will reset and/or blow a fuse, as the solenoid high voltage is being shorted directly to ground.
The coil should fire. If the coil does not fire, it may be a coil that is L/R relay selected. Push the green coin door button into the down position, and press the black button. This will put the game in diagnostics mode. This should de-energize the L/R relay, and turn the power to the coil in question on (if the game is Time Machine to the Simpsons, ground transistor Q29's metal tab to energize the L/R relay, because the coil/flashlamp banks are reversed).
If the coil still does not fire, either the coil itself is bad, or the coil's fuse is blown causing power to the coil to be absent.
"A Coil Doesn't Work, What To Do."