Hi Daniel, How goes it? The coil in question is the one that's attached to the ball trough housing. On the single player machines it comes 'on' at game start, which allows all the balls to roll down the trough and then they can be fired up to the playfield. Normally, when the first point/s are added in a game, this coil then releases which brings the ball stopper piece in the ball trough back to its resting postion. This means that the ball/s, once drained will not be allowed to roll back down the trough to be used again in the same game. However, in a 4 player machine, the balls need to keep rolling down for the various players, so I'm not sure just what's supposed to happen here.