Phasing the electronic ignition

This is kind of hard to explain.  Long story short, the electronic ignition fires three times per engine revolution: once for cylinders 1 and 2, once for 3 and 4, and once for 5 and 6–yes, there are a bunch of extra sparks.  There are three modules (one for each pair of cylinders) mounted on the engine, and they each need to be connected to the electronic ignition controller box.  For some reason, they don’t tell you which module goes to which output on the box, so you have to figure it out yourself.  To do this, we had to move the propeller back and forth in a position where one of the cylinders was at TDC.  This created a spark between the two leads on the module, which told us which module went to which pair of cylinders.

Here I am moving the prop and looking through one of the top spark plug holes to see the piston position.