I posted this in the section specific to Mercury but got no answers. So I'll try here.
My 2009 Merc 9.9 4-stroke will not start, and there is no spark on either cylinder. I am checking everything that I can, and now am testing the ignition coil after removing it from the engine. This coil has two wires, orange and black, on the primary side, and two spark plug wires on the secondary side. The black wire on the primary side is normally connected to ground, and I think the orange wire connects to the Electronic Control unit.
For the primary side, the manual's testing procedure shows to measure the resistance between the orange and black wires, and gives a nominal resistance that is very small. I verified that with my ohmmeter so I assume the primary windings are OK. For the secondary side test, the procedure shows to measure the resistance between the end of a spark plug wire and the orange wire on the primary side, and gives a nominal resistance value of just a few ohms. I did that, but instead of a few ohms, I measured an open circuit on all scales of my ohmmeter. This brings up two questions:
1. Why should the nominal resistance be so low (i.e.,a few ohms) for the measurement between the spark plug wire and the orange primary wire?? (I thought the primary and secondary sides would be essentially isolated from each other).
2. Since I measured this as being a very high resistance (an open circuit), does that mean the coil is bad?
Any help you can give me answering either of these two questions would sure be appreciated.