Re: No Spark in Lower Cylinder.. please help
I am using a voltmeter. Between the two brown wires I am seeing a voltage when I crank the engine over (which appear to go to the top cylinder eventually. Between the black and white wires there is no voltage when i crank the motor over. I then did a continuity check between the white wire and and the coil to the lower cylinder and they are connected. The problem is before the power pack I Believe. Any other troubleshooting techniques? Thank you
Jason
If you expect to check it with a meter you need what is called a DVA meter pr a DVA adapter for a digital multimeter.
The other way to check it is just good old common sense and a knowledge of how it works.
The two brown wires come from the charge coils in the stator. "Charge" refers to charging the power pack, not charging the battery. They provide an AC voltage of around 300 volts, which is rectified to DC and stored in a capacitor in the power pack. So it is obvious that if it charges the capacitor for one cylinder it is also charging the capacitor for the other cylinder because both cylinders use the same capacitor.
The black and white wires come from the sensor that tells the power pack when to fire. The sensor generates a weak voltage between the two wires. Every half turn of the flywheel, a voltage is generated as magnets in the flywheel go past the sensor. The only thing that makes the power pack "know" which coil to fire is the voltage from the sensor reverses in polarity for every half turn of the flywheel. So again, if it is generating +/- on one half turn, it has to be generating -/+ on the other half turn. There is just no way it can do one and not the other. Well unless something happened to one of the magnets in the flywheel, which is unlikely.
The power pack contains the capacitor and two SCR's. SCR's are switching devices. They are switched on and off by the sensor voltage. The two SCR's are switched by opposite polarity. So, when one of them "see's" a (+) voltage from the sensor, it turns on. Likewise, when the other one "see's" a (-) voltage, it turns on. As the two SCR's turn on and off they discharge the cpacitor to it's respective coil. In between discharges, the capacitor is recharged by the charge coils as already explained. Hence, the term "CD" ignition.
So, with all that explanation, if you have spark on one cylinder and not the other, you have a bad coil or a bad SCR within the power pack. Take your pick.
Whew! That's enough typing for one day.
