Asa":1fzwbxz0 said:
So, with an electronic ignition system like the DS2, is there an actual connection between positive and ground? Should I still see power there?
Breakerless ignitions simply use a solid state switch in place of the breaker points. As far as the coil is concerned, there is no difference whatsover. I will try to explain a bit, using breaker points as the example.
With power applied to the + side of the coil and the breaker points closed, current flows through the primary windings of the coil. This causes "electomagnetic lines of flux" to build up around the primary windings. Since the secondary windings are wrapped around in close proximity to the primary, these lines of flux also surround the secondary windings. At some point in time, these lines of flux get as big and strong as they can get at that particular applied voltage, and the coil is then said to be "saturated".
Now, we cause the breaker points to open, which stops the flow of current in the primary windings. The electromagnetic field can no longer be sustained, so it collapses. We know that moving a wire through a magnetic field causes an electrical current to be "induced" in the wire, and the same thing happens when we have a stationary wire (the coil windings) and a moving magnetic field (the collapsing lines of flux).
This collapsing electromagnetic field induces a current in the secondary windings, but since there are about 100 times as many windings in the secondary, there will be a whole bunch more voltage (and a whole bunch less current) in the secondary. One end of the secondary windings is attached to the spark plug (via the distributor cap) and the voltage builds up until it gets high enough to jump the spark plug gap. At this point, the voltage stops climbing, and pushes the current across the gap. It is the heat from the current that builds the fire, NOT the voltage. Voltage is needed to strike the arc, but once the current begins to flow across the gap(s) the voltage actually decreases.
Now we can close the points again and start the cycle all over. This all happens really fast.
This is, of course, Direct Current (DC) so all of the DC rules apply. With the points closed, the Negative side of the coil is at ground potential, so you will not read any voltage there. When they open, you will be able to measure 12 volts at the Negative terminal. I have used this many times to set the static timing on Volkswagens, just connect a test light to the Negative terminal and rotate the engine by hand until the points open; this will cause the test light to glow, indicating the points are open.
You can also test for spark by rotating the engine until the points are closed, energizing the coil, and manually opening the points. Be careful! This can be a shocking experience.
In theory, all of this applies to breakerless inductive ignitions (we won't talk about CDI today). If you just think of the module and pickup sensor as replacing the breaker points, it makes it easier to understand. I did over-simplify, and left a lot out, but I'm telling a story, not writing a thesis.
You can always test a coil just by jumpering power and ground to it, then removing the ground. It's best to connect a plug to ground as well, or the coil may discharge through you
Joe
arty: 
opsie: Oh noooooooo1 I fell like the guy who found out Miss Universe was a, um, guy.
:shockin: :splat: 
Hi Asa.Sounding good.
