Cinnamon 75 Duster \
If nothing else, I have gotten a bit of an edumacation over the last couple weeks while working through this starting problem. I have a good bit of past experience working with electronics, but not much with ignition. So I am writing this post as much to put together what I learned as to help anyone else who might be in over their head figuring out ignition gremlins.
Good drawing of a 5 pin system:
http://www.mymopar.com/downloads/Dual_Ballast_5pin.pdf
More good stuff here:
MyMopar - Mopar Forums & Information - Mopar Wiring / Electrical
Unless you seek out an old 5 pin, most controllers available are now 4 pin and are designed to work in place of either a 4 or 5 pin original. They get full voltage to pin 1 and do their own limiting internally. Pin 3 is eliminated and so is the need for the 5 ohm side of the resistor. Most dual resistors available are going to have 5ohms on one side and 1.2 on the other. Not .5 like some of the old drawings show. Which I assume is fine since the 4 pins using single resistors always were 1.2 from what I can tell.
How it works...
Beginning with the coil, cause it's really the heart of the system creating the high voltage zap needed to spark. It's (-) terminal, the coil ground, goes to pin 2 of the module and opened and closed by a transistor in the module. It is very important that the ignition module has good contact with the body to establish the circuit ground. In addition to scraping a little paint off, I added a star washer to get a good bite under one of the mount screws. The transistor functions similar to a relay. It opens and closes to interrupt the ground circuit when the base is triggered by the pickup in the distributor that is connected to pins 4 and 5 of the module. That happens each time a lobe on the reluctor passes by. You can do this with distributor out and just the 2 wire pickup plug connected. With the key in start position the (+) of the coil is provided battery volts. Spin the dist by hand and you should get a nice spark from the coil tower wire to any ground.
If everything works as it should...Turn key to start position and engine begins to crank. Reluctor triggers the transistor, which cuts ground to the coil to collapse the field and generate the high voltage in the secondary at the right moment to fire a spark in each cylinder as they reach the correct position to be ignited. Engine starts and ignition now goes to run position. Battery power no longer goes to the coil(+). Instead it is powered by the alternator limited by the 1.2ohm ballast resistor. Otherwise the circuit continues to work the same.
Anyway that's my 2cents on ignition. :rolleyes: