On any coil on a distributor vehicle I've ever worked on there have been 2 wires. The firing of the spark from the coil is timed to fire when the dizzy is connected to the correct spark plug wire position, but it happens when ground is disconnected from the coil. It's not producing high voltage in between. The collapsing field is how the voltage is kicked up. My 90, which I assume is very similar to his 89, works this way. When it had a no fire situation awhile back, part of the bench testing with no dizzy involved was making & breaking the ground connection to the coil to get it to fire.
If the coil produces constant voltage that fires when the rotor in the dizzy makes contact with the cap, why is there a pickup signal from the distributor? What is its purpose if not to signal the firing of the coil?
Maybe there is some sort of new constant voltage coil that I don't know about (I think that would called be a transformer & not a coil), but on anything I've worked on, as far back as a 37 Chevy, whether it had points or electronic ignition, used a system to make & break the ground connection to fire the coil at a precise time. I think Model Ts used a coil that just fired repeatedly without that precision timing, & then sent that random timed spark to whichever plug the dizzy sent it to, but there was still was a make & break of current to the coil to cause it to fire, & there wasn't a constant flow of high voltage.
From Miesk5's link in post 2 above:
"How Does The Ignition Coil Work?
Although the following explanation is not theory heavy or full of big technical words/terms, it will help you to see how the ignition coil works.
Knowing a little practical working theory will answer a lot of questions that the article doesn't answer.
It all starts when you turn the key and start cranking the engine and in a nutshell, this is what happens:
In the next page we'll jump right into the first ignition coil test."
- The ignition control module (ICM) and the ignition coil get power (12 Volts).
- Power is supplied to the ignition coil thru' the wire labeled with the number 2.
- The profile ignition pickup (PIP) sensor, which is what Ford calls the crank sensor, gets power from the ICM and as the engine cranks it starts to generate a crankshaft position signal (called the PIP signal).
- This PIP signal is then sent to and received by the ignition control module (ICM).
- When the ICM gets the PIP signal, it starts to switch the ignition coil ON and OFF by interrupting the ignition coil's primary voltage.
- What this means in plain English is that the ignition module interrupts the ignition coil's battery power ON and then OFF. How? By closing and then opening the Ground circuit this ignition coil's battery power needs to get to ground.
- The action of switching ON and OFF the primary voltage (ignition coil's battery power) is referred to as the switching signal.
- Once the ignition coil gets this switching signal, it starts to spark away and as you're already aware, this spark gets delivered to the center of the distributor cap by a high tension wire.
- From this point, the distributor rotor distributes the spark to the cylinders across the spark plug wires.
- By this time, the fuel injection computer is also injecting fuel into the engine, which the spark will ignite, thus the engine starts!