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Discussion Starter · #1 ·
Hello guys. So First time trying to fire my new bronco after getting everything wired up and the engine dropped in. Using my spark plug tester I was able to determine that I do not have spark at the coil after trying to diagnose why I have a crank but no start. After looking at the coil with my probe I quickly realized that I only have one wire powering my coil? Does anyone have any input or a link to the EVTM? Tried searching but didn’t have any luck. Thanks.
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Or use this for reference:
 
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You should only need one wire for the coil, the coil grounds out through the mounting bolts.

As for why no spark… common issue is either the Ignition Control Module, or the Pickup Assembly located inside the distributor (under the rotor and metal dish).
 

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Discussion Starter · #5 ·
You should only need one wire for the coil, the coil grounds out through the mounting bolts.

As for why no spark… common issue is either the Ignition Control Module, or the Pickup Assembly located inside the distributor (under the rotor and metal dish).
Thanks everybody. Just one wire? My last bronco had 2 wires.
You should only need one wire for the coil, the coil grounds out through the mounting bolts.

As for why no spark… common issue is either the Ignition Control Module, or the Pickup Assembly located inside the distributor (under the rotor and metal dish).

thank you. I believe the wire I’m missing would be the wire to provide the power?
 

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No, 2 wires to the coil is correct. One supplies hot to the coil, & the 2nd is alternately connected to, & removed from, ground. That make & break connection to ground is what causes the coil to fire. Hot to the coil is only hot when the ignition is on.
 

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No, 2 wires to the coil is correct. One supplies hot to the coil, & the 2nd is alternately connected to, & removed from, ground. That make & break connection to ground is what causes the coil to fire. Hot to the coil is only hot when the ignition is on.
The coil does not fire… it supplies a constant amplified voltage of 20,000 to 40,000 volts… The distributor rotor arcs this voltage to to the cap, sending the voltage down the spark plug wires to the spark plugs.

On a Distributorless engine the.La yes the coil field collapses to to cause the spark.
 

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The coil does not fire… it supplies a constant amplified voltage of 20,000 to 40,000 volts… The distributor rotor arcs this voltage to to the cap, sending the voltage down the spark plug wires to the spark plugs.

On a Distributorless engine the.La yes the coil field collapses to to cause the spark.

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?





Ford Ignition Coil Test No Spark No Start Tests (4.9L, 5.0L, 5.8L)




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:



  1. The ignition control module (ICM) and the ignition coil get power (12 Volts).
    1. Power is supplied to the ignition coil thru' the wire labeled with the number 2.
  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).
  3. This PIP signal is then sent to and received by the ignition control module (ICM).
  4. 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.
    1. 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.
    2. The action of switching ON and OFF the primary voltage (ignition coil's battery power) is referred to as the switching signal.
  5. 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.
  6. From this point, the distributor rotor distributes the spark to the cylinders across the spark plug wires.
  7. By this time, the fuel injection computer is also injecting fuel into the engine, which the spark will ignite, thus the engine starts!
In the next page we'll jump right into the first ignition coil test."
 

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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?





Ford Ignition Coil Test No Spark No Start Tests (4.9L, 5.0L, 5.8L)




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:



  1. The ignition control module (ICM) and the ignition coil get power (12 Volts).
    1. Power is supplied to the ignition coil thru' the wire labeled with the number 2.
  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).
  3. This PIP signal is then sent to and received by the ignition control module (ICM).
  4. 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.
    1. 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.
    2. The action of switching ON and OFF the primary voltage (ignition coil's battery power) is referred to as the switching signal.
  5. 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.
  6. From this point, the distributor rotor distributes the spark to the cylinders across the spark plug wires.
  7. By this time, the fuel injection computer is also injecting fuel into the engine, which the spark will ignite, thus the engine starts!
In the next page we'll jump right into the first ignition coil test."
Then why doesn’t my coil primary flash but illuminates solid when hooked to a spark tester? But It’s flashing when hooked to a spark plug wire? Also I only have one wire on my coil coming from the ICM just like the OP.
 

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Then why doesn’t my coil primary flash but illuminates solid when hooked to a spark tester? But It’s flashing when hooked to a spark plug wire? Also I only have one wire on my coil coming from the ICM just like the OP.
I don't know. It makes no sense to me. I was taught by my dad when I was a kid that that's how a coil works. Anything I've ever read says that's how a coil works. The article linked in this thread says that's how a coil works. My coil has 2 low voltage wires connected to it. Any I have ever worked on since I worked on since my first engine almost 50 years ago have had 2 wires connected to them. My coil flashes the spark tester when connected to the coil wire & ground. Any time I've ever tested a coil wire on a working coil it throws a spark to ground. If you follow any testing procedure I've ever seen the spark tester should fire when connected directiy to the coil & ground.

Like I said, maybe there is some newer equipment that I don't know about. It certainly won't be the first or last time that's ever happened.

As for the OP's coil having only 1 low voltage wire, my guess was that was causing his no fire situation. How yours works with only 1 wire, I have no clue. I suppose today is the day I will learn something new. Now it's time to go wipe out the invasion of the yams.
 

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Discussion Starter · #12 ·
Thanks guys. I believe the 2 wires that are supposed to connect to my coil are connected to the radio noise capacitator instead 🧐 it sure if this guy messed with the wiring or what. So gonna try switching those around. I noticed that on my last bronco when I would use my spark tester on the coil I would get a flicker.
 

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Discussion Starter · #13 ·
Alright guys here’s a little follow up.. so as I mentioned I only have one wire going to the coil but 2 going to the radio noise capacitator. The 2 that you to the capacitator seem to be the 2 that should be going to the coil? I tested them both and they are both hot at all times. One of the wires going into the capacitator does not have another wire coming into it..
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