Thunderbolt IV, no spark

[1010kristi]

I was also getting no spark on my Thunderbolt IV V8. I have followed every suggestion in this post to troubleshoot the problem. I have replaced the coil (twice because I thought the first one might have been bad), the ignition sensor, the ignition module and all the spark plugs in the correct order. I’ve checked every wire and all the grounds for proper voltage but still no spark.

Finally, after 10 days of pulling my hair out, I followed the last suggestion in this thread to connect a random extra wire to the negative post on the coil. When I rapidly strike it to ground I FINALLY get a beautiful blue spark.

But now I don’t know what to do with that information. Obviously I can’t just have a random wire constantly sparking at the ground to cause a spark. My question: how do I find out why that is the only way to get a spark, remove that wire and fix the culprit?

PS I apologize if adding to this thread is not the appropriate way to add this question. I’ve never used a forum but this thread has been so incredibly helpful!!

 

[achris]

Hello 1010kristi and :welcome: aboard.

I have moved your post to a thread of its own, as we have a 'no posting to threads more than 90 days unless you're the OP' request... And that thread was 4 years old.

I was also getting no spark on my Thunderbolt IV V8. I have followed every suggestion in this post to troubleshoot the problem. I have replaced the coil (twice because I thought the first one might have been bad), the ignition sensor, the ignition module and all the spark plugs in the correct order. I’ve checked every wire and all the grounds for proper voltage but still no spark.

This tells me that the module, coil and sensor are not the problem.

Finally, after 10 days of pulling my hair out, I followed the last suggestion in this thread to connect a random extra wire to the negative post on the coil. When I rapidly strike it to ground I FINALLY get a beautiful blue spark.

That means the extra wire you used is acting like a set of points would, making and breaking a current flow through a transformer (coil) and each time the field collapses, a spark is generated.

But now I don’t know what to do with that information. Obviously I can’t just have a random wire constantly sparking at the ground to cause a spark. My question: how do I find out why that is the only way to get a spark, remove that wire and fix the culprit?

Have you looked at this thread? -> https://forums.iboats.com/forum/engi...n-systems-work

From the diagram of the wiring, and you getting a spark with a bit of wire on the coil negative, I would assume a few possibilities.

1. A bad (constantly closed) shift interrupt switch. Try disconnecting it.
2. A break in one of the interconnecting wires between the module and the sensor. Check for 12 volts on the white/red wire of the sensor. Slowly turn the engine and see that the white/green swings between 0 and 5 volts as the rotor 'window' passes it.
3. A break in the grey wire between the module and the coil negative.
4. A wire connected to the wrong place. Ensure you have the wires connected right...

If you have the ignition module mounted on the distributor, check that you have a good ground to the distributor. (The fact that it's bolted to the engine block does NOT mean it has a good ground. It needs a wire from the engine harness to the distributor body.)

It would also be helpful to know which year (and preferably serial number) of engine you're working on.

PS I apologize if adding to this thread is not the appropriate way to add this question. I’ve never used a forum but this thread has been so incredibly helpful!!

Apology accepted.

Chris..........

 

[79Invader]

There should be two white wires with green stripes on them going to the pickup sensor on the dizzy. One goes to the module, and the other goes to the shift interrupt switch mounted on your controls. Follow the wires and disconnect the one that goes to your controls. If your shift interrupt switch has went bad, it will constantly ground that white/green wire resulting in no spark. Disconnect the one that goes to your controls, and try to fire it up.

Did you replace the module with a known good one? It's possible the module you put in is bad resulting in the same issue.

By you striking the (-) side of the coil to ground just tells you that your coil is good and has power, which is good, but doesn't do much else for you, since that is purely how a coil works.

I have a feeling your shift interrupt switch is your culprit.