Ignition question

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Ignition question

Postby Jason_Coffey » Sun Oct 27, 2013 3:29 pm

What would cause spark to jump from the coil wire on the coil to either the negative or positive posts on the coil. I just noticed this was happening. I pulled the coil wire boot back to ensure the wire is seated properly, and inspected the wire to make sure it didn't have any cracks or wire showing. The wire is new by the way. So, I'm unsure what would cause this.
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Re: Ignition question

Postby Eugene » Sun Oct 27, 2013 3:54 pm

That's the path of least resistance.

Try using some rubbing alcohol to clean up the top and interior of the coil wire tower. And the inside of the coil wire cap/boot and coil wire. Make sure both the wire, boot, and coil are dry.

Check for a crack in the coil wire tower.
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Re: Ignition question

Postby Gary Dotson » Mon Oct 28, 2013 7:17 am

As Eugene mentioned, that's the path of least resistance. That means that either there is low resistance in the areas mentioned or there is high resistance elsewhere in the secondary circuit. If the items he mentioned don't solve the issue, check things out further down the line, make sure the cap & rotor are in good shape, all plug wires are in good condition & properly seated, connections at spark plugs are secure and that the spark plugs are in good condition. Even with high resistance elsewhere in the system, it really shouldn't arc at the coil tower but sometimes they do. You need to find & fix it, though, cause continued arcing at the coil will eventually damage the coil tower, then you'll never stop it from arcing.
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Re: Ignition question

Postby Smokeycub » Mon Oct 28, 2013 7:59 am

:Dito: I agree with the others, however -
Jason_Coffey wrote: The wire is new by the way
Be sure the wires are solid core, non resistance plug wires.
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Re: Ignition question

Postby Jason_Coffey » Mon Oct 28, 2013 8:11 am

The wires, plugs, cap, rotor and coil are new. I recently converted my cub to 12v and installed the 12v petronix kit in the distributor. I also increased the plug gap to .030. I have checked all the wires, connections, and the coil tower for cracks. Everything looks fine. It seems to only arc if I disconnect/reconnect the positive battery cable. It does not seems to happen while running or during normal start up. I'm baffled.
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Re: Ignition question

Postby Jason_Coffey » Mon Oct 28, 2013 8:13 am

I will verify that the wires are solid core tonight. I am not sure about that. I bought a wire kit for a four cylinder tractor from a tractor supply. So, I figured it was what I needed.
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Re: Ignition question

Postby Bus Driver » Mon Oct 28, 2013 8:20 am

Sometimes such arcing starts because of dust and other fine debris on the components. The arcing soon damages those surfaces and makes future arcing even more likely. A good cleaning is possibly the cure.
What is the spark gap presently for your plugs?
If solid core ignition wires are not available locally, Summit Racing has them with stainless steel conductor. Not low cost, but should be durable.
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Re: Ignition question

Postby Smokeycub » Mon Oct 28, 2013 8:29 am

Not sure the Petronix system would require a .030" plug gap but I think I would gap the plugs at .023"(Factory spec). That may be all it needs to stop the spark from jumping.
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Re: Ignition question

Postby Eugene » Mon Oct 28, 2013 8:33 am

Jason_Coffey wrote:I recently converted my cub to 12v and installed the 12v petronix kit in the distributor. It seems to only arc if I disconnect/reconnect the positive battery cable. It does not seems to happen while running or during normal start up. I'm baffled.
Question. Ignition switch off, when you disconnect the battery cable you get a spark? And another spark when you reconnect the battery cable?
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Re: Ignition question

Postby Jason_Coffey » Mon Oct 28, 2013 9:02 am

Bus Driver wrote:Sometimes such arcing starts because of dust and other fine debris on the components. The arcing soon damages those surfaces and makes future arcing even more likely. A good cleaning is possibly the cure.


Everything is new and clean.

Bus Driver wrote:What is the spark gap presently for your plugs?


Set it to .030. I read a post here where someone set theirs at .035 with a Petronix kit installed. I also read the .023 is meant for the lower output mag ignition.

Smokeycub wrote:Not sure the Petronix system would require a .030" plug gap but I think I would gap the plugs at .023"(Factory spec). That may be all it needs to stop the spark from jumping.


I can re-gap them if that is what is causing it. I figured with the extra juice a wider gap would be more efficient. I am unsure how spark plug gap could cause arcing at the coil if the engine is not running though.

Eugene wrote:Question. Ignition switch off, when you disconnect the battery cable you get a spark? And another spark when you reconnect the battery cable?


The ignition switch was in the on position. I discovered this when I was wiring my light switch. I had finished wiring the switch and installing the switch in the dash, then reconnected the battery cable with the switch still in the on position. If the ignition switch is in the off position then it doesn't arc.
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Re: Ignition question

Postby Jim Becker » Mon Oct 28, 2013 9:56 am

Jason_Coffey wrote:
Smokeycub wrote:Not sure the Petronix system would require a .030" plug gap but I think I would gap the plugs at .023"(Factory spec). That may be all it needs to stop the spark from jumping.

I am unsure how spark plug gap could cause arcing at the coil if the engine is not running though.

The voltage required to jump a gap increases with the width of the gap. A plug with a .023 gap may require 5,000 volts to jump. (5,000 is a made up but possibly reasonable number.) If so, a .030 gap will require about 6,500 volts to jump. The spark is going to always choose the easiest path to ground. If the spark can jump across the top of the coil at say 6,000 volts, the increased gap will be enough to cause the problem.

Changing the points out for a petronics unit only upgrades one piece of the system. The rest of the system was not designed for higher voltages and can't be expected to handle them in all circumstances. Look at the auto distributors on breakerless systems and compare them to the older versions used with points. They are much larger in diameter. This was done to increase the distances between the various electrodes and contacts to reduce the chance of crossfiring and jumps to ground.
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Re: Ignition question

Postby Jason_Coffey » Mon Oct 28, 2013 9:58 am

Ok. I will re-gap to .023 and see if it fixes my problem. Thanks!
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Re: Ignition question

Postby Gary Dotson » Tue Oct 29, 2013 8:37 am

This one has made me think a bit. First off, the arcing should be more of a problem when the engine is running and making cylinder pressure. So what I theorize was happening was: 1: Apparently the Pertronix is able to generate a single spark when power is initially applied to it. (should do the same thing when the ignition switch is cycled) 2: The engine rotation stopped at a location where the distributor rotor was between and not very close to any of the spark plug wire posts. 3: Resistance was extremely high in the secondary circuit, a condition that would not exist if the engine were rotating. Basically, the spark had no where to go, so it arced anywhere it could. I still don't think it should arc at the post of a new coil, though. I don't think your spark plug gap had anything to do with it.
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Re: Ignition question

Postby Smokeycub » Tue Oct 29, 2013 12:10 pm

Gary Dotson wrote:1: Apparently the Pertronix is able to generate a single spark when power is initially applied to it. (should do the same thing when the ignition switch is cycled) 2: The engine rotation stopped at a location where the distributor rotor was between and not very close to any of the spark plug wire posts. 3: Resistance was extremely high in the secondary circuit, a condition that would not exist if the engine were rotating. Basically, the spark had no where to go, so it arced anywhere it could.

I agree, this is possible. Again, not sure about the Petronix system but usually in this circumstance the random spark would be generated when the power is disconnected rather than when connected, provided the points are closed and a standard coil is used rather than a mag. In a standard points system with a coil, the low voltage circuit creates a magnetic field in the coil when the circuit is closed. When the circuit is opened the magnetic field in the coil collapses and the coil generates a spark. Apparently unlike the Petronix ignition, this happens in time with the rotor (near a plug terminal in the distributer cap) with the points closed, and the randomly generated spark would go to a spark plug.

Jim Becker wrote:Changing the points out for a petronics unit only upgrades one piece of the system. The rest of the system was not designed for higher voltages and can't be expected to handle them in all circumstances. Look at the auto distributors on breakerless systems and compare them to the older versions used with points. They are much larger in diameter. This was done to increase the distances between the various electrodes and contacts to reduce the chance of crossfiring and jumps to ground.

This is especially true on the GM HEI ignition, with much higher secondary voltages (40 to 60,000 volts). GM originally spec'd large plug gaps (.060" or so) and later reduced them to .040" because of arcing problems even with the large distributer caps and heavy insulated plug wires.

In my opinion, the bottom line is the Petronix ignition will create a spark when powered on and like Gary and Jim implied, could cause the spark to jump randomly, an innate attribute of the system. I thinks solid core wires and a .023" plug gap will help the overall performance of the engine and may help the eliminate the jump.
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Re: Ignition question

Postby artc » Tue Oct 29, 2013 2:18 pm

be aware that you can damage the pertronics by leaving the ignition on for a long period of time. I believe there is a note on the installation instructions. so, disconnect it to play with the light circuit
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