Intermittent spark from magneto

[13fx]

If you need help on the mag, I do them as a hobby. I have the testers that takes the guess work out of it. Also have a magnet charger that gets the magnet up to snuff for a good hot spark.

I'm fairly certain I have this magneto squared away, but I can't imagine this will be the only magneto tractor that I see down the road so if you DM me your information I'll save it and get a hold of you at some point and go from there.

 

[wore out]

I wasn't planning on spending half of a day rotating a motor I honestly thought it was going to be as simple as cleaning the point gap so I wasn't going to go through all of that hassle of grounding the wires. But I am going to disagree on the spark still happening if it isn't grounded. If you pull a plug wire off of an engine and let it dangle in the air with the timing light hook to it you will not get any reading off of that light because nothing's happening there is no flow of electricity. It

"But I am going to disagree on the spark still happening if it isn't grounded."

You are (mostly) WRONG in that assumption.

The high-tension spark generally DOES find it way to ground with a spark plug wire(s) pulled off.

It can arc inside the coil, or "carbon track" the rotor or distributor cap finding it's way to ground.

Cranking the engine knowing sparkplug wires are dangling is sort of an "old farmer's hack" and NOT good policy.

When checking for a misfire I GROUND the individual sparkplug terminals rather than pulling a wire off just for that reason.

Older magnetos that had poorer/less modern insulation in their coils, etc. actually had internal "spark gaps" where the spark could find it's way to ground if a sparkplug wire became disconnected to remove the chance of damage to the mag.

 

[teddy52food]

I'm fairly certain I have this magneto squared away, but I can't imagine this will be the only magneto tractor that I see down the road so if you DM me your information I'll save it and get a hold of you at some point and go from there.

3 two zero 2 nine 3 5 zero zero 5.

 

[13fx]

"But I am going to disagree on the spark still happening if it isn't grounded."

You are (mostly) WRONG in that assumption.

The high-tension spark generally DOES find it way to ground with a spark plug wire(s) pulled off.

It can arc inside the coil, or "carbon track" the rotor or distributor cap finding it's way to ground.

Cranking the engine knowing sparkplug wires are dangling is sort of an "old farmer's hack" and NOT good policy.

When checking for a misfire I GROUND the individual sparkplug terminals rather than pulling a wire off just for that reason.

Older magnetos that had poorer/less modern insulation in their coils, etc. actually had internal "spark gaps" where the spark could find it's way to ground if a sparkplug wire became disconnected to remove the chance of damage to the mag.

I was intrigued by your answer. So I went out to the shop and hooked up my timing light to the #2 wire. While it was still attached to the plug I went and turned the motor to verify spark and give me a base. Next as pictured I removed the wire and let it hang in the air with the light hooked up to it. I cranked the engine over somewhere in the neighborhood of 20 rotations but never once did the timing light light up.

 

[wore out]

I was intrigued by your answer. So I went out to the shop and hooked up my timing light to the #2 wire. While it was still attached to the plug I went and turned the motor to verify spark and give me a base. Next as pictured I removed the wire and let it hang in the air with the light hooked up to it. I cranked the engine over somewhere in the neighborhood of 20 rotations but never once did the timing light light up.

In the photo your timing light has an inductive pickup, it's triggered by CURRENT in the sparkplug wire.

With no current flowing in the disconnected sparkplug wire it wasn't triggered.

Whether or not the sparks found a path to ground in the mag's coil, rotor, or cap is not proven or disproved by the fact the timing light wasn't triggered.

 

[rustred]

I was intrigued by your answer. So I went out to the shop and hooked up my timing light to the #2 wire. While it was still attached to the plug I went and turned the motor to verify spark and give me a base. Next as pictured I removed the wire and let it hang in the air with the light hooked up to it. I cranked the engine over somewhere in the neighborhood of 20 rotations but never once did the timing light light up.

Ok to keep things simple here with the plug not grounded u will not see the spark jump the plug gap. Take that timing light off and do it the simple way as I explained. A timing light don’t show u if the plug is firing. As I said u can have a bad plug also. The timing light is to set the timing and I don’t even need a light to set the timing to the factory settings. You will get no place till u see if all plugs are firing and a timing light over a plug wire won’t show you that. Even on the champion plug cleaner you blast the plug then u watch it fire if it’s good or no good. Us old guys know a thing or two. And good info here. Also a plug can be reset to make it fire good. If the electrode is rounded off and worn, then u open the gap and file it flat then regap the plug to .025.

 

[13fx]

In the photo your timing light has an inductive pickup, it's triggered by CURRENT in the sparkplug wire.

With no current flowing in the disconnected sparkplug wire it wasn't triggered.

Whether or not the sparks found a path to ground in the mag's coil, rotor, or cap is not proven or disproved by the fact the timing light wasn't triggered

I am sorry for the confusion. I should not have been saying spark most of the time. Often when I am talking about spark it is the flow of current through the ignition system, not just the current jumping the gap on a plug. Since I am waiting on the graphites still for the carb I wanted to see if the ignition system was working. So the first thing I did was place the timing light onto the coil wire and rolled the motor over a few revolutions. This is when I noticed that I was getting "intermittent spark" as instead of the light flashing every time the impulse tripped it would flash maybe 1-2 times every two full revolutions of the crankshaft. In 2 revolutions each cylinder should fire giving you a total of four flashes from the timing light. I would count 1-4 as the impulse drive tripped over the two full rotations so I could determine if I was having consistent current flow from the coil to the distributor cap. In the beginning I was not. A couple of times I could make both complete rotations without the timing light flashing once. If I was consistently getting no spark on the same count (say 2 for example) I would know that there was a problem with either the plug, the wire or the distributor cap. If I was getting no current at all i would know I wasn't getting current flow to the distributor cap and could work backwards from the cap till I found the problem or problems. (That doesn't mean there may not be a problem with a wire or plug, but the odds of all four plugs, wires or combination there of to be bad is highly unlikely) now since I was getting current to the plugs at a completely random interval I figured I needed to file the points and regap them. When this didn't change anything i figured I would ask for help on magnetos since I knew nothing about them and it seemed likely to me that I should start there. After taking worn outs advise and completely disconnecting the wire for the kill switch I would get get a flash for #4 and #2 every time, no flash at all for #1 and an intermittent flash for #3. Since I was getting this everything should be working fine until the cap. After cleaning the cap contacts I was able to get #3 to be consistent too. #1 was the only one that doesn't get current from the cap to the plug. I had tried a different wire from one of my VAC-14'S just to rule out the wire. I have switched #1 and #2 around and #2 goes dark and #1 will flash. So with that being the case, I feel very safe saying that the contact for #1 on the cap is bad and the cap needs to be replaced. Once I get the cap, I will then re attach the kill wire and see if I have a problem with the wire or switch. I already have new plugs so Im not going to bother checking if the plugs are good or are grounding out, as I'm replacing them already.
When Jim said "The spark will happen, ground or no ground." I was taking it to mean that even ungrounded I should see the timing light flash. I am sure that due to me using"spark" to refer to the flow of current through the ignition system I was not understanding what he meant, my fault.

 

[Janicholson]

I am sorry for the confusion. I should not have been saying spark most of the time. Often when I am talking about spark it is the flow of current through the ignition system, not just the current jumping the gap on a plug. Since I am waiting on the graphites still for the carb I wanted to see if the ignition system was working. So the first thing I did was place the timing light onto the coil wire and rolled the motor over a few revolutions. This is when I noticed that I was getting "intermittent spark" as instead of the light flashing every time the impulse tripped it would flash maybe 1-2 times every two full revolutions of the crankshaft. In 2 revolutions each cylinder should fire giving you a total of four flashes from the timing light. I would count 1-4 as the impulse drive tripped over the two full rotations so I could determine if I was having consistent current flow from the coil to the distributor cap. In the beginning I was not. A couple of times I could make both complete rotations without the timing light flashing once. If I was consistently getting no spark on the same count (say 2 for example) I would know that there was a problem with either the plug, the wire or the distributor cap. If I was getting no current at all i would know I wasn't getting current flow to the distributor cap and could work backwards from the cap till I found the problem or problems. (That doesn't mean there may not be a problem with a wire or plug, but the odds of all four plugs, wires or combination there of to be bad is highly unlikely) now since I was getting current to the plugs at a completely random interval I figured I needed to file the points and regap them. When this didn't change anything i figured I would ask for help on magnetos since I knew nothing about them and it seemed likely to me that I should start there. After taking worn outs advise and completely disconnecting the wire for the kill switch I would get get a flash for #4 and #2 every time, no flash at all for #1 and an intermittent flash for #3. Since I was getting this everything should be working fine until the cap. After cleaning the cap contacts I was able to get #3 to be consistent too. #1 was the only one that doesn't get current from the cap to the plug. I had tried a different wire from one of my VAC-14'S just to rule out the wire. I have switched #1 and #2 around and #2 goes dark and #1 will flash. So with that being the case, I feel very safe saying that the contact for #1 on the cap is bad and the cap needs to be replaced. Once I get the cap, I will then re attach the kill wire and see if I have a problem with the wire or switch. I already have new plugs so Im not going to bother checking if the plugs are good or are grounding out, as I'm replacing them already.
When Jim said "The spark will happen, ground or no ground." I was taking it to mean that even ungrounded I should see the timing light flash. I am sure that due to me using"spark" to refer to the flow of current through the ignition system I was not understanding what he meant, my fault.

All good, you are doing a great job of figuring out the issue. A mag can produce upwards of 25,000 volts on discharge. that voltage rises until it finds an electron path that it can bridge. That path can be forced to be from the coil tower (mag or distributor coil) through conductors and air gaps to the plug then ground, or if that is not available (wire off the plug) it will jump along insulators or moisture, or your nerve endings in your arm. For good info, look into Kettering Ignition systems, and Magneto operation systems (they have a lot in common. Jim