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Electricity just got confusing

#1

R

Rivets

I know I’m getting old and electrical problems can get very confusing, but in 50+ years I’ve never seen this before. I’ve got an Echo CS346 that I need to get running, I hooked my inline spark tester (neon light) up to check for spark; nothing. Ok, installed new plug; very faint. Pulled the plug, ran a jumper from plug to good ground; faint spark. Disconnected the plug and I don’t know why but I gave the rope one more pull; great spark in tester. Remember I now have good spark without one end of the tester connected to any ground. I must be going nuts, because I can’t understand how I can have current flow on an open circuit???? AIR GROUND??? I know this makes no sense, but I haven’t been drinking this morning and I now think I’ve lost it. Decided to put everything back together and give the saw a try, started to my surprise. After adjusting the carb, the saw is running good and I’m quitting for the day. Can anyone tell me I’m not crazy and give me any explanation? Edit: I tried my other tester, same type, and it also showed spark.


#2

Scrubcadet10

Scrubcadet10

:unsure:


#3

StarTech

StarTech

it because it got one these stupid plug wire terminals.
1717873435790.png
They tend to break the high tension (plug wire) lead internal conductor then make contact sometimes and other times they don't.

Usually you can snip off the section where the hole is and reinstall the terminal.


#4

R

Rivets

It was that style connector, but that doesn’t explain why I show current flow through the tester when one end is connected to the secondary wire and other end is in thin air, not touching anything.


#5

Hammermechanicman

Hammermechanicman

You are applying a mometary high voltage to a glass bulb filled with neon. Enough energy will dissipate into air to excite the gas. It doesn't take that much to excite the neon gas. The air has super high impedance so essentially no current flow. My old school noninductive timing light would work without the plugwire connected to the spark plug but just the timing light.


#6

StarTech

StarTech

Then you will be confused standing under those high tension overhead wires (your local electrical transport system). Underneath them you can hold up florescent light bulb tube (one those four to eight ones) and have it light up. And there no wires attached on either end.

Those neon testers are not really testing for current as much they are just testing the presence of high voltage. Same theory is at work on those non contact voltage testers that they for checking your wall outlets.


#7

R

Rivets

I understand what everyone is saying, it’s just confusing that in all my years of fixing engines I’ve never seen it before. Thank you all for educating this old fart.


#8

J

Joed756

Rivets said:
I know I’m getting old and electrical problems can get very confusing, but in 50+ years I’ve never seen this before. I’ve got an Echo CS346 that I need to get running, I hooked my inline spark tester (neon light) up to check for spark; nothing. Ok, installed new plug; very faint. Pulled the plug, ran a jumper from plug to good ground; faint spark. Disconnected the plug and I don’t know why but I gave the rope one more pull; great spark in tester. Remember I now have good spark without one end of the tester connected to any ground. I must be going nuts, because I can’t understand how I can have current flow on an open circuit???? AIR GROUND??? I know this makes no sense, but I haven’t been drinking this morning and I now think I’ve lost it. Decided to put everything back together and give the saw a try, started to my surprise. After adjusting the carb, the saw is running good and I’m quitting for the day. Can anyone tell me I’m not crazy and give me any explanation? Edit: I tried my other tester, same type, and it also showed spark.
Click to expand...
Without supplying the make, model, and serial number you make it much more difficult for us to troubleshoot.


#9

R

Rivets

Joe, if you read post #1 you will see that I got the unit running. I was just making an observation about electricity which I have not see before. I don’t understand everything posted fully, but I did learn something new.


#10

StarTech

StarTech

Rivets if you don't fix the end of the plug wire it will give trouble in short again.

And Joe Rivets did give the model number of the Echo chainsaw he was playing with...but in this there is two serial breaks but wasn't need for this particular problem.

Now just depend if Rivets has been in my shop or not as a couple bottles of home brew are missing.


#11

R

Rivets

Star, I did repair the terminal. I always remove that spring terminal and use a crimp style with one modification. Take a piece on Ni-Chome wire, bend into a U at least 3/4” on both sides and push into the wire. Then crimp an auto style terminal over the top. Works great especially when you don’t have much wire to work with. Also, I was hoping you didn’t realize that one bottle was missing. Good stuff.


#12

V

VegetiveSteam

Joed756 said:
Without supplying the make, model, and serial number you make it much more difficult for us to troubleshoot.
Click to expand...
😆


#13

R

RevB

StarTech said:
it because it got one these stupid plug wire terminals.
View attachment 68893
They tend to break the high tension (plug wire) lead internal conductor then make contact sometimes and other times they don't.

Usually you can snip off the section where the hole is and reinstall the terminal.
Click to expand...

Get these instead...

NGK (8328) LB01EP Spark Plug Cap , Black


They screw into the plug wire about an inch.
StarTech said:
it because it got one these stupid plug wire terminals.
View attachment 68893
They tend to break the high tension (plug wire) lead internal conductor then make contact sometimes and other times they don't.

Usually you can snip off the section where the hole is and reinstall the terminal.
Click to expand...


#14

Scrubcadet10

Scrubcadet10

RevB said:
Get these instead...

NGK (8328) LB01EP Spark Plug Cap , Black


They screw into the plug wire about an inch.
Click to expand...
I've used those on 4 wheelers and kawasaki mules alot... they are great and have had no issues from them


#15

P

Peva

FYI - You should avoid firing an ignition (whether lawnmower or automotive) without a path to ground either through the specified spark plug gap or direct short to ground.

Here's why: The ignition coil can generate much higher voltage than it takes to fire the properly gapped spark plug. When the spark plug fires, the resistance of the ionized air in the spark plug gap is so low that the coil output voltage can't rise above the voltage that it took to ionize the air in the gap to initiate the spark. When the coil output wire is held out in the air, far from a ground, the voltage rises tens of thousands of volts higher than the spark plug gap allows. The insulation inside the coil cannot withstand that high of a voltage and will arc through the insulation of the coil - which blows a pin hole through the insulation, leaving carbonized (conductive) material coating the inside of that hole - so the coil is now defective - no longer allows the coil output voltage to rise to the ionization voltage of the proper spark plug gap.


#16

Hammermechanicman

Hammermechanicman

The old 2 stroke LawnBoy mowers were very bad for blowing coils if the plug wire wasn't grounded or attached to the spark plug.


#17

V

VegetiveSteam

Peva said:
FYI - You should avoid firing an ignition (whether lawnmower or automotive) without a path to ground either through the specified spark plug gap or direct short to ground.

Here's why: The ignition coil can generate much higher voltage than it takes to fire the properly gapped spark plug. When the spark plug fires, the resistance of the ionized air in the spark plug gap is so low that the coil output voltage can't rise above the voltage that it took to ionize the air in the gap to initiate the spark. When the coil output wire is held out in the air, far from a ground, the voltage rises tens of thousands of volts higher than the spark plug gap allows. The insulation inside the coil cannot withstand that high of a voltage and will arc through the insulation of the coil - which blows a pin hole through the insulation, leaving carbonized (conductive) material coating the inside of that hole - so the coil is now defective - no longer allows the coil output voltage to rise to the ionization voltage of the proper spark plug gap.
Click to expand...
Folks will argue that they do it all the time and never had one fail but what they don't realize is, while it may not immediately fail, they have almost certainly just shortened the life of that coil significantly. So now a coil that really should have lasted the life of the engine fails prematurely.


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