1450 Ignition Coil Keeps Burning Out

[ironman]

Whoever wrote that article is full of $h!t.

[R Bedell]

In our example below the bad spark plug ignition cable has a resistance reading of 5 mega ohms.

Whoever wrote that article is full of $h!t.

That is what I was thinking also.

[West Valley G]

I have no knowledge on the subject at all but would like to know
why the article is full of shinola so I can learn something on the topic.

Ken

[Billy-O]

I was hoping to imply that spark wire or plug with too much resistance can lead to coil failure. So I found the article and quickly scan through it without looking or checking the "math". My bad! The math is very erroneous. 15,000,000 volts, my ass!

Good eye to Ironman and Roland.

[R Bedell]

IF..............a plug wire had 5 Mega Ohms, then there is NO Spark. From all I ever seen any resistance for 10,000 ohms (or more) indicates a "bad plug" wire. I use solid metal core wire on my Kohler(s), with a resistance of less the 1 ohm. NO PROBLEMS with spark.

[darkminion_17]

Coils and condensers need good ground, you can make the connections to the engine nice and shiny.

[ironman]

Originally Posted by West Valley G

I have no knowledge on the subject at all but would like to know
why the article is full of shinola so I can learn something on the topic.

Ken

Why is the AUTHOR of the article is full of “shinola”?

The Facts:

1. The coil is a transformer. There are current transformers and there are voltage transformers. Our coil is a voltage transformer that steps the 12-volt input up to about 12 to 15 thousand output volts to jump the spark plug gap with very little current flow (i.e. a static discharge). The voltage applied to the coil's primary side (i.e. the small lugs) is induced into the secondary side (i.e. the plug wire). The voltage applied to the primary is controlled by the opening and closing of the points. So in effect, the output is controlled by the input.

2. Voltage (i.e. the battery) is the “generator” so to speak, of current flow. Increasing or decreasing voltage has a direct effect on the amount of current flow on the primary side of voltage step up transformer but a lesser effect to the secondary. That is why you get zapped when touching a spark plug wire but not killed. Grab the output of a current transformer and the outcome not so joyful.

3. Resistance (i.e. ohms) is what it implies, a limit to the flow of current. Put a piece of wire across the poles of a battery (a direct short) and you will have maximum current flow and the wire, and or battery will burn up. Put a big enough resistor in line with the wire and you limit the amount of current flow. Bigger resistance less current, too little resistance, and the resistor and wire burn up. Cut the wire and you have an open circuit, in effect INFINITE resistance. (i.e. resistance you can’t even measure)

4. Current is the flow of electrons from negative to positive. As stated above, increasing or decreasing voltage, and or resistance will directly increase or decrease current flow. Current cannot control it’s own flow.

What the author says:

He states that his measurement of the “bad” plug wire reads 5 million ohms. (In any way of thinking, that's big-time resistance)

He claims that the high current flowing thru the coil's secondary has caused it to burn up because the high resistance of the plug wire has boosted the normal 12 – 15,000 output voltage of the coil to literally millions of volts. (Personally, I've never seen a coil that can do that, maybe others have)

What’s wrong?

1. Spark plug wires measured with an ohmmeter can read zero ohms if a straight wire or about 4000 ohms per foot if resistance wire. So of course a wire reading 5 million ohms would be “bad”, so bad that it is essentially “open” so it is doubtful that the engine could even run.

2. As stated above, the coil is a voltage step-up transformer, voltage is induced into the secondary, so the amount of voltage applied to the primary side is what determines the output voltage, not the resistance applied to the secondary. To get the output voltage that the author proposes, you would have to have 1000 to 2000 volts going in on the primary.

3. Since the coil is a voltage transformer and not a current transformer, the flow of current thru the secondary is minimal to begin with, so even giving the author the benefit of doubt, remember, increasing resistance reduces current flow, so how could increasing the plug wires resistance to gigantic proportions cause current flow thru the coils secondary windings to increase?

The formula for current is, current equals voltage divided by resistance (I=E/R).
Since the input voltage of 12 volts always remains the same, you get a normal output of 12,000 volts divided by let's say a good 1-foot piece of resistance sparkplug wire should carry about 3 amps. (12,000/4000=3).
Now, same formula with his 5 million ohm wire - 12,000/5,000,000=.0024.
Wheres the big current to burn out that secondary now?

I hope this helps you in some way.

[West Valley G]

Wow that helps a lot. I now know more about coils than ever before.
I enjoy learning this stuff so much. Now every time I look at a coil I
will no longer be looking at the same part. Before it was always that thing that
makes spark go to the plug.
Hopefully I didn't derail the thread from the original intent. Thanks a
Million or maybe 5 million.

Ken

[RLause]

Link to a very good write up on how an induction coil works.

https://en.wikipedia.org/wiki/Ignition_coil

[TOPDOWNRESTO]

For me on my 1650, had the same kind of issues, after going thru all the usual checking and replacing of the cheaper stuff ( which needed replacing anyway), it ended up being the voltage regulator. Using the blue Bosch coil.