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How Do You Test an Ignition Coil for Good
Posted by: Phil Dally ()
Date: July 28, 2022 09:42AM

Scrounging a coil for Super Market Special 140.

I have 6 but it's unknown if they are any good.

Is there a test procedure to check for function.

I mean besides holding on to a spark plug wire.

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Re: How Do You Test an Ignition Coil for Good
Posted by: Phil Dally ()
Date: July 28, 2022 09:45AM

Yes I could look on you tube but that's too easy.

Plus I don't get all the wonderful guru feedback.

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Re: How Do You Test an Ignition Coil for Good
Posted by: Lane66m ()
Date: July 28, 2022 09:52AM

Ohm Check on primary and secondary windings. I think manual may have it in engine electrical section.

Doesn't mean it will operate on engine, but it eliminates bad ones.

Nope. Not there.

Step 1
Disconnect your engine's main negative battery cable with a wrench.

Step 2
Pull the main ignition coil wire, the one that leads to the distributor, off the coil. Disconnect the small grounding wire, attached to the side of the coil, with a wrench.

Step 3
Turn on the multimeter and set it to the "ohms" function.

Step 4
Insert one of the multimeter's probes into the center opening of the coil, contacting the metal terminal inside the coil. Touch the second probe of the meter to the ignition coil's grounding terminal. The meter should read 6,000 to 15,000 ohms. If it does not, the coil's secondary winding is faulty.

Remove meter's probe from the center terminal and touch it to the terminal bolt on the opposite side of the coil from the probe touching the grounding terminal. The meter should read between approximately 0.4 and 2 ohms. If it does not, the coil's primary winding is faulty.



Edited 1 time(s). Last edit at 07/28/2022 09:55AM by Lane66m.

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Re: How Do You Test an Ignition Coil for Good
Posted by: Saxon ()
Date: July 28, 2022 10:01AM

My 66 supplement says ohms are:

Prim Resistance: 1.28-1.42

Secondary resistance: 7200-9500



My working coil was reading at secondary 10500.

Northern CA
66 Monza Coupe 4-spd 140



Edited 1 time(s). Last edit at 07/28/2022 10:01AM by Saxon.

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Re: How Do You Test an Ignition Coil for Good
Posted by: Phil Dally ()
Date: July 28, 2022 10:16AM

Look in the book.

Thank you both!!

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Re: How Do You Test an Ignition Coil for Good
Posted by: joelsplace ()
Date: July 28, 2022 10:21AM

After you verify the resistance checks out hook it up to power and then make it spark a wider and wider gap until it won't. That will tell you how strong they are in comparison to each other. I used to have a clear plastic tube with a plug wire on each end and threaded contacts inside to do this test. I think it was a Kent-Moore tool.

Joel
Northlake, TX
5 Ultravans, 138 Corvairs and counting...

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Re: How Do You Test an Ignition Coil for Good
Posted by: Phil Dally ()
Date: July 28, 2022 11:08AM

The coils with the best (highest) readings the most stock looking one of all.

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Re: How Do You Test an Ignition Coil for Good
Posted by: Wagon Master ()
Date: July 28, 2022 02:36PM

Which brings up an interesting point. What primary or secondary ohm reading is better, best, hottest, puts out the hottest spark?
Would you see or be able to measure the difference in spark between two coils that measure 1.3 and 1.8?

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Re: How Do You Test an Ignition Coil for Good
Posted by: Phil Dally ()
Date: July 28, 2022 04:16PM

In the end I'm using the Accel coil...even hotter!!

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Re: How Do You Test an Ignition Coil for Good
Posted by: Wagon Master ()
Date: July 28, 2022 06:49PM

And it's primary resistance was.....?
Compared to what, of the other ones?

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Re: How Do You Test an Ignition Coil for Good
Posted by: Phil Dally ()
Date: July 28, 2022 07:24PM

I already don't remember. cool smiley

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Re: How Do You Test an Ignition Coil for Good
Posted by: Wagon Master ()
Date: July 28, 2022 08:15PM

So if you don't remember the numbers, how did you rank them? Lower primary resistance = hotter? Higher primary resistance = hotter?

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Re: How Do You Test an Ignition Coil for Good
Posted by: Saxon ()
Date: July 28, 2022 10:04PM

I used this tool to check the coil spark. [www.lislecorp.com]

It has the adjustable length and transparent tube.

I did not know about the spark strength test.

Thanks Joel Northlake!

Northern CA
66 Monza Coupe 4-spd 140

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Re: How Do You Test an Ignition Coil for Good
Posted by: JimBrandberg ()
Date: July 29, 2022 04:15AM

There's the whole thing about how many ohms you want with the coil and the resistor wire. Stock points should add up to 3.0, half from the coil and half from the resistor wire. From what I understand a 1.5 ohm resistor wire paired to a .6 ohm coil is not a good idea. I could be wrong.
Different ignition systems have different requirements. I still don't have it right in my mind. I think the Clarks chart on what coil works with what ignition system is correct although I don't think they give you the ohm rating, you need to interpret that yourself.
There's been other threads on the subject with explanations from people way smarter than me in this regard.

Jim Brandberg
Isanti, MN
CorvairRepair.com



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Re: How Do You Test an Ignition Coil for Good
Posted by: joelsplace ()
Date: July 30, 2022 07:14AM

I like that Lisle tool. I just ordered one. Thanks Saxon!

Joel
Northlake, TX
5 Ultravans, 138 Corvairs and counting...

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Re: How Do You Test an Ignition Coil for Good
Posted by: Phil Dally ()
Date: July 30, 2022 08:21AM

Tested a known good coil with a proper Fluke meter and started over.

Good
Prim 1.5
Sec 5.95

Accel
Prim 1.5
Sec 11.72

503
Prim 1.7
Sec 9.07

UC23X
Prim 1.9
Sec 5.36

Ford
Prim 1.9
Sec 7.88

UNK
Prim 1.9
Sec 8.75

I give up...which one should I use for my Supermarket Special 140.

Also should I use an external resistor for a temporary quick fire up

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Re: How Do You Test an Ignition Coil for Good
Posted by: Phil Dally ()
Date: July 30, 2022 08:27AM

BTW: #6 has a broken wire stud...junk!!

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Re: How Do You Test an Ignition Coil for Good
Posted by: oldqmguy ()
Date: July 30, 2022 09:35AM

Any of the Coils with an Primary reading of 1.5 to 1.7 Ohms and a Secondary reading of over 5 Ohms should be good for your engine.

With ANY of those Coils you will need to use the Resistor (this keeps the Primary current to 4 Amps)!

The higher Secondary readings mean there are MORE WINDINGS in the Secondary and they will supply higher OPEN OUTPUT VOLTAGE.

One thing that many folks don't realize is the fact that the High Voltage sent to the Plugs STOPS RISING when the Plug 'fires!'

"Assuming" you have a standard setup with a 'standard' Coil, the High Voltage will be around 20,000 Volts with NO SPARK being drawn. As soon as a Plug 'fires' the High Voltage stops rising!

If all your Sparkplugs are clean and set correctly and the engine cylinders are 'perfect' the Plugs will 'fire' at about 15,000 Volts. This will vary as the Plugs gaps open from age, Plug wires get bad, carbon builds up in the cylinders, and the Points wear out. This 'wear' (along with the Battery Voltage dropping to about 10 Volts during starting) is the reason for the "Resistor Bypass" built into the Resistor+Coil circuit.

This is why I spent my collage years changing Plugs, Points, Condenser, and Rotor every 3000 miles!

Now, I have the "computers" in our modern(?) cars checked at each Oil Change and "they" will let me know when I need new Sparkplugs and or Coil (there is a 'small Coil' at each Plug!). They usually last about 100,000 miles, so that isn't too bad!

I hope this helps!

Dale cool smiley

Dale E. Smiley CPBE
Life Member The Society of Broadcast Engineers
RETIRED Broadcast Engineer
CERTIFIED CORVAIR NUT
CORSA/Circle City Corvairs/Corvair Performance Group
Avon, Indiana
WB9SFF
1967 4-Door Monza PG!

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Re: How Do You Test an Ignition Coil for Good
Posted by: Phil Dally ()
Date: July 30, 2022 10:44AM

I have two resistors to use.

40' International reads 3.8

NAPA Echlin that reads 1.5

Same question...which one?

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Re: How Do You Test an Ignition Coil for Good
Posted by: Lane66m ()
Date: July 30, 2022 12:39PM

Phil:

Do you still have the factory resistance wire still in the engine harness. Do ohm check from coil back to connector on that wire.

If less than 0.2 ohms, you need 1.5 ohm resistor before the coil connection.

If wire is 1.4 - 1.6 ohms, no external resistor needed.

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