Testing ignition coil output - Ford Muscle Forums : Ford Muscle Cars Tech Forum
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post #1 of 5 (permalink) Old 08-18-2009, 10:21 PM Thread Starter
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Testing ignition coil output

I've read about all the methods of testing an ignition coil, but what i really want to do is to take some measurments of output. Such as amps delivered, and volts delivered and an output measurement. Is there any way to do this? For example I'd like to measure both output voltage of an accel super coil hooked up to points ignition, and then hooked up to an electronic ignition system. I could then go further and measure voltage and amps at the spark plug as well to see what delivers the best spark in terms of something measurable. Anyone have an idea of how to do this
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post #2 of 5 (permalink) Old 08-18-2009, 10:45 PM
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Re: Testing ignition coil output

There are several variables that relate to coil output. Supply voltage, engine rpm, condition of primary ignition (worn points, weak dist magnet etc.)

I can save you some trouble by telling you electronic ignition is far better than points no matter what coil you use.

What you're looking for is the coil's ability to generate a good, hot spark under all conditions. That means high voltage.

You could use an oscilliscope, Yes they are becoming rare as well as folks who know how to use them.

A cheap and easy way is a spark tester. I've seen ones that hook to a plug wire and clamp to an engine ground. They have a simple scale on them to estimate kilovolts. You simply thread a screw in or out to change the gap and measure the kv available to jump a specified gap. Check your local snap on, matco etc dealer.

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post #3 of 5 (permalink) Old 08-19-2009, 03:03 AM
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Re: Testing ignition coil output

the Snap On tester mention above got one . now for the surprise -- on a sound engine , if you got a point or electronic and everthing else is the same -- no difference in voltage to the plug. be surprized how that 50k volt system is never needed
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post #4 of 5 (permalink) Old 08-19-2009, 07:26 AM
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Re: Testing ignition coil output

My findings are the same as DanH. Just not needed on most applications.
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post #5 of 5 (permalink) Old 08-19-2009, 05:57 PM
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Re: Testing ignition coil output

Ignition coils put out "constant power" under all conditions.
That means that as voltage required goes up the amperage delivered goes down.
The determining factors for required voltage required are:
plug gap
mixture density

The easy way to find out how much voltage your coil will put out is to increase the plug gap until it fails while watching the voltage on the scope.

The best way to find out the best gap for your plugs is to narrow the gap until it mis-fires at idle.

The smaller the gap - the lower the voltage required - and the higher the amperage available to ignite the mixture.


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