No spark but all checks out.

cdestuck

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I have a lawnmower with a 4 1/2 hp Briggs engine. Absolutely no spark as I attempt to start it. So I pull off the coil and check it for resistance and it comes out OK. 2.77 on a 20,000 ohms scale.
I did this with the kill wire totally disconnected. I air gas it when I put it back on with a business card so about 10,000. I put my finger up under the fly wheel and can feel nothing loose like a fallen magnet and before I tighten the coil back up, I turn the flywheel around and it does attach to the flywheel where the magnets are.
So with the coil got in a fresh plug, I spin the flywheel around and can still get no spark as I ground it on the fin of the head. I have tried two different spark plugs so it’s not the spark plug. I used was bad. What am I overlooking here as a possibility to no spark. Engine number is 10 G902.
 

bertsmobile1

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1) All mower coils now days except some EFI engines have an inbuilt Hall effect trigger chip which times the spark
2) you can not test the chip with an Ω meter so your numbers are meaningless
3) the trigger chip is open circuit then grounds to allow the spark to travel through the coils and the tab on the coil grounds the entire coil which prevents the spark being generated in the first place
4) you test the coil ( now called a module & priced 10 times what it should be ) by removing the kill wire and cranking the engine
5) it is a works - does not work situation and "modules " are not repairable other than to replace the HT cable & spark plug terminal boot
 

cdestuck

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1) All mower coils now days except some EFI engines have an inbuilt Hall effect trigger chip which times the spark
2) you can not test the chip with an Ω meter so your numbers are meaningless
3) the trigger chip is open circuit then grounds to allow the spark to travel through the coils and the tab on the coil grounds the entire coil which prevents the spark being generated in the first place
4) you test the coil ( now called a module & priced 10 times what it should be ) by removing the kill wire and cranking the engine
5) it is a works - does not work situation and "modules " are not repairable other than to replace the HT cable & spark plug terminal boot
See I found this on testing coils and this guy was actually testing an engine identical to what I have. Are you saying that what he is doing in this test doesn’t prove anything with the coils he is testing? I did my test identical to what he was doing. Tks

 

ILENGINE

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See I found this on testing coils and this guy was actually testing an engine identical to what I have. Are you saying that what he is doing in this test doesn’t prove anything with the coils he is testing? I did my test identical to what he was doing. Tks

The only thing he is proving is the secondary winding is good. It doesn't test the primary winding or the trigger coil. And momentary voltage through the trigger coil can cause permanent damage. So a meter can actually turn a good module into a bad module.
 

shadetree#1

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Bottom line:

Replace the magneto and test.

Sometimes you can find reduced price clone magneto's on flea bay or Amazon. (with free return refund if they don't work as described)
 

StarTech

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Well IL is right as following will explain.

The configuration of new Magnetron coil may look like they removed the triggering device but in fact it is just a redesign. Now to answer your question what is inside the coil.

1 ea 13mm x 34.5mm single sided circuit board.
5 ea SMD transistors.
8 ea SMD resistors, inductors, and/or capacitors.
(SMDs were destroyed upon board removal so actually identification wasn’t possible.)
1 ea D13003 transistor.

Primary Winding reading is 1.5 - 1.7 Ω.
Secondary Winding reading is about 6 KΩ +- several hundred ohms.

The kill terminal is directly connected to the non-ground side of the primary; hence, explains why you or anyone else can NOT test the primary trigger circuit. Otherwords this means you can not test to find out if a Magnetron coil is good or not without installing it in most cases; unless, you have a specialized coil tester.

The D13003 emitter is connected to non-grounded side of the coil’s primary via two SMD resistors in parallel with total resistance value of 0.5 Ω. (One these SMD resistors marked with the 1R0 code for a
1.0 Ω resistor, ½ watt size.) The collector is connected the coil’s primary winding that is grounded. The base is connected to the rest of the trigger circuitry.

The coil’s transformer turns ratio is approximately 1 to 18 with secondary closest to the core.

In theory if the output D13003 transistor should short the collector-emitter junction and the coil’s primary winding is still good the ohms reading will drop to 0.25 Ω - 0..35 Ω. If the coil’s primary winding should short then the ohms reading should be near zero. If the coil’s primary winding should open then the reading will be well above 1.7 Ω. If anything opens in electronics and the primary is good then you will still see the 1.5 – 1.7 ohms reading. Applying any voltage to the kill terminal would result in either coil’s primary winding shorting or opening due to high current experienced. Applying voltage also can short out the electronics thus making the coil useless. It is also expected that a cold solder joint connecting the external kill terminal to circuit board would lead to a non kill operation.

Also the high tension lead can be replaced if you wish to fight the glue considering the price of aftermarket versions of this coil.

This info was acquired through the destruction of the new OEM version of this coil. It also explains the configuration differences as they have gone to SMD trigger version.

Now for those that wondering why we put diodes in the kill circuit of the dual coil models it because of the feedback loop created causing one coil to kill the other. This explains why they are destroyed when 12V is applied as these is no built-in reverse bias protection. Now with this in mind you might think Kohler coils would be the same wiring. Not so as these diodes are incorporated into coil itself thus preventing many of the problems that the Briggs have because they don’t incorporate these diodes.
 

cdestuck

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Well IL is right as following will explain.

The configuration of new Magnetron coil may look like they removed the triggering device but in fact it is just a redesign. Now to answer your question what is inside the coil.

1 ea 13mm x 34.5mm single sided circuit board.
5 ea SMD transistors.
8 ea SMD resistors, inductors, and/or capacitors.
(SMDs were destroyed upon board removal so actually identification wasn’t possible.)
1 ea D13003 transistor.

Primary Winding reading is 1.5 - 1.7 Ω.
Secondary Winding reading is about 6 KΩ +- several hundred ohms.

The kill terminal is directly connected to the non-ground side of the primary; hence, explains why you or anyone else can NOT test the primary trigger circuit. Otherwords this means you can not test to find out if a Magnetron coil is good or not without installing it in most cases; unless, you have a specialized coil tester.

The D13003 emitter is connected to non-grounded side of the coil’s primary via two SMD resistors in parallel with total resistance value of 0.5 Ω. (One these SMD resistors marked with the 1R0 code for a
1.0 Ω resistor, ½ watt size.) The collector is connected the coil’s primary winding that is grounded. The base is connected to the rest of the trigger circuitry.

The coil’s transformer turns ratio is approximately 1 to 18 with secondary closest to the core.

In theory if the output D13003 transistor should short the collector-emitter junction and the coil’s primary winding is still good the ohms reading will drop to 0.25 Ω - 0..35 Ω. If the coil’s primary winding should short then the ohms reading should be near zero. If the coil’s primary winding should open then the reading will be well above 1.7 Ω. If anything opens in electronics and the primary is good then you will still see the 1.5 – 1.7 ohms reading. Applying any voltage to the kill terminal would result in either coil’s primary winding shorting or opening due to high current experienced. Applying voltage also can short out the electronics thus making the coil useless. It is also expected that a cold solder joint connecting the external kill terminal to circuit board would lead to a non kill operation.

Also the high tension lead can be replaced if you wish to fight the glue considering the price of aftermarket versions of this coil.

This info was acquired through the destruction of the new OEM version of this coil. It also explains the configuration differences as they have gone to SMD trigger version.

Now for those that wondering why we put diodes in the kill circuit of the dual coil models it because of the feedback loop created causing one coil to kill the other. This explains why they are destroyed when 12V is applied as these is no built-in reverse bias protection. Now with this in mind you might think Kohler coils would be the same wiring. Not so as these diodes are incorporated into coil itself thus preventing many of the problems that the Briggs have because they don’t incorporate these diodes.

oh my. Your electronic knowledge is way way way above my pay grade. Ha. I’ll trust you guys and pick up a new coil. Tks.
 

skiman

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I have a lawnmower with a 4 1/2 hp Briggs engine. Absolutely no spark as I attempt to start it. So I pull off the coil and check it for resistance and it comes out OK. 2.77 on a 20,000 ohms scale.
I did this with the kill wire totally disconnected. I air gas it when I put it back on with a business card so about 10,000. I put my finger up under the fly wheel and can feel nothing loose like a fallen magnet and before I tighten the coil back up, I turn the flywheel around and it does attach to the flywheel where the magnets are.
So with the coil got in a fresh plug, I spin the flywheel around and can still get no spark as I ground it on the fin of the head. I have tried two different spark plugs so it’s not the spark plug. I used was bad. What am I overlooking here as a possibility to no spark. Engine number is 10 G902.
did you disconnect the kill lead when you tried to get the spark turning the engine over...if not...disconnect the kill lead from the coil and try for spark...if nothing try cleaning the coil mounting points to insure a good ground connection for the coil...a lot of times a stretched out kill brake cable will not work properly to clear the kill lead part of the assembly...
 

cdestuck

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did you disconnect the kill lead when you tried to get the spark turning the engine over...if not...disconnect the kill lead from the coil and try for spark...if nothing try cleaning the coil mounting points to insure a good ground connection for the coil...a lot of times a stretched out kill brake cable will not work properly to clear the kill lead part of the assembly...
Yes I’ve done all you mentioned. I guess it the coil is shot so have a new one ordered.
 

shadetree#1

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AND if you order a clone coil do not get depressed if it don't spark.

I've had new clone replacements that would not produce a spark and just get another and OKk.

Also they are not coils, usually termed magnetos and several triggering devices inside. (that a ohmmeter won't detect as bad)

The older points type COILs CAN BE OHMMETER TESTED just to see if the primary and secondary coils indicate ok but they may fail a run test.
 
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