Craftsman BackPack Leaf Blower No Spark

StarTech

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You must understand and accept due to the internal design with the electronic trigger, these coils can not be reliably be tested except with special test equipment. For us in the field [repair shops] they are tested as a plug and play item. Otherwords they are mounted and if they work great; if they don't then we replace them. The days of the externally triggered ignitions are now long gone. There a limited number engines still using the hybrid system and of course the antique engines with points and condenser system.

Ignition coils are basically a step up transformer. The testing problem rises because the electronic trigger is across the primary winding and due to the configuration any tests done on the primary side only shows the primary winding resistance. The trigger is higher resistance item but since it is mounted direct across the primary winding you only read the coil's primary resistance; therefore, there no reliable way to first these in the field other than plug and play. The kill tab is connected the floating end the primary so when you test from it to ground all are testing is primary transformer resistance.

Note after market coils for this engine are only around $20. and OEM coils are $70+.

Now there are couple other problems that will cause an engine not to hit on induce fuel mix. One is a sheared flywheel key throwing the ignition timing off and the other is low compression. Two cycles require at least 100 psi normally to even ignite the fuel mixture load. Now there are limited number of two cycle engines that I have seen that fire with as little as 90 psi compression but I use the 100 psi minimum as test rule here.
 

StarTech

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Here is a very basic schematic of the coil configuration.

1641390578788.png
 

upupandaway

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Welchs101, Just for doo doo and giggles, did u try disconnecting the kill switch before taking the whole thing apart?
 

mmoffitt

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How did you know it was behind the blower assembly? I believe you......this is what i was kinda thinking but how did you know? The blower assembly is the side of the blower that is closest to a persons back if they were wearing the blower is this right?
I love it!... Seriously just reading all of these questions and answers, has given me so much usable knowledge ,but it would still take the 10,000 hrs plus another 10k of actual hands on to get good at this. A lot of these people here are some of the best of the best and thank you to everyone for sharing Their knowledge and wisdom!
Happy New Year to all!
 

Gord Baker

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You should have first verified using a tester that there was indeed no current at the plug. Then Replace the plug with known or new good one. Simple stuff first.
 

bertsmobile1

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You have not been able to test small engine magneto coils with an ohm meter since 1994 when the patient for Atom Industries points eliminator expired and every manufacturers fitted coils with embedded Hall Effect Trigger circuits.
In fact some cheap ohm meters can fry the chip and as most work with negative voltages, touching the kill wire to any battery + will fry the circuits as well
The chip is hard wired into the primary windings of the coil so it is not repairable nor replaceable.
This is why there are no service details available
To test it you need a signal generator to stimulate the primary winding while simultaniously read the rising voltage in the primary coil which is in micro volts to see what voltage the trigger trips at when the entire coil is then in series for a micro second or so .

Unfortuneately the WWW is full of totally brain dead 1/2 witts whose mental capacity never progressed past that of a 4 year old .
So when faced with something they do not understand they make some thing up to explain it just like the fairies that we all knew lived in the bottom of the garden when we were 5.
Then these idiots go post a whole lot of twaddle often conflating things that have nothing to do with what they are posting about but seem to be connected in their overworked confused blubber pretending to be a mind to make them feel like they are important & not just oxygen thieves who the planet would be better off if they had been allowed to die at birth .
 

bertsmobile1

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Opps
Sorry I missed page 3 so I have just said the same as Star, in a different way.
Take home is , if you have access to the $ 30,000 worth of test gear then you can dry test the magnetos.
At the factory they simply run a magnet past the coil and measure the voltage generated and the time lapse from exitement to spark.
They do this over a variety of speeds and those that are perfect go into machine factory branded boxes or factory assembly trays.
And measure the number of sparks generated and compare them to the number that should have been generated .
From there on in they get dropped into "lesser" quality ( and price ) bins till eventually they are totally unuseable & they go into the scrap bin .

Now the QC lab might actually pull the odd one off the line and take measurements for the purpose of monitoring and comparing different components but the factory tests & sells them according to their output .
So basically it is the same as works or don't work .
 
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welchs101

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got new ignition coil............NOW I HAVE SPARK. So cool. Can you tell i am a newbie at this?

Ok, so i put some fuel in the spark plug hole and put spark plug back and put ignition coil back and tried to crank it........i guess it kinda turned over but did not run a lot.......i am going to say it ran for 1 sec maybe..........i tried connecting gas tank and priming bulb and starting it this way and it just wont start. So am guessing now it might be the carb? My carb i think has part number 753-05633.....anyone hve any videos on how to repair this one? or what ot look out for?
 

welchs101

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ok, i took the carb apart and cleaned it with carb-spray.....put it back together and ........nothing still wont start up.
this 2 cycle carb has diaphrams and a few other things........not sure how to tell if the diaphram is good or bad..........i cleaned out spraying through all the holes but again not sure if the diaphrams are ok.......any idea on if they sell a carb kit? i have looked all over and cant find one....my carb model number is 753-05633

thoughts on what to do/try ?
 
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