Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

I turned the key on and have no spark from the plug or even the plug wire when turning over the engine

How do I know if it is the coil magneto or the xstar module magneto?

It is a model 38180

Wow trouts2!  Thanks for all that detail.  I know a lot about carb rebuilds, tunes ups etc., but very little about coils.  So that makes a lot of sense that the legs I see are multiple pieces of iron sandwiched together with nothing touching them except where they bolt to the engine.  Setting aside the spark plug wire, there are two wires coming out of the side of the coil.  A small 18-20 gauge yellow wire.  This wire is screwed directly to one of the iron "legs".  The other wire is a 18-20 gauge red wire which connects to the mega fire II ignition module.

I see how the iron core is isolated as you said.  Because of this, as you said, I should get no readings on my basic multi meter when I touch the iron core and any other wire.  This would then include iron core to spark plug terminal and iron core to primary wire (the red wire I keep mentioning) which connects up to the ignition module. 

Would the spark plug wire be connected somehow inside of the winding to this (red) primary wire which goes to the module?  I am not getting a continuity reading when I touch spark plug wire to the primary (red) wire.  This is shown in the lower photo. 

Based upon what you have said, I should NOT get a reading from this primary (red) wire to the iron core.  But I am getting a reading here (as indicated in the top picture).  (short red wire turns into black wire which is the primary wire that connects to the module).  Both the original coil and now (after my 30 second run time) have identical multi-meter readings.

Thank you very much for your time and effort in this diagnosis.

Photo 1 did not load but it shows I am getting continuity from the iron core to the primary wire which connects to the module.

Brocman,
    I please excuse some mis-information above.  Here's the corrections:

1. Your coil has a primary and secondary.  The secondary is also the kill wire. 

2. The spark plug end and the secondary ends outside run internally through coils the other side of which go to ground.

3.  The resistance on the secondary to any ground should be .8 to 1.1 ohms. 

4. The resistance on the primary to any ground should be 5800 to 7940 ohms.

   You had been checking from primary to the spark plug which is a short test.  Do the above two tests on both coils and see what you get for values.

   You posted above that you put in the MegaFire "to replace the original".  The 38180 did come with an XStar module.  Your 381185 did not.  It had points.  ?? Confused by that.

Comparing the MegaFire to XStar.
 
   The XStar module bolted to ground and had one lead which runs to the secondary/kill wire of the coil.  So it's a module with one lead that connects to the primary.

   The MegaFire and other generic modeuls areabout the same.  They have a couple of leads so it can be connected to a positive or negative grounded system.  Not a big deal.  Depending on the ground one of the module tabs gets wired to ground.   With one tab wire connected to ground that leaves one tab wire and that one is connected just like an XStar.

   The picture of the Rotary module setup is good for the MegaFire II.

Flywheels and magnet count:

   The 38180 was made to have an electronic module.  Your 38185 was not.  The flywheels are different part numbers.  You say yours had three magnets and Denny said his had three.  The XStar was meant to run with three magnets.  MegaFire says not to use their module with multi magnet flywheels but guys do that and they work.  Yours may work or it may have blown your coil although I doubt it did.  I'd guess your second coil is good.

   I'd retest both coils on the machine.   Connect the coil and points up without the MegaFire and turn the flywheel magnets sharply past the coil and check for spark.   I put my finger on the sparkplug cap end to ground and feel for a spark.  Wash your finger first as there may be enough dirt to block flow.  Check both your coils.  If you get spark then connect up the MegaFire without going through the stop switch and you should be ok.  If that works wire in the stop switch.  

Below is the 38180.  Blow that is the 38185, no XStar.  ??  Note the XStar has one lead.  The primary splits and would go to ground and the other wire probably to an on/off or kill switch.

 

well i think where making this diagnioses a bit complicated.....lots of good info given which is good but also complicates things alot!!... the system is very simple to diagnose... no mutli meters required... like i mentioned before make sure u have a good connection on the "red wire" to ground....disconnect the kill switch.....and since u had the coil off my sure it gapped at .010-.012... and if u have a adjustable spark tester set it to at least a 1/4 gap...then test...if theres no spark the coil is no good... no more testing needed...

as far as adding a aftermarket module which is fine when your replacing it on a points system (i have used ALOT of these modules with 100% success) ...but when your installing it on a magneto coil (electronic) the module is inside the coil so if the module inside the coil go for a $#%*, then the wire coming outta the coil (red wire) is just the ground for that module inside (which is also connected to your kill switch)...so if the module "(switch)" in side the coil get stuck ON then u can add an aftermarket module kit and it will work..although if the module "(switch)" becomes open (no connection) then an aftermarket module will not work.. hope this makes sense...

Thank you guys for all your input!  This dog gone thing has become somewhat of a quest.  Like I said earlier, I hate to throw away a good machine.  I have seen a coil/module combo on ebay for about $75.  That would be my final effort.

Here is the latest that I have done.  As I stated, last week I bought a used coil.  I also bought a mega fire II ignition module.  The other day I installed everything and got good spark. I then put it all back together and it ran for 30 seconds and quit.  Thats when I started posting on this forum.  Following all these wonderful suggestions for you guys that have donated so much of your time, I carefully cleaned all connections real good.  I took some fine emery paper and lightly sanded all areas that had electrical to metal connections.  I also took some lacquer thinner and wiped all dirt and dielectric tune up grease I had applied to any connections.  I did this thinking that it may have some how been forming some kind of barrier.

I should re-iterate that the flywheel has 3 MAGNETS on it.

Tonight I reinstalled everything and gaped the coil with the recommended business card.     Wire was installed from coil to mega fire II ignition module.     Wire then installed from ignition module to good ground.    NO SWITCH WIRED IN AT THIS TIME.     I then filed and cleaned an edge of an engine cooling fin to hold the spark plug against.    I plugged in the electric starter and while holding the spark plug against the filed cooling fin, I got INTERMITTENT SPARK (although I did not get "zapped" when holding the plug wire).  It would spark for a few seconds quite aggressively and then stop sparking.   It sort of looked like a big thick spark.  Sort of bigger than a normal spark you would see.   Returning say five minutes later, it would spark again and then stop sparking.   I have the plug gaped at about .030-.032. 

Unfortunately I do not know what to guess at this point.  Perhaps the module.   Since I am getting a real good spark now, I am leaning towards the module and not the coil.  Could a coil throw an intermittent spark?    Perhaps I should buy a different aftermarket module?

Hopefully it posts, but below is a photo of the exact setup as removed from the engine of this 38185  sn 2001010.  Notice the module in the photo.  Brand new that baby goes for $125 +.  This is the one I replaced with the mega fire II.

broncman wrote:

ok pictures are good:))..... with that setup in the picture its wired exactly the same way with the replacement module... so the wire coming from the coil goes to the POSTIVE side of the replacement module and of course the other goes to ground side... now personally i would NOT use a business card as a measuring tool becuase business cards vary in thickness alot...and lve repaired more than a few coils gaps being out of adjustment in the past from customers using business cards...i did one this summer that had a gap of .045.. customer said he was told to use a business to gap it... bad idea that machine would not start...all i did was re gap to .012 and it started right up.... so its important to get the right gap set.. set the gap at .010-.015..

as far as having spark then it stops is unusual...maybe your replacement module isnt working properely??...but first get the gap within spec..then if no change i would try another module..

i was just reading up on these modules.... and aparently they will work on 1 or 2 magnet flywheels.... so if yours is has three thats most likely going to be a issuse... need to read more havent ran into this issuse before...of cousre i cant remeber if ive ever installed a module on a three magnet flywheel before... hmmm something to be concerned with for sure..

If you don't have feeler gauges, a sheet of paper is often about 0.003-0.004" thick. You could try a few sheets of paper to try for a 0.012" gap. You could also temporarily try setting the spark plug gap really small (maybe 0.010") just to see if the spark became more consistent.

>>>Could a coil throw an intermittent spark?   

    Yes.  Can happend with a small open in the primary winding.

>>>Perhaps I should buy a different aftermarket module?

    No.  Without a reading from ground to the spark plug end of the coil other parts won't make any difference.  The coil is defective.  If a new module does then your meter is defective. 

    The coil secondary is a single wire from the sparkplug end, wound many times around the iron core then to ground.  The reading you should get from the sparkplug end to ground is 5800 to 7940 ohms.  You get zero and intermittant spark.  That indicates the coil is defective and has a break in the coil wire.   Since your getting intermittant spark the spark is juming the open sometimes and sometimes it dosen't.  That happens at times and not unusual.  The induced voltage is very high and jumping an open not that difficult. 

    A possibility that give the symptoms is a bad connection from the primary coil to the sprk plug hood.