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

Thanks Niper99...I will double check the ground connection and isolate the switch again.  If I take the switch out of the mix, hopefully I will see a spark.  That would be a wonderful, easy fix!  I will make sure to sand down any paint on the flywheel cover and I will install a new bolt which holds the ground wire against the flywheel cover.  It does seem odd that a working coil would go shot so fast.  The thing that makes me think it is the coil is that when I try to establish continuity with the multi meter (from the red wire on the coil to the spark plug terminal), I get nothing.   Thanks for the suggestions.

broncman wrote:
I've never seen this coil before, so "the red wire" doesn't mean anything to me, sorry. What is the red wire? Is it the wire that leaves the coil, going to the spark plug connector? As in you think there's a break within the wire, between the coil and the plug?

This one is a Rotary 8786 from Tulsaenginewarehouse for 12 bucks. Also known as Nova II.

Niper99, check me on this,

   The module has two tangs.   Regardless of color one tang is positive, the other tang negative.  Depending on your grounding one lead goes to the coil wire (the one cut away from the ponts) and the other to ground.     Done.

   If  a stop switch is included how it gets wired could vary slightly. 

   The non-grounded wire from the tang could go to the switch then to the coil.  So the switch would create an open or connection.

   The non-grounded wire from the tang could connect with a wire nut.  From there one wire run to the coil and one to one side of the stop switch.  The other side of the stop swith would go to ground.

     Again depending on your ground being plus or minus one tang is grounded and the other wired as above.  Not for use with battery start engines or flywheels with multiple magnets. 

Thanks for the input guys.  Later today, I will triple check to get good clean connections and temporarily take the switch out of the mix.  I had bought the Mega Fire II Ignition Module.  The info on this module did not state that it would not work on flywheels with three magnets (this machine has 3 magnets).  My spark plug is good and shows continuity.  I wired the module just like the instructions previously posted showed.  Hopefully my photo has posted.  My coil shows continuity between the (partially red) coil wire and the coil arm.  However there is no continuity between the coil arm and the plug and no continuity between the coil wire and the plug.  I think this means the coil has gone bad.  This week I will have to track down another coil.  Say, the mega fire instructions show one wire being grounded with a screw through the hole on the mega fire and then to the engine.  Must the actual metal case of the mega fire be grounded too, or just the ground wire of the mega fire?  I would not think so since the mega fire has a ground wire coming out of it.  The machine was running excellent (for about 30 seconds).  I will keep the forum posted with updates.

Below shows the armature or iron core.  The coil is electriclly isolated from the core.  Yhe test leads as shown should read zero ohms.

Below 24 is the armature or core.  No connection to anything.  48 is the trigger coil for the transistor controlling the low tension side of the coil at 36.  The magnet loads it's flux into the iron core (24) and induces a current on the output side of the coil (86)  The armature core is usually mounted to the engine by a bolt so grounded.  If you get no reading between the armature and the sparkplug end that's good.  You got a reading to the other wire.  Where does that go? 

   The Mega fire case tab should be grounded.  Most directions show the ground wire going on top of the tab and both screwed into the engine, grounding both.  The tab gets grounded and the wire on top gets its ground from the tab.  You’d have to have a physical and electrical schematic to be sure but that’s the way a few makers show them connected.

 

   Megafire and Megafire II directions are different over time but both say both won’t work with multiple magnets or nothing about magnets.  Multiple magnets do not make sence with the design.

   BUT people have success with multiple magnets…...  Depending on when the magnets cross the coil in the timing cycle people get lucky and it will fire properly and either not fire on the following magnets as it’s not ready or be firing into an unloaded combustion chamber to no effect.

 

Testing:

     Generally speaking you could look at the black coil module in the picture you posted as a whole and the two things sticking down could be called arms or legs.  The could be called the arms or legs of the coil when talking about the whole lump of the black thing, the solid state ignition. 

 

   BUT… The coil arm you mentioned is really the arm or leg of the iron core and not specifically the coil in the electrical sense.  It’s isolated from the coil windings, does not touch the coil windings and does not pass current to them directly by contact.  The flux generated by the magnet, gathered and directed by the iron core induces a current in the coil through the air, no touching.   You won’t get a continuity reading from the iron core to any wire unless it goes to ground as the iron core is bolted to the engine.

 

   For regular coils when they talk about resistance testing from the “leg” of the primary to the other side they are talking about going from coil lead wires not the core.  The same for resistance checks on the high tension side.  The  

  

    You got no reading from the core to the spark plug.  I think that’s ok.  I’m not sure about the other wire.  Where did that wire connect?  Unless it connects to ground there should not be continuity to thr iron core arm/leg.

    Once you get the molule mounted you can test by just spinning thr flywheel by hand for spark.

 

   A guy who’s really good at SSI’s is Ed Stoller his website is at  http://home.earthlink.net/~edstoller/

 

   He’s available at the Tecumseh reflector or used to be. He’s a great guy and about the most savvy guy on the net on SSI’s.  If you email to the adder below and he’s around he’d be a big help.

 

    tecumseh_engine_group@yahoogroups.com

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...