Help, no spark on 112 JD

Of course, just when we are to get a blizzard and snowed in, my old reliable JD 112 has no spark. Ran just fine the day before but today she just decided to not fire. It turns over just fine but when I checked the plug there was no spark????? I eliminated the coil by using another coil off a 110. Where do I start to look? It's snowing pretty hard right now, I need to trouble shoot this as fast as I can. This old tractor has been my saving grace. Has the Tehumseh 110 motor. Any advice would be greatly appreciated. Tater

Since it seems you have an external coil on a Techumseh, it has breaker points in an enclosure on the side of the engine, and it's a battery-powered "Kettering" ignition system. If it DOESN'T have breaker points, none of the following applies!

Start by verifying battery voltage on the (+) terminal of the coil, if present, move the test light to the (-) side of the coil.

Crank the engine, test light should flash as the breaker points open and close.

Test light never flashes/on steady = points are dirty/not making contact.

Test light never lights = bad coil (which you've hopefully ruled out) or the points never open or there's a short in the breaker box/breaker point area.

It would help if you gave more info as to type of ign system on eng as the HH100 eng used 3 different ign systems in the 66-72 time frame of the 112 tractors.

In the mid 60's-very early 70's the standard ign was 12v point/coil system,I would like to add 2 other things to Bob's fine troubleshooting instructions for this type ign system.

1-in your hurry to change coil check that you don't have reverse polarity connections on coil,+12v from ign sw to + terminal on coil & condenser connected to - terminal on coil,if polarity reversed/condenser connected to wrong coil terminal,both will cause a no spark condition when coil replaced.
2-if points check ok & you have +12v to/thru coil try replaceing condenser,if same open/shorted or disconnected you won't have spark.

Starting in late 70-early 71 tecumseh went to solid state ign systems,early system usually seen on eng with starter/generator,recoil or rope start & had a spark generator mounted under flywheel that connected to a small black coil mounted on a Y bracket over flywheel & under flywheel cover.

The 2nd solid state system used on eng till the end of HH series production had the normal style starter with a ring gear flywheel & an alt stator mounted under flywheel with a large cast aluminum ign module mounted over flywheel & under flywheel cover,the alt stator has a seperate winding on it to power ign module in addition this system had 2 trigger pins located on rear lip of flywheel to turn module on/off(1 long,1 short)make sure both pins present,IF this is the system you have & you replaced coil also check air gap on LONG pin to trigger leg on module,should be .006"-.010".

As with most solid state ign systems this requiers grounding system to stop eng,DO NOT take a +12v jumper from battery/electrical system to ign kill lead leaving eng when troubleshooting or you will instantly burn out either system.

If system solid state the 1st thing to do when troubleshooting is locate ign kill lead at eng & disconnect it from lead to ign sw,after that crank eng & see if you have spark with a NEW plug(on point/solid state systems on the HH series when they get tired & burn oil they tend to eat plugs)if you now have spark or eng fires/runs then you have elect system problem(shorted kill lead to ign sw,bad safety sw(s) or bad ign sw).

If still no spark with kill lead disconnected/NEW plug the problem on eng,the only way to check either solid state system is to replace spark generator/coil together or alt stator/ign module together,it's rare seperate winding on alt stator for ign module goes bad,but it does happen,good luck troubleshooting.

Thanks for the quick response. It's the older HH100 with the points and condenser, it's a 67 112. I'll be back out in the pole barn today to see what I can find out. I'm sure it's something simple as it was running fine and just up and quit. I'll check for power to the coil. I was very careful to keep the wires in correct position on the coil. Thanks, I'll report what I find out. Terry

If it has the shut off like many do where you have a wire going to your switch or other such parts pull the wire off and see if it then has spark. I have had the shut off part on many lawn mowers etc where it is mounted to the carb linkage go bad and short out and cause that problem. With out digging into my pile of manuals I do not know it is has that or not but if it does I would check it out

He apparently has a battery/Kettering ignition system, rather than a magneto ot self-powered EI.

So it has a power wire, NOT a ground/"kill" wire.

Maybe but replacing a coil could also be he pulled the mag since some people call the mag coil a coil but hard o say for sure with out him filling in the blanks

Rub the points with some 400 grit. Then see if it will start. Hal

Well............Spent this evening out in the barn checking everything out. With the key turned on I had 12 volts to the positive side of the coil. Checking the neg. side I couldn't get any needle movement, with the key on or by turning it over. I started swapping out stuff from my other tractor with no luck. I was about to give up when I put everything back together and it started. What?????? Leaves me pretty unconfident with the tractor. My question would be what should I have at the neg. side of the coil?? Could it be the points? I swapped out the condenser and it appeared to be OK. It still appears that the spark is not very strong. Thanks for all the help!!

Bad condenser can cause that type of problem and or dirty points. With the points open you should see battery voltage but with them close you should see little to no voltage

Well, I found that the points were not opening properly. I removed them, they needed to be replaced. Looking at the push pin, it was barely moving when I rolled the engine over. My futile attempt to remove the pin ended with it snapping........that's just great. Now what? I've actually pulled the motor off the frame and unto the bench. I have a feeling it will be headed to the small engine shop for repair unless it's very basic. This has been a roller coaster for sure. At least it's not snowing.........yet.