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'73 C12 no spark

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Someone help refresh my memory. Not getting any spark at the spark plug or points. Have power to coil and to points with ignition on. Not getting spark at the contacts on the points. Do I have a condenser, points or coil issue?

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Did you clean them points?  :scratchead:

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As Craig said, clean up the points first. Also, try a different spark plug wire. You can unhook the condenser for testing, if your spark returns then the condenser is probably bad.

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Thanks all. You were right, filed dem points and set em, fired right up 🙆

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    • By Muddyfeet
      BeOk first off I have a older 80 400 series .  Was my father's and I am attached to the old lady.. it Was running ok.. 
      This year after a year outside  it just will not start. I am Not a mechanic so working blind. 
      I have the seat switch bypassed, also the PTO saftey switch. Replaced a lot of little parts,.Don't know if there is something else . so.. history aside.. cranks  no start.. using a test light.love my test light.. fixed a lot on some older engines with this.. anyway. Test light not meter. I get power to the points. Power. To the + end of the coil.. a flashing on the neg side of the coil when cranking.. I do get power after cranking on the neg end of the coil.. the two posts not where the spark plugs wires come out.. I do see A white spark seen and heard at the points when cranking and if I pull the points apart when not cranking .. using test light or inline spark plugs test nothing. have not done the pull  plug and ground to see.. but using test light I put in on the cable no light.. no light on the coil tower either.. I replaced the coil, condensor and points like 8 years ago I think.. it was hard to start and I was using the manual.. 
      So no spark if power to the coil but nothing out equals bad coil right??  Well the local shops quote for 280 for a coil was a shock. . but looked online hard to find but a little less.. 
      Cannot rember what I spent before.. 
      So worth buying a coil and if so may as well replace points and condensor at same time?? Am I missing something?? Got power going into this and nothing out as I can see.. but heck what to I know.. 
    • By Mastiffman

       So if you've problem solved all other aspects regarding your non-starting Onan engine with electronic spark control and come to the conclusion that you need to replace the Ignition module, keep reading. This is a decent step by step and doesn't require the engine to be removed the from the tractor. Although it might be a little easier to work on while on a workbench.

       The part numbers for the Module and ring if needed are below:

      Ignition Module: 166-0785
      Spark Ring: 166-0767

      Here is a list of the tools that I needed to complete the job from beginning to the end. They are named from left to right in the photo with the tools at the top of the photo last from top to bottom.

      [From left in Photo]
      1. T25 (for the stator screws but also may be three 5/16" head screws)
      2. Phillips and Flat Head Screw Drivers
      3. Needle Nose and standard slip joint pliers
      4. Flywheel puller with 2 5/16" x 18 grade 8 bolts and washers (mine is technically a steering wheel puller)
      5. 7mm and 5/16" deep well 1/4" sockets
      6. 3" 3/8" drive extension, 3/8" socket 3/8" drive, 5/8" socket 1/2" drive and 5" 1/2" drive extension. 
      7. 1/4" Socket Driver
      8. 5/8" open end box wrench
      9. 3/8" and 1/2" drive ratchets

      [Top of photo- top to bottom]
      10. Flash light (optional but very helpful at times)
      11. Pry bar (used to lock flywheel from turning)
      12 1/2" Torque wrench
      13. Old Tooth Brush (for cleaning of dirt if needed)


      - Obviously the first thing to do for safety sake is to shut of the fuel at the tank and remove the battery cables
      - Next, remove the two screws that hold the fuel pump onto the shroud, move the pump off to the side and replace the screws into their holes for safe keeping.
      - Carefully pull the fuel pump away from the shroud enough to work the hose clamp out and use the pliers to pinch the hose clamp and remove the vacuum line for pump. 

      - Tie the fuel line, wiring harness, choke cable and battery cable all out of the way towards the rear of the tractor allow easy access to remove the shroud.

      - Next remove the air cleaner box cap, then air cleaner cap and air cleaner tray by removing the three 5/16" screws from the carb and the two 3/8" screws from the tray and put all aside and out of the way. 

      NOTE: Close the Choke all of the way and stuff a clean paper towel into the top of the carb to prevent debris contamination.

      - Next, twist the air filter box bracket to the left (right side up and left side down) to clear space and use the 7mm, 5/16" and 1/4" socket driver to remove the black condenser wire, the red and black ignition module wires and the yellow ignition switch wire from the coil and then remove the coil using the 3/8" socket. (optional as it can be kept on the shroud but makes it a little more difficult.)
      -  Next loosen the rear cylinders top shroud and engine hoist mount bolt with the 1/2" 3/8" sock and extension. (no need to remove the bolt as the shroud just needs to move freely. 
      - Next, locate the wire retaining clip at the top of the shroud by the coil and open it up so the oil pressure sensor, stator and ignition module wires can all be removed when taking out the shroud.
      - Last step before removing the shroud is to disconnect the throttle to gov arm spring and the throttle cable using  the 5/16" socket and driver.
      -Next locate all of the shroud bolts and remove using the 3/8" socket.

      - To remove the shroud, pull the bottom out first and then shift the entire piece upwards while working it from underneath the rear cylinder shroud, underneath the filter box bracket and over the flywheel on the left side. Work slow so you don't bend or brake anything and it will come off pretty easily. 
      - Although everything was fairly clean in comparison to other engines at this step, my shroud was dirty and this can slightly decrease air flow which is important to maximize and keep optimal with an air cooled engine. 

      So I took mine outside and pressure washed it to give it time to dry completely before reinstall. 


      Shroud off... 

      - Next, place the pry bar into the fins of the flywheel and lock the flywheel in place by placing the handle of the pry bar under the foot rest. Then use the 5/8" sock, 1/2" extension and loosen up the flywheel bolt about 3/8" -1/2" out of the hole. This needs to stay mostly in as a pressure point for the puller.
      - Next, remove two of the flywheel grill center bolts and then use your two 5/16" grade 8 bolts and attach the puller to the flywheel while keeping the puller parallel to the surface of the flywheel to allow equal pulling pressure on both sides of the puller while cranking on the center pressure bolt on the puller. 

      - Now it's time to remove the flywheel.  It may be a good idea to use the 5/8" open ended box wrench to stop the flywheel bolt from turning while cranking on the puller center bolt. 
      - It should only take a 3-5 good cranks after finger tightening the center bolt and the flywheel will give a good pop and be ready to be pulled off. Don't forget about the flywheel bolt first!


      - Next, carefully pull the flywheel off of the crank being very careful not to get caught on the stator itself. 

      My flywheel was pretty dirty on the inside and between the magnets so I felt it necessary to use the toothbrush and air gun to clean it out. 


      - Now you'll need to remove the stator by using either 5/16" socket or T25 torque bit or driver. 


      - Next, set the stator off to the side securely on a clean rag or similar. Underneath, you'll see the ignition module on the bottom side of crank. There are two 5/16" head machine screws. Remove those and open the wire retaining clip on the side of the gear cover and the module comes right off. Make sure not to lose the black rectangular insulator that goes between the module and gear cover. That needs to be there. 


      I'm not 100% sure but I have a theory that these modules may potentially go bad from getting covered with grass and debris over time from not blowing out the air shrouds with a leaf blower or air gun after each use. This debris builds up enough to cause insulation around the module. The module being an IC (Integrated Circuit) is designed to handle only so much heat. Over time the extra heat and expansion with contraction when cooled back down causes a when point in the modules chip circuitry and eventually breaks. Thus causing the engine to shut off during operation for the first time. Once the engine cools, the chip materials contract, allowing the circuit to bridge again only until the engine heats up enough to break that signal and then becomes a cycle until replaced. 

      - Moving on.. While everything is out, if needed (or your OCD kicks in), clean the cylinder heat syncs and general area before re-installation of the Module, Stator, Flywheel and Shroud. Mine wasn't to bad so I quickly used the toothbrush and air gun to break free any layered gunk and blew it off with air. 

      -Next, once the insulator, module (and spark ring if chosen to) and stator are all reinstalled and screws all snugged up, carefully put the cleaned flywheel back on, install the flywheel bolt with a tiny tad of anti-seize on it and use the pry bar again in the flywheel fins but with the handle on top of the foot rest and use the 5/8" socket, extension and 1/2" torque wrench set to 55lbs and tighten up the bolt. 


      At this point, go ahead and reinstall the Shroud making sure that the fuel pumps vacuum line is accessible through the front hole in the shroud, along with the shroud bolts, coil, coil wires (spark, condenser, module and switch) and tighten rear shroud bolt. 

      NOTE: Yellow Switch wire, red module wire and black condenser wires all go on the Positive coil terminal (7mm nut) which should be on the right side of the coil. Only the black module wire goes on the left terminal. 

      Connect the throttle to Gov arm spring, throttle cable, install the fuel pump vacuum line again and replace mount screws. 

      - Lastly, re-install the filter tray, remove the paper towel from the carb, along with installing the air cleaner, pre-filter and clean cap and shroud to filter tray pipe. Then connect the battery and turn the fuel back on. 

       This should get you going again. 

       I think that I got everything but please feel free to comment on anything that I missed as far as documenting the steps or ask any questions about the process. 

       Hope this helps you see that it's not that bad of process to replace the ignition module (And spark ring if needed as some recommend replacing the module , ring and coil all at the same time).

      I had to first remove this module from a P220G that was on my bench and awaiting repairs but the whole process took me a few hours. A good Saturday Morning task to be up and running by the afternoon for some work before the heat hits. I also ran the tractor for well over and hour after install to insure all was well. I went from a warm up process of idling and then a lap around my property. Did that a few times while repairing a cutting deck and then installed the cutting deck and mowed the lawn. No issues. Ran great! 

      Take Care and God Bless!

      Andrew C.
    • By 69-Raider-10
      Hello All. Picked up this little feller here a couple days ago and just got around to wrenching on it last night. I cleaned up the carb, put a new plug in, new oil and fuel, and it doesn't want to fire. Checked the spark and I don't see anything. 
      Ran fine 2 years ago the guy said and I have every reason to believe him. I guess I have two questions:
      1.) What is on this, magneto? Where can I buy one to replace?
      2.) I have a Trailblazer 7 with a 7hp Tecumseh pull Start. Think I can pull that magneto off and use it? (Assuming it is indeed a magneto).
      As always, Thanks for the help!!

    • By mmmmmdonuts
      I was snowblowing the other day and got about half way through my driveway and all of a sudden my tractor died and I could not get it restarted. The first thing I noticed when it died was that the battery went down rapidly to about 7V but I think that had to do with my external alternator hooked up and not spinning but I could be wrong. I got the tractor back in the shed and could not get it turned over at all. The starter spins and everything seemed to move freely but I was not getting a spark. Changed the spark plug yesterday because it looked pretty gummed up and still nothing. This morning I was diving into the electrical system and got to the points where I was going to reset the timing and I realized that the points plunger does not move when I rotate the flywheel by hand.

      I guess at this point I don't entirely know what I have to do. Is it an easy/worth it fix or does the whole engine need to come apart? Can I change it to a different type of ignition system? Any other thoughts to try? Repower?
    • By Smokey
      Recently my C121 decided it didn't want to start and I've been trying to figure out the reason (s). When I turn the key I get nothing, No click, No sound at all.
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      To make things just a little more peachy, My multi-meter bit the dust as soon as I started trying to track down the problem.   Ordered another one but in the meantime looking for a clue.
       So, What I know so far is this-
      New battery, Fully charged. Terminals clean, Ground points on tractor cleaned. Replaced crusty negative battery cable.
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      If I run that jumper wire to the outgoing (to starter) bolt on the solenoid the starter spins but the tractor doesn't start. Lights do not come on.
      If I run the jumper wire from positive battery post to the + post on the coil the lights come on with the key turned to the first position but go out when I turn it all the way to the start position.
      I am not a mechanic or electrician by any stretch of the imagination but I'd like to see if any of you wheelhorse doctors have any advice on what might possibly be the problem?  Ignition switch?  Bum Chinese made solenoid?  Any help is appreciated.