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Uh-oh. Mf12 Not Starting!


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#1 Finch OFFLINE  

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Posted June 05, 2012 - 08:42 PM

I joined up here just last night, posted up some photos and now my Massey is giving me grief!!! I was mowing last night and my tractor wasn't running the greatest, I just chalked it up to bad gas or maybe some condensation in the tank, it eventually stalled out on me because I smacked the choke by accident. Seeing as my battery went south I didn't have the energy to push it over to the driveway for a boost so I left the old girl out overnight. I bought a new 410 CA battery today and put it into my machine but now it won't start!! Machine turns over good, compression is fine, engine is getting gas ( drained the tank, cleaned and refilled it) but I noticed that my spark is almost non-existent. Kinda makes sense seeing as it's been starting kinda crappy and now it floods before it starts pretty much.

With these issues in mind where should I begin to trouble shoot the ignition? I see that many have completed the SSI Coil modification but I'd like to start with some simpler fixes before I finally bite the bullet and tear down the tractor. I am an electrician by trade so I DO have meters and know how to operate them and the SSI fix shouldn't be too bad for me but I'd like to exercise any other options first, mostly because this is the worst possible time for this to happen as I'm swamped at work for the next few weeks and can't really dump hours into sitting in the garage tinkering.

In the meantime I'm going to read Ed Stollers webpages and see what I can get out of them as to my next move in getting enough spark to get me through the next couple weeks of mowing, until I get the chance to really get under the hood on a nice Saturday.

Thanks in advance for the help everyone, the tractor is a 1974 MF 12, with the H120. Which ignition type is on this model of engine in particular? I'm a total dork when it comes to fixing this tractor because until now I haven't had to really do much with it, it's been a garage queen for awhile.

#2 HowardsMF155 ONLINE  

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Posted June 05, 2012 - 08:48 PM

I am far from an expert on these, but I would say that you should pull the shroud off the flywheel side of the engine and take a look at the flywheel, and particularly the two pins that form the trigger for the electronic ignition.
Gonna go check your pics now................................

Ok, you said it was a 74 so it is probably electronic ignition. I'd check the pins and make sure they are free from rust and that the outside of the flywheel is clean also. I don't remember what the gap is supposed to be between the pins and the coil sensor. I'd also check the electrical connections there at the coil and make sure they are rust free. I think that is a ground wire on the spade terminal, so don't expect to find voltage, nor should you try to jump voltage to it, as that will certainly fry the coil sensor. Check and see if that ground wire is shorting to ground. Try a new plug, I've had them go bad.

Edited by HowardsMF155, June 05, 2012 - 08:56 PM.


#3 MH81 ONLINE  

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Posted June 05, 2012 - 08:58 PM

Well, the first and second things you need to do are pretty simple.
First, find the wire that comes down from the ignition switch which would be a short to ground with the key off. This is your engine kill and you need to isolate and disconnect it from the system. Try to start the tractor. Be ready with a screwdriver to short out the spark plug to ground as the key will not shut it off. Hopefully this is what happens and you just need a new switch. Probably not.

Next is a little less pleasant, but for a guy who's probably felt voltage before, it won't be bad. Take your pinky and hold it to the frame, take the wire that you disconnected from the one that goes on over to the engine (not the switch end) and grip it or an extension wire with your thumb and finger and have someone turn the engine over. You should feel a slight tingle. Ed refers to this as the "tickle" test. You are feeling the pulse from the pickup that charges the CDI.

That's enough for a first step, let us know what you find.




#4 MH81 ONLINE  

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Posted June 05, 2012 - 08:59 PM

Good call Howard, I forgot the spark plug first. If it says Champion, I don't trust it.

#5 Finch OFFLINE  

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Posted June 05, 2012 - 09:31 PM

The plugcurrently in the machine is indeed a Champion RJ19LM, so i'll pick a new one up tomorrow because it can't hurt to try. I will also get the cover off and see if there is any oxidation on anything there shouldn't be. I'll keep everyone in the loop!

#6 IamSherwood OFFLINE  

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Posted June 06, 2012 - 12:06 AM

I don't think that's the right plug for a hh120?

If using Champion, it hould be J8 , which is now J8C.

Edited by IamSherwood, June 06, 2012 - 12:21 AM.


#7 Finch OFFLINE  

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Posted June 06, 2012 - 06:11 PM

Well, sadly I went out and bought a RJ19LM, but I can stop again tomorrow and pick up a J8C to try. Either way, I'm still no better off. What kind of spark should I be seeing if my ignition is functioning properly? There is spark, but I'm not sure if it would be considered enough spark. I tried to clean the two poles off on the flywheel, the whole area under the shroud was totally dirty, as in a solid 1/4" of junk covering just about everything under there. Am I able to remove the coil without wrecking anything so I can also clean the unit where the poles pass? I'm trying to not get discouraged but it's tough not to right about now. Checking the gap between the pins and the coil seems impossible, am I missing something there? How would you adjust the pin height?

Sorry for the stream of questions, I'm just a little bummed out.

#8 IamSherwood OFFLINE  

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Posted June 06, 2012 - 08:01 PM

Sounds like you got some cleaning to do.
Useing a feeler gauge, you can check the gap. It should be between .006" and .010".
You adjust the gap, by moving the coil.

#9 MH81 ONLINE  

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Posted June 06, 2012 - 08:51 PM

Yeah, clean, clean, clean... Heat is a killer of not just electronics, but engines too.

you might want to read thru this thread: http://gardentractor...ws/#entry170813
  • IamSherwood said thank you

#10 Finch OFFLINE  

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Posted June 06, 2012 - 10:53 PM

Yeah, I'll start the grand disassembly tomorrow night and give it a good cleaning and then start to go over the electronics right from the switch all the way to the plug, sounds like the only solid plan. I took the carb out and cleaned it all this evening and it looked quite clean even before I did that. If I can't nail it down I just might have to go with ignition upgrades if I can't seem to get a bit more spark happening. Again, thanks for all the help guys, and I'll keep you posted with photos if need be!




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