Farmall F-12 No Spark

[wowsk]

I went to start the F-12 yesterday and wouldn't start. I thought it was something with the carb or due to the cold. Had my cousin help pull me try to pull start it and nothing except an occasional light pop. I took the plugs out and they were wet so plenty of fuel. Checked spark and nothing but you could feel a light spark when holding on. Took out the points and they were ok, but cleaned them up and put them back in an regapped. Still nothing but a light spark when holding. The points probably could used replaced but should make a spark. I've been starting it fairly often this summer and had just started it a week or two earlier fine. It can take a little bit to start sometime (10-20 cranks) but always starts.

What are some things to look at on this? I was thinking condenser as next step but wanted to run it by you guys for any ideas too. This is the tractor I got going that was sitting 50 years and only thing I did to the mag was dress the points and it worked well, so nothing has been replaced yet.

Thanks,
Noah

 

[560Dennis]

Well if it that old , might be the coil in the magneto. Might the wires ,cap ,rotors contact corrosion , thunder the old tractor needs some parts
, check Brillmans get some good stuff . Hit it with a shot gun approach change everything or , one thing at a time up to you , starts at one
end work you way to the other, if you want. Plugs and wires cap rotor. ! Points and condenser . Mag coil up to you , dont assume anything
,you got the entire magneto system to check out.

Magneto wires are copper. Brillman has them .

 

[golfcartman]

I would try new points and condenser first and if you dont get a good spark then, it will prolly be coil or weak magnets in the mag.

 

[redforlife]

I had trouble with an F-4 mag about a year
ago. Seemed to have spark, but apparently
it was weak. I cleaned and polished points,
and it didn't help. Changed the points out
with a used set that I thought were atleast
better than the points that were in there.
It still didn't help anything. I ended up
changing the condenser out with another old
one that I had (I had a whole box full of
old F-4 mag parts). That must of been it,
because I then had a strong enough spark to
run the tractor.

This wouldn't have to be your problem. But,
it'd be my next thing to try if it were
mine. And probably the thing to do before
messing with the coil or magnet.

If the magnet is strong enough to be stuck
to the side of the frame rail or radiator
and be able to support its own weight, it
has adequate strength to throw a good
enough spark. And one thing is key about
the F-4 magnet (or so I have been told),
the IHC logo needs to be to the outside
where you can see it when the mag is bolted
onto the tractor.

 

[FBH44]

Yes.

 

[wowsk]

Thanks for the advice everyone. Sounds like condenser is the next thing to check. I forgot to say I did replace plugs and wires when I first got it running.

 

[JIM MN]

You need a good blue spark.. You need to re-magnetize the magneto rotor.. Plus if the spark-plugs got gas wet, put in a new set and check their gap..

 

[wowsk]

Update. Today I took off the mag and replaced the condenser with one from a parts tractor. No guarantee it was good either, but since I didn't have any on hand I thought it was worth a shot. Didn't change a thing still not much of a shock from it and isn't enough to jump the plugs.

Another thing I was thinking that may be relevant is at the end of August I was running it in a parade. I drove it in to the parade (it has a Heisler overdrive) and by the time I got it in there (took about 30 min) it was not running that great. It made it through the parade but would sometimes start missing. Never had any issues till now but haven't gotten it real hot again.

With that I wonder if the coil was going bad then. I'm thinking I'll order a new points, condenser, and coil and see if that doesn't improve anything. Anything else I should check?

Thanks,
Noah

 

[Janicholson]

Starting a Mag ignition tractor does not turn it over fast enough to make enough magnetic energy to make a real spark. The Mag uses a impulse spring in the drive to provide the speed needed. This is done by a holding mechanism that stops the mag allowing a clock spring to windup for a few degrees of rotation. the latch (pawl) that stops it is then released allowing the magnet to spin forward those degrees at a much faster speed. The mag makes a very audible click twice per engine rotation. If this click is not happening, ir is quite dull or not crisp, the mag will not fire spark plugs. it will give a tingle, but not nearly enough. The impulse coupling is speed dependent, and stops at a few hundred RPM. Pull starting the tractor (safely) will spin the engine enough to make the spark. Jim

 

[James Williams]

call brillmans and be done with it

 

[wowsk]

Impulse is good and did try pull starting it though. Didn't help.