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Farmall model A, no spark at plugs

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adambeck3475
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PostPosted: Fri Jun 11, 2021 6:58 am    Post subject: Re: Farmall model A, no spark at plugs Reply to specific post Reply with quote

Update: I took the magneto apart, cleaned the points, fixed the connector that goes on the wire that connects the condenser to the points, and timed the gears. I have a little jolt at the plugs, Im guessing it not enough to cause a spark. What do I need to do to get a bigger spark? Im assuming this is still the reason it wont start.
 
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Janicholson
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PostPosted: Fri Jun 11, 2021 9:55 am    Post subject: Re: Farmall model A, no spark at plugs Reply to specific post Reply with quote

Rotate the engine slowly (neutral with brakes locked, hand cranking is best.) each rotation of the crank should produce 2 very clear solid clicks. Like pinching a wooden spring cloths pin and letting it snap shut. if that is not happening, or if it is lacking crispness in the snap, the impulse coupling may be failing. An impulse coupling is located in the drive to the mag, just inside of the mounting flange and part of the mag, not the tractor. The device (bear with be on this) is like holding a kid back by the suspenders, then letting them go. In the mag, there is a certain rotation speed of a magnet that generates the power to make spark. when cranking (electric or hand) the magnet is not moving fast enough to make crisp spark. The coupling latches the rotation of the mag internal parts for several degrees of rotation, winding up a spring, then releases them so they travel fast enough to make spark big enough to jump the plug's gap. if you are uncomfortable with trepairing or analysis of the mag. put the engine on TDC compression #1 cylinder, and take the mag off. Several companies and even people on this site (Teddy52food is one) repair mags. Jim
 
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adambeck3475
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PostPosted: Fri Jun 11, 2021 1:14 pm    Post subject: Re: Farmall model A, no spark at plugs Reply to specific post Reply with quote


I had the mag apart earlier today. I had the impulse out and the dogs were snapping back, not sticking at all. When I rotate the engine over I do hear a really crisp clicking noise. Could a new set of points and condenser give it more spark to jump the spark plug gap?
 
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old
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PostPosted: Fri Jun 11, 2021 2:14 pm    Post subject: Re: Farmall model A, no spark at plugs Reply to specific post Reply with quote

New points maybe if the old ones are getting bad. As for a new condenser you stand a 50/50 chance that it would be bad right out of the box. I haven't replaced a condenser in over a decade due to that problem
 
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Janicholson
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PostPosted: Fri Jun 11, 2021 5:32 pm    Post subject: Re: Farmall model A, no spark at plugs Reply to specific post Reply with quote

The magnet in a Mag can have the magnetism fade. They were not very high tech magnets. They can be recharged by a mag repair place. A distributor
can be used in place of the mag but requires some rewiring. Jim
 
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tractorguy2
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PostPosted: Fri Jun 11, 2021 8:38 pm    Post subject: Re: Farmall model A, no spark at plugs Reply to specific post Reply with quote

Weak spark can be caused by,

A weak coil
Dirty, burnt, or improper gapped points. New points must be cleaned before installing.

Suppression plug wires. Mags need copper core wires.

Rotor gears not timed correctly.

I have bought and sold H4 mags for over 15 years. Haven't had one yet with a magnet so weak it wouldn't work. Fairbanks Morse mags a different story.
 
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teddy52food
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PostPosted: Sat Jun 12, 2021 5:35 am    Post subject: Re: Farmall model A, no spark at plugs Reply to specific post Reply with quote

The magnet in the H4 mags don't lose their strength. I have more than one from the 40's that is still good & never been charged
 
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Dave41A
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PostPosted: Sat Jun 12, 2021 7:44 am    Post subject: Re: Farmall model A, no spark at plugs Reply to specific post Reply with quote

CVPost-teddy52food wrote:
(quoted from post at 14:35:23 06/12/21) The magnet in the H4 mags don't lose their strength. I have more than one from the 40's that is still good & never been charged


Yes. Teddy is correct. The magnet will not "wear out."

Some thoughts: check the plugs. You want NON-RESISTOR plugs. I suggest Autolite 3116's, but everyone has their favorite brand. You also want COPPER wires. I got surprised on this with my '41H when I converted from coil to mag--it is an easy mistake to make (easy for me, anyway). It is also helpful to have the rotor and cap be a "matched set." By this I mean the height of the rotor (as measured setting on a table) varies a little between different aftermarket brands. Some are "too low" for the cap, while I have had others where the rotor actually hit the cap on the inside while turning. Try putting the originals back on. I think you are very close. Dave
 
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