Author Topic: Garden Tractor - magneto issues  (Read 847 times)

Offline Chuck Farley

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Garden Tractor - magneto issues
« on: April 28, 2017, 01:04:09 AM »
2 cyl, (opposed) 19 hp B&S engine.   Just did a recondition on it - new plugs, new belts, new blades, sandblasted & painted the deck
Fired it up, ran and worked like a brand new machine.   Mowed the lawn (an acre) and put it away.
Next time I went to use it, it fired instantly, ran for about 5 sec and quit cold.   No spark whatever
OK - got a new magneto, installed that - it fired right up and I did my second mowing of the year.  Once again - it ran flawlessly.  Put it away in the garage
Today, it was time for third mowing of the year- it fired right up and quit after about 2 seconds run time.   Zero spark again!   
Any ideas on why I am running through a mag per use? 

Offline lostmind

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Re: Garden Tractor - magneto issues
« Reply #1 on: April 28, 2017, 08:35:28 AM »
I would investigate a faulty safety switch somewhere. Maybe even the ignition switch.
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Offline slip knot

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Re: Garden Tractor - magneto issues
« Reply #2 on: April 28, 2017, 05:00:29 PM »
try taking the old one off and putting it back on. There may be a corrosion issue keeping it from firing.
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Offline Chuck Farley

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Re: Garden Tractor - magneto issues
« Reply #3 on: April 29, 2017, 07:15:56 PM »
It did it AGAIN!  'Nother new mag, ran like a dream.   Finished the whole lawn again.   Put it away.  Today - no spark again.  My son went onto the interwebs and found that this happens just often enough that Mr Briggs and Mrs Stratton have a kit to fix the issue.   Not sure what the kit does - seems to just be a length of wire from the starter switch to the mag kill wire, with another piece of wire to the voltage regulator. (And costs $31.00!!!)  Now I'm REALLY confused.

Gonna try disconnecting the mag kill switch from the ignition key switch and run a wire from the mag kill to ground with a toggle switch in line, use the toggle to kill it on shut down.  (Or as my son suggested - don't use the key to shut it off, just reduce power to bare idle and pull the choke to kill it instead of turning off the ign.)

My son's theory is that there is some sort of power surge upon shut down that fries the windings in the mag

If THAT works out, I'll put a diode in the mag-grounding wire.

Meanwhile, I'm beginning to remember some of the curse words I used to know.

Offline Chuck Farley

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Re: Garden Tractor - magneto issues
« Reply #4 on: May 09, 2017, 06:52:21 PM »
So after running it with new Mag and the ground wire disconnected, I was able to re-start it later  beerdude

A LONG study of the wiring diagram showed that the ONLY place where alternator wiring and mag ground wire arrived at the same place was at the key switch.

So - in the well-known spirit of "keep throwing parts at it until something works", I replaced the ign switch (along with yet another magneto)   Touch wood - it seems to work OK now. confusedx   headscratch

Offline Chuck Farley

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Re: Garden Tractor - magneto issues
« Reply #5 on: May 12, 2017, 12:23:22 AM »
Success!  The new ign switch did the job.   Starts good, runs well, and re-starts after shut down!  Strange symptoms but the switch was burning out the mag coils.   All fixed now!

Offline Chuck Farley

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Re: Garden Tractor - magneto issues
« Reply #6 on: September 28, 2017, 03:02:59 PM »
Looks like it freakin' did it AGAIN!   Half way through cutting the lawn yesterday, it quit cold and yup - no spark. 

This time I just lost patience - it's now at the stealership for diagnosis/repair.   If I try to fix it again, my tool of choice would be a BFH!

Offline Barks

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Re: Garden Tractor - magneto issues
« Reply #7 on: October 07, 2017, 09:49:33 AM »
Did the professionals identify the problem and correct it?

Offline Chuck Farley

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Re: Garden Tractor - magneto issues
« Reply #8 on: October 09, 2017, 01:40:24 PM »
No idea what they found (so far) - it's still at the shop and I've been away for the past few days at a swap meet (at Monroe, Wa)

Offline Chuck Farley

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Re: Garden Tractor - magneto issues
« Reply #9 on: October 24, 2017, 05:42:44 PM »
Finally!   Turned out to be the fuel pump causing the surging.   The magneto issues were, in fact, the ignition switch burning out the coils and they had sold me the wrong ign sw.  Switch was replaced at no cost (and the latest mag, as well).   New Fool pump & filter installed.   Seems to run like a brand new one now.   We'll see.   Any more issues and I'm gonna be searching Mr Slist's site for a replacement tractor/mower

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Re: Garden Tractor - magneto issues
« Reply #9 on: October 24, 2017, 05:42:44 PM »

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