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Discussion Starter · #1 ·
Hello all!

Perhaps is should describe my problem as an intermittent RUNNING problem as it spends more time in the non-running state than running.

I recently picked up this MF-12 and it doesn't like to run for any usable amount of time. Most of the time it will start right up but die shortly after. It dies quickly. No sputtering or stumbling beforehand--just quits as if I turned off the key. After dinking with it for some time, I noticed that it would run up until I let the key off the "start" position and into the "run" position. So as long as I hold the key in "start" it seems to run OK. I imagine keeping the key in the "start" position is probably not a wise long-term solution!!

Very rarely, it will continue to run in the "run" position, but only for a handful of seconds.

Can anyone offer any guidance? Is there any reason to consider possible causes other than the key switch itself?

I downloaded the MF-10/12 electrical schematic from the forum library, but it leaves a lot to be desired. I'm hoping that the manual which that schematic was taken from has some more in-depth information, but I downloaded all the manuals that I thought would pertain to my 12 and haven't found that same schematic in any of them. (Am I blind?) Can anyone direct me to that manual?

Thanks to all. Anxiously awaiting your wisdom!
 

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Discussion Starter · #2 ·
Ok, so I may have answered my own question. Let me know if my reasoning is flawed...

I dug out my old test light and probed around the key switch.

I got no voltage at the "D" terminal of the switch (PINK wire) in the "RUN" position, but the test light did come on when I turned the key to "START" and cranked the engine. I assume the PINK wire is what powers the ignition system and it should be live in both the "RUN" and "START" positions, but it appears to be dead in "RUN".

Based on this, I think the problem is a bad switch.

I'm curious to know what the letter labels for the switch terminals in the diagram mean. I think I can guess three of the four. "B" would be "Battery" for power coming into the switch, "C" would be "Charging" since the wire from it goes to the regulator, and "S" would be "Starter" as it goes to the starter solenoid. But what does "D" stand for???
 

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Proud to be Deplorable
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The ignition switch is probably failing.I have taken them apart and tried to fix with mixed results. Probably not worth the frustration
It is VERY important you get the right one or you will be destroying hundreds of dollars in ignition components.
I would ask the site sponsors here to sell you the right product.
 

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I would start with the key switch. And check the wire going to the solid state ignition, that it is not grounding out on some metal, which will shut the spark off, same as if you shut the key off. Some thoughts I had. Good luck with it.

Noel
 

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Discussion Starter · #5 ·
Thanks for the input so far.

Can anyone tell me if the pink wire is supposed so supply power to the ignition system, or if its purpose is to ground out the ignition system to shut the engine off?
 

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It dependends on which engine you have. If your engine has a magneto the switch grounds out the wire to the magneto, to kill the engine. Never put power to the magneto wire. It will cost alot. The correct switch for a magneto system will have a tab labelled "M".

A coil based ignition system needs power to work. The switch will have a tab labelled "I". Most schematics will show the labelling of the switch tabs.

I think that your switch is worn out or you have a short in the magneto wire. Mice are great at causeing problems like that. Good Luck, Rick
 

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Don't mess with an ignition switch if gets stuck you could burn all the wires the voltage regulator and even the tractor. Buy a new one fast.
 

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Discussion Starter · #9 ·
Thanks for all the replies. Now that I know that the ignition system is grount-to-kill, it seems like the switch is probably behaving correctly, but I'm still a little stumped.

I'd like to turn the conversation towards the schematic I mentioned. Here's a link to it. (Probably should have included the link in my first post.)

http://gardentractortalk.com/forums/files/file/1544-mf10-mf12-wiring-diagram/

This wiring diagram is clearly just one page of a larger document. Can anyone tell me what document this schematic came from? Is it in the library? I can't seem to find it.
 

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Electric Tractors
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Thanks for all the replies. Now that I know that the ignition system is grount-to-kill, it seems like the switch is probably behaving correctly, but I'm still a little stumped.

I'd like to turn the conversation towards the schematic I mentioned. Here's a link to it. (Probably should have included the link in my first post.)

http://gardentractortalk.com/forums/files/file/1544-mf10-mf12-wiring-diagram/

This wiring diagram is clearly just one page of a larger document. Can anyone tell me what document this schematic came from? Is it in the library? I can't seem to find it.
The link you post is the wiring diagram for the MF10, MF12 tractors, it is part of the manual that came with the tractors.

The pink wire that goes to the key switch is for killing the ignition, connects it to ground to stop the spark.

The ignition is self powered and should NEVER have battery voltage applied to it.

There are 2 wiring diagrams for the MF10, MF12 tractors, very early models had points, later ones have the SSI ignition.

http://gardentractortalk.com/forums/topic/33809-m-f-10-m-f-12-wiring-diagrams/

I would say your problem is the key switch or a wiring problem grounding out the ignition intermittently.
 
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