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oldlineman

I need some help

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oldlineman

Hi guys my 312h has no spark. I can't seem to find a wiring diagram for it. engine M12S, 312H, 3112KE01, spec.# 471527, ser.# 1925707943. I believe the problem may be with the safety switches.The PTO switch has 5 terminals on it and I only get continuity from the one on the side and one of the other four when PTO is off. There was an orange wire off at the PTO switch but there is two terminals left on the switch.  Is there a way to test the magneto to eliminate that as the problem. I know you can not let voltage get to it,and I am a little nervous working on it. I also saw a relay and not sure how to test it. Any and all help is greatly appreciated.   Ps the seat switch has already been bypassed. Thank you for any and all help! Could someone explain what the start relay does and is there a replacement for this tractor. Wiring is not my strong point. 

Edited by oldlineman

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gwest_ca

If you can disconnect the ignition wire and isolate it that should allow the ignition to work. Ground the disconnected ignition wire to shut the ignition off.

 

There are two pto switches fastened together. One for the ignition and one for the starter. One terminal on each switch is not used.

Your tractor has magneto ignition so the use the 420-LSE pto switch wiring. The 310-8 to 417-A in these diagrams are for battery ignition.

 

You have one relay and it prevents the starter from operating with a low oil condition.

 

Garry

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oldlineman

Thank you Garry! Would the Dk Bu wire M on the switch be the ignition wire Garry?

Edited by oldlineman

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oldlineman

what wire and color would be considered the ignition wire and where would you disconnect it from. Sorry wiring is not my strong suit. Thanks Bob  

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oldlineman

Garry am I correct in saying according to the wiring diagram that if the orange wire from the seat switch is removed from the PTO switch and the tractor engine is turning over, that it must be a bad magneto if I don't have spark? If I understand the wiring diagram the only things that would ground the magneto are the starter switch when shutting down and the PTO switch and would keep from having a spark.If I removed the Bk wire from the switch that would eliminate the switch as being bad correct. Sorry for my lack of understanding. Bob 

Edited by oldlineman

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gwest_ca
2 hours ago, oldlineman said:

Thank you Garry! Would the Dk Bu wire M on the switch be the ignition wire Garry?

Yes

 

If you removed the orange and blue wire from the pto switch the ignition should work. Now the only thing that would prevent the ignition from working would be a short in the blue ignition wire to ground between that pto connector and the engine or the engine and the ignition switch. I would remove the connector from the ignition switch and remove the blue wire from the connector. Plug it back into the switch and see what happens. With the blue wire disconnected from everything and not touching a ground ignition should work. Just won't shut off.

 

Know how to remove a Packard terminal?

 

It is not very often that the ignition fails on these models. Have you tried a new spark plug? Plugs will fire out of the engine but fail to work when under compression when in the engine.

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gwest_ca
1 hour ago, oldlineman said:

Garry am I correct in saying according to the wiring diagram that if the orange wire from the seat switch is removed from the PTO switch and the tractor engine is turning over, that it must be a bad magneto if I don't have spark? 

Not necessarily

 

If I understand the wiring diagram the only things that would ground the magneto are the starter switch when shutting down and the PTO switch and would keep from having a spark.

The pto switch could be grounded by the seat switch.

 

If I removed the Bk wire from the switch that would eliminate the switch as being bad correct. Sorry for my lack of understanding. Bob 

No because the switch is still mounted to the metal chassis. Best to remove the blue wire from the connector and plug the connector back on the switch.

or

use an ohmmeter between the black ground wire and the blue wire with the switch in the RUN and START positions - should have no continuity. Should have continuity only in key OFF position. Do this test with the battery negative cable disconnected from the battery. This may not work depending on the quality of the ohmmeter.

 

Will work if you pull the connector off the ignition switch and just check the switch terminals.

 

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oldlineman

Thank you Garry I will try all of the above and let you know what I have. I believe I understand that the starter circuit does not affect the coil other than the PTO and seat switch. The seat switch is bypassed and orange wire is not connected to the PTO switch. So my problem lies with the spark plug, coil wire, coil or start switch, sound right. Thank you for all your help Garry.

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Gregor

If you really wanted to completely isolate the magneto wire, to test the magneto, and you have enough wire to do so, you could cut the Dk Bu wire right where it comes out of the motor, before it connects to any other wire or device.  This would isolate the magneto from any safety switch. I know it may seem a bit drastic, but if you want to fix a problem, you first have to know what the problem is.

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oldlineman

Yes I believe the coil is bad I removed the grounding (kill) wire from the coil and had very little spark. Does anyone know the ohm values for this horse M12S. and test procedure for testing. Coil # is 4758403s. Thanks again Bob 

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gwest_ca

Looks like this test can be done without taking anything apart. The laminations (A) are bolted to the engine block so any good clean ground  would make a test connection.

Only thing not verified is the ignition wire insulation that can not be seen behind the tinwork.

 

Taken from Service manual page 8-3

Kohler M-Series ign coil test.jpg

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oldlineman

Update I need help no spark, I replaced the coil and all is well, even though the coil is not usually a part that fails I got the one that has, who knew! Just wanted to thank all that replied to my problem, especially Garry your help is very appreciated. Bob

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