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Need Help With Wiring

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#1 Dieselcubmike OFFLINE  

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Posted December 27, 2013 - 03:42 PM

Not sure if this belongs here so if someone needs to move it go ahead. Alrighty so here's my problem. Im not a wiring genius by any means couldn't even tell you how to wire something up. Ol'red aka MTD 990 has a starting problem. When you go to start it like a conventional starter generator it cranks over til it starts. With my problem I have to let it crank over then let go of the key and it will try to start by itself and it is rather annoying to do this especially on a cold day. Not sure if its wiring related or not? My dad says its something from the ignition? Maybe a bad coil or something along those lines but I have to let it crank over a few times then let go of the key to see if it will try to pop start. Any help would be greatly appreciated. My father is rather busy working as much as possible and I work evenings and he works mornings so we don't have much time together.   

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#2 glgrumpy ONLINE  


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Posted December 27, 2013 - 04:29 PM

Am I to understand that it cranks when going to OFF position?  Just sounds like a bad key switch. Might be shorting out or insides falling apart from water in there now freezing, or just water not freezing. Water from rain/snow if outside or from thawing out after plowing snow say?  Key is in downward slant on dash and water could collect easy and enter keyway.

  Can check wires one at a time and see where they go to and check ends or lengths for not touching a ground or each other.  Kinda hard to do this I know with wrapping on the harness. Look for same color wires going in and out on the wrapping. A wire diagram will be real helpful too to make sure they go right places. I'm still betting on the switch tho. Just make sure to get one for a Magneto when you buy new one. Most any tractor dealers should have those or can get easy. ebay under mtd 990 search has lots for these tractors.

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#3 HDWildBill OFFLINE  


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Posted December 27, 2013 - 04:33 PM

What I understand your saying is that you hit the starter and then let the switch go to the on position and hope it pop off. Sounds like a bad ignition switch to me. One of the contacts inside the switch is bad.

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#4 Chopperhed OFFLINE  

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Posted December 27, 2013 - 04:39 PM

Its possible that the power is being cut to the coil when the key is in the start position or the coil is being shorted when in the start position..

Also, Depending on the engine, you may have a carb solenoid that cuts fuel to the carb when the key is shut off.

I have a B&S 15.6 with the solenoid on the carb. when in the start position the switch cuts power to the solenoid. It exhibits the same behaviour.

I will have to change out the switch or add a diode between the start and run terminals on the ignition switch

Edited by Chopperhed, December 27, 2013 - 04:43 PM.

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#5 JDBrian OFFLINE  


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Posted December 27, 2013 - 04:52 PM

I'd pull the ignition switch and check it with an ohm meter. They tend to get cranky  (pun intended) when old. I've fixed a couple of them by taking them apart and cleaning them, then reassembling. It doesn't take a whole lot of resistance to lower the coil voltage enough to make it difficult to start. Also the wiring connections on the back of the switch can go bad at the connectors or the terminals on the switch can also get loose where they are riveted onto the switch. 

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#6 Dieselcubmike OFFLINE  

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Posted December 27, 2013 - 11:16 PM

Thanks everyone. If possible ill get a new ignition then and go from there. I was using it on a regular basis until I started having carb problems. I rebuilt the carb and now it would start. Dad thinks maybe from the ignition to the coil. Thanks for the help though guys.

#7 Canawler OFFLINE  



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Posted December 28, 2013 - 09:23 AM

Wait, did this starting problem just begin after the carb rebuild?  Or was this the way it's been all along?