20 hp Command won't start when hot

grizzlyblair

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I am new to the forum so please bear with me. I read a previous thread concerning the same problem and it was suggested that the owner try disconnecting the kill wire from the ignition switch. So, if I disconnect the wire and the engine starts does that mean the ignition switch is bad? My mower is a 1997 Simplicity Sunstar and it hasn't been but a few years since I replaced both coils. I checked the solenoid on the carb and it clicked as it should. Ignition switches are fairly inexpensive I was wondering about replacing it since I don't see the kill wire. Any help is appreciated. Thank you.
 

bertsmobile1

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First of all , go to the simplicity web site and download your wiring diagram.
Even if you can not understand a wiring diagram you will be able to follow what you are being told to do.

There are separate circuits although they go through the same switches.
There is a cranking circuit that rotates the engine
There is an ignition circuit that allows the magneto to spark, or earths out the spark.

Once the engine is running there is the safety circuits that turn things off to protect you bystanders should something go wrong.

The last two work by providing an alternate ground path for the magneto primary windings.

When you take the engine cover off you will see the magneto coil ( Coils ).
They will have 1 wire on a plug underneath them .
This is the kill wire.
So with this disconnected nothing in the mowers wiring can turn it off.
So as a diagnostic tool you remove the wire if the engine will crank but not fire.
If the engine bursts into life, then one of the cut off circuits is at fault.

When people with no idea of what they are doing work on wiring I usually tell them to disconnect this wire as if you accidently send voltage through that wire the magnetos will be toast and they are expensive.

On the back of your ignition switch are tiny letters which tell you which wire goes where.
The ignition switch bridges the M wire ( the one you have been told to disconnect ) and the ground G wire.
This connection never ever gives any problems because it is up out of the weather & debris.
 

grizzlyblair

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Thank you bertsmobile1. This info tells me a lot. I can't wait to find time to follow what you have shared. I'm relatively sure the problem isn't the coils and this gives me insight into viewing from a different angle. Last night I noticed sellers have sold a ton of ignition switches which are fairly inexpensive. I suppose that could be the culprit, but I will go with your advice first. Thanks again.
 

ILENGINE

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They sell a lot of ignition switches because every time somebody has an electrical problem they think it is the ignition switch, when in reality switch failure is rare.
 

bertsmobile1

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They sell a lot of ignition switches because every time somebody has an electrical problem they think it is the ignition switch, when in reality switch failure is rare.

Followed closely by removing the seat switch despite the fact that it is not in either of the starting circuits.

Now back to your problem
One of the safety cut outs is working too good
This will be the brake + seat switch
PTO + Seat switch
If it is a zero turn add
Brake & lap bars
And if you have a reverse cut out.
Reverse & PTO switch.
All of the safety switches work in pairs.

So individually they can be fine with a problem in the wire between them
'And to make matters harder, all of the safety cuts outs are ground circuits, so finding a short to ground of a ground wire is a PIA.

Depending upon how old your mower is, some of these switches will have multiple contacts and some will be power wires ( cranking circuit ) so be careful, if you cross over a ground & power wire then it is bye bye coils and you already know how expensive they are.

THE service manual for your mower is also available on line.
If you can not find it, start another new thread titled looking for a manual for a ???????????????.
There are some really internet clever people on here who can ferret this stuff out really well ( better them me in any case )
 

grizzlyblair

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They sell a lot of ignition switches because every time somebody has an electrical problem they think it is the ignition switch, when in reality switch failure is rare.

Thank you ILENGINE as well. This forum is fantastic. Getting a lot of great info. I also see you are located in Beecher City, IL. I live between Mattoon and Charleston. Thanks again.
 
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