# MTD HMSK80 Wiring Help - Ignition Switch



## OneManWithAPlow (Sep 4, 2016)

good afternoon.

Went to replace the carburetor on a hmsk80 8hp yard machine and noticed some issues with the ignition switch wiring.

What would be the best way to eliminate the need for a key entirely? I'm assuming I can't ground the wires, but I'm having trouble finding a replacement key as well. I called the dealer, they were unable to figure out the required key, and also couldn't tell me where these wires need to be connected to. Any advice is appreciated. Thanks.



http://imgur.com/wVPE7


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## Mebes (Feb 7, 2004)

Key for HMSK80-155530S should be Tecumseh 35062
Not sure if this is your exact model or not but they are not that hard to look up online with the exact model number.

Assuming that the second picture you posted is the same wire as the first image the ring (or hook) terminal should go to ground and the broken spade terminal should either go to the key switch or a connection at the throttle linkage that touches the linkage when you turn the throttle all the way down (slow) 

The system shuts down by grounding the ignition coil (or magneto)
If you look at the key switch you will see a wire (like a spring) that touches metal when the key is removed. when you insert the key it pushes the spring away from the metal (when there is no connection to ground the engine runs)
The throttle may have a similar setup that grounds a wire when you run the throttle all the way down.

If you have both a key switch and throttle switch you can disconnect one and use the other


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## OneManWithAPlow (Sep 4, 2016)

Mebes said:


> Key for HMSK80-155530S should be Tecumseh 35062
> Not sure if this is your exact model or not but they are not that hard to look up online with the exact model number.
> 
> Assuming that the second picture you posted is the same wire as the first image the ring (or hook) terminal should go to ground and the broken spade terminal should either go to the key switch or a connection at the throttle linkage that touches the linkage when you turn the throttle all the way down (slow)
> ...


It's an HMSK80-155545 
Those two images are two separate wires that presumably connect. The one that is intact is from the ignition switch, the other one(broken one) is probably to the coil?

The broken wire mounted near the throttle lever. I saw both the springs/wires, one at the key and another near the mount of the throttle lever or broken wire. How would I go about disconnecting one (throttle or key) to only use the other?


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## Mebes (Feb 7, 2004)

I found 3 versions of the HMSK80-155545 engine.
HMSK80-155545T
HMSK80-155545U
HMSK80-155545V
The same key (Tecumseh 35062) is used in all of them so odds are very high that this is the key you need if you want to go that route.

There should be a dark green wire that comes out from under the engine cover. This wire is attached to a terminal on the spark plug coil. 









This wire should then either split and go to both the key and throttle, or it may simply go from throttle to key or vice versa.
images on this page may help.

Find this wire and hook it up to one or both switches and you should be good to go.
You can also wire it to a toggle and skip the other 2 switches all together if you like. All you need is to ground this dark green wire to stop the engine (it does not matter how you do it)


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## OneManWithAPlow (Sep 4, 2016)

Mebes said:


> I found 3 versions of the HMSK80-155545 engine.
> HMSK80-155545T
> HMSK80-155545U
> HMSK80-155545V
> ...


The green wire that comes out from under the engine cover is the one that is broken in the picture. It is still attached at the spark plug coil but seems to be disconnected near the throttle lever. Im assuming that the other green wire from the key ignition ALSO went to the area near the throttle lever. The area im referring to is the plastic piece with a little metal hook seen in the first picture immediately left of my index finger. I need to crimp another connector on there and connect it into the bottom of that piece. But I cant figure out where the hook shaped (sickle) connector goes. In the images you linked it appears to go to a ground-screw on the carburetor mount but in that picture the wire also appears to be mounted somewhere, where as on my blower its a short wire directly to the ignition switch.

It doesnt seem logical that I would insert a key. It than pushes the piece of metal back completing the circuit, than goes directly to a ground 3 inches away?


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## Mebes (Feb 7, 2004)

The extra wire in the pictures I linked is there most likely because the metal that the metal spring touches does not have a good (or reliable) enough ground to stop the motor.
When you remove the key the spring that has the green wire (from the engine) attached to it touches nearby metal and the ignition coil gets its ground, but if the metal is not grounded in some way (lets say it is mounted to plastic) the engine will not stop. To solve this a new wire would be attached to the metal that the spring touches when the key is removed to carry the current to ground somewhere else (carb, or engine bolt, etc.)

Edit: The key breaks the circuit by moving the metal spring away from ground


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## Mebes (Feb 7, 2004)




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## OneManWithAPlow (Sep 4, 2016)

Mebes said:


>


Yes. I got it. Thank you. So the green wire from the key switch (the hook shaped terminal/connector) goes to the ignition coil? In the pictures linked, it appears to go to ground. On my unit it's a short wire, maybe only 6 inches long.

Honestly I can't help but feel like I'm missing a wire. My key switch literally isn't connected to anything.

Like there's no connection to be grounded.


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## Mebes (Feb 7, 2004)

OneManWithAPlow said:


> Yes. I got it. Thank you. So the green wire from the key switch (the hook shaped terminal/connector) goes to the ignition coil?


Nope...
That wire looks to me like it was a an additional ground wire probably went from the carb mounting bolt to metal somewhere near the key switch.
This provides a good ground for the key switch to operate correctly.
It will not hook to the green wire that goes to the ignition coil.



OneManWithAPlow said:


> Honestly I can't help but feel like I'm missing a wire. My key switch literally isn't connected to anything.
> 
> Like there's no connection to be grounded.


The spade connector that fell off in your first picture did not look OEM to me, so I'm guessing that the wire from the key switch to the throttle switch either fell off at some point or was removed before you purchased the snowblower.

You only need one hooked up to stop the machine, so If I were fixing it, i'd probably just crimp on a new spade connector to the wire that comes from the coil and only hook it directy to the throttle switch and skip the key switch entirely.

If you want to hook up the key switch you can run a second wire from the key switch to the throttle switch using a piggyback connector


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## OneManWithAPlow (Sep 4, 2016)

Mebes said:


> The spade connector that fell off in your first picture did not look OEM to me, so I'm guessing that the wire from the key switch to the throttle switch either fell off at some point or was removed before you purchased the snowblower.
> 
> You only need one hooked up to stop the machine, so If I were fixing it, i'd probably just crimp on a new spade connector to the wire that comes from the coil and only hook it directy to the throttle switch and skip the key switch entirely.


So I do not need a key to start the machine if thats the case...? Guess i need to find out why it isnt starting! It appears as if I am not getting a spark. I ordered a new plug, the machine started about 3 weeks ago and ran beautifully. Wouldn't start, so i figured id replace the carb anyways. Still no cigar

I dont recall ever having a key unless it fell out/i lost it in the past few weeks.


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## Mebes (Feb 7, 2004)

Disconnect the green wire from all switches, make sure it is not touching ground and then check for spark.
Random youtube video explains.


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## OneManWithAPlow (Sep 4, 2016)

Mebes said:


> Disconnect the green wire from all switches, make sure it is not touching ground and then check for spark.
> Random youtube video explains.


Thanks, ill place a piece of rubber or electrical tape by those green wires and check for spark as soon as i get home from the gym


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## Mebes (Feb 7, 2004)

If you *do* have spark, pour about 1 teaspoon of fuel in the spark plug hole before installing the plug and try to start it again. If the spark is there the fuel should allow the engine to start and run for ~3 seconds.
If the engine runs then stalls you have a fuel delivery problem (choke not closing, plugged jet in the carb, no fuel in the carb, plugged screen in the bottom of the tank etc...)

If you *do not* have spark skip the fuel and follow the green wire back to the coil looking for shorts


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## OneManWithAPlow (Sep 4, 2016)

Mebes said:


> plugged screen in the bottom of the tank etc...)


I will have to check for this. I saw a bit of sediment in the bottom of the tank when draining fuel. Also i know fuel is making it TO the carb, as if i prime a 4th time a bit of fuel will drip out the back of the carb.

Also, carb is brand new but i did purchase a second one just in case.


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## Mebes (Feb 7, 2004)

Yea its possible, the last one I did for a buddy at work, it was so bad i actually took a picture of the inside of the tank.


Spoiler














If you disconnect the fuel line from the carb and hold it over a spray paint cap it should come out pretty fast. The cup should fill up in under a minute.


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## OneManWithAPlow (Sep 4, 2016)

It appears to have been the plug. It was either gapped poorly or a bad plug. When I went to remove it i could hand loosen it oddly enough. I was still getting a spark, but it was too dark to tell how it was arcing, and with a light on it i couldn't tell the color. In the dark, any bit of light seemed strong so it was difficult to differentiate. I have a new plug on the way, but once i put some fuel into the plug (about an ounce) it started right up and ran normally. It didn't shut off after the 3 seconds so fuel delivery seemed fine.


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