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Need Help on Tecumseh HMSK80 Engine on Snowthrower


OldCat82's Avatar
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02-28-07, 02:00 PM   #1  
Need Help on Tecumseh HMSK80 Engine on Snowthrower

Unlike most people, my problem is not with starting, it's with stopping the engine. My particular snowthrower (4 year-old Yard Machine by MTD) has a plastic "ignition key" that interrupts a stop circuit. When you push the key in, it interrupts a circuit (engine stop?) and allows the engine to start. When you pull the key out, the circuit completes itself and the engine stops - at least that's the theory. Recently, this stopped working. Pushing the throttle lever all the way down doesn't work either. In any case, there's a green wire that runs from the ignition key assembly to the circuit interrupt mechanism for the throttle lever (full down position). Unfortunately, there's a suspect wire (also green) that is just hanging in the area of the throttle lever interrupt - it looks like it has been cut. This hanging wire goes into the engine area that I can't see without major surgery. I think the problem is obvious...the hanging wire needs to be connected somewhere...but where?!?

I have the original engine owner's manual, but it doesn't have wiring diagrams, nor does the Tecumseh Troubleshooting Manual that has been posted in this forum. Any ideas where I can find a wiring diagram or can someone give me an idea where this hanging wire is supposed to be connected? Thanks in advance!

OldCat82

 
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repair_guy's Avatar
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02-28-07, 07:10 PM   #2  
Since the engine wont cut off I would say that the hanging wire that you mention needs to be connected to the ignition coil.

 
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03-01-07, 07:53 AM   #3  
That plastic key you are talking about does indeed ground out the ignition when you remove the key. Inside the slot where the key goes is a small shorting spring that contacts the inside of the carb cover when the key in removed. It often happens over several years that rust builds up on the spring and/or the housing and prevents the spring from shorting out. I usually double up a narrow strip of sandpaper and work it in and out of the slot a few times to remove the accumulated rust and restore the grounding ability of the spring.
The green wire is probably the shorting wire as mentioned previously and when grounded out to the carb cover, will stop the engine. For whatever reason it may have been removed from it's normal position, it needs to be reconnected to the shorting clip inside the carb cover. You will likely have to remove the carb cover to access the shorting clip.

 
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03-02-07, 04:42 AM   #4  
Just for clarification, your kill circuit schematic is as follows: 1- Single green wire from the ignition coil to an insulated junction block (mounted to an L-shaped bracket which attaches to the engine under a blower shroud bolt) which will be just below the throttle/speed control bracket. 2- Twin green wires running from the junction block with one going to the "key" switch and the other going to the throttle/speed control switch. And, just so you are aware, you will likely have one other wire from the engine which will be a single black wire with a white connector coming from under the gas tank and this is the lighting/accessories circuit wire, which has nothing to do with the kill circuit.

 
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03-03-07, 03:33 AM   #5  
Thanks all! This is the info I was looking for. As soon as it gets light enough, I'll go find the place to re-conect that wire. I had already sanded off the rust.

OldCat

 
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03-03-07, 07:14 AM   #6  
Sorry for my pestering...I'm generally handy, but not very experienced with small engines. I've posted a link to a picture that shows my dilemma.

http://hometown.aol.com/bjohansson/index.html

The picture is taken from the left side of the snowthrower looking forward. The carb cover has been removed. The ignition key assembly is hanging from the carb cover mount on the side of the carb - it is normally attached directly to the carb cover. The throttle assembly is in the middle right of the picture and shows that the throttle interrupt ass'y is attached to the ignition key interrupt ass'y by a single green wire. The picture also shows the dangling green wire that appears to be coming from the coil. It's hard to see in the picture, but it looks like the dangling wire should be connected to the throttle interrupt ass'y but where?

I really appreciate the help!

OldCat

 
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03-03-07, 07:35 AM   #7  
Never mind my last post. It's finally light enough (and warm enough) outside. The dangling wire needs to be connected to the lower connector on the throttle interrupt assembly. I'll report back once I get this accomplished.

Thanks again for the input!

OldCat

 
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03-03-07, 07:38 AM   #8  
Azis
I can't be sure but I would imagine you need to find a spring metal piece that has a small hole that the bare wire would stick into. Its hard to describe but you may even find a small piece of bare wire still in the hole. When the throttle goes to the kill position it should contact this metal ...strip, piece...look under and behind the throttle bracket..
from the pic I think to the right of the carb under and behind where the green wire is routed going to the dangling piece...

I am not Positive this is what you are looking, as I am not familiar with snowkings , but it is common for Tec. and seeing you online and recently posted maybe this will help.
gl

 
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03-03-07, 09:24 AM   #9  
I had to go out an buy a new connector....the wire connector that went from the throttle cutoff switch to the ignition key switch had 2 wire connections on it...the one that used to hold the "dangling wire" wasn't visible until I pulled it out of the plastic housing. I just tested the new connector and wiring and it works as advertised. Thanks again to all who provided input!

To finalize this thread, the wiring went as follows:
Single green wire from ignition coil to a connector that slid vertically up into the the throttle interrupt assembly plastic housing. That same connector also connected to the green wire that went from the throttle interrupt assembly to the "ignition key" interrupt assembly mounted to the carb cover. This wire (to the "ignition key") has a 3/16" female flat connector. I couldnt find a similar double male 3/16" connector, so I just made my own out of two 3/16" male blade connectors from Radio Shack. I used some spare 16 gauge wire (same as the green wires) to connect the 2 together...the male connector accepted both my connector wire and the "dangling" green wire from the coil.

Life is good.

OldCat

 
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01-22-13, 10:44 AM   #10  
Use your own switch.

This happened to me, too. A simple two-dollar (waterproof, 240volt rated) toggle switch was the fix, one side tied to the "green wire" and the other a short wire to the nearest ground-screw. Works like a charm. This has the effect of grounding the green wire and thus stopping the engine.

If you have any trouble with the existing wire junctions as they've become rusty as mine were, just (carefully) use the "root" one coming out from the area of the internal engine housing and put that directly into your switch.

Switch wiring: If it's labeled "On" / "OFF" then the "on" position as labeled on the switch translates to, shorting-to-ground and thus engine-off. Solution: simply mount switch accordingly. In my case, mounting it "upside down" was the best, as the operators expected that when it was toggled "down" the engine was off.

Voltage rating:
Probably, this wire is a very low-current and 12volt feed off the primary ignition coil, but I suppose it could be 24 or 48. In my case we went with a 240v panel switch, with a waterproof rubber boot. Less than $3 on ebay.

It was very easy to drill a new round hole for it, and this one won't rust.

--TK

 
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02-02-15, 07:11 AM   #11  
HMSK80 Engine Kill Switch

Hi folks,

Quick Question.
I am assuming that the Green ground Wire that connects to the Throttle Kill Switch & the Ignition Key Switch run's back up to the Ignition Module ?

I tested and cleaned the Ignition Key Switch so that I saw it was providing a nice clean Ground connection. I did this by connecting an Ohm meter to the Carburetor Metal framing and the green wire connector. ( Through the white spring switch inside the housing )

Now that I have this working, I then thought about looking at the ground strap itself.
This is where I discovered that the green wire has 0 ohms between itself and the engine ground with both switches taken out of the circuit !
I am testing the green wire as it exits the engine housing by the carburetor & the metal frame.

Is this consistent with a blown ignition switch ???
I would expect there to be either a high resistance between the green wire & ground or no current at all.

Thanks

 
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02-02-15, 04:54 PM   #12  
Having trouble with 2 cycle snow blower. Ran great last year, stored it with fuel stabilizer pulled it out this year and it will only run on full choke then it works fine. It's an older unit have only had it for one season, but it could be 3-5 years old. Could it be the fuel?

 
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02-03-15, 07:49 AM   #13  
HMSK80 Engine Kill Switch

Hi Folks !
With a little more testing, I found out that my old meter was not reading correctly.
I plugged in a newer Ohm Meter between the Green Kill Switch Wire and Ground.
I now read 350 Ohms between Wire and Ground.
It is not a complete short to ground.

I suspect then that the ignition pack is OK.
( If someone knows that not to be true please correct me )

I think the next test is the old :"gas in the spark plug hole trick".

 
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