# Tecumseh cutting out after 5 minutes



## antny (Nov 2, 2018)

I bought an old Simplicity with a Tecumseh 8HP engine (HMSK80-155361S).
I got it running pretty smooth. Cleaned the carb (and got a new adjustment screw), changed oil, changed plug, checked governor (3550 RPMs), ran B'Laster small engine tune up spray through it. 
It starts up and runs good for about 5 minutes, then cuts out at full throttle. I thought it may be the gas cap not venting properly. So, when it started to cut out, I unscrewed the cap, but that didn't help (even after restarting it with gas cap very loose). So, now I'm thinking it's the starter coil. I can't find a video for checking the coil on this type of engine. Can anyone help?


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## cranman (Jan 23, 2016)

Another thought may be some obstruction in the gas line that prevents gas to flow fast enough into the bowl to keep running. It runs the gas out of the bowl faster then it can refill. Just a shot in the dark...


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## Grunt (Nov 11, 2013)

After it cuts out, remove the spark plug, attach the plug wire and lay the plug on the head. Pull the recoil or hit the electric start button and see if you have spark. (preferably with a new spark plug)


Page 66 of the manual has a trouble shooting guide.
http://www.barrettsmallengine.com/manual/tecumsehlheadmanual.pdf


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## antny (Nov 2, 2018)

But, if it was lack of spark, wouldn't I have problems starting it in the first place?


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## RedOctobyr (Mar 2, 2014)

Sometimes ignition coils can work when cold, but fail as they get hot. So you might get a spark when it's been sitting for a while, then lose it as the engine heats up. If you have an inline spark tester, you could run with that connected, and watch what happens to your spark as the engine dies. 

If it *is* ignition-related, it's worth taking a look at the ground wires that kill the ignition, to shut the engine down. Just in case something is making contact and grounding out the ignition, when it shouldn't be.


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## antny (Nov 2, 2018)

I replaced the plug, but when I removed it to spray the engine tuner spray I noticed a lot of black carbon on the new plug. Wasn't sure at the time if that was normal for a new plug. I read that it most likely was due to rich fuel mixture. Maybe I had the wrong mix at the time, but may have fixed that. I'll try to clean it with a wire brush and see if that helps. Also, my kill switch doesn't work, so there may be a grounding issue. After I start the blower, I can't turn it off with the kill switch. I have to turn it off by throttling all the way down. Does that sound like it's a grounding issue?


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## RedOctobyr (Mar 2, 2014)

There should be some sort of ground that kills the ignition when you lower the throttle lever fully, or turn a key off, if it has a key. So you're missing a ground at the moment. Maybe a wire is disconnected and floating around? 



I'd start by investigating this, if it were me, since something about your ignition is not wired quite-right. And if that presumably-disconnected wire is moving around and touching bare metal, it might be grounding out and killing your ignition.


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## antny (Nov 2, 2018)

Stay tuned. I'll check it out. Thank you.


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## 1132le (Feb 23, 2017)

Fuel line collapsing's maybe


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## cranman (Jan 23, 2016)

1132le said:


> Fuel line collapsing's maybe


my thought as well


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## antny (Nov 2, 2018)

A collapsing fuel line makes sense. The engine runs for about five minutes on full throttle and starts to die. At that point, if I throttle it back to low, it stays running. I guess when I do that, I give the slow moving fuel line a chance to "catch up". If I then go back up to full throttle, it'll run again for a few minutes before dying. I checked the plug after it dies, and I still get a spark. 
I guess there's no easy way to test the fuel line. It looks difficult to access/disconnect to drain into a pan to observe the flow. Any alternative to taking the shroud off and replacing before I know for sure that is the issue? 

Also, the kill switch doesn't work, but I don't think that's the cause of my problems. I checked and don't see any loose or bare wires. I did notice the throttle touches a pin when pushed all the way down which cuts the power. I guess this is grounding it out. I guess I have a bad kill switch.


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## RedOctobyr (Mar 2, 2014)

If there is an inline fuel filter, or a filter at the bottom inside of the tank (at the location where the fuel line attaches), check those. They may be plugged. My Tecumseh has a rectangular area of fine screen over the exit from the tank, as a filter. 

But looking at your pictures, you have a drain "button" on the bottom of the carb bowl. The brass-colored spring-loaded item off to the side in your 2nd picture. Push that up, and the carb bowl's contents should drain out. 

Pressing that as the engine dies will likely not produce much of a fuel dribble. Based on you saying that, at idle, it will keep running, which does seem consistent with inadequate fuel flow. So you can test your fuel supply rate by putting a container under the carb bowl, and pushing that button, to see what kind of flow rate dribble the carb will maintain, once the bowl is empty. 

If you have a screen at the bottom of the tank, and it's plugged, maybe you could clean it somewhat with a long plastic-bristled brush, or something similar.


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## oldackonoak (Feb 11, 2018)

*Ingnition Coil*

I have had problems like you are talking about and when the Ignition coil gets hot they cut out. Some one had mentioned the same thing. I would look for the bad ground first if that is floating around it would cause this problem as well. If the fuel line looks old just replace it cheap enough and easy to do. When I do them on a Tecumseh motor I connect the old one with the new one at the tank and gently feed it though. that way you don't have to take the recoil off. It just follows the path of the old line. Hope this might help. Let us know what you find. A crack in the plug insulation can cause this as well. I worked on an ATV with the same problem and found a hair line crack in the plug. Happy hunting!!


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## antny (Nov 2, 2018)

Thanks guys. I'll try these out and report back.


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## tadawson (Jan 3, 2018)

One other way to replace the line is to run a coat hangar (or other stiff wire) through the old line, pull the line leaving the wire in place, and then run the new line in over the wire. No way for a splice coming apart that way and leaving you screwed . . .


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## broo (Dec 23, 2017)

If your spark plug is carbon black (dry), it may also mean your gap is wrong.

Whatever your problem is, when you have fixed it you should get rid of that carbon. Use a fuel additive designed to do that for a couple tanks and check your plug again. It'll tell you if you need to continue or switch product.

I have a older car (1981) which had this black spark plug problem. According to Haynes manual, this should mean running too rich, but in fact my plug gap was wrong. Once fixed, after 3 tanks with an additive the plugs were back to normal.


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## antny (Nov 2, 2018)

I checked the gap previously and it's .030, which is good. I added blue (marine) sta-bil to the fuel, but only ran about a half a tank. Maybe it'll improve after a few more tanks run through. Also, I'm not so sure it's dry black (carbon). It may be more on the wetter side. I'll have to pay more attention next time I take it off. 
Good idea with the coat hanger tadawson.


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## broo (Dec 23, 2017)

Sta-Bil isn't a cleaner, it's a stabilizer. By cleaner, I mean Gumout, STP, Seafoam, Marvel and others labeled as "fuel system cleaner" or "injector cleaner". Most snowblowers don't have injectors, but injectors cleaners need to be stronger and therefore do clean carburetors too, along with the combustion chamber & plug.



If your plug's black deposits are wet, this is bad. It means you have oil burning in the combustion chamber. Unless your machine is a two stroke, you may have a serious problem here.


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## antny (Nov 2, 2018)

I was afraid of that. I'll take a closer look this weekend. Thanks


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## vinnycom (Nov 6, 2017)

carb float set to low and/or not installed correctly, needle valve issues, bowl not installed correctly


.


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## antny (Nov 2, 2018)

I'm getting frustrated with this blower. I replaced the fuel line. I cleaned the carb again and replaced the carb gasket. I had trouble getting it started. I thought maybe some residue got in the carb from removing the old gasket. I added "mechanic in a bottle" and let it sit overnight. Now, it will start only when primed and will run for a few seconds and cut out.


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## Motor City (Jan 6, 2014)

Have you done a compression check? I had a Tecumseh that would barely run, because the compression was really low. Couldn't draw the fuel in, to run decent. This would only account for the hard start, not the cut out after 5 min.


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## RedOctobyr (Mar 2, 2014)

Is the gasket between the carb and the engine intact? Will it keep running if you keep hitting the primer button? 

A new eBay/Amazon carb may be worth considering, in case something is more-fundamentally wrong with the current carb. 

Are you still getting good gas flow to the carb? Though I guess if it only runs a few seconds, that isn't enough time to run the bowl dry anyhow. That takes maybe around a minute on my machine, at least if I'm at partial throttle, after closing the fuel shutoff.


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## antny (Nov 2, 2018)

The old gasket was a mess and it took a lot to get it off. i used 1000 grit sandpaper and brake cleaner to get it off. I don't know if I caused an issue with debris getting in. I installed a new gasket. The carb is in good shape. The float appears to be good and has the proper gap. Before doing all this, I could get it to run for about 5 minutes before cutting out. Now, it only runs a few seconds and won't start again until I prime it. I'm wondering if it's a valve issue. If so, I'm not sure I'm equipped to handle that and I'm not sure it's worth the $ to fix. Anyone have a ballpark estimate of a valve replacement at a shop?

Also, in response to RedOctobyr, I did not do a compression test. When pulling the pull start slowly, there is good resistance at the beginning of the pull and the end of the pull, but no resistance in the middle. I'm not sure if that helps the diagnosis.


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## RedOctobyr (Mar 2, 2014)

It was Motor City's good suggestion, not mine. If you don't have a compression tester, they are a useful tool to have available. Just one example: 
https://www.amazon.com/INNOVA-3612-Compression-Tester-Piece/dp/B000EVU89I/ref=sr_1_4?s=automotive&ie=UTF8

If you pull the cord slowly, you should feel significant resistance during part of one revolution, then the next revolution should be pretty easy, then significant resistance should return during part of the revolution after that. 

It's a flathead engine, you could pull the cylinder head, to observe the valve operation, including being able to look at the valve seats. 

But before doing that, you could check the valve clearances using an inexpensive set of feeler gauges, like: 
https://www.amazon.com/dp/B000BYGIR4/ref=sxts_kp_lp_3?pf_rd_p=8778bc68-27e7-403f-8460-de48b6e788fb&pd_rd_wg=yDoid&pf_rd_r=0W80Z0G6WCQAYEG6J5VE&pd_rd_i=B000BYGIR4&pd_rd_w=1U1eR&pd_rd_r=77ea9dcb-b5d7-4c0b-8acb-204335e5e9b3&ie=UTF8&qid=1546911735&sr=3

By removing a small cover on the side of the engine, you can watch the operation of the valve stems, to at least see if they're both moving. And you can use the feeler gauges to ensure you have the proper valve clearances. This helps ensure that the valves are both closing fully, and are both operating. And it can be easier than removing the cylinder head, and avoids maybe needing to replace the cylinder head gasket during that process.


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## jsup (Nov 19, 2017)

RedOctobyr said:


> There should be some sort of ground that kills the ignition when you lower the throttle lever fully, or turn a key off, if it has a key. So you're missing a ground at the moment. Maybe a wire is disconnected and floating around?
> 
> 
> 
> I'd start by investigating this, if it were me, since something about your ignition is not wired quite-right. And if that presumably-disconnected wire is moving around and touching bare metal, it might be grounding out and killing your ignition.



Exactly what I was going to say. I've seen that happen alot. Sometimes I just replace that mess with a rubber booted toggle switch and be done with it.


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## antny (Nov 2, 2018)

Well, looks like it's fixed. As a last resort, I ordered a new carb. After installing the new carb, it's purring like a kitten. 
I haven't tested it under load with snow yet, but it seems to be running great. 

This forum is a great resource! I appreciate everyone's help.
Thanks very much!


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## Kiss4aFrog (Nov 3, 2013)

Good to hear it's up and running again. Thanks for letting us know what you found.

.


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