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Discussion Starter #1
Here goes. I have a Sno-Tech snowblower that simply would not start on Sunday even though it was running well on Saturday. After a good 25 minutes of trying to start the darn thing I over heated the starter and had fuel dripping from the exhaust. Lets get the simple things out of the way first. Fuel delivery was good. Spark was VERY good. Here is where I am confused........... Somewhere in my memory bank I remember someone decades ago telling me to try and cover the exhaust while starting. I did this and the snowblower sprang to life. It also ran like a top for three hours straight! Next morning same thing. I fired the starter for a few short bursts then covered the exhaust and boom fired right up. Once it has been running for a few minutes I can pull start it easily.

What is the problem?





Tom
 
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I’ve never had experience with this but I remember reading that it causes enough unburned fuel to accumulate in the combustion chamber. Kinda like it is getting too much air and not enough fuel and covering the exhaust brings it closer to equilibrium. Sorta the opposite of choke? Definitely gonna try that the next time I’m scratching my head with a carb engine that won’t start.
 

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Sounds like it may have flooded.Do you shut off the fuel when your done with it? When I start mine I pump the primer 5 or 6 times some fuel will leak out the overflow give it full throttle and choke then one very hard pull.Starts every time.
Maybe your exhaust valve has too much carbon on it and is not seating all the way.
 

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Discussion Starter #6
Tom -
Check Post No. 7 here:
https://www.thetruckersreport.com/truckingindustryforum/threads/no-start-condition-cover-the-exhaust-with-a-rag-and-it-starts.188959/

And Badger's post, above.

Looks like 2 different theories leading to the same result!
This was all I could find.

My recommendation would be to blow-off snow work, build a fire, pop some corn and crack a bottle of fine Bourbon.
Play some games.
Or put on some porn...
I found this exact thread prior to posting this! Too funny. I always try to figure this stuff out prior to asking others but that was the ONLY thread I found on these symptoms. Thank you.


Tom
 

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Discussion Starter #7
Sounds like it may have flooded.Do you shut off the fuel when your done with it? When I start mine I pump the primer 5 or 6 times some fuel will leak out the overflow give it full throttle and choke then one very hard pull.Starts every time.
Maybe your exhaust valve has too much carbon on it and is not seating all the way.
I am not good about shutting off the fuel for a simple overnight rest. Long term storage however I do shut it off and run the bowl dry.

Could this have something to do with the way the motor is set up? It claimed to have some function that made it easier to start in extreme cold temperatures? Not real specific on how they went about accomplishing this goal....... Thank you for your reply!



Tom
 

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It's the modulator valve.. ;)
 
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Blocking the exhaust causes some gasoline to build up in the cylinder (for a richer mixture) .

SECONDLY I've read (but haven't thought through the concept) that if you cover the exhaust tightly it keeps some of the compression in the cylinder from escaping so on the next compression stroke you have a little more compression and a little richer mixture. This equals an easier start usually. Especially if your choke is not functioning correctly. So they say...

Lots of snow blowers have "auto-chokes" that stick and don't work (choke) fully on cold start. I've seen this at least three times.

Warm engines need less choke, i.e., a less rich mixture to start.

My guess is by holding the exhaust your keeping fuel from blowing out of the chamber for a richer mix, just like a properly working chike should do. Check your choke operation.. would be step one I think.
 

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I'm happy to report that I have never actually even seen a snow blower in person...thank God!
However, I did buy a snow shovel on sale a few years ago and have used it twice.
Next time it snows enough to matter, I'll just tell Betty that it won't start...something to do with the choke. Or something.:rolleyes:
 

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Back in the late 60s my dad had a Mustang that was hard starting. His mechanic buddy came over to help get it fired up and all he did was stuff a rag in the air cleaner intake and it jumped to life. I don't know much about car carbs but later on my dad would hold down the round brass flap in the carb and it would start right up. Full choke is I guess what this did but if he did not hold that round plate fully shut it would only go to half shut on it's own. I am not sure if the carb had an auto choke or not but pretty sure it was not working the way it should have been. I suppose the blocking of the exhaust has the same effect.
My Snowdog track sled has a 2 stage choke setting and if it is super cold I must use the full choke to fire it up while on warmer days I only need the half choke setting. Does your snowblower even have a separate choke or is it fully automatic?

GaryL
 

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Have you inspected choke mechanism for proper function as well as which type it is? I assume it is not a manual choke. The thermostatic coil type is often adjustable via the cover ; heat as well as the vacuum piston then open the butterfly plate. It is possible the piston has some stiction causing erratic operation. choke-thermostat.jpg choke-piston.jpg
 

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Don't forget to check the chicken..

Have you inspected choke mechanism for proper function as well as which type it is? I assume it is not a manual choke. The thermostatic coil type is often adjustable via the cover ; heat as well as the vacuum piston then open the butterfly plate. It is possible the piston has some stiction causing erratic operation. View attachment 188804 View attachment 188806
 
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Thanks, good thinking! This should solve Tom's problem with the snowblower.
 
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That's chicken choken at it's best...!
 

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Discussion Starter #17
Back in the late 60s my dad had a Mustang that was hard starting. His mechanic buddy came over to help get it fired up and all he did was stuff a rag in the air cleaner intake and it jumped to life. I don't know much about car carbs but later on my dad would hold down the round brass flap in the carb and it would start right up. Full choke is I guess what this did but if he did not hold that round plate fully shut it would only go to half shut on it's own. I am not sure if the carb had an auto choke or not but pretty sure it was not working the way it should have been. I suppose the blocking of the exhaust has the same effect.
My Snowdog track sled has a 2 stage choke setting and if it is super cold I must use the full choke to fire it up while on warmer days I only need the half choke setting. Does your snowblower even have a separate choke or is it fully automatic?

GaryL
It has a manual choke. It is basically a quarter turn dial so it IS adjustable to some degree. The engine ALWAYS needs to be choked even after a 3 minute shutdown.



Tom
 

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Discussion Starter #18
Have you inspected choke mechanism for proper function as well as which type it is? I assume it is not a manual choke. The thermostatic coil type is often adjustable via the cover ; heat as well as the vacuum piston then open the butterfly plate. It is possible the piston has some stiction causing erratic operation. View attachment 188804 View attachment 188806
It is a manual choke and until Sunday I have never had a reason to tear it apart. No heated garage or warm place to work on it either!

One new discovery is that the hose between the priming bulb and carb is disintegrated completely! Capping the carb where the hose attaches did nothing to help it start....

The mystery continues. Again, once it starts it runs like new!


Tom
 

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It is a manual choke and until Sunday I have never had a reason to tear it apart. No heated garage or warm place to work on it either!

One new discovery is that the hose between the priming bulb and carb is disintegrated completely! Capping the carb where the hose attaches did nothing to help it start....

The mystery continues. Again, once it starts it runs like new!


Tom
Perhaps this explains it, if the primer hose was beat there was not enough fuel to start it. Covering the muffler was enough to keep some fuel in the chamber?
 

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A cracked primer bulb might also let carb suck in some air rather than fuel reeking air/fuel mix havoc. Maybe that explains why the back pressure from Tom's hand tuned exhaust can get running.
 
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