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Discussion Starter #1
Hello,

I have a TroyBilt 7524, about 15+ years old. Tecumseh engine. It's always run like a champ. This season, it started surging badly, and sputtering, misfiring, stalling, etc. My old carb had a fouled jet, so I replaced the carb. Replaced the spark plug, and spaced it. Oil is changed every year. Gas always drained in off-seaon, and stabilizer added during the season.

Now, with the new carb, the surging has stopped, but it's still misfiring, and stalling out frequently. The misfires are constant, every few seconds.

Today, it started right up, although still misfiring a bit, every few seconds, it gives a loud putt. I ran through snow for about 30 seconds, and it stalled out. Fired up right up again. Again, stalled out after 30 seconds. Blowing snow or not blowing snow, doesn't seem to make any difference.

When I start it, I use full choke, it starts right up, then I turn choke all the way down. It's always run great this way. Today, I noticed that when it was about to stall, if I gave it full choke again, that kept it running. But after about 30 second of full choke, it started to stall, and then I had to turn the choke all the way off to keep it running. It kept behaving this way. I can keep it running by constantly moving the choke on and off when it gets to the point where it sounds like it's going to stall. And I've tried the in-between choke settings too. Nothing works for more than a few minutes.

I eventually kept it running long enough to do the driveway, but it had stalled like 8-10 times over 45 minutes, and required me to fool around with the choke constantly.

What's going on? Any hope that it isn't time for a new snowblower?

Thanks in advance!
John
 

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Sure sounds like it's running lean. Fuel tank vent clogged? Bad gas? (Even if "fresh" that does happen.) And just because the carburetor is new does not mean that it's a good one, especially if it was a cheapie.
 

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sounds ignition system related to me. replace the cap and work your way back to the coil.

why replace a carb due to a "fouled" jet?

Id also check the valve clearances and underneath the shroud for a nest.

a machine cant run like a champ forever without some basic maintenance and parts!
 

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Discussion Starter #4
There was a grass mouse nest in the base where the belts are. (I had to replace a belt too) But that's the only one I found.

I replaced the carb because they aren't expensive. I assumed the carb was the problem, so rather than remove it, check it out, try to clean it, deal with the old crumbling gasket, etc, I thought it was just better to replace the whole thing.

Replacing the carb did fix the constant surging and poor starting, but the misfiring and stalling is the same.
 

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gotcha

if there was a nest in the belt area there is also a chance of one under the shroud too.

A big one can cause an engine to overheat and damage it.

Mice also like chewing on and pissing/crapping on ignition wires underneath the shroud

.
 

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WVguy and Tdipaul are right. Do those.

You want to check what is easier and cheaper first.

I would also check the magneto gap, sand the magnets, remove the flywheel to check the shear key, check the compression, lap the valves, finally replace the magneto.
 
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Have you tried loosening the gas cap? Sometimes they don't vent correctly, and create a partial vacuum in the tank, so gas can't flow.

Are you getting good gas flow at the carb, if you pull the line off it?

Have you checked your valve clearances?
 

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Discussion Starter #8
I'm actually not very mechanical, so replacing the carb was about the extent of my abilities. I'll have to send it to the snowblower repair place for anything more involved. Just hoping to avoid that.

The gas cap is interesting. I put the snowblower away a few hours ago. I just went out and unscrewed the gas cap and when I did, I heard a rush of air. So maybe I'll try a new gas cap first.
 

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The gas cap is interesting. I put the snowblower away a few hours ago. I just went out and unscrewed the gas cap and when I did, I heard a rush of air. So maybe I'll try a new gas cap first.
No need to buy a new gas cap just yet. Leave the old one a little bit loose so air can get in easily and see how the engine runs then. The rush of air you heard MAY have been air going in, but maybe it was fumes under pressure going out. Unless you could feel it there's no good way to be sure.

If the vent on the gas cap is clogged, as the fuel is consumed no air can get in to replace the volume of the fuel that is used so eventually the engine starves of fuel. Leaving the gas cap loose is a temporary diagnostic measure. Don't run it that way to clear snow or you'll risk losing the cap when it vibrates off and/or allow dirt in the tank.
 

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The gas cap is interesting. I put the snowblower away a few hours ago. I just went out and unscrewed the gas cap and when I did, I heard a rush of air. So maybe I'll try a new gas cap first.
To me, that's pretty telling.

No need to buy a new gas cap just yet. Leave the old one a little bit loose so air can get in easily and see how the engine runs then. The rush of air you heard MAY have been air going in, but maybe it was fumes under pressure going out. Unless you could feel it there's no good way to be sure.

It could be. But shouldn't the vent let that positive pressure out, too?

John413, try running with the cap loose. Or if you want a similar test, that's a little bit more secure, grab a plastic bag. Remove the gas cap, put it over the tank's opening, and secure the bag with a rubber band, so it's tight around the tank's opening. Poke a few little holes in the bag, like with a pen or pencil tip, to act as a vent (you don't reinstall the cap). Unlike a loosened cap, this won't rattle itself snug (defeating the test), or fall off and disappear.

If it suddenly runs OK, your cap has a plugged vent, and needs to be replaced. Or possibly cleaned, if you want to go that route.
 

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Discussion Starter #11
John413, try running with the cap loose. .
Yes, I'll try this first, as it's the easiest thing to test.

The fact that I could hear air whooshing when I unscrewed it makes me think the cap isn't working as intended.

But if the cap was the culprit, I don't understand why I'd have to give it alternately more choke and then less choke. I would think if there was a vacuum, and not getting enough fuel, then it would run better under choke all the time until it finally stalled out.

This runs under no choke at first, then I need to give it full choke, then when it's about to stall, I turn it to no choke, etc. Seems like it's going back and forth between the two.
 

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:welcome: to SBF John413

I hate to say this but maybe you have more than one problem going on there. The cap should have a vent and you could open it up with a pin or piece of wire. There is usually a disc under the cap that keeps the sloshing fuel from coming out the vent. I'm not talking about enlarging the hole just poking something through it to make sure it's open.

 

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Discussion Starter #13
Ok, I'll check the cap vent tomorrow. But if it was working properly, it shouldn't make a whooshing noise when I open the cap, right?

About the carb, I got an OEM one, so hopefully it's not total crap. It was surging constantly pre-carb change, and that problem has gone away, so I think the new carb is at least better than the old one.
 

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John, I hate to be an ass, but you just spent almost 4 hours trying to figure out how the cap vent works instead of trying the suggestions and eliminating the possibility of a bad cap. Once you cure the problem, you can think about how it works while blowing snow.
 

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Ok, I'll check the cap vent tomorrow. But if it was working properly, it shouldn't make a whooshing noise when I open the cap, right?
I wouldn't think there should be a whoosh. I don't get that when I open my tanks.
 

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Discussion Starter #16
Got a new gas cap today, fired it up, and it seems like it's no longer stalling. I notice on the old cap that the black rubber venting cup inside seems totally flattened, such that the metal disk is all the way up at the top of the cap, not down at the bottom of that red plastic rod that sticks down in the middle.

So I'm cautiously optimistic that that resolved it, or at least enough that I can run it without stalling constantly.

The next snowstorm will be test.

Thanks everyone!
 
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