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I received a Craftsman push mower (Model 917.377543) from my sister. She had left it outside all winter in the snow/rain.

I have got to the point where the mower will run for 15-20 minutes initially before dying (it runs good when it does). After that, I have to let it sit for 5-10 minutes before it will start again, and it will only last 5-10 minutes, and eventually will stop starting.

Heres a list of things that I have done (the mower wouldn't start at all at first)

  • Replaced the air filter
  • Removed old gas & oil and replaced
  • Took the carb apart (the bottom tin can part) and cleaned with carb cleaner. This is what got the mower running in the first place.
  • Replaced rotted gasket in the carb
  • Mixed some cleaner into the gas to help clean the engine out as well
  • WD-40'd necessary spots

Is there anything else I can try to get this thing running? I am about to just go buy a new mower, but I am no mechanic so there may be something else little I can try out.

The only other part visible on the mower that may be the culprit is this black tube that i believe is hooked up to the oil tank, and it runs near the carb, it is rotted at the end and it seems air may be able to get in. Looking at the engine parts here, it may be the 'breather tube' (part #12). Would this make sense with what is happening (shutting off after some use)

Another thing I notice when it shuts off, is that if I remove the oil cap white smoke comes out. Is this normal?

Thanks for any help. (I can try to get some pics of the tube that is rotted when I go home)

EDIT Someone suggested my gas cap may be bad, and no air is venting in the the gas tank causing it to shut off. This past weekend I was able to cut my whole lawn without it shutting off. When it began to die out, I unscrewed the gap for a few seconds and it kicked back in! I will have an update in a couple of weeks to ensure thats the issue. I don't trust this mower!

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There's a thought that'd never occurred to me - the gas cap. That could indeed cause a problem like this - it'd shut down the mower fastest when the tank's nearly full, slowest when it's nearly empty. Be sure to let us know how it worked out, OK? –  TDHofstetter Aug 30 at 1:31
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It has been 2-3 months and the mower is running great when I make sure to give the tank some air every 10-15 minutes. Now that you mention it, it does seem to kick out sooner if the tank is more full. It all makes sense now. –  RyanG Sep 2 at 14:50

3 Answers 3

up vote 1 down vote accepted

The issue ended up being a bad gas cap. When the mower starts to sound like it is dying, I simply unscrew the cap for a few seconds and it kicks right back in.

I will replace it eventually but it has been running for 2-3 months now without issues as long as I let the tank get some air every 10-15 minutes.

I am sure cleaning the carb & replacing the carb gasket, filter, and old gas/oil helped as well but the main culprit was the cap.

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Your best bet at this point is to replace the carburetor. It sounds as though the old gas has clogged the carb and made it so the gas will not flow as it is supposed to. Personally I have attempted to rebuild carbs for small engines with absolutely no luck. Replacing the carb, while costing more, is a cheap option when you look at the frustration factor and the amount of time you've already sunk into it.

When purchasing the part, find the engine model number, which should be on a plate somewhere on the engine itself (might be behind one of the cowling plates (this might actually be the number you provided, but I don't know for sure). Sears does not manufacture its own mowers or motors for their mowers. They have them built for resale. If you have the exact model number of the engine itself, you should be able find the carb online for much cheaper than from Sears. In fact, I just looked it up. This is a Tecumseh motor. You can pick up a replacement carb on eBay for about 1/3 to 1/4 the cost of what it will cost from Sears.

In the future, use Sta-Bil or some other fuel stabilizer in the gas. I have used it in all of my small equipment for the past several years and have had absolutely zero issues with them.

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My initial kneejerk for this one is a little different - since it sat outside, and since it runs FOR A WHILE before it shuts down, and since a cooldown does get it running again... I think it's overheating. I think mice may have crawled inside the cooling cowl (this is an air-cooled engine), had a party, and some of 'em decided to shack up there over the winter, where the cats couldn't bust 'em.

The extra heat buildup in the cooling fins will, among other things, heat the fuel tank more than it was ever designed for... pressurizing it and potentially forcing the float valve open, flooding the carburetor. If allowed to go further, it'd seize the engine.

If I'm right, change the oil after cleaning the nests out from under the cowl. Excess heat does NOTHING good for motor oil.

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