2018 Cub Cadet 159cc dies immediately after starting


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Old 05-30-24, 04:41 AM
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2018 Cub Cadet 159cc dies immediately after starting (with video)

I've got a 2018 Cub Cadet SC300HW 159cc that refuses to stay running. It acts like it's fuel starved, but fuel flow to the brand new carb has been verified. It will turn over with a shot of carb cleaner but, again, dies after a second or two. I've replaced the spark plug, air and fuel filters, and the oil was changed. Could it be a valve issue? I'm at my wife's wits end and my lawn is an ever increasing jungle. Video link below of the symptom

https://drive.google.com/file/d/1a7r...w?usp=drivesdk

 

Last edited by CellarMonkey; 05-30-24 at 04:52 AM. Reason: Title change
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Old 05-30-24, 04:54 AM
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If it only runs on carb cleaner then you've got a fuel problem. Usually it's the carburetor.
 
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Old 05-30-24, 11:36 AM
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Thanks. So, its a new carb, installed yesterday. A buddy recommended a break in by keeping it running for a few moments with the carb cleaner. Not sure how valid that is, but I am willing to try it. After-market carb, btw.
 
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Old 05-30-24, 12:44 PM
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Was that also the initial problem before changing the carb?
 
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Old 05-30-24, 02:57 PM
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It was indeed! Kept it running with carb cleaner in the intake (not too long) I checked the fuel cap, and it's not clogged. Scratching my head big time here.
 
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Old 05-30-24, 03:17 PM
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If it was doing this before you replaced the carb and you changed the plug and fuel filter, then about the only things left would be the air filter and the valves.
 
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Old 05-30-24, 03:49 PM
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I was thinking valves but that's uncharted territory for me. I guess a compression test is in order?
 
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Old 05-30-24, 08:27 PM
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Valves on a small engine like this are not too hard. There are a bunch of good (and some bad) vids on Youtube that walk you through the process.
 
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Old 05-30-24, 11:09 PM
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Take the carb bowl off and watch the flow of gas into the bowl. Is it barely a dribble or is it a good trickle?
 
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Old 05-31-24, 05:01 AM
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I will reverify fuel flow into the bowl this afternoon post work. If it is valves, I’m having a hard time finding clearance specs. I saw a bunch of posts about the MTD site having them, but my search was lacking. Will keep looking while at work.
 
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Old 05-31-24, 04:42 PM
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It's not the valves. They may benefit from being adjusted but it runs with a shot of something combustible.
 
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Old 06-01-24, 09:05 AM
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I think this would be enough to keep a single cylinder going, but maybe I'm wrong...

Valves were in good shape. Intake .10 exhaust .15

https://drive.google.com/file/d/1cms...w?usp=drivesdk
 
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Old 06-02-24, 06:10 PM
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Oh, it's just pouring out with the engine not running... that's the inlet needle not sealing inside the carb. You'll need to drop the bowl (the gold cup on the bottom) and look for trash/debris and check float/needle operation. Since it happened with the new carb, you may have trash coming in from the tank.
 
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Old 06-09-24, 06:33 AM
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Float working properly I’m at a total loss.
 
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Old 06-09-24, 06:58 AM
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Had a friend who had a similar issue. We pulled the carb and ran it through an ultrasonic cleaner. The only disassembly we did was take the bowl, float and valve out. Reinstalled the carb and had the same problem, Pulled it again and this time we removed every valve and jet we could and sprayed carb cleaner down every port we could. That did the trick. There must have been a small piece of something in one of the ports that we got with the spray.
 
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Old 06-09-24, 09:01 PM
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A closer look and there is a hole in the bowl. The bowl drain is missing... I thought the engine wasn't wanting to run, nut now the problem is the gas just runs straight out on the ground?
 
 

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