Engine Won't Start After Compression Test

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MonkeyCam

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I'm trying to to troubleshoot & fix a problematic 12.5 HP B&S Intek on a Snapper rear-engine rider. I suspect that the engine has a compression problem, so I got a compression tester. According to their official website, B&S doesn't publish compression numbers; they insist that you take the engine to a dealer for a leak-down test. Instead, to get a ballpark figure on what a good compression number would be, I decided to run the test on my walk-behind, self-propelled Toro mulching mower that is only a couple of years old, runs good, & has a 149cc Kohler on it. I ran the test last night, disconnected the tester, & put the mower back together. The problem is that now I can't get the damn thing to start, & I never had any problems with it before. :mad: Any ideas??? I'm confused. :confused2:
 
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ILENGINE

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Did you get the spark plug wire connected correctly to the spark plug. Sometimes they act like they go on but don't actually connect.
 
cpurvis

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MonkeyCam said:
I ran the test last night, disconnected the tester, & put the mower back together.
Click to expand...

Other than removing and replacing the spark plug, what else did you have to disassemble in order to run this test?
 
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MonkeyCam

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ILENGINE said:
Did you get the spark plug wire connected correctly to the spark plug. Sometimes they act like they go on but don't actually connect.
Click to expand...

I made sure I pushed it on securely. I felt it snap into place. I also made sure the spark plug was screwed in snugly.
 
primerbulb120

primerbulb120

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1. Pull the air filter cover and filter. (Not the base, just the cover and filter.)
2. Give the engine a quick shot of starting fluid down the carburetor throat.
3. Try to start the engine. Does it start and stall, start and keep running or refuse to do anything at all?
 
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MonkeyCam

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I checked it w/ a spark tester & found that it’s getting a spark.

Next, I removed the tester, reattached the spark plug, took off the cover & air filter, & sprayed some starting fluid into the air intake. I gave the rope several pulls, & the mower sputtered & almost started a few times but didn’t. When I was about to give up, I pulled again, & the mower started & ran fine. I let it run for about a minute, then shut it off & put the filter & cover back on. After about 10 min. I came back & tried again. Nothing. So I removed the cover & filter again, sprayed in some more starting fluid, & pulled several more times. All I got was a backfire thru the air intake. :mad::confused2:
 
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motoman

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Can you see a choke butterfly when you remove the air filter and is it closed when cold? Is it wet with gas so that removing the air filter leans out the starting mixture when you turn over the engine several times?
 
primerbulb120

primerbulb120

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This is an autochoke engine, correct?
 
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MonkeyCam

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Yes, I can see the choke valve, & it's closed when cold.

And, yes, this is an autochoke engine.

Today (Saturday) I had time to, w/ the help of a couple of YouTube videos, remove & clean the carb. I plucked a wire from a wire brush & used that to pass thru all the tiny holes, & then I blasted the orifices w/ carb cleaner & compressed air. I wiped out the bowl w/ a paper towel. I didn't see any gunk or obstructions inside the bowl or carb. The float & needle were fine. I put everything back together, bolted the carb back on, hooked up the linkages, & got *zero* improvement. The mower still won't start, not even after spraying starting fluid into the air intake.

I replaced the spark plug at the beginning of this season & have only mowed the yard a few times since, but I took it out & checked the gap, anyway. It was off (too close), so I adjusted that, hit it w/ some carb cleaner, put it back in, & then hooked up the spark tester to make sure I'm getting spark, which I am.

I'm baffled. :confused2:
 
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