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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. Any ideas??? I'm confused. :confused2:

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.

MonkeyCam said:

I ran the test last night, disconnected the tester, & put the mower back together.

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

cpurvis said:

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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The air filter. Here's the YT video I followed: www.youtube.com/watch?v=U0DuLtoHbWg

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.

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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.

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?

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. :confused2:

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?

This is an autochoke engine, correct?

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:

ppl around here are disconnecting that auto-choke dealio.

Are you sure it is not full Choking it when trying to start it ?

7394 said:

ppl around here are disconnecting that auto-choke dealio.

Are you sure it is not full Choking it when trying to start it ?

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I've tried to start it w/ the choke both opened & closed. Doesn't make a difference.

Somebody somewhere must know what the problem is. If I can't get an answer on a small-engine forum of all places, then that's pretty surprising, & I guess I'll have to start shopping for a new mower (or at least a new engine) to replace the 2-yr.-old, well-maintained one that suddenly & inexplicably crapped out.

I've got compression, fuel, & spark, so what's the problem??? :confused2:

1. Take off the muffler and try to start the mower without it. If the mower starts, the muffler is clogged.
2. If the muffler is not clogged, try replacing the spark plug. Inline spark tester will not tell you if you have a shorted spark plug, try a new one and see if it helps.

primerbulb120 said:

1. Take off the muffler and try to start the mower without it. If the mower starts, the muffler is clogged.
2. If the muffler is not clogged, try replacing the spark plug. Inline spark tester will not tell you if you have a shorted spark plug, try a new one and see if it helps.

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Bought & installed a new spark plug & removed the muffler. Still won't start.

I can't help but think that this problem was brought on by the compression test I did; everything was fine until then . . . or else it's just a very misleading coincidence, which I have a hard time believing.

I can't believe that a mower I bought new, took good care of, & used for only 2 seasons is on the verge of needing to be replaced b/c it mysteriously & stubbornly refuses to start after a simple compression test. What the hell?!?! :confused2:

I feel we are overlooking something simple. I am wondering if you are actually getting spark under compression. There was an issue with some of the XT engines a few years ago where the the tab the brake cable connects to would flex over time and hit a point were it would release the flywheel brake but not enough to get a reliable spark.

Maybe disconnect the kill wire from the module and see what happens.

ILENGINE said:

I feel we are overlooking something simple. I am wondering if you are actually getting spark under compression. There was an issue with some of the XT engines a few years ago where the the tab the brake cable connects to would flex over time and hit a point were it would release the flywheel brake but not enough to get a reliable spark.

Maybe disconnect the kill wire from the module and see what happens.

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I removed the blower housing & saw that the brake pad fully disengaged from the flywheel when the lever was held against the handle.

But your comment reminded me of something I noticed earlier today: with the spark plug removed, the starting rope is nearly as hard to pull as when the spark plug is screwed in firmly. Shouldn't it be a lot easier instead? Could that be a clue?

Definitely something odd there. I may of missed it but what was the compression reading that you took. And if possible recheck it and see it it changed. I am wondering if something was going on at the end of your last mowing session, and is now come to light.

MonkeyCam said:

I removed the blower housing & saw that the brake pad fully disengaged from the flywheel when the lever was held against the handle.

But your comment reminded me of something I noticed earlier today: with the spark plug removed, the starting rope is nearly as hard to pull as when the spark plug is screwed in firmly. Shouldn't it be a lot easier instead? Could that be a clue?

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Yes, it should spin relatively freely with spark plug removed. That Compression tester ? Did the threaded hose end have longer threads than the spark threads ? I'm now wondering if it hit something in the combustion chamber ? You never posted any readings (or I missed them).

The compression reading after 6 pulls on the starting rope was 105, & I performed the test 2 or 3 times. And the screw-in nozzle on the compression tester doesn't reach as far into the chamber as the spark plug does.

BTW, thanks for the replies; I really appreciate it. :smile:

It's late, & I need to get to bed, but I'll do another comp. test tomorrow & post the result.

Just curious...why were you wanting to check the compression on a two year-old mower, well-maintained mower?

If it doesn't spin easily without a spark plug, that could mean that the blade brake is dragging. My daughter had a Craftsman mower with Briggs engine which incorporated the kill switch into the blade brake function. There was an arm on the left side of the engine that was pushed forward by the housing of the safety cable (dead man's switch). That cable became so stretched that it wouldn't push that arm forward enough to allow the engine to start. After I replaced that cable, the problem was fixed.

ILENGINE said:

Definitely something odd there. I may of missed it but what was the compression reading that you took. And if possible recheck it and see it it changed. I am wondering if something was going on at the end of your last mowing session, and is now come to light.

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I did another compression test tonight, & I got about the same reading I was getting earlier. Before it was approx. 105, & tonight it was closer to 110.

This whole things seems odd. I don't know if it has been checked but have you inspected the flywheel key. I don't know why it would be sheared, but with everything being checked that is about the only thing we possibly could of missed.

ILENGINE said:

This whole things seems odd. I don't know if it has been checked but have you inspected the flywheel key. I don't know why it would be sheared, but with everything being checked that is about the only thing we possibly could of missed.

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I haven't checked the flywheel key, but I'm the only one who uses the mower, & I haven't hit anything w/ the blade that would have caused a sheared key. And at this point I've about reached the end of my patience. I'm demoralized & disgusted, & by now I'd rather beat the thing to pieces w/ a sledgehammer than take it apart enough to have a look at the flywheel key.

I don't know whether to take this mower to the repair shop, buy a replacement engine, or just get a whole new mower. I want to scream. :frown:

After having 24 hrs. to cool off, I went ahead & removed the blower housing & cup to take a look at the flywheel key just for the hell of it. It looked fine. I've attached a pic.

Could the problem be a faulty ignition coil? I'm getting a spark, but could it be that it's too weak of a spark? That's about the only thing I can think of at this point, & I found a guy on YouTube who says that these Kohler XT series engines have a tendency for the coils to go bad. www.youtube.com/watch?v=SvAE78iFdl8

I would try a new plug. If you dropped it or even pressed a little hard sideways on the insulator when removing and installing it it could be cracked or damaged.

MonkeyCam said:

After having 24 hrs. to cool off, I went ahead & removed the blower housing & cup to take a look at the flywheel key just for the hell of it. It looked fine. I've attached a pic.

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That is not the flywheel key.
That is the PTO drive key.
The flywheel is on the top of the engine and has the magnets that generate the spark in it.

bertsmobile1 said:

That is not the flywheel key.
That is the PTO drive key.
The flywheel is on the top of the engine and has the magnets that generate the spark in it.

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The gray spoked wheel is definitely the flywheel, so I'm 99.9% sure that's the flywheel key in the picture above.

MonkeyCam said:

The gray spoked wheel is definitely the flywheel, so I'm 99.9% sure that's the flywheel key in the picture above.

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Well as you obvious;y know more than this full time mower mechanic I can be of no further assistance good luck & good bye

bertsmobile1 said:

Well as you obvious;y know more than this full time mower mechanic I can be of no further assistance good luck & good bye

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You get your feelings hurt *that* easily??? Wow. :laughing:

These are the possibilities I've been able to come up with:

1. Intake valve is not opening for some reason.
2. Intake gasket is messed up somehow.
3. Coil could be bad or gapped incorrectly.
4. New spark plug could be faulty.

I am leaning towards 3 or 4 as the cause of the problem. You got it to start and run good ONE TIME since the compression test, right? Coils and spark plugs can suddenly go bad, and they can also work intermittently.

primerbulb120 said:

These are the possibilities I've been able to come up with:

1. Intake valve is not opening for some reason.
2. Intake gasket is messed up somehow.
3. Coil could be bad or gapped incorrectly.
4. New spark plug could be faulty.

I am leaning towards 3 or 4 as the cause of the problem. You got it to start and run good ONE TIME since the compression test, right? Coils and spark plugs can suddenly go bad, and they can also work intermittently.

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I think it's the coil. I've eliminated everything on the list but that. I've also eliminated the carb as the problem. In my surfing, I came across a guy on YouTube w/ this same engine who has a video on how to replace the coil, & he says that these Kohler XT engines are known for the coils going bad. I ordered a new one several days ago, & it should arrive tomorrow. After I install the new one, I'll post the results.

Good idea. :thumbsup:

If you check for spark with plug grounded to engine and it is decent it would be unlikely to be a coil, but strange things happen.
I've had a few weak ones that would only run right with a smaller plug gap like . 022- .025.

I changed the coil, & it started & ran on the very 1st pull--even w/out using starting fluid. :biggrin:

There were a couple of things that made this so confusing & hard to diagnose:
1. The engine ran fine until after I performed a compression test, then it suddenly wouldn't start. Apparently that was just a very misleading coincidence.
2. I was still getting a spark both when I used a spark tester & when I grounded the spark plug to the engine. Obviously, it was an *insufficient* spark. I'll remember that lesson for future reference.

My experience confirmed what I'd read on the Internet: Kohler XT series engines are known for the ignition coils going bad. You guys might want to file that factoid in your mental Rolodexes.

Finally, a heartfelt thank you to those who took their time & gave me the benefit of their knowledge to help me solve this maddening problem. I *really* appreciate it. :thumbsup:

Glad you figured it out. I don't really know if xts are known for coils but there are so many millions of them out there I'm sure you can find quite a few instances of them going bad.
I service 15 or 20 per season and have not had a bad coil yet. I did have a bad coil on a Kohler 7000 series that was made September of 2015. This one was bad last summer so it only made it a year. Also had a couple of duraforce lawn boys go bad and an alarming number of older Kohler commands from around 2003. I figured those are just due to age.

:thumbsup:

MonkeyCam said:

I changed the coil, & it started & ran on the very 1st pull--even w/out using starting fluid. :biggrin:

There were a couple of things that made this so confusing & hard to diagnose:
1. The engine ran fine until after I performed a compression test, then it suddenly wouldn't start. Apparently that was just a very misleading coincidence.
2. I was still getting a spark both when I used a spark tester & when I grounded the spark plug to the engine. Obviously, it was an *insufficient* spark. I'll remember that lesson for future reference.

My experience confirmed what I'd read on the Internet: Kohler XT series engines are known for the ignition coils going bad. You guys might want to file that factoid in your mental Rolodexes.

Finally, a heartfelt thank you to those who took their time & gave me the benefit of their knowledge to help me solve this maddening problem. I *really* appreciate it. :thumbsup:

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Had a CV23 come in on an exmark that won't start and had fire at the plugs when grounded and also with another tester, The correct Kohler tester showed both modules are bad.

There must be more to the pattern failure. For instance if the coil is nearer the head than other setups. The Intek V at least has the coils mounted on very large castiron "heatsinks" which no doubt help keep the coils below their failure temp. Also viewing a spark with naked eye , or cold, can mask a failed coil which will not perform at hot or under compression. These things drive us all crazy, right? And again, as others recommend , do not buy anything but brand name coils. The cheap ones may never have been turned on, and contain defective components. Even dealers get lot failures with the "major brand" electronics and do not make recalls, only angry customers.

An article on electric cars mentioned a heat tolerance of only185F which I believe is too low, but it is something that affects lawnmowers, electric cars and your stereo.

Pattern of failures ?

I get more engines in with sever head damage from overheating with perfectly good coils than I do with faulty coils.
The whole one piece coil & module is a planned obsolessence thing.
The points coil & hall effect trigger set up is 2/3 the price of a modern combined unit and a lot more reliable.
Spark testers are just that .
I have 6 different ones but one would not expect a home owner to have $ 200 worth of test gear as most either work or don't work.
Of the modules I replace around 1/2 simply have a broken connector in the HT lead and the local Mens Shed digs the old one out & replaces them.
They rebuild old mowers for fun and usually give them to pensioners so anything that costs only time is good for them.