# Why is this happening to my lawn tractor?



## jslewis67 (Sep 1, 2014)

So I've changed the carburetor. The engine dies after almost completing the lawn. Thought it was a vacuum problem in the gas tank, but ran it with the gas cap off. After it dies, it won't start and run. Flushed carburetor with cleaner, engine started but died. After about 5 minutes it started and ran. However, it is still hard to start. The engine won't crank, or cranks only partially when I first try to start it. That was supposed to be the carb flooding the engine, but the carb is now new. What could be causing it to die after almost 40 minutes of running? What could be causing it to be hard starting? I'm ordering new fuel lines today, but could that be the only problem?


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## 30yearTech (Sep 14, 2006)

Check and make sure you have ignition spark when the engine dies.


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## jslewis67 (Sep 1, 2014)

*How do I check that?*

The engine will generally turn over, it just won't stay running until that period of about 5 minutes passes. After it starts back up, it runs good allowing me to finish the lawn. Very strange. So how do I check for spark at the time the engine dies?


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## 30yearTech (Sep 14, 2006)

An inline gap type spark tester works best, it goes between the spark plug and plug wire. You can visually inspect to see if there is spark when it won't start.

http://www.autozone.com/test-scan-a...k-adjustable-ignition-spark-tester/10257_0_0/


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## jslewis67 (Sep 1, 2014)

*Is that much different*

than this type:
https://shop.harborfreight.com/catalogsearch/result?q=spark+tester

I'm not sure how this one works vs the one in my link.

Thanks.


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## 30yearTech (Sep 14, 2006)

Gap type tester is better, as these will show spark with very low voltage that may not actually be enough to jump the gap at the plug, that's why I recommend a gap type tester.


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## jslewis67 (Sep 1, 2014)

*ok*

then I will buy that kind. Thanks.


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## jslewis67 (Sep 1, 2014)

*Ordered on Amazon.*

I get free shipping, and it's worth the extra $2.50 to not have to go find it at a store that's about 35 minutes away from my house.

I bought this one:
http://www.amazon.com/gp/product/B0002STSBM/ref=ox_ya_os_product_refresh_T1

How do I use it exactly?


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## jslewis67 (Sep 1, 2014)

I bought this one:
http://www.amazon.com/gp/product/B00...uct_refresh_T1

How do I use it exactly?


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## 30yearTech (Sep 14, 2006)

Just adjust the air gap 1/4 to 3/8", plug the spark plug wire in on the side opposite the clamp, and attach the clamp to a good ground, or the spark plug. Then crank the engine over and observe to see the spark jump the gap between the contacts in the shielded tube. 

You may have to do it in subdued lighting as spark can sometimes be hard to see, especially in bright sun light.


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## jslewis67 (Sep 1, 2014)

*no luck*

so I finally had the chance to do this after a weekend of rain and a weekend of being sick. the tractor wouldn't turn over today. so I took out the tester. I had to cut part of the spark plug boot wire because the tester I got was not long enough on the end you plug into the wire. but no spark at all. but the engine tried to turn over when I had the spark plug wire disconnected. I figured i'd see what happens with the plug out, and the engine would turn over, but not start of course. what could the problem be?


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## 30yearTech (Sep 14, 2006)

jslewis67 said:


> so I finally had the chance to do this after a weekend of rain and a weekend of being sick. the tractor wouldn't turn over today. so I took out the tester. I had to cut part of the spark plug boot wire because the tester I got was not long enough on the end you plug into the wire. but no spark at all. but the engine tried to turn over when I had the spark plug wire disconnected. I figured i'd see what happens with the plug out, and the engine would turn over, but not start of course. what could the problem be?


If you don't have spark when cranking the engine over, then you need to isolate the engine kill wire from the tractor and test again, this will eliminate any of the safety interlocks or relays as the source of the problem. 

If you still have no spark, then the ignition module is most likely bad and needs to be replaced. If you have spark, then you will need to trouble shoot the electrical system of the tractor to isolate where the problem is.


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## jslewis67 (Sep 1, 2014)

how do I isolate the engine kill wire? i have no idea where to look for that. and what is the ignition module? is that the key switch? I tested that a while back and have good continuity in the switch.


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## 30yearTech (Sep 14, 2006)

There is a wiring harness that plugs into the engine from the tractor. Usually the white wire in this harness attaches to the ignition module to stop spark to the engine when you turn the key to the off position. The safety interlock on the tractor also operates though this circuit to kill the engine if the operator gets off the seat with the blades on or the clutch / brake pedal released.

The ignition module is the component on the engine that creates the ignition spark for the engine. Follow the spark plug lead wire up under the engine shroud and you will find the module. Some engines use a spark advance module (S.A.M.) and these units utilize a power wire to operate the module.


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## jslewis67 (Sep 1, 2014)

*Isolate*

So I may have a chance to look at this this weekend. What do you mean exactly by isolate the kill wire?


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## 30yearTech (Sep 14, 2006)

jslewis67 said:


> So I may have a chance to look at this this weekend. What do you mean exactly by isolate the kill wire?


Disconnect it from the engine, so the electrical system of the tractor cannot be a factor, preventing the ignition from working.


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## jslewis67 (Sep 1, 2014)

*wow*

so it seems I would have to remove the blower housing and baffles, and the cylinder head and baffle. I got a copy of the engine service manual from kohler. it's the CV460-465. if I do that, can I still try and start the engine while all that stuff is off? And then, my next question is, if the engine still doesn't start with the kill lead removed, what does that indicate?


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