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Discussion Starter #1
Hi all - I'm new to the forum and am looking for a little help on my LA110. It's from '06 or '07, I've had it for about 7 years. I've serviced it myself and it's run great as long as I've had it. It's fairly lightly used these days and winters over in a dry garage. This spring I put in fresh gas, a new fuel filter and new spark plug and started hauling wood that had blown down over the winter. All went well until afternoon, I'd started and turned it off probably 10 times that day, and when I went to fire it again it cranked fine but wouldn't fire. It cranks for 2-3 seconds, coughs/backfires once, and repeats. Here's everything I've checked since then, with zero change:
- fuel cap is clear and I've cranked it with the cap off completely with no change
- fuel pump works and I'm getting fuel to the cylinder
- carb solenoid (safety switch) is working correctly
- plug fires when grounded to block and cranked
- battery is good and I even switched for a brand new battery with no improvement
- carb was disassembled and cleaned thoroughly
- all wires, switches and grounds appear to be correct
- spraying carb cleaner into carb when cranking has no effect
- turning the flywheel by hand feels like I have compression...easy for a bit and then harder as compression builds, then easy again

I'm leaning towards an engine issue but hesitate to tear into it without knowing what I'm looking for. I'm hoping someone out there has experienced something similar and can offer guidance. Many thanks!

Ian
 

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Hi all - I'm new to the forum and am looking for a little help on my LA110. It's from '06 or '07, I've had it for about 7 years. I've serviced it myself and it's run great as long as I've had it. It's fairly lightly used these days and winters over in a dry garage. This spring I put in fresh gas, a new fuel filter and new spark plug and started hauling wood that had blown down over the winter. All went well until afternoon, I'd started and turned it off probably 10 times that day, and when I went to fire it again it cranked fine but wouldn't fire. It cranks for 2-3 seconds, coughs/backfires once, and repeats. Here's everything I've checked since then, with zero change:
- fuel cap is clear and I've cranked it with the cap off completely with no change
- fuel pump works and I'm getting fuel to the cylinder
- carb solenoid (safety switch) is working correctly
- plug fires when grounded to block and cranked
- battery is good and I even switched for a brand new battery with no improvement
- carb was disassembled and cleaned thoroughly
- all wires, switches and grounds appear to be correct
- spraying carb cleaner into carb when cranking has no effect
- turning the flywheel by hand feels like I have compression...easy for a bit and then harder as compression builds, then easy again

I'm leaning towards an engine issue but hesitate to tear into it without knowing what I'm looking for. I'm hoping someone out there has experienced something similar and can offer guidance. Many thanks!

Ian
How old is your battery?

These engines can crank but lack sufficient reserve to function the ignition system. If you have a failing battery, it will be in a state discharge while the engine is running. The longer it runs, the further discharged the battery will become creating confusion because mentally, we think if it cranks, the battery must be good. Verify battery condition and move on to the ignition system since its not firing on carb cleaner.
 

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Discussion Starter #3
Thanks Brian, the battery is from 2012, so - considering what you mentioned - I've swapped it for a new, fully-charged battery and it hasn't made a difference. When you say ignition system, can you give me a few more details?
 

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Starting Fluid

Rather than using carb cleaner, try some starter fluid. If that does no good, try pouring a small amount of gas directly into the cylinder via the spark plug hole, reinsert the plug, and try cranking again. Make sure your choke isn't stuck in the closed position. Years ago I had an issue with my L120 and found I had a bad coil.
 

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Remove the valve cover at front of engine and see whats going on there. Common issue with rocker arm studs backing out or push rods disconnected.

Sent from my LGL52VL using Tapatalk
 

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Thanks Brian, the battery is from 2012, so - considering what you mentioned - I've swapped it for a new, fully-charged battery and it hasn't made a difference. When you say ignition system, can you give me a few more details?
Your next step is to verify it has spark. Spark testers are available from auto parts stores but you can do the same thing with an insulated screwdriver. Put the screwdriver in the spark plug boot touching the connector and put the shaft about 1/4 inch from the spark plug tip or any metal that goes to ground. You should see a clear spark jump that gap. Its possible you have a bad ignition module. A spark test would be my next movef ollowed by a compression test if the spark test passes. If the valve train is a known problem on your partcular engine series, pulling the valve cover(s) and watching function during cranking can clue you to an issue. It would also show up in a compression test. If you were getting backfiring and your battery wasn't the cause, engine timing is a strong possibility and your valve train is a good choice to examine.

Remember every engine needs 3 critical things to function. 1. Fuel 2. Air 3.Spark (diesels use compression to initiate spark) Remove any one item and you have a boat anchor.
 

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Discussion Starter #7
Thanks all, I have spark and since it's backfiring I'll pull the valve cover and see how things look.
 

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Discussion Starter #8
Tonight's update:
- checked coil for connectivity = good
- pulled valve cover and hand cranked engine, everything is clean and functioning properly
- tried cranking motor via battery and no change...crank crank crank puff crank crank crank POP crank...

Any more suggestions?
 

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Tonight's update:
- checked coil for connectivity = good
- pulled valve cover and hand cranked engine, everything is clean and functioning properly
- tried cranking motor via battery and no change...crank crank crank puff crank crank crank POP crank...

Any more suggestions?
Do the compression test. If that checks out I'd inspect the key that indexes the flywheel to the crankshaft. If the flywheel/crank are not lined up perfectly/correctly the engine will be "out of time". Meaning that the spark plug can fire at the wrong time. This would explain the backfire.

I have found a sheared key a few times over the years. My ex BIL gave me a STX38 because nobody could figure out why it wouldn't start. I suspect tractor was left outside with the hood open and the air cleaner removed. While whoever was trying to figure it out. Water got into the intake and the next time they cranked over the engine the key broke.
The first no start problem ended up being a bad PTO switch. I suspect that the broken key came afterwards.
 

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Discussion Starter #11
I had a similar piece of advice from a coworker today, and I agree the partial combustion while cranking points in this direction. I'll check it out...
 

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Discussion Starter #12
Well fellas, I pulled the flywheel and the key was perfect. I cleaned up everything underneath and reinstalled. Then switched the coil for a new one just in case it was bad and not throwing enough spark. Now it cranks like crazy but the intermittent exhaust pop or backfire is the same. It won't start even with starting fluid. I have spark, I have fuel (plug is wet when pulled after cranking), the engine turns over great...bad negative ground? It's gotta be simple, I've checked just about everything. Thanks for any ideas.
 
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