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Discussion Starter · #1 ·
Hi all. Last year, while mowing lawn, I ran my 318 out of gas, limped it over to my shed, refilled the tank and couldn't get it to start. I let it sit overnight and came back to it the following morning, only to find that I could barely start it and the idle was stumbling terribly. I thought, maybe I sucked up some junk from a filter or something and decided to see if I could start it, let it run for 10 minutes to see if it would clear. And it did! After 2-3 10-15 minute runs, it cleared for an entre year.

Fast forward, three months ago and the problem returned.

History: Back in 2019, I took my tractor to two different John Deere Dealers and had terrible experiences. The TDC Module had failed and I thought, she was probably due for a tune up. Well, the tune up never really happened. Instead I had plugs that looked like they were tightened with an air ratchet, zerk fittings that weren't touched, not enough engine oil and points that were way out of spec = $200 bill. I got my money back on that one but I've learned over the past 20 years that if you want it done right, do it yourself. After the tune-up tractor ran great for a year until I ran it out of gas.

Work Completed: From that experience, I pulled the gas tank, replaced all of the rubber lines, in tank pickup screens (and little clear fishtank looking lines), had the carb professionally rebuilt, replaced the points breaker box, gapped it properly, replaced the fuel pump, new plugs, replaced the Onan Intake Manifold (brand spanking new from Onan Parts), brand new intake and exhaust manifold gasket as well as carb mount gasket. Fuel filter was replaced twice (I broke one of the plastic barbs) and the fuel filter was replaced twice.

Problem: Tractor runs like a top for exactly 15 minutes either low running idle or high RPM, starts stumbling, backfiring, gasping and will eventually stall. I can re-start but it'll only run for a minute or two. It is not a sudden stall but a slow very noisy process. Come back to it the following morning, same issue. Doesn't matter if its 45 degrees or 85 degrees outside.

Troubleshooting:

  1. Blew out all of the rubber lines - before and after the fuel pump
  2. Disassembled the carb, checked the jets and bowl - Zero junk, clean as a whistle
  3. Purchased a small go-kart tank, installed that right before the fuel pump, problem persists
  4. Found a small intake leak, decided to replace the entire manifold and install new intake and carb gaskets.
  5. Compression test (not leak down) opposite plug out, throttle up and choke in, the right bank shows 76.5 and the left, 80.5. From what I've read online, this is barely minimal operating range but, it looks like the engine is evenly worn.
The tractor doesn't smoke at all, and minus the RPM running a bit higher than normal after I had the carb rebuilt, this tractor has been loyal to me for more than ten years. Valve's? Coil? Worn out engine? Any help would be greatly appreciated.

Cheers,

Ed
 

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Early 2017 Vintage 1025R TLB (260/H120)
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I had a similar problem- Tractor (L130) would run great then starve of fuel. The cause was a clogged tank vent (in fuel cap), as fuel was pulled from the tank it created a vacuum the pump couldn't overcome, collapsing the fuel line till the fuel cap was removed and vacuum released. Was a pain to troubleshoot, but simple to fix. It was sawdust in the cap causing the vent blockage.
 
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Matt, Those were my first thought too, but Ed replaced fuel source with go-kart tank...no difference. I responded in MTF saying replace condenser and test coil. Bob
 

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Discussion Starter · #4 ·
Matt, Those were my first thought too, but Ed replaced fuel source with go-kart tank...no difference. I responded in MTF saying replace condenser and test coil. Bob
Bob you're on point! Thought I'd poll the masses. Matt, a good point as well but Bob is correct. The go-kart tank was vented and eliminates my entire fuel system from the fuel pump back. For kicks, I tried it a few moments ago without the cap on and the problem persists. Starts like a champ and runs for exactly (I timed it) 13 mins and than the idle kicks way down, bogs, sputters and will slowly start to roll into a stall.
 

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Early 2017 Vintage 1025R TLB (260/H120)
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Matt, Those were my first thought too, but Ed replaced fuel source with go-kart tank...no difference. I responded in MTF saying replace condenser and test coil. Bob
Yup saw that, and didn't think that it would solve "this" problem, but might help someone else.. or just in case the new tank wasn't vented.

Fuel pump? It sounds like there is a problem once the motor warms up, not being familiar with the specific motor, is it possible once the fuel pump gets warm it's failing to pump fuel? This would likely be next troubleshooting step.
 
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I wonder if the breather is plugging and building pressure in the crankcase and stops the pulse to the fuel pump ?????????????
 

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Discussion Starter · #7 ·
I wonder if the breather is plugging and building pressure in the crankcase and stops the pulse to the fuel pump ?????????????
Already double checked that :) When I did the tune up on the tractor back in 2019, I remembered that my old Sears Suburban's had some super funky metal (brillow) elements that needed to be replaced. For my 318, I replaced the element and the angled rubber. I am going to try the replacement coil and condenser once the Amazon Gods drop it off. Fingers crossed!
 

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I would check fuel pump just run it into cup for 30 seconds if it pumps lots of fuel then no issues.. but you said it runs good for certain amount time then starts to mess up sounds like a bad coil they can do weird things when messing up..
 

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Discussion Starter · #10 ·
Really great troubleshooting tips here!!!! The entire points assembly was replaced back in 2019 and the note about checking that small wire out of the points box is a good one. Gap is good and I jacketed just about every wire I could get my hands given how warm the engine surfaces can be.

For those reading/following, the root cause was the coil. The rough erradic idle, slight backfiring, and stalling now make sense. Condenser was replaced in 2019 and I doublechecked everything. I set the idle down just a tad and I've ran it for several hours with zero issues (knock on wood).

  1. What is the proper service method for "de-carboning"? Sea Foam?
  2. I don't hear any tapping or clacking, no loss in power or any smoke condition (white or black). This tractor has had little to no real use in the past eight years. Should the valves be checked?
  3. The engine does just fine with pulling, mowing and blowing snow. Should I be concerned with the current compression levels, 76.5 and 80.5?
Thanks again for all of the tips and suggestions!
 

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Seafoam will extend the hours between actually having to de-carbon the heads and valves. Use Seafoam in the oil and gas according to label directions, it will continuously clean carbon, but you may need to change oil more often. You can "you tube" de-carbon Onan engines, someone may have done a video on it and valve adjustment. It means that the rings are losing contact pressure with the cylinder walls (caused by wear), so a rebuild is in the future, if it has not already been done.
 

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Seafoam makes a spray product, or you can just dump the regular product down the carb to de carbon a head.
 
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