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Discussion Starter #1
I repowered my Bolens 1253 this year with a 11 HP single cylinder air cooled diesel engine. The engine was made in China but is a clone of the Yanmar L100.

The engine started up and ran great at first. I've used it for over 10 hours of plowing and tilling so far, but now it won't start.

Last week while tilling, I noticed two brief instances of black smoke and loss of power, but after a short pause, it went back to work. The next day, it wouldn't start.

It cranks over (electric start) at the normal speed and after a couple of seconds I see what looks like unburned fuel coming from the exhaust. As it turns over, it sounds like it has normal compression. It speeds up alot if I use the compression release.

The air filter was filthy, but has been carefully cleaned. I had been running biodiesel, but have drained that and put in fresh regular diesel.

I pulled the injector and found the tip was covered with what looks like carbon. I cleaned it (carefully I hope) with brake cleaner and a paper towel

The oil was changed and oil filter screen cleaned at 10 hours. The engine now has 17 hours on it.

From what I've read, there are few things that could cause this. The most likely causes are a clogged injector or clogged injector pump. Some people say don't touch these parts, take them to a professional diesel mechanic. On the other hand, there are reports of lots of Yanmar clones like these being field maintained in third world countries.

Does anyone have a suggestion on what to try next?

Thanks,

Mike
 

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Mike,

Is it possible the injector line is siphoning air? This WILL cause poor performance and great (almost impossible) difficulty in starting. Is your engine equipped with a shut-off vavle and a fuel filter?

I would start by replacing fuel filter AND O ring on the bowl (if so equipped), filling the fuel tank with fresh fuel, add some Cetane booster like PowerService, gently crack/loosen injector line and allow the fuel pipe to drain away any minute particals of debris and trapped air.

Mark

edit: The Cetane booster is not about performance but ridding any condensation or water trapped in the fuel tank...and system.
 

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Remove the air filter elements completely and then try and start the tractor. If you have fuel running out, then the cylinder must be getting fuel. I think your problem may be a lack of air. No harm in trying this. Running with no filter for a minute or so isn't going to do any damage but it will tell you if the filter you think is clean, really is clean enough.
 

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It's probably more likely an injector that is stuck open or leaking,injectors really aren't that complicated or hard to service but the pressure and spray pattern need to be checked to make sure they work properly,I would think that would be even more important on a single cylinder.
 

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Just passing through
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Black smoke is due to a air to fuel ratio imbalance, either the fuel system is delivering too much fuel into the engine or there is not enough clean air (oxygen ) a few things to look for :

Faulty injectors <<<previously mentioned by other posters
Faulty injector pump <<<previously mentioned by other posters
Dirty air cleaner <<<previously mentioned by OP...:D
 

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Take the injector line loose from the injector and crank the engine, watch for fuel to weep around the injector fitting that has been loosened. If you dont get anything, then your not getting fuel to the injector and your gonna have to start back tracking thru the fuel system to see where the problem is. Could be as simple as a blockake between the fuel tank and the injector pump. These pumps are usualy self priming when there is air in the system, but maybe yours is being difficult. Mike
 

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Take a window screen and put it over your intake ... then take a rag soaked in gas and hold it over the screen and see if it starts... Dont let it take the rag from you...
 

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Just ran into a similar situation on a Yanmar clone generator. One valve adjusting set screw had broken off. It's worth taking the valve cover off and watching the valve action as you turn the engine over by hand. Also check that both valves have some clearance. I wouldn't use gas as a starting aid. A little WD40 or carb cleaner is safer.
 

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Discussion Starter #9
I didn't have much time to work on it today, but I did check a couple of the suggestions:
Caseguytoo said:
Remove the air filter elements completely and then try and start the tractor. If you have fuel running out, then the cylinder must be getting fuel. I think your problem may be a lack of air. No harm in trying this. Running with no filter for a minute or so isn't going to do any damage but it will tell you if the filter you think is clean, really is clean enough.
I removed the air filter and cranked it over but it didn't help. I don't have fuel "running out", I have a fine mist of what I believe to be fuel coming out of the exhaust when I try to start it. This does not happen if I turn off the fuel valve so it seems pretty likely to be fuel.
bstrucker said:
It's probably more likely an injector that is stuck open or leaking,injectors really aren't that complicated or hard to service but the pressure and spray pattern need to be checked to make sure they work properly,I would think that would be even more important on a single cylinder.
You may be right, but I don't know how to check the pressure or spray pattern.
PaulChristenson said:
Black smoke is due to a air to fuel ratio imbalance, either the fuel system is delivering too much fuel into the engine or there is not enough clean air (oxygen )
I suspect that the little bit of black smoke I saw was caused by the filthy air filter, but it could be something else.
cadetpwr said:
Take the injector line loose from the injector and crank the engine, watch for fuel to weep around the injector fitting that has been loosened. If you dont get anything, then your not getting fuel to the injector and your gonna have to start back tracking thru the fuel system to see where the problem is. Could be as simple as a blockake between the fuel tank and the injector pump. These pumps are usualy self priming when there is air in the system, but maybe yours is being difficult. Mike
I'll try that tomorrow, but it looks like I'm getting fuel to the injector.
Kbeitz said:
Take a window screen and put it over your intake ... then take a rag soaked in gas and hold it over the screen and see if it starts... Dont let it take the rag from you...
This one makes me a little nervous. I'll have to do a little checking around before I try this.
bhoward said:
Just ran into a similar situation on a Yanmar clone generator. One valve adjusting set screw had broken off. It's worth taking the valve cover off and watching the valve action as you turn the engine over by hand. Also check that both valves have some clearance. I wouldn't use gas as a starting aid. A little WD40 or carb cleaner is safer.
I pulled the valve cover and checked out the valves. The screws look OK and there is a small gap when both valves are closed. I haven't measured the gaps yet, I'll do that tomorrow.

Thank you all for the suggestions.

Mike
 

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Take a window screen and put it over your intake ... then take a rag soaked in gas and hold it over the screen and see if it starts... Dont let it take the rag from you...
Being around diesels for over 40 years, there's one thing I would never do, and that is tell a novice, or anyone actually, to put a gas soaked rag over the intake of a diesel engine! I saw this done by one of my men before I knew what he was doing and it nearly destroyed a fairly new 6-71 Detroit on an irrigation pump. Gas will make a diesel run wild. One of my men took off his coat and wrapped it around the intake to shut the engine down or it would have exploded due to the increasing RPMs. We pulled the engine apart to check for damage and found some push rod damage. I never heard a diesel turn up that fast and never want to hear it again. If I ever caught any of them doing it again, it was instant dismissal. PJ
 

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Discussion Starter #11
I tried loosening the fuel line to the injector and it did weep fuel when I turned it over. Also the mist coming out of the exhaust stopped with the line loose.

I checked the valve clearance. The Yanmar specs say 0.0059 inches or 0.15 mm for both intake and exhaust. I found both to be about 0.015 inches or 0.38 mm. Quite a bit off, but adjusting them to .006 inches didn't help.

What little I know about diesels tells me I need:
  1. Air (which I seem to have)
  2. Fuel, in the right place and the right time. (I have fuel coming out of the injector, but don't know how to judge amount, spray pattern and injector timing)
  3. Compression at the right time (It feels and sounds like I have compression. The valves seem to be operating correctly, but I don't know about the PSI or valve timing)
As far as know, there are no electrical requirements other than the starter turns the engine fast enough. It used to start easily by hand with one pull.

Is there anything else I can try before starting to look for an experienced diesel machanic?

Thanks,

Mike
 

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I've never messed with single cylinder diesels but on big diesel engines there is usually a cover to take off on the pump that shows your timing marks,if yours could have gotten out of time somehow,that's about the only other thing that I could think of.I'm still leaning towards a stuck or leaking injector,I don't know why it would happen in a short amount of time that you have on the tractor but if that's what it is,I'd keep an extra injector around.It might be a good idea to see if your injectors are even serviceable,on an engine like that,they might not be.
 

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I am by no means a diesel expert but I have owned and maintained diesel pickups for many years.

Reading through the posts a few ideas come to mind. Seeing diesel fuel from the exhaust after cranking the engine tells me that fuel is being injected. The injector pump may be injecting at the wrong time with respect to TDC. Generally the injection event is several degrees before TDC on the compression stroke.

Diesels get hard to start if they are cold. I wonder if you heat the cylinder head with a propane torch (carefully) if you can get it to fire.
Fuel is critical for starting. Too low of a cetane rating will make it impossible to start. Do you know the fuel is pure diesel and not contaminated by something else?

If all else fails, it may be that the injector is at fault as suggested above. If stuck open it will cause a no start. Also if the injector is contaminated with trash it may not open at the correct pop off pressure. Both of these problems will require injector rebuilding.

I am not familiar with the Yanmar L100 clone but it must use some type of fuel shut off to kill the engine. If this is not allowing full fuel flow to the injection pump it may cause starting problems.

Good luck.
 

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I'm suspect of the injector mainly due to the biodiesel. Biodiesel tends to thicken up badly if not heated ahead of injector pump. There may be thick sludge blocking the tip.
 

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A little gas on a rag wont make a diesel run wild... I've done this many times... Sometimes it barely runs...
 

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I'm suspect of the injector mainly due to the biodiesel. Biodiesel tends to thicken up badly if not heated ahead of injector pump. There may be thick sludge blocking the tip.
:ditto: :ditto:
 

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This engine should have a provision to add motor oil to the cylinder as a starting aid. It should look like a rubber cap adjacent to the valve cover. Remove it, fill the chamber with oil and re-install the plug.
 

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Cleaned my Cat payloader's air filter by rinsing with gas last year. Left filter in sun for an hour. Seemed completely dry and didn't smell of gasoline at all. Put it in the air filter housing, started the engine & she went WILD! Had to throw it in gear & hit the brakes hard to get the R's down. I swear that thing musta went 50% over max speed if not more. I will NEVER use gasoline near a diesel ever again. Not wanting to go against you at all Kevin, but it almost cost me dearly using gasoline to clean that filter.
 

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Discussion Starter #19
I did try a bit of motor oil in the plug on the valve cover. It didn't help.

I removed the injector, disassembled it, and have had the nozzle body soaking in seafoam for several hours in the hope it would dissolve any carbon or gunk in the jets. There was a little carbon left on the outside of the nozzle body (I cleaned most of it off earlier) but it doesn't seem to be affected by the seafoam.

Does anyone have any other suggestions on what to soak it in that might dissolve the carbon that might be in the jets?

Thanks,

Mike
 
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