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Diesel 'tuning' Question


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#1 OldBuzzard ONLINE  

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Posted November 24, 2013 - 04:44 AM

Guys, I ran into something over at the WPGTA Plow day when I was pulling.

 

It was the first time I really ran the Mitsubishi K3D hard, and at near full throttle, it had a bit of a miss(?). When that would happen, I would back off the throttle a bit until it quit, but I would like to figure out just what is causing that to happen and a 'cure' for it.

 

This was at about 3,000 RPM on the tach.  In the manual, it says that it's rated for 22 Hp. @ 3200 RPM.

 

So, the question is, what might be the cause?

 

The Tach is a mechanical tach, so I guess it could be wrong and maybe I was over revving?

 

Maybe not enough fuel flow?  Dirty injectors? Weak fuel pump? Something else?

 

I could use any leads you guys might be able to provide.


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#2 skyrydr2 ONLINE  

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Posted November 24, 2013 - 05:31 AM

Did it loose power when this happened ? If not , it may have a weak valve spring? Or something worn or loose under the valve cover.
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#3 AVB OFFLINE  

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Posted November 24, 2013 - 05:31 AM

Most diesel engines have no throttle butterfly, rpm is controlled by limiting the fuel. Normally fuel issues result in reduced power, but not necesarily skipping. For the engine to "miss" it is normally either a problem with fuel quality, air in the system, or a mechanical issue. It is either mechanical or the cylinders aren't getting an equal amount of fuel. With it only happening near full throttle I would look for mechanical issues. Check the valve springs as mentioned and the valve clearance. It could be an injector issue, but a fuel supply issue generally only limits the engines power and rpm causing the engine to bog not skip. It could also be a govenor or injector pump issue.

 

You can single out the problem cylinder by doing a balance test by cracking open the fuel lines one at a time. See if one cylinder makes less of a difference in the way it runs and make sure each cylinder is getting about the same amount of fuel.

 

Make sure there are no fuel leaks between the injector pump and the injectors too.


Edited by AVB, November 24, 2013 - 06:04 AM.

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#4 JDBrian OFFLINE  

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Posted November 24, 2013 - 06:06 AM

I think that is a 2 cylinder engine isn't it? If so, would it be more likely to exhibit a miss than a 3 cylinder. I know that the 3 cylinder Yanmar in my 2320 will overload and bog down quite easily if I run it hard before it's warmed up. As said by others above it does not miss in that situation or ever for that matter. It doesn't smoke much when this happens, probably because the stock fuel pump settings are on the lean side. If you haven't checked the fuel system from tank to injectors now may be a good time to do that, so it won't be an issue later. Let us know what you find. Diesel troubleshooting is something that many of us don't have a lot of experience with. 


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#5 OldBuzzard ONLINE  

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Posted November 24, 2013 - 06:16 AM

It's a 3-cyl Mitsubishi K3D.

 

Don't know it was losing power when it was 'stuttering' as I didn't pull with it doing that.  I would go to full throttle, and then back off until it stopped before I started moving.

 

Even at less than full throttle, it had plenty of 'snort' :D :D :D


Edited by OldBuzzard, November 24, 2013 - 06:17 AM.

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#6 AVB OFFLINE  

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Posted November 24, 2013 - 06:25 AM

It won't really lose power, it just won't make full power if it isn't getting enough fuel. For what you are describing you should be able to rule out anything between the fuel tank and the injector pump as the cause.

 

Check all the return lines too, make sure they are all clear. A restriction in a return line can limit the fuel getting to the injector.


Edited by AVB, November 24, 2013 - 06:29 AM.

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#7 boyscout862 ONLINE  

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Posted November 24, 2013 - 07:54 AM

I would check your timing first. If that is okay then check you fuel filter. Something may have gotten in the fuel. My Ford and Buda diesels have only had trouble when there was something in the fuel. Clean the filter and try a fuel conditioner. If that doesn't work, look at more complicated analysis. Good Luck, Rick


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#8 AVB OFFLINE  

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Posted November 24, 2013 - 08:12 AM

Unless someone has messed with the injector pump the timing should be ok. It did cross my mind, but usually it will be smoking or hard to start if the timing was off. It could be contaminated fuel, but I would expect it to cause problems at all rpms it it was.

 

I would definitely check the fuel, but I wouldn't expect it to cause the problem described unless the cetane was too low.


Edited by AVB, November 24, 2013 - 08:20 AM.

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#9 DougT ONLINE  

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Posted November 24, 2013 - 09:56 AM

If 3200 is the governed speed and you were free revving it at 3000, you might have been bouncing on the gov. If you started pulling and then went to wide open throttle, did it still seem to miss? A tool that I've found handy for checking diesels is the infra-red temp gun. If you have a cylinder that isn't doing its fair share, the exhaust port will be cooler than the rest.


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#10 AVB OFFLINE  

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Posted November 24, 2013 - 10:18 AM

That is a good point and a good tip on the temp gun. You can also sometimes use a spray bottle of water in a pinch, it doesn't work as well for log type manifolds though.


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#11 OldBuzzard ONLINE  

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Posted November 24, 2013 - 12:04 PM

If 3200 is the governed speed and you were free revving it at 3000, you might have been bouncing on the gov. If you started pulling and then went to wide open throttle, did it still seem to miss? A tool that I've found handy for checking diesels is the infra-red temp gun. If you have a cylinder that isn't doing its fair share, the exhaust port will be cooler than the rest.


That could be a possibility.  To tell the truth, I wasn't ready listening to the engine all that much WHILE I was pulling.

 

At this time, maybe the best thing is to do nothing, since it doesn't seem to be 'broken', other than that 'stutter', and then when I go over in the Spring for their pull, listen t it when I'm plowing and pulling to see if it does go away once a load is on it.



#12 AVB OFFLINE  

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Posted November 24, 2013 - 12:53 PM

If it ran smooth under a load I probably wouldn't worry about it, especially since it was the first time you ran it that hard. It could just be a normal characteristic of that engine. Some engines just shake at certain rpms. I have seen warehouse tractors with John Deere engines that would nearly shake the tractor apart if the idle was set too low, and Doosan forklifts where the return spring on the inching pedal would vibrate so bad at idle that the spring would cut through the mounting bracket.



#13 OldBuzzard ONLINE  

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Posted November 24, 2013 - 02:19 PM

It was running great under load.

 

I was pulling a dead weight sled.  It had 2,250# on it when they ran out of weight, and the tractor still had a lot left in it.



#14 DougT ONLINE  

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Posted November 24, 2013 - 02:43 PM

Don't know if you changed filters when you first got it or not. I think the only things I'd worry about are clean air and fuel filters.



#15 OldBuzzard ONLINE  

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Posted November 24, 2013 - 03:30 PM

Put a new air filter on it when I got it, and hasn't really run enough hours to make cleaning/changing it necessary.

 

Put a new fuel filter on it in July.






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