High RPM Smoke

[Dallas_Lilly]

Good Morning All, I am at a dead end with a problem and I thought maybe some one else could inject a fresh idea into my head.

Here is my problem. I have Montana 3040 with 800 hours on it. It has a Mitsubishi SL4 engine. At the RPM range from idle to 2K RPM everything runs and sounds fine. If you get it above 2K RPM it starts a blowing plume a light blue smoke. I know blue usually means oil being burnt but you can smell unburnt diesel and the oil level rises because of diesel dilution.

The first thing I did was started loosening injector lines at the injectors to determine if it was just one cylinder or multiple cylinders. I have determined that it is #3 cylinder. When you crack #3 the smoke dissapears, completely.

I didn't have an adapter for my compression tester however I was able to bring each cylinder to TDC and apply compressed air through the glow plug hole. There is not excessive leakage on any cylinder, infact it is might difficult to hold the wrench on the crankshaft bolt to keep the piston from moving down. I do not think I have bad valve seats or bad rings.

So I sent the injection pump and injectors to a injection shop and they rebuilt all injectors and the pump. That did not fix it, it still has the identical problem.

My next step tonight is to take a look at the valve springs on #3 and possibly switch them with the companion cylinder #1 and see if the problem moves to #1.

I am thinking it is a long shot but at this point I am out of ideas, anybody have more thoughts?

Oh and I have already adjusted the valves.

Thanks

 

[Short Game]

Initially, I can think of only three paths from #3 for diesel to dilute the oil in the crankcase. One is from the underside of the #3 injector pump (and one would think you have eliminated this already), one is past #3's rings, and the last would be #3's intake valve guide (hard to imagine). Considering the RPM threshold, it certainly is baffling. Check the LS thread at http://www.tractorbynet.com/forums/ls-tractors/214883-ls-4147ez-motor-problem.html. His was an S4Q but you have the blue smoke in common.

 

[Dallas_Lilly]

Initially, I can think of only three paths from #3 for diesel to dilute the oil in the crankcase. One is from the underside of the #3 injector pump (and one would think you have eliminated this already), one is past #3's rings, and the last would be #3's intake valve guide (hard to imagine). Considering the RPM threshold, it certainly is baffling. Check the LS thread at http://www.tractorbynet.com/forums/ls-tractors/214883-ls-4147ez-motor-problem.html. His was an S4Q but you have the blue smoke in common.

I also do not think it is coming through the injection pump into the crankcase, it was just rebuilt and it smokes even after a fresh oil change.

I know just putting air in the cylinder is not as good as a compression test. I might see if I can re-thread the compression tester adapter I have just to verify compression. That would eliminate rings I think? I think if I had ring problems the problem would persist through all RPM ranges?

Thanks for your thoughts, I am about to beat my head against the wall with this one. I am not a diesel mechanic by trade but have been around the automotive industry my whole life and this one just does not make a whole lot of logical sense to me yet.

 

[RPW]

On the surface sounds like their control ring has failed. A compression check won't show anything.

Good luck.

 

[Short Game]

I am not a diesel mechanic either. I'm more of a tinkerer. I have been though a couple injection issues with a K3M Mitsubishi. I took down my injector pump while an expert talked me through it on the phone. I felt like one of those stories where the pilot of the plane has the heart attack and I landed the plane on instructions from the ground. My problem was solved when I fixed my $1300 pump with a seven dollar part. No diesel guy I brought in, and there were plenty, could diagnose the problem. I only found it by tearing the pump down. The injection specialty shop guy who talked me through the operation had never seen that particular failure.

My best guess for your issue would be a broken ring. I certainly hope it turns out to be simpler than that. A broken ring could be RPM sensitive, but it would not likely be a stable situation, and would develop in a short time into bigger problems at lower RPM.

 

[Dallas_Lilly]

Can you help me understand how that would allow fuel to enter into the crankcase? I can see a control ring alowing oil to be burnt but not fuel to pass past the compression rings and into the crankcase.

On the surface sounds like their control ring has failed. A compression check won't show anything.

Good luck.

 

[Short Game]

Can you help me understand how that would allow fuel to enter into the crankcase? I can see a control ring alowing oil to be burnt but not fuel to pass past the compression rings and into the crankcase.

Your point is so well taken that it keeps me going back to the pump. That is where fuel in any significant amount would be able to go into the pan. For it to go into the the crankcase through the combustion chamber in any quantity and not be burnt along the way just doesn't make sense. If the smoke is from too much diesel going into #3, then that is the pump too, as that is where the fuel is metered.

I have a hard time thinking that the fuel injection shop missed it if they rebuilt the pump. My K3M metered the fuel with a rack gear, controlled by a rod from the governor, turning pinions on each of the individual pumps. It was one of those pinions that broke a single tooth in my pump. But that problem shut me down. RPM is not the same as amount of throttle.

 

[Dallas_Lilly]

Your point is so well taken that it keeps me going back to the pump. That is where fuel in any significant amount would be able to go into the pan. For it to go into the the crankcase through the combustion chamber in any quantity and not be burnt along the way just doesn't make sense. If the smoke is from too much diesel going into #3, then that is the pump too, as that is where the fuel is metered.

I have a hard time thinking that the fuel injection shop missed it if they rebuilt the pump. My K3M metered the fuel with a rack gear, controlled by a rod from the governor, turning pinions on each of the individual pumps. It was one of those pinions that broke a single tooth in my pump. But that problem shut me down. RPM is not the same as amount of throttle.

I did let them know that I had fuel dilution and they did pressurize the pump in a bath of oil and said they did not see bubbles. I am not sure that I understand how they accomplished this.

After I got it back and found the same problem to double check their work I swapped the guts of the injection pump in #3 cylinder to #2 without a change. You could still crack #3 line and the smoke goes away. I also double checked their injector work with swaping injectors, still not a change.

Thanks for everybody's ideas, keep them coming I might just figure this out.

 

[Short Game]

From a PDF of the S4L at www.agregat-sdm.ru/data/files/240.pdf.

Under: Table 11-4 Exhaust smoke is white or blue:

Faulty fuel injection nozzles

Contact your local Mitsubishi dealer
(uneven injection among cylinders)

=====================

I was going to suggest swapping injectors around.

When I rebuilt my pump, the guy told me to be sure to not get any parts from one pump mixed with another. I put all the parts from each pump in its own bread pan.

 

[Dallas_Lilly]

Thanks for that manual!

I will probabbly swap the guts from the pump back to where they are supposed to be tonight, I just needed to verify that I did not have a barrel and plunger or delivery valve problem.

I cannot figure out why the oil dilution is happening. I just cannot imagine the fuel being pushed past the rings, and if the rings wer bad I would think I would burn oil, I do not appear to be doing that.

Thanks again for your help.

 

[Short Game]

I found another PDF of a Dutch made version of the S4L at: http://www.sejl.de/pdf,word,programer mm/Operation manual M4.15, M4.17.pdf

See Page 59.

 

[art]

just a chance, that if number three had a broken ring and wasn't getting enough compression to fire that it would leave the fuel unburnt and able to get to the base!

 

[Short Game]

just a chance, that if number three had a broken ring and wasn't getting enough compression to fire that it would leave the fuel unburnt and able to get to the base!

It would likely run quite rough at low RPM and probably have sufficient compression at high RPM to fire. It would seem to me that it would pump the lion's share of the unburned atomized diesel out the exhaust valve.

When the line to #3 injector is cracked open, the smoking stops. It makes no difference when the injectors are swapped.

It sounds like #3 pump is both delivering too much fuel to the injector, at 2,000+ RPM, and at the same time, leaking out to the crankcase.

 

[Dallas_Lilly]

That is what I keep thinking about broken ring, another note is I have absolutly no blowby

I am very baffled by it all and the worst of it is I am stuck behind a desk at work and cannot get away

I have convinced myself that I am going to swap the valve springs tonight. It is easy to do and will eliminate one more thing without spending more money. While I am at it I am going to measure the installed height against another set of valves just incase I have a seat that is wasted.

I know all of this seems like a long shot but I am pretty sure I covered the basis of the fuel system. I think

 

[Short Game]

When you loosened the injector lines at each of the injectors, did about the same amount of fuel escape and the fuel pressure and volume seem about equal for each cylinder?

800 hours seems too soon to have a problem like this.

Floating an exhaust valve could be it (or part of it). It would allow the fuel from that cylinder to burn up in the hot exhaust from the other cylinders, possibly creating smoke. It would be something that would happen at higher RPM. It would likely stop if the fuel line were cracked loose. It would not account for fuel going into the crankcase, however.

Removing and swapping valve springs is easy? Doesn't that require pulling off the head? That would strike me as major surgery.

 

[RPW]

If you can run air into the cylinder to hold the valve you can do it without removing the head. I had mention only the oil control ring but it could still be the compression rings also. Until you can get a proper compression tester on the cylinders you won't know. I have seen a wide variation on compression and the motor "sounds" ok but in reality wasn't. Pressurizing your cylinders with air is not the same as getting a compression test. Shop air is only about 150psi max. That would be ok for gas but diesels have a much higher compression. At shop air pressure you may not have sufficient air to know if you have blow by. At the higher RPM's you won't have a higher compression but the amount of air/fuel will be greater and have a higher chance of blow by. Without going back over all the posts I don't remember you mentioning how fast you're getting oil dilution. Also even if you have a broken ring(s) you "may" not see oil being burned. As an example on my truck it uses "burns" some oil but you can not see it from the exhaust but it gets used.

Good luck.

 

[Dallas_Lilly]

When you loosened the injector lines at each of the injectors, did about the same amount of fuel escape and the fuel pressure and volume seem about equal for each cylinder?

800 hours seems too soon to have a problem like this.

Floating an exhaust valve could be it (or part of it). It would allow the fuel from that cylinder to burn up in the hot exhaust from the other cylinders, possibly creating smoke. It would be something that would happen at higher RPM. It would likely stop if the fuel line were cracked loose. It would not account for fuel going into the crankcase, however.

Removing and swapping valve springs is easy? Doesn't that require pulling off the head? That would strike me as major surgery.

Yes it seems to be about the same amount from each line, as near as the eye can tell. I also was there when they tested the pump after installing new parts, they were able to measure the cc's and everything looke ok.

I can pressurize the cylinder with air and the valves will stay up, no need to remove head for the spring swapping.

Wish me luck I am headed to go see what I can figure out, I will update in the morning.

 

[Dallas_Lilly]

I hear you loud and clear on the shop air vs the compression test. I think I can modify one of my adapters and rethread it and posibly get a compression test tonight.

When I said I do not have blowby I meant out of the dipstick tube, oil fill or the breather. I may just be in the begining stages of failure but when I have seen broken or worn rings in the past you could remove the dipstick or oil cap and visually see blowby, I am not seeing that.

The oil was about a quart high with about 30 minutes of off and on testing and running. In other words it is diluting really fast!

If you can run air into the cylinder to hold the valve you can do it without removing the head. I had mention only the oil control ring but it could still be the compression rings also. Until you can get a proper compression tester on the cylinders you won't know. I have seen a wide variation on compression and the motor "sounds" ok but in reality wasn't. Pressurizing your cylinders with air is not the same as getting a compression test. Shop air is only about 150psi max. That would be ok for gas but diesels have a much higher compression. At shop air pressure you may not have sufficient air to know if you have blow by. At the higher RPM's you won't have a higher compression but the amount of air/fuel will be greater and have a higher chance of blow by. Without going back over all the posts I don't remember you mentioning how fast you're getting oil dilution. Also even if you have a broken ring(s) you "may" not see oil being burned. As an example on my truck it uses "burns" some oil but you can not see it from the exhaust but it gets used.

Good luck.

 

[RPW]

Wow, a quart in about 30 minutes! That's a goodly amount. Will be interesting to see the results from your compression test. BTW I know you've probably ruled this out but it is diesel that diluting the oil and not water. Only reason I ask is a quart is a lot of fluid and I can't see that much diesel being able to be pumped in that time frame but then it wouldn't be the first time I'd have been accused of being blind

 

[Dallas_Lilly]

Well I swapped the valve springs with out changing anything in number 3. I was able to get a compression tester hooked up and #3 was slightly lower than the rest. It would get to 400psi and the other three would get to 450psi. That is still within specs in the book however it was a sign of the real problem.

I removed the valve cover again and removed the rocker rack. This allowed all the valves to be closed and I could put air in the cylinders and leave it there to try to figure out where I was loosing compression. I was tired and could be wrong but I am pretty sure that it is coming from the intake valve. I am going to remove intake manifold, exhaust manifold and the oil drain plugs and use a smoke machine to try to figure out exactly what I am in for before I pull the head.

As far as the diesel in the oil that may be another sign that I need to pay attention to but with out seeing this engine run yourself it is hard to describe. At near WOT I was getting a really dead cylinder, all that fuel has to go somewhere, it was not combusting hardly at all.

Thanks for all who have commented and helped. I feel stupid not figuring this out before I blew $700 or pump and injector rebuilds. I will continue to live and learn!