Smoky Yanmar Part 2

[Acadia]

Hello,

A little while back I was having intermittent blue smoke and posted this in my “Smoky Yanmar” Post.

Well here is the continuation of my saga.

As I mentioned in the other post I am new to diesels but I am learning very quickly thanks to books, but mostly all of you here on this forum... So thank you very much!! This site is invaluable.

So I think that what may have been happening was that a fuel injector that was starting to get bad. The blue smoke that I was seeing may not have been as blue as I thought and was probably unburned diesel.

I “almost “always check my oil before start up but the last run was an upwind motor back home against the chop. Checked the level the next morning and I was DOUBLE over the fill line!! So I drained the oil right away discovering that I had 12 Litres in there (max is 6.5). I am thinking this is diesel fuel and not water. It’s diluted, not milky or foamy and the water level is the same.

During troubleshooting that day I also discovered that I have one of my injectors not working properly by cracking the fuel line while the engine was running. There was no noticeable change in that cylinder but the others sure affected the RPM. Oh, and I’m getting a slick at the back of the boat when idling in gear above 1000 RPM. So, one injector is on order for spare and the others will be sent to the shop.

I didn’t have time yet but I will be taking apart the lift pump and I already have a diaphragm for that.

So, 5 litres of fuel diluted in my oil, I'm sure that’s not good for it. I am a little concerned that I may have caused a bit of excessive wear on the engine.

I will be doing a compression test next week to see how that is.

Could a bad injector solely get that much diesel mixed in with the oil? If any at all? I’m thinking if the injector just dribbles the fuel in the cylinder, would it seep down through the rings?

I will let you know about the lift pump diaphragm when I have a chance to get to it next week.

Is there anything else I should be checking? Any suggestions or tips you can pass along will be greatly appreciated. I won’t have a chance to look at the boat again till late next week.

Thanks for your help.

[Alan Wheeler]

OK, firstly to set you at ease, although diluted lube oil is not good, it should be OK for the short time you have had the engine running. Long term, the main item that fails is the Big end bearings as they take such a huge pounding. The cam shaft can in some instances suffer from scoring. Apart from those two high load area's, the engine can get away with a little abuse like that. so I would not worry about that. However, there is still a worry. That is a lot of fuel to have in the engine. I would first suspect the lift pump, as it is really the only way such a high volume of fuel can get into the engine in that short a time. But the lift pump will not cause a smoking issue. That is a puzzle and maybe a separate fault. Even if an injector was not working a squirting fuel straight in to the cylinder so as it would not fire, I don't see how that quantity of fuel would get down the bore into the engine sump. The rings would have to be shattered or the piston has a hole in it. Either way, the smoke would not be an only nor subtle telltale of damage. So it is quite feasible that you have tow separate issues. Faulty lift pump and faulty injector. I hope that will be your case, it will be the cheapest and easiest to cure.

[Acadia]

Thanks Wheeler,

I just thought of something else when I was reading your post. When I had that issue with the fuel supply during the trip, I turned on the electric fuel pump and left it on untill I shut down the engine. So that electric fuel pump may have supplied enough pressure that the lift pump didn't really have to work hard at all, as well as pushing more fuel in the lube....

Thanks for your input, informative as always

[Acadia]

oh and as for the 2 diff faults I agree with that. I'm looking forward to replacing those 2 items to see what the outcome will be.

Can you think of anything else that would introduce fuel into the crankcase?

[Alan Wheeler]

There is nothing else.
So just to be clear, did you fit the electric lift pump because the mechanical pump was not working?? Because that would have been the cause of so much fuel in the oil.

[captden]

A word of caution: When this happened on my old boat that had a yanmar, after running the engine all day I approached my mooring and when I throttled down the low oil pressure alarm went off. I proceeded to advanced the throttle just a bit and the engine went into a run away condition, talk about freaking out. Anyway I ran down to the engine room as I could not shut the engine down, I was thinking how to stop it before it blew itself apart and started to pull off the air filter to try to stop the air flow by blocking it off with something ( the only thing I could grab near by was an orange) when I got the air filter off out shot a ton of fuel-oil mixture and the engine stopped. What I'm getting to is these engines can run away from excessive back pressure caused by the high oil level, so be very careful. I never though an engine could run at that high rpm for so long (about two minuites) without comming apart.
After rebuilding the injectors and fuel pump it seemed the problem was solved, but can't confirm as I sold the boat but never heard from the new owner as to any problems there after.

Hope this helps
captden

[Acadia]

Wheeler,

The pump was installed by the PO and I was told he used it for priming while changing filters. I used it for the same reason with the exeption of running it for that last trip with the fuel restriction problems.

Question; Is it only the mechanical lift (or feed) pump that could introduce fuel in the oil. Can the bigger fuel injection pump do the same?

Captden,

That didn't sound like too much fun... I'm glad I caught mine in time for that to happen (I might have to keep a few oranges in the galley). Did you remember the lift pump element being fairly damaged? And did you have injector proplems before this runaway or you had them done as a result of this?

Thanks

[Alan Wheeler]

On some or many engines, and I have to ask Chiefengineer or Never Monday if yours in one of these, the pump mounted on the block has a gap between the fuel diaphragm and the back of the pump mech. So a hole in the diaphragm can allow fuel to travel right through the pump and into the sump. Now if you have a positive pressure on that lift pump at all times, supplied by the electric lift pump, then fuel could be squirted through in quite some quantity. Some of those electric pumps can produce a good 30PSI of pressure before they regulate. Waay more than the mech lift pump was designed to handle.

CptDen, what you experienced is common to the sump becoming so full, the oil made its way to the sump breather that goes between the aircleaner and tappet cover. By removing the aircleaner, the the oil lost its path to the intake and hence the engine stopped. The noise is frightening and can do damage. Not usually over reving, but through detonation. That is what creates the noise and the seemingly over reving feeling.
Two other faults can cause the same issue. Badly clogged air cleaner pulling too much suction through the sump breather, adn the mos common, too much blow by causing the sump oil to fill the tappet cover instead of draining to the sump.

[captden]

Did you remember the lift pump element being fairly damaged? And did you have injector proplems before this runaway or you had them done as a result of this?


Hi Bus
The lift pump was fine before and after this happened. This was the first time I had any problems with this engine, always ran perfect. After going through everything the conclusion I came up with that one or two injectors were leaking so bad that I must of had blow by the rings from excessive fuel.

Hi Wheels
That is exactly what happened the oil did make it's way through the breather. I did't hear any detonation though, I didn't check the tach when it was running away but it sure sounded like it was over reving. I didn't think the engine would rev that high at full throttle with the transmission in neutral. Funny thing is I checked the oil level that morning and it was fine, this happened after running all day around 2000 rpm. Everything was fine the whole day, only when I came up to my mooring and I pulled the throttle back to idle the alarm sounded. I just brought the throttle up a bit just to see if the pressure came up and it ran away. After I replaced the injectors I put about another 50 hrs on it with no problems, the oil level was normal. I then sold the boat that winter and the last I heard from the new owner all was fine
captden

[Alan Wheeler]

Hi Bus
The lift pump was fine before and after this happened.

Oh I have misunderstood. I though the electric pump was being used because there was an issue with the mechanical one. If the mechanical pump is OK, then the issues lies elsewhere. It it possible that the fuel has leaked down the bore, but you must have run the engine for sometime to have this quantity of fuel in the sump. Most of the raw unburnt diesel would have or should have gone out the exhaust. But??? It's the only other possible that I can think of.

Detonation in a Diesel can only be likened to a sound that would resemble every piston in the engine wanting to punch their way through the top of the head. Very loud, very harsh and very scary. Plus the cloud of exhaust smoke would make a WW2 battle cruiser envious of the smoke screen.

[Acadia]

Wheels/Captden,

Took the injectors out today and they are gone to the shop. The intersting thing however was when I took the fuel feed pump apart. To my surprise (and the same case as your pump Captden) it looked fine. I did change it anyway since I had the thing apart. So the only thing that I can think of is that there must of been a heck of alot of blowby from faulty injectors. I'm looking forward to see what the shop had to say about them and how my engine will work with the rebuilt injectors.

I'll keep you posted....Cheers

[Alan Wheeler]

Look forward to it. The more you experience, the more experienced you become.

[Chief Engineer]

We are looking forward to the solution....