Yanmar Problems

[Dockhead]

Originally Posted by Andrew Troup

Dockhead: I share your enthusiasm for simple, non-electronic engines, but then they go and stick a turbo on them, which kind of stuffs things up, in several ways.

Including on startup: it's normal for lots of unburned diesel to pass through such an engine until it reaches a steady-state equilibrium.

This happens because the turbo doesn't initially supply the engine with the required amount of air, because it has to "bootstrap" its output from the thermal energy of the exhaust gases ... and of course on starting, the latter is in short supply.

The electronic engines (when running properly) should navigate this phase more elegantly, by injecting only as much fuel as the CURRENT supply of air will sustain. Some would see that as an argument for electronics; it suits me to see it instead as an argument against turbos (for auxiliary engines)

ON EDIT: It's often said the smell of unburnt fuel is a giveway when trying to distinguish it from lube oil haze. I don't have a keen sense of smell, but even to me it's sometimes helpful for diagnosis. For me it means getting down near the exhaust.

Hmm, that does make sense. Although I'm not sure that the turbo is actually doing anything at lower RPM's. But it sounds somehow right to my ear.

I don't really have a categorical position against electronically governed engines; of course all cars have been like that for ages. The main thing is the result -- if they are really bulletproof (as they seem to be in cars), then I guess there is no reason not to have them in boats, although they don't seem right to me.

Now as to turbos -- I like these on diesels. They bring a lot of benefits. Higher thermodynamic efficiency, but best of all, a smaller, lighter engine can do the same amount of work, if it has a turbo, as a big old iron lump like a Perkins Sabre. Useless weight is not good in a sailing vessel. Also, they are quieter and smoother (the turbo absorbs exhaust impulses; the turbo balances the pressure between intake and exhaust cycles). I don't think they add all that much complexity, considering all the benefits they bring -- a turbocharger is an extremely simple device, with just one moving part.

[d design]

Please be more specific on when it smokes. What rpm and under how much load.

[Loredo]

"All Yanmars smoke"... Well, since there are a couple replies in this thread saying that their Yanmar does not smoke, let's re-word that sentence, almost all of them smoke. At least, all Yanmar owners I've talked to have the same smoke "problem".

I have a 4Jh3-TE with 800 hours on it and it has always smoked. No coolant or oil consumption at all. I've talked with a couple very good ( Yanmar ) mechanics and both said " they all smoke leave it alone".
I'm a bit ashamed to say, that's exactly what I did.

Yet, I believe I do have a rather precise idea what causes the smoke and that's retarded injection timing. At least that's exactly how my exhaust smells. Inject the fuel a little bit to late ( after TDC ) and what you get is that greyish / white smoke my engine has. Another cause for the greyish smoke could be a combustion chamber that's not perfectly matched with the injector spray pattern but I don't think that a company like Yanmar could possibly do that.

I have NOT researched what kind of injection pump there is on my Yanmar but I would suspect that it has a static timing. In other words, the timing depends upon the installation of the pump.

Like I said, I choose to not bother about the smoke since "they all do that" but if I wanted to research this issue further I'd first of all try to time in the injection pump a bit more advanced.

A lot of mechanical injection pumps for turboed engines do have an AFC.
What the AFC does is to increase the fuel injection rate as the boost pressure raises. More boost ( air ) more fuel can be burned, right?

Dockhead, if your Yanmar does have an AFC then that's the first place I'd look into for the stumble you report. The boost pressure line going into the AFC being the first simple check to do.

[DeepFrz]

Somewhere, and I don't have a clue where although it may have been one of the engine service manuals, I read that the air cooler should be cleaned every time the turbo needs cleaning. Anyone have any information on this?

[d design]

My yanmar dosnt smoke. Not even at startup. It only smokes if you over load it. If you have a smokey engine throw it over the side and get a electic motor instead. No smoke, no noise, no smell, no vibrations, almost no mantinance, more tourqe, no emissions, dolfins come right up to you, cost nothing to fill up, regenerative sailing.

[a64pilot]

Originally Posted by DeepFrz

Somewhere, and I don't have a clue where although it may have been one of the engine service manuals, I read that the air cooler should be cleaned every time the turbo needs cleaning. Anyone have any information on this?

I don't have it in writing, but the aftercooler is immediately down stream of the turbo so if the turbo is coked up from oil ingestion from blow-by, then so is the aftercooler

[Kenomac]

Dockhead,

I know we've been through this same problem together about 18 months ago, but have you eliminated the prop as a possible issue? The prop pitch and calcium/marine growth build up on the prop and prop shaft turned out to be the cause of our problem regarding insufficient revs & black smoke. If I don't dive under the boat to scrape, brush and clean everything at least once a month, the revs will start to drop and the Maxprop will begin to bang around. Sometimes, it doesn't even look that bad.


Ken

[Loredo]

I guess we need to define the "Yanmar smoke" a bit better to get the picture.

Dockhead said:
"The smoke is gray-bluish, and comes out in billows on startup. The smoke just about disappears at normal operating temperature and speed. Since the engine doesn't consume any oil (maybe half a liter between 100 hour changes), I presume that this is not oil smoke, but fuel."

That's exactly what I'm seeing too and most other Yanmar owners.

That smoke is different from the black smoke a prop with growth causes!

Black smoke is either unburned fuel or overfuelled engine or too much timing advance.

The gray blueish fuel is a different animal. No oil consumption rules problems with the internals of the engine out. Next thought would be carboned up injectors but multiple sources say that cleaning injectors or new injectors do NOT cure the problem. I did run various aditives too but to no avail.

The only thing left with gray smoke in a direct injection engine is the injection timing.

[a64pilot]

Originally Posted by Loredo

The only thing left with gray smoke in a direct injection engine is the injection timing.

Dirty injectors will cause smoke and a noisy engine, especially at low RPM / load.
Not saying that is the cause, just that more things other than injection timing can cause smoke. Dirty injectors can have a poor spray pattern that in effect retards timing due to it's less than optimum atomization of fuel.
I suspect poor fuel quality can cause it too

[Dockhead]

Originally Posted by a64pilot

I don't have it in writing, but the aftercooler is immediately down stream of the turbo so if the turbo is coked up from oil ingestion from blow-by, then so is the aftercooler

My turbo has always been very clean.

But I am more and more -- and thanks to someone on here for the initial idea -- thinking about the intercooler. I talked yesterday to the Yanmar main dealer who spent dozens of hours five years ago, when I first bought my boat, trying to find the cause of the smoking, and he confirmed that although they had the turbo and injection pump rebuilt, he did not look at the intercooler. "It will be full of oil and crap", he warned, when we discussed how to take it apart. "So why didn't you clean it out, when you were doing all that other work!!??" I wanted to ask, but bit my tongue.

So I think I will pop it off this afternoon and see what there is there.

[Dockhead]

Originally Posted by a64pilot

Dirty injectors will cause smoke and a noisy engine, especially at low RPM / load.
Not saying that is the cause, just that more things other than injection timing can cause smoke. Dirty injectors can have a poor spray pattern that in effect retards timing due to it's less than optimum atomization of fuel.
I suspect poor fuel quality can cause it too

I replaced all my injectors a couple of years ago with new. Didn't make any difference at all.

[Dockhead]

Originally Posted by Kenomac

Dockhead,

I know we've been through this same problem together about 18 months ago, but have you eliminated the prop as a possible issue? The prop pitch and calcium/marine growth build up on the prop and prop shaft turned out to be the cause of our problem regarding insufficient revs & black smoke. If I don't dive under the boat to scrape, brush and clean everything at least once a month, the revs will start to drop and the Maxprop will begin to bang around. Sometimes, it doesn't even look that bad.


Ken

I don't have any black smoke, and my engine smokes less under load and less when well warmed up.

And I have a self-pitching Brunton Autoprop, so it's certainly not a prop pitching question.

When my problem is at its worst, I can't get max revs even in neutral.

[westwinds]

Originally Posted by Dockhead

I'm using a 30 micron filter now, but had no problems with the 2 micron filter, either.

Probably a larger filter than usual for this application. The 2 micron filter is required for the modern electronically controlled fuel injection system, also known as common rail. These have about ten times the pressure as the older mechanical systems and have better pollution control. If you are going to use a 2 micron filter, then start with a 30 micron filter and then run that into another filter of 2 microns.

[Dockhead]

Originally Posted by westwinds

Probably a larger filter than usual for this application. The 2 micron filter is required for the modern electronically controlled fuel injection system, also known as common rail. These have about ten times the pressure as the older mechanical systems and have better pollution control. If you are going to use a 2 micron filter, then start with a 30 micron filter and then run that into another filter of 2 microns.

The 30 micron filter is in my Racor 500 primary filter. There is a finer filter from Yanmar downstream, on the engine itself. I'm not sure what the specification of that filter is, but I think it is coarser than 2 microns. I think it is 5 microns.

We get really excellent quality fuel here in the UK (and Channel Islands, where I like to buy it because it is tax-free), and I've never had any fuel problems (knocking on wood). I regularly clean my fuel tank just to be sure (I am paranoid about fuel problems), but when I last opened it up, it was spotless, with no speck of dirt or drop of water in it. Never had any crud in my fuel filters. That's over about 800 hours and five years.

[Dockhead]

Originally Posted by DeepFrz

Somewhere, and I don't have a clue where although it may have been one of the engine service manuals, I read that the air cooler should be cleaned every time the turbo needs cleaning. Anyone have any information on this?

Sounds logical.

I've definitely got intercooler cleaning on my list now. I am thinking however to outsource it as I have an endless list of other things to do. I am thinking about having a real Yanmar mechanic clean out the heat exchanger and intercooler, pressure test the intercooler, set the injection timing, and adjust the valve clearances.

I might change my mind after I get his quote, but at the moment I am thinking that it will be worth spending some money to have the hands of a real Yanmar engineer on my engine.


I have not, by the way, figured out how to adjust valve clearances on this engine. There's nothing about it in the service manual. I've done it a thousand times on petrol engines, but never on a diesel. I am a little daunted by the question of how to turn the engine to TDC (no spark plugs to pull out to relieve compression!) and how to find TDC. Anybody have any hints about how to do this?