Yanmar Problems

[CarlF]

The "intermittent" nature of the problem also rules out a lot of possibilities.

My Racor 500's will move the needle a bit on the gauge even with new filters.

Yanmar fuel pumps are not particularly strong. Yanmar specs 30 micron fuel filters (and occasionally threatens that using finer filters will void the warranty).

I would think a low cost bit of insurance would be to put an electric fuel pump upstream of the primary filter. Should be easy to find one at a garage. That might give just a little extra pumping oomph to make up for problems in the fuel system.

Carl

[impi]

Here's a long shot in the dark, but I knew a guy who had a similar intermittent problem with a different motor ... turned out to be a long split pin he had used to lock the clevis pin in place where the throttle cable links to the governor. Every now and then the end of the split pin would rotate and wedge itself preventing the throttle from opening fully. Perhaps a good look around at the cables ...

[Dockhead]

Originally Posted by Jim Cate

G'Day Dockhead,

I can't add any wisdom re turbo problems, but I'm struck by the fact that you report ZERO pressure drop on your fuel filters. IME, even new filters should show a bit of drop when the engine is running (at least that's the case on mine, but they are not racors). So, is it possible that your vacuum gauge is not working, and thus giving you false info about pressure drops in the fuel system?

HOpe that you can solve this and get on with your cruise.

Cheers,

Jim

Thanks for that. I'll look at it again and reset the recording needle. How much of a pressure drop do you see?

[Dockhead]

Originally Posted by CarlF

The "intermittent" nature of the problem also rules out a lot of possibilities.

My Racor 500's will move the needle a bit on the gauge even with new filters.

Yanmar fuel pumps are not particularly strong. Yanmar specs 30 micron fuel filters (and occasionally threatens that using finer filters will void the warranty).

I would think a low cost bit of insurance would be to put an electric fuel pump upstream of the primary filter. Should be easy to find one at a garage. That might give just a little extra pumping oomph to make up for problems in the fuel system.

Carl

Sounds like a good idea. What circuit, I wonder, to wire it into?

[Dockhead]

Originally Posted by impi

Here's a long shot in the dark, but I knew a guy who had a similar intermittent problem with a different motor ... turned out to be a long split pin he had used to lock the clevis pin in place where the throttle cable links to the governor. Every now and then the end of the split pin would rotate and wedge itself preventing the throttle from opening fully. Perhaps a good look around at the cables ...

I'll have a good look at it. I don't think this is the problem, because if I get max revs, the throttle is all the way forward and backing off the throttle even a tiny bit reduces revs. If the engine is not making full revs, then I can back off the throttle quite a bit without changing the revs. That seems to tell me that the throttle linkage is working ok.

[impi]

Originally Posted by Dockhead

I'll have a good look at it. I don't think this is the problem, because if I get max revs, the throttle is all the way forward and backing off the throttle even a tiny bit reduces revs. If the engine is not making full revs, then I can back off the throttle quite a bit without changing the revs. That seems to tell me that the throttle linkage is working ok.

hmmm, that's odd. Sounds like a damaged spring or something in the governor i.e. the rack is not moving all the way (I am not sure specifically how your engines governor works) ... this is a puzzling since it only happens in rough seas ... otherwise I would have thought to look in the governor itself based on what you just told me

[Dockhead]

Originally Posted by impi

hmmm, that's odd. Sounds like a damaged spring or something in the governor i.e. the rack is not moving all the way (I am not sure specifically how your engines governor works) ... this is a puzzling since it only happens in rough seas ... otherwise I would have thought to look in the governor itself based on what you just told me

It doesn't only happen in rough seas. It has been intermittent for a while and now is more or less continuous. Sometimes when the engine is only just warmed up I can get full revs with no load. But the problem seems to get worse -- SEEMS -- I could be imagining it or it could be a coincidence -- to -- after rough seas, or especially, a prolonged period of slow running, as in when negotiating a river with a speed limit, or a long period of motor-sailing at low RPM.

But as to how the governor works -- I think they all work the same, don't they? The position of the throttle calls for a certain RPM. Any given RPM requires more or less fuel depending on the load. The governor will increase or decrease fuel (by moving the injector pump fuel rack) to maintain a steady RPM, that RPM called for by your throttle input. Now I'm not a diesel engine expert, but isn't that how it works? So it seems to me only natural that when my engine fails to make full RPM, pushing the throttle all the way forward does nothing. The governor is not able to increase the RPM up to the RPM called for. So I can pull the throttle back as far as the RPM which the engine is able to produce, without changing the RPM.

The only thing which bothers me with this is that the engine does not smoke when I apply "overthrottle". If the engine were overloaded, and the governor was unable to get the engine up to full revs because there is simply too much load on, then the engine would definitely smoke, because fuel is being injected corresponding to full load at full RPM, but the engine is running at lower RPM. This tells me that the engine is not overloaded (the prop question again), and I suppose it is not smoking because there is not enough turbo boost. There is a boost compensator on the injection pump which increases the fuel injected depending on the amount of turbo boost. More fuel is not injected because there is no (or little) boost. Thus there is no smoke. It seems to me that this is another indication of a turbo problem.

[S/V Pearl]

I have the same Yanmar with dual racors and the T handle vacuum gauges.

Shut off the fuel intake valve with engine running and watch vacuum gauge to test whether it is working.

I installed a $50 fuel pump after my Racors - suction side pulls fuel and output goes to fuel return as a fuel polishing system. On my to do list is to install (or have parts aboard) to route output to engine instead of return as a backup fuel pump.

Sounds like the fuel system is checking out ok - turbo issues concern me the most. Good luck.

[perchance]

Is there a change in exhaust colour when the problem occurs?

[Dockhead]

Originally Posted by S/V Pearl

I have the same Yanmar with dual racors and the T handle vacuum gauges.

Shut off the fuel intake valve with engine running and watch vacuum gauge to test whether it is working.

I installed a $50 fuel pump after my Racors - suction side pulls fuel and output goes to fuel return as a fuel polishing system. On my to do list is to install (or have parts aboard) to route output to engine instead of return as a backup fuel pump.

Sounds like the fuel system is checking out ok - turbo issues concern me the most. Good luck.

Great idea! Why didn't I think about that? I'll do that today to verify vacuum gauge working.

[Dockhead]

Originally Posted by perchance

Is there a change in exhaust colour when the problem occurs?

Not that I can tell.

Seems no smoke at all that I can see.

Which is somewhat odd since over the last three years and almost 600 hours I have had a persistent smoking problem which has baffled everyone who has looked at it. Engine smokes a lot on startup; much less after it's good and hot and under a load. No one has ever figured out what it is -- blue-greyish smoke which is definitely not overfuelling.

Doesn't seem like it could be oil smoke since the engine doesn't use any oil between 100 hour changes. But maybe it is oil smoke -- from a turbo seal, and has been oil smoke from this source the whole time. Hmmmm.

[Dockhead]

I guess the definitive turbo test would be to buy a manifold pressure gauge and test the boost pressure. I don't know why I didn't think of that before. I will try to buy one on Monday here in St. Malo. Has anyone tested his turbocharger this way?

[Dockhead]

Here's an interesting bit of information:

When an engine cannot obtain its rated rpm's we have to look at the possibilities. Lets start with air. Look at the exhaust under load. Is it deep black and cloud like? If so the problem is probably air related. Either a clogged air filter, a turbo that is not spooling up or clogged exhaust system.

Black smoke could also mean an overloaded engine. A dirty bottom or barnacle covered prop are classic reasons why an engine will not reach the rated rpm's. If this is the case we should also see high exhaust gas temperatures.

If the exhaust looks clean we begin to suspect to our fuel system. We may have a classic case of faulty lift pump or semi clogged fuel filter. In this situation we find the injection pump is able to supply almost enough fuel to provide most of our needed horsepower, but not quite enough to get us to speed. In this situation we would have a clean exhaust, and cool exhaust gas temperature. It's not much a problem except the engine simply does not have the fuel to produce the needed horsepower.

The simple check is to find a place to crack open the fuel return line. Diesel should be flowing back to the tank. If not this is a sure sign the engine is starving for fuel, but no so starved it shuts the engine down, thus the mystery.


Solving marine diesel engine mysteries


Another good test to run. I'll run the engine up with the return line off and observe.

[Dockhead]

Originally Posted by perchance

Is there a change in exhaust colour when the problem occurs?

I've just run the engine up after it rested for a couple of days. It produces grey-blue smoke at startup, as it always has since I've owned the boat.

It now runs up to 3300 -- 3400 in gear, and produces no or very little blue-grey smoke. If I push the throttle all the way forward it will gain a few revs, then fall back to 3300 -- 3400 and stutter a little bit. I listened to the turbocharger as recommended in the Yanmar manual but could not find the intermittent change of tone which Yanmar says is a sign of a bad turbo.

Without a load, today, the engine will run up nearly to its redline -- about 3900 rpm. It stumbles a little (fighting for the last 100 rpm I guess) and produces a fair amount of blue-grey smoke (not as much as on startup). No unusual turbo sounds -- can't tell whether it's whistling normally or not, but there is no intermittent change of tone. If I put the engine back in gear, the smoke goes away. Idling after being run hard, no or very very little smoke.

Still puzzled. Will perform a few tests:

1. Check fuel flow out of the return line when engine is at full throttle under load.
2. Check function of the Racor vacuum gauge against closed fuel stopcock.
3. Check vacuum again in the fuel system at various states of load.
4. Check boost pressure when engine is at full throttle under load; compare to specifications.

Anything else I should be thinking about?

[impi]

... one more question ... are the revs constant when you have lost power, or does it ever give a 'hunting effect'?