Yanmar Problems

[Captain Bill]

Originally Posted by capngeo

Yeesch... Lets not get ahead of ourselves.....


Yanmars will certainly not turn up under load with a clogged turbo/intake, but will almost always hit the rev limit when full rack/no load. The 4 cyl engines have always had an issue with turbo corrosion from salt "humidity" once shut down because the mixing elbow is so close.... BUT the turbo is free spinning and the intake is clear, so forget the air side for now.

Going back to fuel and air... I would think that an air leak bad enough to limit your RPM under load would also make the engine nearly impossible to start, which brings me back to fuel restriction.

Speaking of mixing elbows are you sure yours is nice and clean? A clogged elbow can limit RPM.

[capngeo]

Originally Posted by Captain Bill

Speaking of mixing elbows are you sure yours is nice and clean? A clogged elbow can limit RPM.

+1! Good thought!

[Dockhead]

Thanks for all the helpful replies.

I am far from home on my summer cruise, so need to try things one at a time, avoiding any heavy engineering work which is merely experimental until I can get home.

I think my lift pump must be with the fuel tank and between the tank and the Racor, because it is nowhere to be found in the engine room. That would mean that I can't trust the vacuum gauge, so gunk clogging the fuel pickup seems to be a candidate. Or a bad lift pump? Do these things go partially bad? Evidence for this would be the fact that it seems to get worse after heavy motion. Evidence against is that the other users of diesel fuel on board (genset, central heating) don't have any symptoms. More evidence against: the Racors are spotless. But I'm due for a tank cleaning anyway (last time three years ago), so maybe I can find a tank cleaning service around here somewhere. It would be a relatively easy elimination of one thing. Maybe I can get a look at the pickup while it's being done.

I don't think it can possibly be the mixing elbow, because a clogged mixing elbow is not an intermittent fault. But because it's an easy fix, why not pull it off and have a look? Think I'll do that today. Wouldn't hurt in any case to give it a good cleanout. Good suggestion; thanks for that.

I'm think after contemplating that oil I saw oozing out of the compressor side of the turbocharger that maybe really it's the turbo. If the seals are blown, it means the bearings could be getting starved or contaminated with exhaust gas. Now that could be an intermittent fault -- bearings don't run smoothly so drags the turbo down, sometimes more, sometimes less. Evidence for: turbo doesn't whistle like it is supposed to. Oil oozing out, which can't be normal. Against: will not rev without a load (although revs more than with one).

When I open the throttle, especially if the engine has not been running for a long time, it will rev up over 3000, then fall back down. What the h*ll? That's not really consistent with any theories so far. This eliminates throttle cable (I've checked that anyway). Do diesel engine governors go bad? Could it be that? I've never heard of such a fault, but then I am not experienced with diesel engines.

[C4 King Cobra]

I agree that 99% of the time it is fuel. But in this case again in IMHO you have described a text book turbo charger problem. IE Oil in charger, off and on, lack of power, etc. Is it worse under load ie in gear? Does the engine sound like it is lacking air, I would how ever continue to follow the fuel to the end as this is the easiest and cheapest route. Installing a cheap automotive electric fuel pump, $30 US, past your primary but before the secondary will help decide fuel or not. Good Luck

[noelex 77]

If the fuel pumps electric, no matter where it's located pull the fuel hose off the fuel filter. Turn on the ignignition and you should have a nice stead stream of diesel, far more than any sailboat engine needs.
If the above is the case it rules out a fault in the fuel pump etc.

[Dockhead]

Originally Posted by noelex 77

If the fuel pumps electric, no matter where it's located pull the fuel hose off the fuel filter. Turn on the ignignition and you should have a nice stead stream of diesel, far more than any sailboat engine needs.
If the above is the case it rules out a fault in the fuel pump etc.

OK, I did that. No fuel came out, even when I started the engine. Can it be that the lift pump is integrated with the injection pump? The service manual says: "Fuel oil in the fuel tank is sucked by the feed pump built in the pump through the fuel filter and sent to the fuel inlet of the fuel injection pump." This "feed pump" is shown as being on the end of the injection pump, sharing its drive.

So I guess there is no electric pump, and the lift pump ('feed pump') is sucking through all the filters. So the vacuum gauge on the Racors would show any problem with a clogged tank pickup. So I guess we can just about eliminate fuel feed problems, unless this "feed pump" is bad, or the fine filter is clogged (but it was just changed, and made no difference in the problem).

Today we pulled the exhaust elbow off. It is not in any way clogged. It had very minor carbon deposits which we wire brushed out.

It is of a design which would be hard to clog. It is a double wall stainless pipe of very thick gauge. Sea water flows between the inner and outer pipe and is discharged into the exhaust stream out the back end where the inner pipe ends. Basically it is open all around the circumference of the inner pipe so basically impossible to clog.

So we've more or less eliminated fuel feed and exhaust elbow. I guess the turbo is looking like the primary suspect? I felt it again today when we had the elbow off and it doesn't feel sticky.

[Dockhead]

Originally Posted by C4 King Cobra

I agree that 99% of the time it is fuel. But in this case again in IMHO you have described a text book turbo charger problem. IE Oil in charger, off and on, lack of power, etc. Is it worse under load ie in gear? Does the engine sound like it is lacking air, I would how ever continue to follow the fuel to the end as this is the easiest and cheapest route. Installing a cheap automotive electric fuel pump, $30 US, past your primary but before the secondary will help decide fuel or not. Good Luck

Thanks.

Just one thing bothers me about the turbo theory -- isn't it true that turbo boost is not needed to get up to max revs when there is no load? Because although I get more revs without a load, it still won't pull the redline, when the problem is present. So the problem -- whatever it is -- is preventing the engine from revving up even in neutral.

[C4 King Cobra]

This is why I suggest the electric pump. It will deliver fuel even if the mechanical pump is not. If you have fuel the engine will run. The turbo could keep the engine from reaching rpm

[Dockhead]

Originally Posted by C4 King Cobra

This is why I suggest the electric pump. It will deliver fuel even if the mechanical pump is not. If you have fuel the engine will run. The turbo could keep the engine from reaching rpm

Well, the engine does run. It starts instantly and at worst will pull 2300 rpm under load.

[C4 King Cobra]

Sooo I think you can eliminate fuel delivery as the problem.

[C4 King Cobra]

Just to add if the charger is the problem and is spinning freely. It probably is not going to die anytime soon. It may not perform 100% but will continue to operate for sometime. It should allow you to continue until such time as repairs are easier. IMHO

[Sailmonkey]

Originally Posted by Dockhead

Well, the engine does run. It starts instantly and at worst will pull 2300 rpm under load.

At the point in time when you're loosing power and sloshing around are you looking at the Racor vacuum gauges?

My thinking here is that some sort of debris, something too large to get sucked up into the fuel pickup, is getting under the pickup and nearly blocking it. Then it gets moved by another violent motion and you've got good fuel flow again with nothing being displayed by the Racor vaccum gauges except for the brief time that the obstruction to flow exists.

[chrisjs]

Have you checked your prop??

[Dockhead]

Originally Posted by chrisjs

Have you checked your prop??

Yes. The boat was lifted three weeks ago and I serviced the prop and changed the anode.

Anyway, the problem appears also in neutral.

[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