Noisy Nanni Diesel in Merry Fisher 805 (with video)

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cashmax

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Not what I had hoped would be my first post on the forum!

Not sure if the sound in the video is good enough and its not helped by me failing to turn off the VHF, but the engine seems very noisy and has a kind of iregular topend knock/rattle that is very audiable with the covers closed and floor down.

I am going to go down and check it out in more detail next week, but wondered if anyone had any ideas. I think the unit is the Nanni 4.390TDI rather than the T4, the boat is 2005.

 
cashmax said:
Not what I had hoped would be my first post on the forum!

Not sure if the sound in the video is good enough and its not helped by me failing to turn off the VHF, but the engine seems very noisy and has a kind of iregular topend knock/rattle that is very audiable with the covers closed and floor down.

I am going to go down and check it out in more detail next week, but wondered if anyone had any ideas. I think the unit is the Nanni 4.390TDI rather than the T4, the boat is 2005.

Click to expand...

eek, you may want to do a search for Nanni cylinder head problems, there has been a regular thread on here from someone who had similar issues and seems quite common on this particualr Nanni unit. For whatever reason I could not see video..

edited bit; this is the thread.. http://www.ybw.com/forums/showthrea...-engine-problem&highlight=nanni+cylinder+head
 
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Sounds like a diesel knock, try cracking the pipes in turn, the one that makes no difference is the the one to look at, could be the injector gone down.
 
Typical crude Diesel boat engine IMHO. Most of these units are thirty years behind current car technology, and some of those are not much better...
 
I've got two of these, no problems ever. I'm not sure the head's issue regards the 4.390. The base Toyota 1KZ has been used for several versions, also later electronic injected types.

For your ref. here's another of the same model


PM me if you want the workshop manual.
 
I presume in the 1 st Video the engine is cold and not under load
Obviously the 2nd is
So maybe not a true comparison, a handy comparison though Spi D
I noticed some valve 'clatter' which may not be there if the motor is at running temperature and underload
My last boat did this but it was a Volvo
It drove me mad for a while so I checked the valve clearances
1 Cylinder was always the culprit and the reason was a 'soft' cam follower which nessecitated tappet adjustment every 300 hours or so
In the end I just let it rattle and it did another 500 hours no sweat but always when not underload
Just a thought
 
The its the same under load and noticeable with the covers shut. I saw the other video and that unit is WAY quieter than mine is.

It does sound metallic on the top end. Diesel knock / faulty injector / bad clearances would be a result frankly.

The engine starts on the button, it doesn't make any noise or run on for any period of time on shutdown.

The engine is quieter when cold and first started and gets more noisy after a minute or so.
 
No Regrets said:
Typical crude Diesel boat engine IMHO. Most of these units are thirty years behind current car technology, and some of those are not much better...
Click to expand...

I thought this engine was reasonably current (last 5-10 years) just with the electronics removed to reduce the risk of problems?
 
Cashmax,

You say engine is Nanni 4.390 TDI in fact the Toyota base engine is an IDI engine and combustion noise is absolutely characteristic of an indirect injection diesel engine when cold, the quick video flash of the gauge panel seemed to show the temperature needle still on the pin. Reason for typical IDI combustion noise is the very high compression ratios employed in indirect injection, generally around 20:1 and consequently very high internal temperature/pressure gradients particularly when cold. It is those very high temperature/pressure gradients around the pre-combustion chamber which have always represented an issue for designers and why ANY IDI diesel is more susceptible to cylinder head cracking.

However at certain engine speeds I do detect a distinct metallic rattle which is what I think you are referring to.

With engine WARMED through, find engine speed where the metallic rattle is most apparent and set the throttle. As suggested by another poster crack off each injector in turn, note the rpm drop and listen to see if noise goes away.

I do not know enough about these little motors however it could employ two stage injection and if noise is eliminated by cracking off a certain cylinder could be a two stage injector fault. Simply send the ONE injector to a fuel pump shop with a decent reputation for checking. Ignore any advise to rip out all four.

Complete step #1 and report back.
 
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Latestarter1 said:
Cashmax,

You say engine is Nanni 4.390 TDI in fact the Toyota base engine is an IDI engine and combustion noise is absolutely characteristic of an indirect injection diesel engine when cold, the quick video flash of the gauge panel seemed to show the temperature needle still on the pin. Reason for typical IDI combustion noise is the very high compression ratios employed in indirect injection, generally around 20:1 and very high internal temperature/pressure gradients particularly when cold. It is those very high temperature/pressure gradients around the pre-combustion chamber which have always represented a design issue for designers and why ANY IDI diesel is more susceptible to cylinder head cracking.

However at certain engine speeds I do detect a distinct metallic rattle which is what I think you are referring to.

With engine WARMED through, find engine speed where the metallic rattle is most apparent and set the throttle. As suggested by another poster crack off each injector in turn, note the rpm drop and listen to see if noise goes away.

I do not know enough about these little motors however motor could employ two stage injection and if noise is eliminated by cracking off a certain cylinder could be a two stage injector fault. Simply send the ONE injector to a fuel pump shop with a decent reputation for checking. Ignore any advise to rip out all four.

Complete step #1 and report back.
Click to expand...

+1
 
Pm sent
I have the same engine and the noise you are hearing is the same as when I brought my boat . At idle speed they sound terrible but under load they sound a lot better. I resolved the problem when I changed my head gasket and had the valves re shimmed and it made it a hundred times better.
Regards Jamie
 
So a quick update from today. We spent some time on the boat today and used a stethoscope to listen to the engine. When listening on the injector fuel pipes no's 3 & 4 were noticeably louder than the other 2. Cracking either of them off when the engine was running reduced the noise significantly. It was hard to get decent results with both of them off of course.

Given that there are few bits that need to come off to get a single injector out, we removed all 4 (once finding a long reach 21mm socket that had enough clearance) and I will take them to be tested.

Picture of them attached. 4,3,2,1 in that order from left to right. You can see carbon on the outside of 1 & 2, but none on 3 & 4.

20150309_184728.jpg
 
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