Isuzu Clacking sound

[Guest Crafty 1]

T

 

When Mitzi introducd the Sigma it had two issues..

 

1. Most Multi grade oils (especially Mobil) would go thru them like a dose of salts

 

When i bought my Mitzi i remember one mechanic telling me if it ya Mitzi doesnt chew through oil or stops chewing the oil then its a darn good sign something is wrong with it!

 

 

 

Yeah he probably had a oil supply contract with Mobil (Mobil XHP was a shocker in Sigma's)

[too_tall 15]

Consider getting the injection timing checked - if the injectors are "firing" a little soon, you are actually going to be getting an explosion before the piston reaches TDC - the top of its travel. This causes high fuel consumption, engine wear, lower power, and most notably in the short term, a LOT of noise, exactly as you are describing. I have played around with tractors and over fueling them ( getting more GG's from the engine ) and often a lot is achievable, but its not just putting more fuel in that delivers, its getting the timing to be more accurate.

 

As a side note, for those who don't know, modern common rail Diesels are often a lot quieter as their injection timing is far superior to a mechanical drive. They actually can pulse the injection of the fuel, and this not only means that the fuel burn is extended ( matching the engine RPM ), allowing for more torque ( which modern diesels are absolutely phenomenal at delivering ) but also far quieter running. Think of one big explosion vrs maybe 8 smaller explosions. Also common rail has other advantages such as far higher injector pressure resulting in better fuel vaporization in the cylinder. This explanation of course is very simplified!

[Guest]

Thanks Tootall. I'll look into the injector timing. Can it be set up by a home guy with a feeler guage or do we need help?

[wheels 543]

No it's not simple to alter timing.

But now we are entering a lot of guessing and we all could come up with heaps and heaps of possibles. There are lots of things that can cause noises and it maybe best to ask a few questions rather than just throw out possibles.

First off, has the engine been OK up untill now and it has just started doing this?

[Guest]

Its been like this since I bought her. I've just been on board running the engine in gear and at 2000 rpm the noise is not noticeable, drop the rev's to 1500 or less and it becomes loud. With it running at 1500 rpm and making noise I loosened the pipe that delivers fuel to the injectors, one cylinder at a time and apart from stalling the motor the noise remained the same. Yet at 2000 or 2500 rpm it sounds like a new motor.

[too_tall 15]

Bbay, lets put it like this - if you have to ask if its a simple job, then it most certainly is a job you need to leave to an expert.

 

If you know its a difficult job without the correct tools and knowledge, then its a job best left to an expert.

 

If you have all the appropriate tools and knowledge, then its actually a very simple job to do. One of the tools I use when doing tractors is a dynometer - not something that will work easily in a boat situation!

[idlerboat 116]

Timing of some Izi engines (like mine) are done by shimming individual injector pumps on each cylinder.

You have to do a bit of reaserch into the engine.

This style of engine fuel system is less effcient than a single pump system.

It does have the ability to run on (badly) a disconnected cylinder.

The need to adjust those shims woud be well into a first complete engine rebuild.

The clacking sound can also be "normal" (ask anyone who has an old yanmha or lister...

at start up it is very loud.

 

I hesitate to go any further on my advice. If you where adjacent to me on my marina, I am sure we could sort it out. (a B row tradition but that is another story)

 

The only piece of advice that I can give you without exception is " if it worries you...dont go to sea until it dosnt"

[wheels 543]

Arrr righty then. I would say you have a normal runnign engine then. Diesel injector pumps can be very noisy and some engines can have quite a loud "clack" as they fire. About the only thing I would check is the tappets. That is easy and they can get noisy as they wear and they do need periodic adjustment to keep them as quite as poss and the engine at best power. Air intake is always a source of noise and so when you combine all, the engine can certainly be a noisy brute. Apart from the tappets, I wouldn't worry.

[Guest]

Very reassuring Wheels. I'll get the injector timing checked, the valve clearances I can do myself and I'll use the best oil. I may have to put sound insulation onto a couple of spots. its been a steep learning curve the last few years getting a handle on these engines. So what oil is prefered or suggested for this application?

[Guest]

I think I've discovered a blown head gasket. White steam in the exhaust and it drives the coolant out through the overflow bottle!

[Guest]

I talked to the guys at Zenith Engineering today about this noise and the tech guy said it could be the gears controlling the fuel injection may have some back lash. These guys are really helpful and have parts in stock.

[Guest]

Yay! Found the problem and fixed it...........The engine sits on a steel frame thats bolted to the keel. Two of the fastenings on the fwd end had come loose and this was causing the clacking sound that was driving us mad. Tightened the nuts and she sounds like a new motor. This was causing vibrations to go through the galley like crazy. Very cheap fix.