More strange noises...injectors maybe??

[Heavy Metal Doctor]

I see a few threads about some similar things. I figured I beter not be a hijacker, though....
I have some noises coming out on my recently aquired Kubota L2350. Tach / hr meter broke at 280hrs - not telling when that was.
The very first time I ran it, it was cold (30-35 degrees F) and it gave off some odd noises untill it warmed up. Not uncommon in my gerneral mechanical experience. It smoothed out completely after 10 minutes or so. I had it running for another 15 or 20 minutes messing around with with, everything worked, 3PH and PTO have never even been used so I bought it and took it home.
Then I had time to play with it and now I'm wondering if it doesn't need one or more injectors. Everything seems ok to a point. It starts right up and runs smoothly, no smoke beyond a little puff at startup. But it has a series of noises that range from high pitched ticking to lower a tone knock. The consistant features of the mystery noise are this : The speed seems like firing speed (not RPM's but about 1/4). Anytime the noise happens, a few knocks or ticks, a simple adjustement of the throttle makes it go away - up or down either way and it stops. The noise sounds "high" up the engine - when we (buddy who was around that day) first heard the high picthed noise we thought it was something outside the engine under the hood loose / rattling.

I did also notice a suspicous looking stain right adjacent to one injector when I looked it over. Thick, black / oily stuff blown onto the back side of the intake manifold. You can tell by the spattering pattern that it was something under pressure leaking. It is also obvious that the same injector has had a wrench on the line recently - marks are fresh on the nut.

It's hard to see much under the hood since it's stationary with removable side covers. I'm gonna open up all the sheet metal tonight / tomorrow to try to get a closer look for evidence.
I was also considering some form of "injector flush" cleaner I've heard about in the past, but I have no idea if that is even worth trying.

 

[Don87]

The 'splatter pattern' tells me that the injector may not be torqued properly, and that will also cause valve rattle.(from losing compression).

High engine noise is usually valve train.

I would adjust valves, check torque on injectors........and go from there.

As far as 'cleaners'..........I'm not sold on them, but check the 'fuel and lubricants' thread. Someone may have a different experience than what I've had.

 

[6thgpSF]

On my Yanmar I had an injector that was dumping too much fuel and the result was a bent valve....russ

 

[Heavy Metal Doctor]

Sheet metal came off this evening. I found the same splattered crap also in a thick layer of hard pasty crud built up around the injectors. I started it up and started checking around some more. I realized there was some seeping / bubbling going on in that sludgy crap. I scraped it off and found that all the injectors are slighlty loose, one moreso than the other 2, and the crud must be fuel / combustion leaking and collecting dirt. I'll try a set of seals and the valve adjstment suggested before and see what happens.... The fun part looks like getting the injectors out without dropping that crud down inside the hole.....

 

[jonyyuma]

Brush and scrape all the crud away.Blow clean with degreaser, none of it goes into the holes. Injector cleaner will not hurt your nozzels, dirt in fuel or water in fuel will kill them. You might pull them just to look at the ends, but the holes are usually not very clear.New seals should be applied, when put back, they should be torqued to spec. No leakage allowed.

 

[fieldserviceengineer]

Cold knock in a diesel engine is normal especially if the engine has pre combustion chambers. It is due to a higher peak pressure and delayed timing due to lower fuel atomization. It is very normal to become quieter when it warms up.

 

[Bison]

If i where you I would have the injectors tested at a injection repair facility/diesel shop while i had them out

 

[Heavy Metal Doctor]

Not much has happened - I got crunched for time due to weather and working very weekend for about 6 weeks prior to this past one..... I had to throw everything back together once the weather broke for garden prep. Still making noise, but runs fine -- I think I'll have to baby it through for another couple hours of use and then get it fixxed right.