KAD42 engine knocking

Hi,

I have this KAD42 that makes a knocking sound.

Im pretty new to marine and Volvo Penta engines, and I have not much experience with diesel engines.

However it sounds bad to me, and from my experience with gasoline engines it could be a problem with a rod bearing. But also the sound is very constantly (ofcouse follows the rpm) no major changes in sound if its idle or under load.

And that challenges me a little, I have heard some warn rod bearings in my time with BMW.
But sound did varies as load increases or decreases dramatic making it more a rattle sound like than a knock.
But here its always a knock from the first fire up and down in rpm and with or without load.

I have by loosen the fuel lines and thereby narrowed it down to be at cylinder 2 becouse the knock stops when no fuel is supplied to that cylinder.

I have uploaded a video to youtube as can be seen here:
https://m.youtube.com/watch?v=O0Wt08c_fsQ

Also it tends to smoke white quite a bit when starting, however it could be do to the fact that I live in Greenland with water temperatures between 1-3 degreess celsius.

Also today trying to diagnose I took the boat out to the water 20min or so with trying everything between idle and full speed (34 knots) after aproximately 5min at full speed and down to idle the engine turned off right away and I had a pretty hard time to get it started again. Thats pretty unuseable becouse when I started the engine before the trip (cold start) it started at first crank, and that is pretty okay taking into account that outdoor temp was 4 degrees celsius and the engine have no glows.

The engine temp at running speed is sharp 80 degrees celsius and the oilpressure are between 4-5 bar (60-75psi) under load and 2-2.5 bar (30-35psi) idling.

Anyone have an idea to further throubleshooting or can tell me what it certainly is?

Best regards
Thomas

Hi,

Today i tried change two injectors, an indeed the problem followed the injector, So I have properly found the source of the knock.

The failing injector was totally dry with alot of sod om it.
The other one was a little moist.

It seems that the failing injector not supplied enough fuel and maybe runned lean, causing it to pre ignite.

now I will change the failing injector and crossing my fingers that the cylinder or piston did not damage.

Best regards
Thomas

I would have expected the white smoke and knocking to be from a leaking injector rather than one 'running lean'. I would get all the injectors checked and serviced if that is possible

I have today been at the Volvo work shop and they did not have a new injector. But I then got a nozzle tip instead. And I wanted to change that. When I did disassemble the injector i instantly found the flaw. The spring inside was broken. So all this are caused by a little spring, sadly they did not have this spare part in greenland.

Will it do any damage to the Volvo engine if lets say I going to run on 5 cylinders for aproximat 8 hours? Ofcourse without fuel supply to that cylinder.

Broken spring would have meant overfueling so that all makes sense. What will you do with the bad fuel line if you run on 5 cyl? I don't know whether it would be safe to try and make all that fuel go via the return line and you can't just block it off.

Okay so it was overfueling and therefore the smoke okay nice to know.
I my plan was just to pipe/hose the fuel back in the tank from the injector pipe and seal up the fuel return connection.

Not something I have ever tried. The cylinder will still get oiled from the crank etc so I guess that it would not seize if running without fuel. So if you can deal with the fuel line you might be able to run it gently but I wouldn't run too far or hard to be safe. No one has a similar engine you could borrow an injector out of?

I have today inserted the injector to the engine without spring and the washers inside. Connected it to the fuel return line. Mounted a hose on the fuel pipe letting the fuel back to the tank.

Started the engine okay, running ofcourse not as steady as with all cylinders but does idle okay. Tried revving the engine seems no great trouble and no knocking as was my starting problem.

There does comes compressed air back through the injector becouse of the compression.

I have tried all over greenland to find some with a spare injector new or secund hand. I tried writing on 3 Facebook groups with boats in greenland no one even has a warn out one that i could use the springs from. I have been at three Marine work shops including Volvo reseller they can order one by ship its like 4 weeks away WTF. They did however have the nozzl that i got but it does not fix my problem sadly. I have ordered two springs from Denmark and the shipment is maybe next week. Dammit

Have you tried looking at any diesel truck parts for a spring?

Hi again, i sailed to Maniitsoq this weekend on 5 cylinders without and throubles.

Ofcouse the engine and boat was not as responsive as normal and max speed was 25 knots, where it normally is 35.
however it did the job, and I talked to a marine service in the down, and after a long time we did find one old and dirty injector matching the ones in my engine. We installed it and it worked like a charm.

So now its running great again. With a free of charge injector.
I now just wait for the pressure springs so i can get the original injector in place.

Sadly when we was on the way home we sailed into a rock in shallow water, bend the propeller so the marine service did sell me a new set of J5 propeller so completely free was this injector not.

Thanks for the update. I am glad you got it sorted. Bad news on the props. They are not cheap items unfortunately. Can you get the old ones straightened or are they missing pieces now?

Sadly they are not, but thats the game
The damage to the prop is not that big, so the answer is it can be fixed. However theres no type of company in greenlan doing it so it needs to be shipped to Denmark and back again. And then the expences are to great and the time too long considering the short sommer here in greenland.
I got a new prop for 1000 USD including them installing it with the boat in the water.

If you can, use a gas torch to heat them really hot (just the blades) and straighten them yourself with a hammer. They won't be perfect but you can probably get them close enough that you can carry them on the boat as emergency spares in case of another rock or if a prop hub starts slipping.