Another post about smoky diesels . . .

[gravygraham]

We went for a little poodle about just outside the harbour in this afternoon's sun. After about ten minutes I opened her up but could only get 2100rpm out of the port lump, and worryingly it belched out black smoke. At and below 2100rpm she runs sweetly and cleanly. My first thoughts were an air inlet problem and further ponderings make me think of a turbo problem. We stopped the engines and lifted up the hatch and were greeted by nothing obvious - I felt the turbos on each engine (not very scientific I know) and both seemed to be at similar temperatures. The engines are Nanni 4390 tdi's, and they're barely run in!

Any ideas and/or comments gratefully received.

Graham

 

[carlton]

Black smoke = overfueling = (prob'ly) turbo. Especially if it was fine up to 2100 rpm.

 

[jonno45]

Sounds like boost problem, sticky wastgate, loose hose, intercooler leak etc.. black smoke is because engine delivering fuel for throttle opening but no boost to burn it correctly check boost pressure on good engine at load not tied to the dock and compaire it to the bad.

 

[hlb]

Loads of simpler expanations, rope round prop, water in filter. Air lock. Pipe came loose.

 

[Frontier]

Air Filters clean?

 

[rich]

How clean is your bottom, it makes a lot more drag then you think.

 

[Viscount]

True but by implication his starboard engine was performing normally. GG, what was your starboard engine RPM?

 

[Latestarter1]

Engines always get the blame, in pretty much all cases it is an external factor.

If both engines pass high idle test (I know some of you have trouble with the term) when warm, and only the port engine is failing to make WOT in gear you have something around the shaft plain and simple.

Rest easy about the engine, just find out what is overloading it.

 

[Bilgediver]

I must say this is the type of problem one would get from a stuck turbo or open waste gate if fitted.

Did you try running the smoky lump on its own ( so you can hear it) and see if you can hear the turbo.

C an you get at the turbo inlet easily and see if you can spin the rotor when the engine is stopped????

 

[gravygraham]

I didn't take too much notice but it was certainly up to 2800 - 3000rpm. And yes, the hull's clean.

 

[Latestarter1]

Take the focus off the engine (lump) I hate the term, sounds like Jeremy Clarkson speak.

If turbo had stuck due to say thrust failure or consuming debris which is most unlikely motor will smoke trying to make high idle which appears not to be the case.

Turbo bearings/thrusts ONLY fail due to external effects, lack of or contaminated lube, excessive exhaust back pressure or inlet restriction. As for wastegates they generally fail shut in marine applications leading to excessive boost. I think all this is highly unlikely.

Poor old engine is trying to do its job and still getting the blame.

Get into the oggin and take a look at your stern gear for fouling.

 

[jonno45]

You would still achive high idle off load if boost was down, I would use high idle as a test for poor fuel flow.

 

[Latestarter1]

If engine was naturally aspirated due to seized turbo of course high idle would be achieved, that is charteristic of correctly set throttle and the governor setting. However with total absence of any puff from turbo this would be a smoky affiar particularly as the aneroid would not be functioning.