One for the Volvo diesel experts

[Playtime]

Further to my previous thread (Engine problem or fouled prop???) the mystery deepens. Beyond the lack of revs/thrust first noted, a pronounced 'clatter' above a certain throttle opening has become apparent. Also the oil (changed in January) has gone black much quicker than it normally would.

To recap, the engine is a Volvo D2-40, 8 years old with approx 800 hours running. It was serviced (by me) in January and the symptoms, as reported in the previous thread. first became apparent in March. The original thought of a fouled prop have since been discarded (see below) and also most previously suggested solutions have been tried with no improvement.

The current symptoms are as follows -
Engine starts easily and runs smoothly below a certain throttle position.
Above that (approx) position a 'clatter', as I would describe it, starts with smelly blue exhaust and traces of oil (diesel?) appearing in the water.
This happens around 1500rpm in gear and 2200 rpm in neutral (which eliminates the fouled prop idea).

My Volvo 'expert' is convinced the clatter is diesel knock (not bearings as I was fearing at one point) and the smoke and oily water are from unburnt fuel. Exactly why we have unburnt fuel at this throttle opening remains a mystery so far as we have eliminated the obvious possibilities, as follows -
Tappets - checked and adjusted (basically all OK)
Compression - all OK (but note only tested at starter speed)
Borescope camera - some slight scoring and marks in No 1 cylinder; other 3 OK. No 1 is obviously of some concern.
Injectors - tested and reconditioned (although they were not bad)
Injection pump - tested out OK.

The next thought is to remove the head. However, I am still having difficulty envisaging a failure mechanism that matches the symptoms, now we have eliminated the obvious.

If anyone has experience of a similar problem on a relatively 'young' engine or any suggestion of what the root cause might be, I would love to hear your thoughts. Thanks.

 

[neilf39]

Worn valves or guide seals seems to be a cause of blue smoke (or sticky valves). Perhaps oil is getting into the cylinders when the engine is above a certain load. May explain why sump oils is going blacker more quickly as combustion by-products are also going the other way. Maybe the clatter is pre-combustion as the oil is giving pre-combustion.

 

[pvb]

In the previous thread, you said you were going to check the exhaust elbow. Did you? What was the verdict?

Is the oil level in the sump correct?

Does the engine reach the correct operating temperature?

 

[Beneteau381]

Further to my previous thread (Engine problem or fouled prop???) the mystery deepens. Beyond the lack of revs/thrust first noted, a pronounced 'clatter' above a certain throttle opening has become apparent. Also the oil (changed in January) has gone black much quicker than it normally would.

To recap, the engine is a Volvo D2-40, 8 years old with approx 800 hours running. It was serviced (by me) in January and the symptoms, as reported in the previous thread. first became apparent in March. The original thought of a fouled prop have since been discarded (see below) and also most previously suggested solutions have been tried with no improvement.

The current symptoms are as follows -
Engine starts easily and runs smoothly below a certain throttle position.
Above that (approx) position a 'clatter', as I would describe it, starts with smelly blue exhaust and traces of oil (diesel?) appearing in the water.
This happens around 1500rpm in gear and 2200 rpm in neutral (which eliminates the fouled prop idea).

My Volvo 'expert' is convinced the clatter is diesel knock (not bearings as I was fearing at one point) and the smoke and oily water are from unburnt fuel. Exactly why we have unburnt fuel at this throttle opening remains a mystery so far as we have eliminated the obvious possibilities, as follows -
Tappets - checked and adjusted (basically all OK)
Compression - all OK (but note only tested at starter speed)
Borescope camera - some slight scoring and marks in No 1 cylinder; other 3 OK. No 1 is obviously of some concern.
Injectors - tested and reconditioned (although they were not bad)
Injection pump - tested out OK.

The next thought is to remove the head. However, I am still having difficulty envisaging a failure mechanism that matches the symptoms, now we have eliminated the obvious.

If anyone has experience of a similar problem on a relatively 'young' engine or any suggestion of what the root cause might be, I would love to hear your thoughts. Thanks.

I hate trying to diagnose from a distance, however, the symptoms are of a bad cylinder, the injection system not working properly. If you look at the exhaust when it is clattering you will see loads of greyish bluish smoke, caused by unburnt fuel. The clattering caused by injecting raw fuel in instead of it atomising. Difficult to do and slightly hazardous, but get yourself set up, set the sped at clattering and quickly slack the injector nut on number one. Be very careful, a lot of hi pressure fuel flying around, cover with rags to dampen the effects. If the noise stops, and the engine doesnt slow it is that cylinder. Then swap the injector over with number two and see if it happens on two. If so its the injector, if it doesnt, its either the cylinder or the pump.
Do you follow my thoughts?

 

[Playtime]

In the previous thread, you said you were going to check the exhaust elbow. Did you? What was the verdict?

Is the oil level in the sump correct?

Does the engine reach the correct operating temperature?

Exhaust elbow - no. Thanks for reminding me. There has been a long gap between the original thread pre-lockdown and the recent investigations. Will be checked before the head is removed.

Oil level is correct.

Engine temp is OK.

 

[Playtime]

I hate trying to diagnose from a distance, however, the symptoms are of a bad cylinder, the injection system not working properly. If you look at the exhaust when it is clattering you will see loads of greyish bluish smoke, caused by unburnt fuel. The clattering caused by injecting raw fuel in instead of it atomising. Difficult to do and slightly hazardous, but get yourself set up, set the sped at clattering and quickly slack the injector nut on number one. Be very careful, a lot of hi pressure fuel flying around, cover with rags to dampen the effects. If the noise stops, and the engine doesnt slow it is that cylinder. Then swap the injector over with number two and see if it happens on two. If so its the injector, if it doesnt, its either the cylinder or the pump.
Do you follow my thoughts?

I agree that cylinder no. 1 is suspect. However, all injectors and the injection pump have been tested (Powerdrive in Portsmouth) and the injectors, although not bad, have been refurbished. It has made no difference to the symptoms.

I did try cracking off each injector before lockdown but only at around 1400rpm, just before the clatter. Each one caused the engine to slow down (i.e. injector OK) and this was confirmed by the later injector test. Have not tried the test again when the clatter is happening but might be worth doing before the head comes off to identify the faulty cylinder, if I can stand the noise! Given that it's unlikely to be the injector at fault it will still need the head off to fully check out the suspect cylinder.

 

[Playtime]

Worn valves or guide seals seems to be a cause of blue smoke (or sticky valves). Perhaps oil is getting into the cylinders when the engine is above a certain load. May explain why sump oils is going blacker more quickly as combustion by-products are also going the other way. Maybe the clatter is pre-combustion as the oil is giving pre-combustion.

My Volvo expert thinks it's unburnt fuel - the question is why (or how). Compression is good and very similar on all 4 cylinders (admittedly only at cranking speed) and the fuel delivery system has been fully checked.

 

[pvb]

My Volvo expert thinks it's unburnt fuel - the question is why (or how). Compression is good and very similar on all 4 cylinders (admittedly only at cranking speed) and the fuel delivery system has been fully checked.

Is your "Volvo expert" a technician in a Volvo Penta dealership?

 

[Playtime]

Is your "Volvo expert" a technician in a Volvo Penta dealership?

He was - for 20 years, I understand. He now runs his own marine engineering company. I won't mention any names until we get some sort of resolution.

 

[pvb]

He was - for 20 years, I understand. He now runs his own marine engineering company. I won't mention any names until we get some sort of resolution.

Sure, no problem. But how recently was he in a VP dealership? Your D2-40 isn't a very old engine, and if there are problems with it, the VP dealerships may have more information.

 

[Playtime]

Sure, no problem. But how recently was he in a VP dealership? Your D2-40 isn't a very old engine, and if there are problems with it, the VP dealerships may have more information.

I understand he set up the business in 2017.
The D2-40 has been around for more than 10 years AFAIK. It was superseded by the D2-50 in 2016, I understand.
All I can say is that he has not seen this exact mix of symptoms before.
The blocked exhaust/elbow is certainly worth pursuing before the head comes off. One other symptom when we had the borescope in No 1 cylinder was some unidentified marks on the cylinder wall - possible rust was mentioned. If this was caused by backflow of cooling water I'm now wondering if could have led to hydraulic lock (if that's the right expression) and maybe breaking a ring giving the slight score marks in No 1. A broken ring might then result in unburnt fuel and pre-ignition . . . maybe?
It sounds plausible and would just about fit the symptoms.
We'll check the exhaust elbow next week before we go any further.

 

[Beneteau381]

I understand he set up the business in 2017.
The D2-40 has been around for more than 10 years AFAIK. It was superseded by the D2-50 in 2016, I understand.
All I can say is that he has not seen this exact mix of symptoms before.
The blocked exhaust/elbow is certainly worth pursuing before the head comes off. One other symptom when we had the borescope in No 1 cylinder was some unidentified marks on the cylinder wall - possible rust was mentioned. If this was caused by backflow of cooling water I'm now wondering if could have led to hydraulic lock (if that's the right expression) and maybe breaking a ring giving the slight score marks in No 1. A broken ring might then result in unburnt fuel and pre-ignition . . . maybe?
It sounds plausible and would just about fit the symptoms.
We'll check the exhaust elbow next week before we go any further.

when you say No 1, is that at the front or at the back nearest the exhaust elbow?

 

[peteK]

Water mixed in with the fuel will give a knocking sound at top of engine,try some fresh diesel from a separate can.

 

[black mercury]

Hi, yes you need to make sure elbow and exhaust are clear. If there is too much back pressure causing exhaust gasses to enter the cylinders through the exhaust valves when on valve overlap it can cause an excessive clattering noise. The symptoms may have started out at first with a lack of power before any noises were heard? You would normally get a greyish smoke if it is bad, but every case is different. It could explain some rust in the cylinder if some water was also being forced back. It would also explain the blackening of engine oil sooner than expected. If the compression was OK and equal on all cylinders I doubt if the ring is broken on cylinder 1.
If the elbow is clear check the rest of the exhaust system. If you have a pipe same diameter as the exhaust you could set up something temporary, you could even run engine without water for a few seconds if you are worried about water in the temporary exhaust, especially if it's directed upwards. You just need to run engine enough to diagnose if the noise disappears. See how you get on, but check these things before starting to pull engine apart!

 

[Rafiki]

I have the same engine, but luckily not the same problem. Mine is 2008 AFAIK, I dont think the engine has been superceded by the D2-50, that latter engine has a larger capacity.

I removed my exhaust elbow to check it for the first time ever. It seemed perfectly clear, so I doubt that is your problem. Easy to remove though, but a new gasket will be required to refit it.

 

[Playtime]

when you say No 1, is that at the front or at the back nearest the exhaust elbow?

No 1 is at the front, furthest from the exhaust elbow. I appreciate this makes my thought above less likely. I will check next week with the guy who was using the camera that he was referring to the front cylinder. I was there but didn't actually look which cylinder he was inspecting when we saw the marks on the cylinder wall.

 

[Playtime]

, I dont think the engine has been superceded by the D2-50, that latter engine has a larger capacity.
/QUOTE]
The D2-40 went out of production in 2016 and the nearest replacement in the Volvo line-up is the D2-50. Apparently engine mounts and saildrive connection are the same as the D2-40 although the engine is slightly bigger.

 

[Stemar]

Possibly a daft question, but when were the tappets last adjusted? Maybe check the clearances?

 

[pvb]

Possibly a daft question, but when were the tappets last adjusted? Maybe check the clearances?

Read post 1 again...

 

[Playtime]

Good news (I hope). The exhaust elbow was almost completely blocked with very hard white deposits (salt and other minerals no doubt) with a generous layer of greasy soot covering it and almost completely closing the remaining small hole. It was even caked up in the water inlet. So, thanks are due to those who mentioned this as the possible cause.
Because of the 'clatter' (diesel knock) the engine was making and the smoke and lack of revs, both my diesel 'expert' and myself were thinking fuel problem. If I had acted on the blocked exhaust suggestion 3 months ago, before lockdown, I would have saved myself a lot of time and a wad of cash. Moral - do stuff now not next week when you have forgotten what it was you were going to do! It's an age thing.
I have ordered a replacement stainless steel elbow from Keypart (actually cheaper than the standard Volvo cast iron replacement) which, hopefully, will completely solve the problem and last more than 800 hours that the Volvo one managed. If it doesn't I'll report back with any new symptoms.