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Old 11-12-2006, 10:50 AM   #1
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Default Smoky Volvo engine

My Volvo engine smokes a fair bit so this query is addressed to anyone who has come across that problem and any comments, feedback and/or suggestions would be much appreciated.

The engine is a year 1990 Diesel Turbo charged Volvo TMD31A, 100 HP, 4 Cylinders with a gear box 2.6:1, a 3 fixed blades 21 prop with 13 Pitch. Maximum rev is 3800 RPM and I typically run at 2500 RPM to get 6 to 6.3 Knots. The engine burns 4.5 liters of diesel per hour. The boat is a sailing Ketch Vagabond 47, full displacement hull with a GRT of 25 Tons.

The engine was overhauled last year, meaning the whole thing was removed from the boat, stripped down, all components checked for tolerance. Pistons, liners, rings and some bearing were replaced with new parts, Valves and seat tolerances were checked and found satisfactory. The injector pump was disassembled by a Bosch specialist; worn parts were replaced as well as injector tips.

Back in the water there was a fair bit of blue smoke at first which would be expected. The engine then blew black smoke and quite a bit when idling and a little less when loaded. I had the fuel pump removed again for inspection by the same specialist who claimed that he could not find anything wrong with it. I also talked to a couple Volvo dealers who were honest enough to admit that particular model has a smoking problem, which was one clue. The original design of the engine included a flapper valve in the mixing elbow that was designed to reduced the amount of smoke at low rev, the valve would partially close at low rev and progressively open up at the RPM increase. Unfortunately I could not test the efficiency of the valve as the mechanism was disconnected when I bought the boat. However it might not have worked as I had to replace the mixing elbow (it was found cracked) and the new genuine Volvo part is now designed without a flapper valve which seems to indicate that it never worked. That makes it the second clue.

The third clue is that the engine burns no engine oil whatsoever. I check my oil level before each start up and change it out every 100 hours along with the oil filter. That allows me to notice that the blackening of the engine oil is progressive and linear with engine hours.

So besides having a permanent black stern, that also spoils the varnish work, the unburned diesel can be noticed on the water surface which does not help the environment. This is also a bit of an annoyance in Marinas and when motoring with very light stern wind that blows the exhaust fume back toward the cockpit.

Now coming to the point, would anybody have a similar experience and was a solution found? Comments and suggestions would be very welcome.

Thanks and apology for the rather long post.
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Old 11-12-2006, 11:40 AM   #2
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Hi Francis,

I am affraid I do not have a solution for you but I know of the problem. I spent 3 years on a Coast Guard cutter which was fitted with twin Volvo TMD 120 engines (I hope I got the number right). Despite belonging to the Coast Guard, where we had access to some of the best technicians arround as well as Volvo service personnel those engines always smoked. WHen starting up the always spewed a drop or two of diesel into the water (embarassing) and then smoked thereafter. Having said that, it is worth mentioning that the greater the revs the less the engines smoked.

Maybe this is just a Volvo thing?

Hope you find a solution

Yours aye,

Stephe

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Old 12-17-2006, 11:35 AM   #3
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I've looked at your information about fuel use and not 'using oil' and can't read anything abnormal there although I'm not a Volvo 'expert'. I guess the logical thought has been eliminated. I find if Bedouin has any fouling on her prop or the hull has much growth the exhaust gets smokey. I've had dirty prop problems as frequently as every few weeks depending on location. If the hull and especially the prop is clean there is no smoking exhaust. The other thought is the importance that the grade of engine oil being used is the one recommended for the motor. If the motor manufacturer recommend a mono grade oil, as is the case with Yanmar 3 cylinder motors, and a multigrade oil is used then one will experience engine smoking at start up no matter what the engine condition is.

Black smoke indicated unburnt fuel or that there isn't enough load on the motor. diesels do need to have a load on the motor to give a good burn to the fuel. I'm tending to think it is unburnt or poor fuel burn more than an oil smoking problem in your case.

Keep us updated as your not the only one with the problem,

Regards

Peter
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Old 12-17-2006, 04:49 PM   #4
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We had a Volvo in our MV - it also smoked, especially at start-up. I asked around and found that all the boats in the marina with Volvos all smoked. The Volvo agent also said that this is a Volvo "thing" and that there was no problem. Something (possibly flapper valve) could be fitted to the engine to cut this out but in my opinion it was not worth the expense and effort to get rid of a little smoke (and a little embarrassment).
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Old 01-01-2007, 07:33 PM   #5
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Hi Francis,

I've not owned a volvo yacht motor but had trucks for years. The volvo I had [TD70b]always smoked light blue smoke when cold till it was well warmed up and I know of many others from late 1970s to mid 1980s the same. If your getting black smoke, and the fuel pump is ok check your air intake, mainly the filter for blockages[our problem was dust but yours could be algae or damp paper in the filter]. Remember for every litre of fuel burnt you need 8000 litres of air in a diesel.

Cheers Terry.
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Old 01-02-2007, 03:59 AM   #6
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Hello Francis,

Not an expert, but these are some "general" diesel procedures and suggestions you may want to look at if it pertains to your specific motor. Unless fully qualified, I would put these to a diesel mechanic and defer the actual work to them.

Check compression pressure. If the compression is good, suspect bad valve guides. After the engine sits the oil on top of the cylinder head leaks down into the cylinder and then upon start up the engine smokes until the oil burns off. Fuel on the water is common in the older engines. Blue smoke is oil. Blowby can happen if tolerances were not kept. You said the valve tolerances were satisfactory but was compression tested? The fact that it was not replaced as part of the overhaul makes me nervous since these parts were "unmated" from other parts when checked.

Check combustion pressure. Improper combustion will send deatomized fuel right out the tailpipe. Black smoke is fuel.

Check the temperature thermostat and change it to a higher temperature not exceeding engine specifics and see if fuel burns cleaner.

Check your timing for proper firing sequence...if okay, check that timing belt marks align correctly at appropriate cylinder TDC.

Measure your cylinder temperatures. Although not as important, improper temperature can also suppress proper combustion ionization. Cylinders hotter than others could mean restricted cooling passages. Circulate some acidic solution until it comes back clean. Raw water is a whole job in itself!

Check fuel/air mixture ratio. Lean her out if you can. The turbo might need tuning.

Check the injectors pressure if you have them. The glow plugs when the engine is cold.

A block heater helps all diesels quite a bit in reducing smoke...consider an installation, which is a relatively cheap item.

Run her at higher RPM and see if the smoke is further reduced and what reaction is witnessed when you drop her down to idle quickly.

Find out from the dealer if that issue was corrected in younger models and what was replaced to correct it.

Try to find the elbow with the flapper and install it, or have one machined to specifications. This would be my first effort.

Worst comes to worst, the exhaust will have to be submerged and you will have to live with it until a repower.

Sorry to hear about the bad news...sounds like more than an inconvenience. Best of luck.

Fair winds,

J
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Old 01-02-2007, 08:07 PM   #7
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Thanks to all for your suggestion. Boat is out of the water due to a failed depth transducer and found a corrosion problem on the rudder shaft. Should be back in the water mid January, that will be the time to try your suggestions.

Happy new year.
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Old 10-26-2009, 12:03 AM   #8
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Francis: I'm new to cruiserlog forum so my advice is probably too late to help you. However, I do have experience with your problem and a solution. We have a 1987 Vagabond 47 with the Volvo TMD 31A engine. When we aquired the vessel in May 2002, the black smoke issue and black transom were very apparent causing calls from other boats. I found the exhaust elbow flapper valve to be non operative due to a failed relay. Hence, the valve was always closed and the poor engine was laboring against a tremendous back pressure. I tied the valve open with a good partial clearing of the problem. I've since installed a new elbow with no valve. However, there was still a high exhaust back pressure caused by a very high vented loop and the high lie of the exhaust seacock. I brought the exhaust loop down to about 18 inches and installed a fully open vent by leading the vent line up into the cockpit. I have a gauge on the exhaust manifold to measure back pressure which generally runs at about 20cm. I've just finished varnishing the transom after about 20hrs of motoring and found no residue.

I think with the lower loop you must close the exhaust seacock if you are sailing with a following sea. I've also installed drains on my water lift muffler and at the bottom of the exhaust line. There's a lot of water in that system. I recall that Calder recommends back pressure of 12cm maximum for a turbocharged engine. The only way you could accomplish that level is to change the exhaust seacock to a midship position. As a practical matter the changes I've made have solved the problem. I can send you a picture of my actual measurements before and after the exhaust line changes.

Yours, Mike, S/V WingNPrayer
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Old 10-26-2009, 07:57 AM   #9
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Old 10-26-2009, 02:00 PM   #10
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There are two errors in my posting of yesterday which I didn't pick up on editing. The measurements are all in inches not centimeters. I've just returned from two months in Europe, hence the confusion. Second, I introduced the subject of vented loop which of course is the water injection loop. That loop still remains high in the engine compartment, but I did change to a completely open vent visible at the helm which gives me a good visual monitor of any obstruction to exhaust flow. The exhaust loop is at 18 inches. I'll be on board tomorrow and take some new measurements with a laser level which should be a good exercise.
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Old 11-11-2009, 01:16 AM   #11
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I have experienced black smoke in a Volvo MD engine. Run the engine at the cruising RPM and note the boat speed.

You should be at hull speed for your boat. Take the prop to a propeller shop and have it re pitched to give you the

hulll speed for your boat. I did this and the black smoke stopped. It will have to be re pitched to either increase the

RPMs or reduce the RPMs, a shop the specializes will know. I am assuming that the injectors are clean, with good

tips and spray tested.
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Old 02-22-2013, 04:34 AM   #12
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Does anyone know the life expectancy of a Volvo TMD31A in hours?
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