I'm looking at a 2006 52DB with ~288 hours on the QSM11 engines. I had oil samples pulled after a sea trial the other day, the starboard engine came back with a 5.5% "Fuel Dilution" reading in Contaminants on the oil analysis report. The notes from the lab on this point read "Since unit is new, rings may not be completely sealed and allowing fuel to get by the rings.". That's all the information I have so far (I've gone back with some more questions and am waiting on answers). Anyone have any thoughts on this reading? How concerned would you be/should I be? Is it common given the age/hours? Is it something that would cause you to walk away from the boat, or something that you would still buy the boat with (but then have some specific checks/work done, and if so what exactly would you ask the mechanics to do?)? etc. etc.
High fuel dilution reading in oil sample on a Cummins QSM11 (w/288 hours)
- Thread starter jff
- Start date
- Oct 12, 2006
- 1,974
- Boat Info
- "On Vacation"
2006 40 Sundancer
Raymarine E125 & HD Radar + Garmin 5208
- Engines
- QSB5.9 380 Cummins
Sounds like something to be concerned about. My QSBs came in at less than .5% with an acceptable range going up to 2.5%. Hours are around 200. What is the acceptable range for the QSMs? (I suspect it is the same 2.5% value?)
Also, I'd be wondering if the PO added anything to the oil? Some of the oil additives out there (eg SeaFoam) could cause the fuel dilution number to bump up a bit due to the chemical composition of the additive.
Also, I'd be wondering if the PO added anything to the oil? Some of the oil additives out there (eg SeaFoam) could cause the fuel dilution number to bump up a bit due to the chemical composition of the additive.
SkippersList.com
New Member
- Dec 22, 2012
- 32
- Boat Info
- 1980 SeaRay Express Cruiser SRV 360
- Engines
- Twin 3208s - Turbo Charged
You could request a pressure test on the engine to determine if it is a ring or valve seating issue ... I would first take the sample report to a CERTIFIED CUMMINs mechanic and get their input. You could then present the information to the seller and determine the next step ... if any.
It COULD be that the break-in is still in progress ... some engines aren't considered broken in till they have 500/hrs on them (no clue what Cummins break-in is), the fun in getting to break them in is some manufacturers want you to avoid running the engine at a set RPM for any extended length of time ... if it is a break in-issue get the details from Cummins on their suggested break-in process.
Hope it works out in your favor!
It COULD be that the break-in is still in progress ... some engines aren't considered broken in till they have 500/hrs on them (no clue what Cummins break-in is), the fun in getting to break them in is some manufacturers want you to avoid running the engine at a set RPM for any extended length of time ... if it is a break in-issue get the details from Cummins on their suggested break-in process.
Hope it works out in your favor!
Thanks all. After much discussion with various Cummins techs I think it's fine. The fuel in there wasn't exactly new (it's since been run through and new fuel is in the tanks), the boat had likely been idled excessively recently and the engines need a full service - but they are operating perfectly overall. Cummins is pretty convinced with new fuel, running the boat and a full service this issue will disappear. It was also important to note (sorry, forgot to mention this above) that the viscosity readings were normal, that's a good sign. If there was really bad dilution the viscosity would be impacted.
- Oct 6, 2006
- 12,155
- Boat Info
- 1996 450DA
- Engines
- 3116 Caterpillars
I know this is going to be a long answer, so bear with me............
High fuel dilution is a problem. I seriously doubt the ring seating theory on engines run under load for 288 hours. If they were going to seat, they would have by now. If they aren't seated, then you probably have other problems going on like low compression that I would think would show up with high iron and chrome from ring and liner wear or from lube oil components like molybdenum, antimony, magnesium or barium. I suspect the high fuel dilution reading are coming from an injector problem or an internal fuel leak. On electronic engines, the fuel is charged with pressure in the rail then dispersed by the injectors. Injectors are supposed to atomize fuel; if one sprays droplets rather than a mist, then you can get unburned fuel due to incomplete combustion of the droplets. Low fuel pressure could also be the cause. A piece of carbon on an injector tip can interrupt the atomization and yield droplets instead. Unfortunately, there could be other issues now if this incomplete combustion process has been allowed to persist. Unburned fuel will run down the cylinder wall and drip into the oil pan. The fuel running down the cylinder washes the lube oil off the liner wall so there may be cylinder liner and ring wear by now. The course of action from here isn't clear and won't be until you get an experienced mechanic to properly diagnose the problem and its solution can be anywhere from a few hundred $ for pulling the injectors and bench testing/cleaning them all the way to many thousand $ if there is low fuel pressure or cylinder wear.
Fuel dilution should be less than 2% on Cummins engines, so 5.5% is at a critical level or requiring immediate remedial action. However, the test for fuel dilution is by weight, is not very precise and can have a ±3.5% tolerance. This is one of those areas that highlights the importance or regular sampling and trending of results. If this were a boat you have owned for several years and did regular sampling and found 1 high fuel dilution reading, you might change the oil and run it for another 25 hours then resample before going further, but that isn't the case here.
What approach to take here gets complicated:
A.) You can require the seller to have Cummins repair the engines and then run the boat after the repair and resample...but there are risks with doing this:
1.) they just change the oil run it at the dock and have you resample and you can't tell what was really done.
2.) you do not know if the problem was properly diagnosed in the first place.
B) You can get a Cummins estimate on doing what they suggest to diagnose the problem then agree with the seller on some form of splitting the cost for an accurate diagnosis where you pay some of the cost if the results turn out to be favorable or none of the cost if you reject the boat and walk away.
C.) You can reject the boat as it is and cut your loss and exposure to the unknown future risk.
A fluids analyses with high readings poses some tricky questions and can easily cause a buyer to take some risks he might not otherwise take. In this case, I don't think the seller is hiding anything, or he would have changed the oil before putting the boat on the market, however, something is amiss here and it may be nothing more than a boat that has never has an oil change since new (although the other oil sample results would probably show that in high soot/combustion by products) all the way up to a washed out cylinder that needs a rebuild ...a very expensive process on a sedan bridge.
Good luck with whatever you decide
High fuel dilution is a problem. I seriously doubt the ring seating theory on engines run under load for 288 hours. If they were going to seat, they would have by now. If they aren't seated, then you probably have other problems going on like low compression that I would think would show up with high iron and chrome from ring and liner wear or from lube oil components like molybdenum, antimony, magnesium or barium. I suspect the high fuel dilution reading are coming from an injector problem or an internal fuel leak. On electronic engines, the fuel is charged with pressure in the rail then dispersed by the injectors. Injectors are supposed to atomize fuel; if one sprays droplets rather than a mist, then you can get unburned fuel due to incomplete combustion of the droplets. Low fuel pressure could also be the cause. A piece of carbon on an injector tip can interrupt the atomization and yield droplets instead. Unfortunately, there could be other issues now if this incomplete combustion process has been allowed to persist. Unburned fuel will run down the cylinder wall and drip into the oil pan. The fuel running down the cylinder washes the lube oil off the liner wall so there may be cylinder liner and ring wear by now. The course of action from here isn't clear and won't be until you get an experienced mechanic to properly diagnose the problem and its solution can be anywhere from a few hundred $ for pulling the injectors and bench testing/cleaning them all the way to many thousand $ if there is low fuel pressure or cylinder wear.
Fuel dilution should be less than 2% on Cummins engines, so 5.5% is at a critical level or requiring immediate remedial action. However, the test for fuel dilution is by weight, is not very precise and can have a ±3.5% tolerance. This is one of those areas that highlights the importance or regular sampling and trending of results. If this were a boat you have owned for several years and did regular sampling and found 1 high fuel dilution reading, you might change the oil and run it for another 25 hours then resample before going further, but that isn't the case here.
What approach to take here gets complicated:
A.) You can require the seller to have Cummins repair the engines and then run the boat after the repair and resample...but there are risks with doing this:
1.) they just change the oil run it at the dock and have you resample and you can't tell what was really done.
2.) you do not know if the problem was properly diagnosed in the first place.
B) You can get a Cummins estimate on doing what they suggest to diagnose the problem then agree with the seller on some form of splitting the cost for an accurate diagnosis where you pay some of the cost if the results turn out to be favorable or none of the cost if you reject the boat and walk away.
C.) You can reject the boat as it is and cut your loss and exposure to the unknown future risk.
A fluids analyses with high readings poses some tricky questions and can easily cause a buyer to take some risks he might not otherwise take. In this case, I don't think the seller is hiding anything, or he would have changed the oil before putting the boat on the market, however, something is amiss here and it may be nothing more than a boat that has never has an oil change since new (although the other oil sample results would probably show that in high soot/combustion by products) all the way up to a washed out cylinder that needs a rebuild ...a very expensive process on a sedan bridge.
Good luck with whatever you decide
Thanks Frank - good information. Sadly I don't think the oil ever has been changed, but we don't have records to show that one way or another. I'll continue to discuss with Cummins. On a side note, interestingly we found a similar reading in the generator - could it not be related to the old fuel that was in the boat (and/or maybe neither gen or engines has ever had an oil change) since we're seeing this on two 'engines'?
Regards,
Jason
Regards,
Jason
- Oct 6, 2006
- 12,155
- Boat Info
- 1996 450DA
- Engines
- 3116 Caterpillars
For the fuel to get into t he oil, it has to get past the rings. I don't see how the age of the fuel can cause that. real, Real old fuel may not burn thoroughly and might cause it, but you would see blue smoke like a locomotive if that were the case. I don't know the circumstances, but if you can require an oil chance and get some run time on the engines and generator then re-sample, you might see that there isn't a problem at all.
As a data point, I have done regular oil sampling on QSM-11's starting at 400 hours when I aquired the boat. Both engines showed very similiar results with either negative or less than 1% fuel dilution on oil sampled every year with approximately 90 hours on each oil sample.
I diddo Franks comments (at least I didn't have to retype the essay!)
There may be something with the old fuel / excessive idle conditions. As Frank said, best situation is to have a history of oil samples to make an informed descision, but in this case, its a tough one.
I diddo Franks comments (at least I didn't have to retype the essay!)
There may be something with the old fuel / excessive idle conditions. As Frank said, best situation is to have a history of oil samples to make an informed descision, but in this case, its a tough one.
