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Old 28-11-2011, 18:48   #1
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Diesel Fuel in Crankcase Oil

Hi Folks During survey today it was discovered that the crankcase had 1 gallon too much oil in it.The tect removed the excess ,smelling the removed oil it smelled of diesel,the surveyor had some type of field testing paper that indicated diesel in the oil.Upon advice from Yanmar we ran the engin up to 160 degrees shut down and in a sterile container drew some out for checking.The tect suspects the lift pump is back letting fuel pass into the engin oil.If this is the case has this harmed the engin,No one knows how long this has been going on no help from the now owner,The engin hour meater shows 2700 hours,Should I walk away now? Or wait for the oil check.The engin is a Yanmar 55 hp 4 cyl diesel new to the boat appx 6 yrs ago.I beleive its called a 4JH4E,Many thanks again
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Old 28-11-2011, 19:11   #2
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Re: Diesel fuel in Crankcase oil

They are tough engines.....and diesel is pretty slippery. Cure the leak, do a compression and leak-down test... If it passes forget it ever happened
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Old 28-11-2011, 19:23   #3
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Re: Diesel fuel in Crankcase oil

I concur....fix/replace the lift pump first.
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Old 28-11-2011, 21:05   #4
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Re: Diesel fuel in Crankcase oil

Quote:
Originally Posted by Chief Engineer View Post
I concur....fix/replace the lift pump first.
All of the above.
And change the oil, of course.

See the hole in the end of the shaft. That's where the diesel comes in. Replace the diaphragm and buy a spare (if you buy the boat).

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Old 28-11-2011, 21:45   #5
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Re: Diesel Fuel in Crankcase Oil

Here is a link to the same problem. I have not been able to track down the problem Yanmar Lift Pump
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Old 29-11-2011, 04:14   #6
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Lift pump bought it.
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Old 29-11-2011, 05:28   #7
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Re: Diesel Fuel in Crankcase Oil

Ok in my personal opinion do a professional compression test for there is a certain way of doing it and just to tell you this problem happend to us with the exact motor, it was actually the seal from the fuel injection pump that was shot. We did replace the lift pump first but did not solve the problem. Next we checked the orings of the injectors and all ok next the injector pump. If you are happy with the rest of the boat, just nock off 1000$ or a little more, anyhow you are probably going to have to some work on motor in some time as we all do, better get to know your motor know will pay off in the future. And get a mechanic to check it, not a surveyor!!!! The motor that is. And to check the internet for info, your problem is actually called (oil Dilution)
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Old 29-11-2011, 05:33   #8
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Re: Diesel Fuel in Crankcase Oil

As the lift pump is mechanical, therefore creating a direct connection between fuel and lubricating oil through the diaphram, this is not an uncommon issue. We carry a spare. Replace the mechanical pump as bypassing it will make it difficult to manually prime your engine in an emergency situation. Add an electric fuel pump and install it ahead of the mechanical and prefilters. This will give you the added feature of polishing your fuel while the engine is operating.
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Old 29-11-2011, 09:07   #9
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Re: Diesel Fuel in Crankcase Oil

Raphaella:

Did you take the injector pump out yourself. If so can you share the procedure? I have to track down the exact source of my problem but I have replaced the lift pump and have not run it hard enough to tell whether or not it is the lift pump.
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Old 29-11-2011, 10:07   #10
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Re: Diesel Fuel in Crankcase Oil

As in the other thread post #16, there is a direct link between the injection pump and lube oil thru the lube line. If the pump piston seals are leaking, the fuel goes right into the same cavity as the lift pump and then back into the lube system and make oil just as if it were the lift pump.


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Old 29-11-2011, 10:47   #11
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Re: Diesel Fuel in Crankcase Oil

One more thing. To test a lift pump; remove the pump from the block, leaving the fuel lines attached, then hand pump the cam follower lever. Some pumps have manual levers on the external side to help bleed the system, if so use the manual external lever. Pump the lever until the system is fully pressurized and look for fuel leakage from the backside of the pump, where the cam follower lever is.

This will tell you one way or another.
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Old 29-11-2011, 11:36   #12
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Re: Diesel Fuel in Crankcase Oil

DEER has a study and came up with some motor piston blowby dilution results. >>>
http://www1.eere.energy.gov/vehicles...jundaswamy.pdf

And some more info;

Quote:
Fuel Dilution
Frequent starts of an engine, excessive idling and cold running conditions can lead to moderate fuel dilution problems. Severe dilution (excess of two percent) is associated with leakage, fuel injector problems and impaired combustion efficiency. These are symptomatic of serious conditions that cannot be corrected by an oil change. According to one reference, 0.36 percent of total fuel consumption ends up in the crankcase. Problems associated with fuel dilution include:
Diesel fuel dilution in cold operating conditions can cause waxing. During startup, this can result in low oil pressure and starvation conditions.
Diesel fuel carries unsaturated aromatic molecules into the motor oil which are pro-oxidants. This can result in a premature loss of base number (loss of corrosion protection) and oxidative thickening of the motor oil, causing deposits and mild starvation.
Fuel dilution can drop the viscosity of a motor oil from say, a 15W40 to a 5W20. This collapses critical oil film thicknesses, resulting in premature combustion zone wear (piston, rings and liner) and crankcase bearing wear.
Fuel dilution from defective injectors commonly causes wash-down of oil on cylinder liners which accelerates ring, piston and cylinder wear. It also causes high blow-by conditions and increased oil consumption (reverse blow-by).
Severe fuel dilution dilutes the concentration of oil additives and hence, diluting their effectiveness.
Fuel dilution by biodiesel may result in higher than normal problems compared to diesel refined by crude stock. These problems include oxidation stability, filter plugging issues, deposit formation and volatility resulting in crankcase accumulations.
Soot
Soot is a by-product of combustion and exists in all in-service diesel engine motor oils. It reaches the engine by various means of blow-by during engine operation. While the presence of soot is normal and expected for a given number of miles or hours of service on an engine oil, the concentration and state of soot may be abnormal, signaling a problem with the engine and/or a need for an oil change. Following are some issues related to soot contamination:
Combustion efficiency is directly related to the soot generation rate. Poor ignition timing, restricted air filter and excessive ring clearance cause high soot load. Combustion problems are not solved by an oil change.
New diesel engines designed for lower emissions have higher injection pressures. This corresponds to increased sensitivity to abrasive wear (for example, from soot) between rocker, shaft and rocker bearing and can lead to rocker arm seizure. New exhaust gas recirculation (EGR) units on diesel engines amplify the amount and abrasivity of soot production.
Viscosity increases with soot load. However, high dispersancy associated with some modern engine oils may increase viscosity with soot even more. High viscosity corresponds to cold-start problems and risk of oil starvation.
Soot and sludge in engines deposit or separate from the oil in the following areas, all presenting risks to engine reliability including rocker boxes, valve covers, oil pans and head deck.
Deposits on engine surfaces interfere with combustion efficiency and fuel/oil economy.
Soot polishes off protective antiwear soap films in boundary zones such as cam and cam-follower zones.
Carbon jacking from the buildup of soot and sludge behind piston rings in grooves can cause rapid wear of rings and cylinder walls. This can cause broken or severely damaged rings during cold-start conditions.

Please reference this article as:
Jim Fitch, "Four Lethal Diesel Engine Oil Contaminants". Machinery Lubrication Magazine. May 2007
And Biodiesel adds another story to the book.>>> http://www.ufop.de/downloads/Kurzfas..._engl_0709.pdf
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Old 29-11-2011, 12:07   #13
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Re: Diesel Fuel in Crankcase Oil

Quote:
Originally Posted by delmarrey View Post
As in the other thread post #16, there is a direct link between the injection pump and lube oil thru the lube line. If the pump piston seals are leaking, the fuel goes right into the same cavity as the lift pump and then back into the lube system and make oil just as if it were the lift pump.


I will have to study this more. What I understand you saying is -- " an injector pump piston seal leak will cause diesel fuel to go through the lube line and into the lubricating oil system." Then you continue to say, "It will make oil just as if it were the lift pump" My question is -- If you bypass the lift pump so that it is no longer getting fuel from the tank, then connect the hose that leads from the lift pump to the secondary filter back to the intake port of the lift pump, and finally run an electric pump connected from the tank to the secondary filter on the engine will this prevent the injector pump from making oil. It will obviously prevent the lift pump from making oil but what I don't understand is will this prevent the injector pump with a bad seal from making oil?

I had isolated the lift pump and thought my problem was diagnosed. Replaced the lift pump and replumbed the hoses to their original configuration and thought my problem was resolved but since then I have not used the engine much. I run it at about 75% (2200 RPM) when I use it but I turn it off as soon as I can go sailing. It may run for ten minutes or it may be an hour. Last time I went sailing I ran it for two hours and it seems like the engine is making oil but not enough to be certain.

Because I am a little confused in reading this I will restate my question and hopefully you can understand one of the two ways I have asked the question -- If a leaking injection pump is the cause of making oil will isolating the lift pump from the fuel prevent the injector pump from making oil?
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Old 29-11-2011, 13:00   #14
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Re: Diesel Fuel in Crankcase Oil

Quote:
Originally Posted by Charlie View Post
I will have to study this more. What I understand you saying is -- " an injector pump piston seal leak will cause diesel fuel to go through the lube line and into the lubricating oil system." Then you continue to say, "It will make oil just as if it were the lift pump" My question is -- If you bypass the lift pump so that it is no longer getting fuel from the tank, then connect the hose that leads from the lift pump to the secondary filter back to the intake port of the lift pump, and finally run an electric pump connected from the tank to the secondary filter on the engine will this prevent the injector pump from making oil. It will obviously prevent the lift pump from making oil but what I don't understand is will this prevent the injector pump with a bad seal from making oil?

I had isolated the lift pump and thought my problem was diagnosed. Replaced the lift pump and replumbed the hoses to their original configuration and thought my problem was resolved but since then I have not used the engine much. I run it at about 75% (2200 RPM) when I use it but I turn it off as soon as I can go sailing. It may run for ten minutes or it may be an hour. Last time I went sailing I ran it for two hours and it seems like the engine is making oil but not enough to be certain.

Because I am a little confused in reading this I will restate my question and hopefully you can understand one of the two ways I have asked the question -- If a leaking injection pump is the cause of making oil will isolating the lift pump from the fuel prevent the injector pump from making oil?
I would say no!
The lift pump and the leaking seals in lower section of the injector pump occupy the same space. I suspect that the pressure from the leaking injection pump is forcing the fuel down the lube line and back into the oil system. That is the only way fuel can get from the lift/injection pump back into the crankcase, other then bypassing the cylinder piston rings. A compression check should indicate that.

The oil pressure is 100 PSI or less. The fuel pressure on a 4JH is around 3000+ psi. If the injection pump seals are leaking it's most likely forcing fuel back up the lube line.
If you pull off the lube line and there is fuel in it, there you go!


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Old 29-11-2011, 13:18   #15
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Re: Diesel Fuel in Crankcase Oil

Maybe these pictures will make better sense. The red arrow being the flow of the fuel.


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