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Thread: Diesel in Engine oil

  1. #1
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    Default Diesel in Engine oil

    I have an AD41 that diesel fuel is getting into the engine oil, any ideas on where to start looking? I suspect my fuel pump because it started acting up at the same time.
    Thanks for any help.
    Mark

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    Lift pump or low pressure pump if you have a mechanical unit or the high pressure injector pump. Always the first suspect

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    dribbling injector or rings are getting sloppy. Try looking on BoatDiesel.com might cost a membership but tons of info on those and all diesels on there. Fuel pump/lift pump supplies fuel to injection pump so i'd doubt it has anything to due with fuel in oil. I'd say your problem starts at the injectors and goes downstream from there. You might try calling http://mcdonnellmarine.com/ they are very knowledgeable on the 41's, long way away from here but a good source of info. I've heard to many nightmare stories with the shops around here so don't have a referral for ya. How many hours and what series(letter) is that 41 ?? How much oil is it making ??

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    I second Potbuilder on this as lift pumps supply to the injector pump, there is not a direct channel to the oil from there unless there is a crack in the pump housing. Compression test the cylinders would be where I would start.

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    Quote Originally Posted by screwcutter View Post
    I have an AD41 that diesel fuel is getting into the engine oil, any ideas on where to start looking? I suspect my fuel pump because it started acting up at the same time.
    Thanks for any help.
    Mark
    Cavitation from the diesel engine can bore tiny hole in the cylinder walls. That maybe the cause.

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    Third on what potbuild said.
    Blowby on the rings, or injector over supplying fuel, i have seen this quite a bit with over the road engines that idle for long periods.
    Really only reasons i know of for a motor to make oil. (diesel in oil)

    just my 2 cents
    Mike

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    Quote Originally Posted by Armed_alaskan View Post
    Cavitation from the diesel engine can bore tiny hole in the cylinder walls. That maybe the cause.

    then you'll get coolant in the oil.

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    Potbuilder,
    It is an AD41P-A with 400 hrs, it is making about a quart an hour. I havenot noticed any performance issues other than some smoking at cold idle.
    thank you for any help
    Mark

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    Quote Originally Posted by screwcutter View Post
    Potbuilder,
    It is an AD41P-A with 400 hrs, it is making about a quart an hour. I havenot noticed any performance issues other than some smoking at cold idle.
    thank you for any help
    Mark

    WOW sounds serious to me.

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    If the smoke is blueish at cold idle it is most likely stuck open injector/s and overloading what the cylinder/s and burn-- creating blowby. if you can get to where you can smell the smoke it will smell like fuel.
    If the smoke is white, rings are most likley the culprit because smoke will be mostly oil.

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    forgot to mention, though diesel is the lubricant for your fuel pumps-- it will dilute your engine oil and cause lots o damage with continued use.

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    Not familiar with Volvo diesels, having been an aircraft mechanic/pilot all my life and now retired...but I'll bet the yet unmentioned source of your engine "making oil" is coming from your Fuel/Oil heater! Most diesels have such a beast, with the benefits under normal operation being twofold. Both engine oil and fuel are pumped through a heat exchanger unit of some type, with incoming fuel heated by hot engine oil and the fuel also helping to cool engine oil temps. This is the one place on an engine where both fluids are being used in the same unit and the cause of likely 90% of cross contamination issues. Im not much of a gambler, but "ll bet on this one". Hope this helps and good luck.

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    Quote Originally Posted by HCL View Post
    Third on what potbuild said.
    Blowby on the rings, or injector over supplying fuel, i have seen this quite a bit with over the road engines that idle for long periods.
    Really only reasons i know of for a motor to make oil. (diesel in oil)

    just my 2 cents
    Mike
    Long periods of idle causes Wet stacking and the excess just goes to the exhaust system.

    Other possible problem is that the injectors or an injector is dripping fuel and is not functioning correctly and allowing fuel to go into the sump through the bores past the piston, this can usually be seen when you first start the engine after its sitting idle overnight, the engine blows out an excessive cloud of black smoke through the exhaust.

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    At a quart and hour i'd think its more than a dribbling injector. The engine only holds about 4 gallons of oil if i remember correctly. I wonder if the tip or tips of some of the injectors is blown off ??? A buddies 41 had springs inside the injection pump let go and the engine wouldn't idle then just died then took off, it was interesting getting him docked to say the least. Cure was a new pump for a mere couple of grand plus.
    There is a oil cooler by the filter if a remember right but i don't know what cools it ?
    Volvo in all their wisdom made the P engines without any zincs on the engines so anyplace you have a raw water to oil ,air,fuel cooler the cores will eat up quickly without the protection of a zinc. $$$$ for volvo selling you parts.

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    Try this with a stone cold engine
    Engine at idle cold in neutral take off the oil filler cap and put the palm of your hand over filler hole tight. "Feel" for any significant pulsation (cheap and easy blowby test). Also look for visible "smokey vapor" coming out of the filler hole. You may feel a little pulsation and the engine should not be smoking.

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    Sorry to dig up an old thread, I figured you all gave me advice, I should let you know what happened. As I suspected the fuel pump I took it off and put it in the vise, hooked up fuel and pumped, was getting wet on the wrong side. I could not pump as fast as the engine goes by hand, so it wasn't pouring out, so I replaced the pump. While I was testing/working on it I had my injectors tested and one was dribbling fuel. Now my oil level stays where it should. Thanks again for the help.
    Mark

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