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I have ran by an issue that needs the expert advice from the members of this forum. A friend has a 3306B and it is mixing the engine oil into the fuel tanks and engine is missing bad what can cause this issue. I have seen fuel in oil and in coolant before but not oil in fuel. Thanks to all for your advice it will be highly appreciated.
 

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"Check o-rings, injectors and cups" sees to be the consensus.

1LEZ28 had this to say a while back:

"I was a mechanic at a CAT engine dealer for years. Is there fuel in the oil? Usually you get fuel in oil, and oil in fuel at the same time. If there is fuel in the oil also then I would put some dye in the fuel and run the engine(at operating temp) with the valve cover off. Use caution, and use a blacklight to verify any leaks from injector areas. Does the truck smoke white, blue, or any more issues?"

Other comments, same thread on a similar problem with a CAT 3126 are here:

http://www.thedieselgarage.com/forums/showthread.php?t=58763

Please post when you figure it out. Thank you.
 

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Since the 3306B is a mechanical inj the problem would have to be lift pump, or main pump related. maybe the lube return on the main pump got plugged. just the places that I would start to look
 

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I have work the 3306 for years and never saw oil in fuel.So i would say go back and look at it some more and see if its not just black fuel. Black fuel can come from a nozzle open. Some here is going to say it will not happen but i have see it a few times. The valve in the nozzle is stuck open due to what ever and the compression goes back thru the injector line into the injection pump back to the tank and yes it will miss.The injectors on this engine is out side of the head with no o/rings.
 

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Never heard of oil in fuel for 3306 engine, do a sample check to verify that oil is in the fuel, and if oil is in the fuel does you engine oil level drops.
I have worked at cat dealer and never heard of it, the manuals also don't mention such a probelm.
 

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the manuals also don't mention such a probelm.
There are many possibilities in the "troubleshooting guide" section of manuals that leave plenty of them out. LOL

Typically, the fuel will get in the oil, and not the other way around.

Black light and dye is one good test. I'd also pull a fuel sample from the fuel tanks, and send it to a lab.

I wouldn't rule out combustion gasses getting in from a bad injector.

Had a John Deere combine with a HPCR engine push combustion gasses into the fuel tank. Swelled the poly tank up so bad it bent steel and broke other stuff too. The injector hold down was upside down on #1, and the injector wasn't seated in the hole. Fuel tank vent couldn't relieve the pressure fast enough.
 

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I would have to add I can not ever remember seeing oil in the fuel in a 3306.
If you remove the primary filter and it has a black coating on the top that is carbon. you could make up an clear plastic extension on the return line and loop it around the mirror and take it for a drive looking for combustion gases.
The dye if you want to try that is part number from Cummins 3376891, you can add that to the oil and it does not hurt anything. That also would show up in the return line with a black light. I just use a standard flashlight it seams to work.
 

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What u find in thes problem ??
I have ran by an issue that needs the expert advice from the members of this forum. A friend has a 3306B and it is mixing the engine oil into the fuel tanks and engine is missing bad what can cause this issue. I have seen fuel in oil and in coolant before but not oil in fuel. Thanks to all for your advice it will be highly appreciated.
 
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