My lube oil has fuel in it

[myaticj51]

My Yanmar 3GM engine only has 142 hours on it. The engine started knocking and blowing smoke yesterday so I got a tow. We checked a number of things and when I pulled the oil dip stick oil gushed out and is very thin. The next day we pumped out over seven qts.; should have been less than three! It is thin and most certainly has diesel fuel in it. My mechanic thinks a faulty injector pump or a bad injector though he said these are rare occurrences and he seems unsure. I am on a freshwater lake without much of choice in mechanics. Any thoughts as the source of my problem?

[Vasco]

Either the diaphragm from the lift pump or the injector pump is leaking. If you're lucky it might only be the lift pump.

[JimsCAL]

I agree with Vasco - probably seals in either the low pressure pump or the high pressure injection pump. A bad injector would not put that much fuel in the crankcase without serious running problems.

[timebandit]

I would replace the lift pump first and if that does not solve the problem you will at least have a spair if it is not it.

Move to more dificult problems next.

[myaticj51]

More evidence; contaminated oil continued to rise overnight without running the engine. the diesel tank is mounted high so I understand that gravity could move the oil. I have ordered a new lift pump and hope to install it before the weekend.

thanks

[donradclife]

If the oil is leaking through while the engine is sitting, its most likely to be a broken diaphragm in the lift pump.

[myaticj51]

the new pump arrived and was installed yesterday. We will determine today if any fuel is still getting in the crankcase. I did discover that in Southern Illinois where the boat came from that bio diesel is what most stations carry and I am sure that he was filling the boat from a plastic can for the marina up there might not have a diesel pump. Our marina at Stockton lake, MO does not cell bio and no one here has ever had a similar fuel problem from what I can tell. We are pumping out all old fuel and replacing all filters. thanks for the help!

[myaticj51]

The boat is fixed. The lift pump was replaced. The raycor and fuel filters (very clogged with varnish like sludge) have been cleaned and replaced, the fuel tank has been pumped of all bad fuel, and fuel lines were inspected for damage. The engine runs like a champ and fuel is no longer leaking into the crankcase. Lesson learned; beware of bad diesel and most likely biodiesel. I discovered that Illinois is the no. 1 consumer of biodiesel in the nation and the boat came from southern Illinois.

[Vasco]

Great. It's nice to know it wasn't the injector pump.