Diesel in crankcase Cummins 555

Hi all,
I have discovered a serious amount of diesel in the crank case of my VT555m.
I drained the oil and it was very diluted. I also drained around 7 litres of diesel that was floating on top of the oil.
Any ideas ?
I’m thinking an injector

At least 7 liters of diesel in the crankcase is a huge amount. The engine should have been smoking like a coal fired freight train.

Yes bad injectors or injection pump could be the cause or a piston with a hole in it.

David

Thanks David,
Most of the diesel appeared to be floating on the oil.
I’m thinking the leak continued after I shut it down

I think the possible sources of the leak will be very engine-specific. For example, many engines have parts of the fuel path running through parts of the head, and various piping inside the valve covers. Any of that could be the source. I'd post on SBMAR's forum which specializes in Cummins to get advice specific to the 555. And if you have a manual, you could sort out the fuel path and start inspecting it. If it's easy to do, perhaps pull the valve covers to see if any areas have been obviously washed with diesel. And even run the engine with the valve covers off and look for leaks.

One of the most common sources of fuel in the oil is a failed seal in the lift pump (not the injector pump). That engine should have a mechanical lift pump. Usually, if the engine is still running normally, it's most likely the lift pump and not the injector pump.

Ted

OC Diver is correct. I forgot about the fuel pump being a likely cause.

David

I recall reading a post somewhere about a similar issue with a 555. Turns out the fuel delivery on a 555 is not typical like a 6BT and there is a situation where it's possible for an injector to fail open with the rack in a certain position and if you have a gravity fed tank it can fill the cylinder/crankcase. If I can recall where I read it I'll put up a post.

EDIT: It was a 903, but believe they have similar fueling systems.

The 555 has a PT (Pressure-Time) injection system with a pump supplying a variable pressure, and individual unit injectors setting the time. It is very different from the more modern Cummins, with many opportunities for fuel leakage into the engine oil.
The shaft seal on the PT pump is one possibility. The fuel supply and return to/from each injector is via drilled passages in the head sealed by O-rings on the injector body. These O-rings are the most likely source. If the fuel level in the tank is above the top of the engine all of these can leak when the engine is shut down.
I would start by taking the rocker covers off to look to look for signs of leakage as twistedtree suggests. Since the fuel sat on top of the oil it is obviously leaking when the engine is shut down!
Bill

Thanks Guys,
Took the covers off and found a broken injector push rod. I’m tipping this caused the fuel.
I find it unusual that I never heard anything, engine was running fine.
I took the injector out and it looks ok.
I thought that if it had seized that might have caused the broken rod.

That's definitely a problem, but any idea why it would have caused fuel to dump into the crankcase? It's likely the dots connect, but I'm not seeing it.

The only thing that can apply enough force to the injector push rod to bend and break it is the injector. It may look OK but I suspect it is not!

That’s what I’m praying for !
I cut the oil filter open and it was clean as a whistle.

Liambennett said:

Thanks Guys,
Took the covers off and found a broken injector push rod. I’m tipping this caused the fuel.
I find it unusual that I never heard anything, engine was running fine.
I took the injector out and it looks ok.
I thought that if it had seized that might have caused the broken rod.

Click to expand...

I can't imagine how the engine sounded normal with a broken push rod. Missing on one cylinder usually makes a big difference in the sound.

Hope it's just an injector and a push rod.

Ted

Here goes again. This engine is quite different from most diesel engines. THe PT pump does NOT produce the pressure to operate the injectors. There are three rocker arms, one larger central, one to operate the injector, two to operate the valves. All operated by the cam shaft.

I will warn you to get the manual , owners, which covers the adjustments of the valves AND the injectors and they need to be done in order, not helter skelter like most engines. Failure to observe this caution will cause even more damage as one fellow discovered some years ago onB.D..

Go to BOAT DIESEL and look up the owners manual of which there are now a few posted and follow them which is a change from when I posted mine about 20 yrs ago. READ IT. Take the time to understand them.

I pulled all my injectors '2019 due to a fuel leak which triggered an alarm at the oil test lab. Not hard but time consuming. The O rings were failing and fell apart at the rebuild shop.

You can contact me through this forum or Boatdiesel.
I am no expert as I am just an owner but there are some caveats to be paid attention to.

Yes, contact Seaboard Marine, run and owned by Tony Athens, but be prepared for little help as he wants nothing to do with these engines any longer., that's my impression.

I would pull all the injectors and get them gone over completely. Pull the PT pump also and get it rebuilt. I was told mine was showing signs of internal wear and had it not gone in at that time it would have suffered enough damage as to be a toss away and a replacement was north of $5000. As it was the price was about 2,000.

My engine , a 1976, has about 7,000 hrs and still runs well after the injector work.