Isl blowing fuel out of slobber tube

[heybc]

I have a 2004 Dutchstar with the Cummins ISL 370. It has started blowing excessive amounts of fuel/carbon out of the slobber tube. Went 70 miles up I-5 from San Diego on Monday with no problems. Today we headed up I-15 through Riverside and across on I-10 to Arizona. When we stopped the toad and the back of the motorhome were covered with diesel spray. It was obvious that it came out of the slobber tube. Any thing I can look for before I take it somewhere.

Thanks

[tylerdmoore]

Ohhh boy! Excessive crank case pressure is what you seeing if it's coming from the vent tube. This can be caused by multiple things...none of them good. Typically a burnt piston or broken rings is the culprit. You should notice a loss of power associated with both of these. Often the motor will still feel smooth though with little audible change.

The fact that you say the rig was covered in fuel is odd though. The majority of what you see should be dark like oil...it may smells like fuel though as much of the bad cylinders fuel is bypassing the piston into the crank case before being expelled out the vent tube.

This is definitely something that needs to be professionally addressed before you run the engine much more. A single cylinder overhaul is far cheaper than a destroyed engine.

[Smitty77]

Any recent oil changes or added oil? If so, could be oil settling back to normal level?

Please let us know root cause - and best of luck!
Smitty
(Also with the 04 ISL 370)

[sc3283]

overfull oil level due to too much oil or a fuel injection problem pouring too much fuel into the engine...both could create excess blow by

[Mr_D]

Quote:

Originally Posted by Smitty77 Any recent oil changes or added oil? If so, could be oil settling back to normal level? Please let us know root cause - and best of luck! Smitty (Also with the 04 ISL 370)

Yep, a real possibility.
If I fill the crankcase to the full mark our ISC will throw oil out till it gets down to about ½ way between the full and add. Now I just fill it to that point and the toad doesn't get covered in oil!

[spike45]

Quote:

Originally Posted by heybc I have a 2004 Dutchstar with the Cummins ISL 370. It has started blowing excessive amounts of fuel/carbon out of the slobber tube. Went 70 miles up I-5 from San Diego on Monday with no problems. Today we headed up I-15 through Riverside and across on I-10 to Arizona. When we stopped the toad and the back of the motorhome were covered with diesel spray. It was obvious that it came out of the slobber tube. Any thing I can look for before I take it somewhere. Thanks

You did not mention any misfiring or other rough running. I doubt that you have any issues as some have said. Blowby gases normally consist of oil vapor. The ISL crankcase breather on that vintage engine is not at all good at separating oil vapor from the air. It easily gets overwhelmed resulting in much liquid oil carryover into the tube. You can research this forum and find where many have added a longer tube and a catch bottle to capture the liquid oil and allow the blowby gas volume to escape. The fuel part is troubling but, again, you did not mention misfiring or running rough which should rule out injector failure. It does sound like this occurrence is new and not a situation that got worse.

This not one of those times to delay taking it to Cummins. If you are in Arizona, take it to Cummins Rocky Mountain in Avondale (west Phoenix suburb). If still in Southern California, you are limited to Cummins Cal Pacific in El Cajon.

Spike45
Retired Cummins engineer

[heybc]

Have a Mon morning appt at Cummins Rocky Mtn in Avondale. It is not smoking, and no decrease in acceleration or rough running. We were passing the trucks climbing the grades from Riverside. Talked to Cummins and they thought rings or fuel pump. I guess I better hold on tight to my wallet when we get there.

[Gary RVRoamer]

My 2004 ISL 370 began pushing sooty oil out of the oil filler tube 18 months ago. Blew the filler tube cap right off and sprayed yucky oil back onto the toad and rear of coach. As a last resort before heading to Cummins, I changed the oil and filter. Problem ceased and never came back (any my wallet breathed a huge sigh of relief).

Try it - maybe you will be lucky too.

[MJFZ]

If the oil level seems to be increasing, it could be a stuck or slow fuel injector. As the fuel washes past the rings, it thins the oil promoting vaporization that exhausts through the breather (slober) tube.

Mike

[heybc]

Been sitting all day at Cummins Rocky Mountain near Phoenix. Turned out to be a fuel pump issue. Fuel leaking into crankcase diluting the oil and then excess going out the slobber tube. Going to leave a couple of grand lighter in the wallet, but not as bad as I feared.

Thanks for the replies.