Help: Cummins Diesels Fuel dripping from Air Cleaner-gctid820030

[TenMile]

Hey all,

At the start of a family trip and I seem to have an engine issue. I opened the bilge to find a layer of fuel in the bilge. Traced it out, and it appears to be leaking from the air cleaners on both engines. Starboard engine seems to be leaking more, but both are doing it. Engines are Cummins 4BTA 250HP by the way. Just did a long 5 hour trip (Victoria to Sunshine Coast) mostly at 2500 RPMs.

Engines are running fine. Pressure is consistent with both engines. No black or white smoke when running. I do have some diesel sheen on the water.

Anyone have experience here in what causes this issue and how to remedy?

[TenMile]

Found a very good article by Tony Athens describing the whole Crankcase Vent system. I have the Walker Air Seps. Might have the stuck valve issue he describes.

https://www.sbmar.com/product/enviro...bt-6bt-series/

[Bay39]

Interesting issue. Fuel in the bilge or exhaust is not something to mask or live with. Do you experience much more soot on the transom from the exhaust coupled with the un-burned fuel on the water aft of the boat or losing top-end RPM (sure symptom of loss of power)?

Easier suspects are injectors and injection pump (calibrate and rebuild).

Probably the best test would be a blow-by test which measures the amount of gas pressure in the crank case. If its off the scale? Either the valves are not seating properly or exhaust gas was blowing by the rings. This would require a valve job which is a comparatively easy fix. Have your mechanic check the cylinders for wear with a bore gauge. How many hours on the engines?

[Norton_Rider]

"TenMile" post=820037 wrote:
Found a very good article by Tony Athens describing the whole Crankcase Vent system. I have the Walker Air Seps. Might have the stuck valve issue he describes.

https://www.sbmar.com/product/enviro...bt-6bt-series/

I believe that it is coming from the crankcase vent, but that normally would result in engine oil leaking, not fuel. If what you are getting is indeed fuel, then somehow diesel is getting into the crankcase. Check the oil to see if it looks/smells like it is diluted with diesel. Also a rise in oil level indicates that fuel is making its way past the piston rings.

[p91473]

Yah, blow by does not make since. It would be oil. If you are 100% sure it's fuel, and it's coming from both engines via air cleaners, that's very strange. Maybe you have a fuel leak that's misting and being sucked into the intakes. Sounds more realistic then both engines having an issue at the same time. Maybe run her back up to 2500 under load to visually see what's going on.

[Shawnh]

I would get some oil diapers under your engines and around your bilge center and start by seeing where the drip is really coming from. Then using a clean white rag, run your rag along all your fuel lines to make sure you have a tight fuel system.

Getting both air cleaners to drip at the same time seems like you may have a diesel mist that your air cleaners are filtering out of your engine room while under way. (My guess) It might not show up without running your engines up to speed.

I just found a fuel leak coming from a fuel return line back to the tank on the starboard engine. It took 2 hours to find it. No oil in the bilge, but I could smell diesel in the cabin and really strong in the engine room. Even a slight weep will really smell up a boat.

Good luck finding it.

[TenMile]

Thanks for the help. It could be oil. The bit of liquid in the bilge is certainly black. There isn't much. Checked the air filters and the crap is certainly coming from there. Maybe 2-3 tablespoons per day. Boat has not done this before.

Should mention that injectors were new this fall (all 8) as my 4bta engines had the units with the potentially faulty tips. I did a valve job at the time about 100 hors ago. Engines have 1250 hours. No smoke or soot. Just the puke in the bilge.

[TenMile]

Ooh btw. The fuel return leak is a great idea. I had some issues with the banjo fittings leaking fuel when i redid the injectors. Will get out my 10 mm wrench and hit all 8 again.

[Shawnh]

If it is oil on your filters, you may do well with this kit:

https://www.sbmar.com/product/enviro...bt-6bt-series/

I have them on my 6bta's and have found they really cleaned up the oily film in my engine room. Not to mention, my oily air filters

[TenMile]

Found my issue. One of the injector feed line bolts had wiggled it's way loose on the port side engine cylinder #2. Was leaking fuel onto the engine, evaporating and getting sucked into the air intake, condensing and dripping out into the bilge. Finally caught it when I noticed one of the engines drop a few hundred RPMs suddenly. Had backed it's way to finger tight. Opened the hatch while running and could see the leak clearly.

Purchased 3 x fuel absorb logs and got them into the bilge. Gave the engines a good rinse with water and allowed them to evaporate off. Quick and easy fix. Thanks for the help.