Universal M-18 engine in my CD30

[samgoucher]

Well, my Universal M-18 has decided to start spitting diesel blow by from the exhaust at anything above 2,200 rpm. RPM's will not advance past 2,400 no matter how much throttle input. I used to see blow by @ 2,600-2,700 rpm but could still advance the rpm's to 2,900-3,000. Could this be something simple like an injector, or am I looking at something much more involved like a rebuild? Still learning, so anyone's expertise in diesel power is appreciated.

[sgbernd]

You probably already thought of this but I would start at the exhaust mixing elbow and make sure it is not constricted with rust and salt. If the engine runs fine at low rpms but struggles at high rpms, it may be that simple.

After that, the possibilities get much more expensive (like bad rings, glazed walls, poor compression, etc).

In my experience, bad injectors don't atomize the fuel so well so the engine smokes a lot and may have trouble cold starting, but otherwise they still run pretty well under load. I could imagine one so bad that instead of a nice spray, it is just dripping but can't imagine that would be easy to get started, especially when cold.

Steve Bernd

[gonesail]

from my experience you would see white smoke and steam if the mixing elbow was clogged .. but then again your problem with higher RPM could be indicative of restricted exhaust flow.

[Boyd]

There are other possibilities:

A fouled prop which is putting too much load on the engine. This causes my MD 2020Ds to exhibit similar symptoms, but not the oil slick.

The engine is and has been running too cold for a while. This causes soot to buildup on the injectors, piston rings, and will eventually lead to a rebuild. An IR non contact thermometer will show this.

Something that is probably not a cause, but good to do anyway is replace all filters and verify you dont have a fuel supply issue.

While your busy changing filters, you can try is putting a load of fuel injector cleaner thru the engine...eg. Seafoam. Fill the entire secondary filter with it and run a while. It will smoke like crazy.

Rebuild and or replace the injectors. Verify that the above issues with engine temp have been cleared up.

Run a compression test. that will tell you if you have ring or valve problems. Also check the valve lash. If you dont have enough, it will limit power output.

An exhaust restriction is a possibility and easy to check.

Boyd Bundy
S/V Cat-a-tonic
Prout catamaran
Fort Lauderdale, Fla.

[Kickin Bears]

I second doing a fuel system run through first, as listed below, with the addition of:

- clean your air intake filter (on the volvo this consists of taking the filter off, soaking in diesel, the blowing out with compressed air ... multiple times if necessary).

Adding some performance fuel treatment to the tank wouldn’t hurt either.

I’d start with the simple stuff first. i.e. filters, fuel additives, fuel system cleaners ... for blow by would get to cylinders next for inspection .... then injectors if cylinder’s aren’t root cause

There are other possibilities:

A fouled prop which is putting too much load on the engine. This causes my MD 2020Ds to exhibit similar symptoms, but not the oil slick.

The engine is and has been running too cold for a while. This causes soot to buildup on the injectors, piston rings, and will eventually lead to a rebuild. An IR non contact thermometer will show this.

Something that is probably not a cause, but good to do anyway is replace all filters and verify you dont have a fuel supply issue.

While your busy changing filters, you can try is putting a load of fuel injector cleaner thru the engine...eg. Seafoam. Fill the entire secondary filter with it and run a while. It will smoke like crazy.

Rebuild and or replace the injectors. Verify that the above issues with engine temp have been cleared up.

Run a compression test. that will tell you if you have ring or valve problems. Also check the valve lash. If you dont have enough, it will limit power output.

An exhaust restriction is a possibility and easy to check.

Boyd Bundy
S/V Cat-a-tonic
Prout catamaran
Fort Lauderdale, Fla.

[Boyd]

Something I forgot earlier:

You can check the intake valves for leaks easily. Pull the air cleaner and pull the fuel shut off. Rotate the engine by turning the crank pully. Listen carefully at the same time at the air intake...if you hear hissing... you may have leaking intake valves.

On one of my previous engines, the #3 exhaust valve was in bad shape and causing a major loss of compression. The engine is typically mounted at an angle and since #3 cylinder is at the low end, steam from the injection elbow after the engine is shut off causes corrosion. A head rebuild is not all that hard to do. Just pull the head and send it to a head shop for repair. Been there done that.

Hope its something simple.

Boyd
S/V Cat-a-tonic
Prout 34
Fort Lauderdale

[samgoucher]

Thanks for all the input. Pulled the exhaust riser and mixing elbow. All clear. Further investigation reveals a engine temp issue and I will be removing the heat exchanger for inspection and cleanout. Will address a couple of questions on that in a new post.