6v92 tad 1990

[Rogerh]

When I brought her down off of cruise running about 2000 RPM two things happened. She only dropped to about 1200 RPM and she started pushing out alot of black smoke. Got her down to 800 RPM and tried to shut her down but she would not shut down. I used the emergency stop which closes air to the air box and this shut her down. No obvious signs, fluids all looked good. Temp was about 175 when this happened.
First question is should I try to start her back up, after opening the air box lever?
Any ideas where to start?
I am fairly handy but will go the mechanic route if it is out of some relatively basic task.
Thanks for your input......

 

[FF]

Any ideas where to start?

You will need to remove the valve covers and watch the rack on both sides. Sounds like a stuck injector .Open and close the throttle and watch for identical movement .

Some can be freed by simply moving the injector , it comes from sitting a bunch with out either using storage oil in the fuel system (in Da Book) , or at least moving the throttle open/closed once a week.

Second choice is water in the fuel that blew an injector tip.

At about $40 each rebuilt it might be time for 8 rebuilts.

The air shut off is always risky , depending on the RPM it can suck the seals out of the blower.

A good mechanic will have the REQUIRED tool to set injector height and know how to run the rack (all injectors fuel the same) ASK QUESTIONS , the folks that can make a DD sweet are getting older.

 

[Rogerh]

generally we use her at least two times or more a month. We may have not used her for three or four weeks this time. Good info about moving the throttle once a week. Hopefully the seal is OK since I was able to get her down to 800 RPM by quick throttle up and down several times. I did check the throttle linkage and it is working fine. Will look into the injectors. Sounds like that might be what happened. Does black smoke in this instance mean to much fuel? IE pointing to the injector stuck open?

 

[Scary]

Usually too much fuel

generally we use her at least two times or more a month. We may have not used her for three or four weeks this time. Good info about moving the throttle once a week. Hopefully the seal is OK since I was able to get her down to 800 RPM by quick throttle up and down several times. I did check the throttle linkage and it is working fine. Will look into the injectors. Sounds like that might be what happened. Does black smoke in this instance mean to much fuel? IE pointing to the injector stuck open?

Usually too much fuel. FF has good advice, the rack is tricky too adjust, it takes a learned feel to get everything balanced. I don't know how the throttle effects the opening or closing of the injectors as I believe they are cam driven via push rods and the rack. Correct me if I'm wrong. Running the engines once a week up to temperature is a good practice.

 

[Ski in NC]

Take rocker covers off and manually move the rack control tubes. Watch all six injector racks and see that they move smoothly in and out of the side of the injector. Probably will find one stuck or binding. If one binds, governor has to control racks against the spring of the stuck one, causing high or low idle.

 

[Francois]

Last summer, I got black smoke coming out from one of my 6V92 engines. I had develop a small exaust leak in the engine room (for a few months I estimate) which clothered my air filter. Black smoke no longer occurred once the leak was repaired and air filtered changed,

 

[kulas44]

IR gun will pin point a bad injector. Depending on type of exhaust manifold.

 

[River Cruiser]

IR gun will pin point a bad injector. Depending on type of exhaust manifold.

+1

 

[Rogerh]

Reporting back with what I found. Two injectors sticking pretty bad. Two others have spots that seem to stick a little. Replacing injectors and hopefully we will be back to running. Working with the mechanic and learning a lot. If this ever happens again I should be able to deal with it my self. Thanks for all your inputs!

 

[FF]

If this ever happens again I should be able to deal with it my self. Thanks for all your inputs!

Watch carefully when he adjusts valves and adjusts injector height.

Then watch REALLY carefully when he runs the rack on both sides.

BUY the correct injector height adjusting pin , and while at the DD shop you might consider the DD hand pump for finding leaks in a jumper strut.

For most its the easy way to prime the engine , should you run it out of fuel. About $85 or so.

It takes a good while to get it right , but when it is RIGHT! there is nothing like a DD on the pin!!