Engine Possibly Running Rich?

[engineerj13]

Last weekend I was out with the family skiing and noticed the engine doing a slight surging or misfire when I was cruising in the mid to upper 30's. Yesterday I brought the boat to my house and hooked it up to the hose and ran it and didn't notice any surging or misfiring.However, I did notice while running the engine that it looked like fuel was coming out of the exhaust with the water (it was hard to tell if water or oil, but the color was close to clear and i could smell gas a little). Is it possible that a rich running engine would cause this or is there another cause to this happening. The engine was warmed up when this was happening (as well as while the engine was warming up). Has anyone else experienced this? Any ideas for a solution?

The boat is a '00 Ski 196 with the GT-40 engine with only 420 hrs.

[DanielC]

RE: Engine Possibly Running Rich?

I had to deal with a GT-40 in a 1998 Ski Nautique that wouls occasionally run rich. (black smoke, real rough running) I did have a fuel pressure gauge with me one time when this happened. The fuel pressure was normal. I then borrowed a mechanics stethoscope to listen to the injectors, but I did not have it with me at the time the engine was running rich. The problem was very intermittent, and I never did find the root cause of the engine running rich, it is running fine currently, and has for the last 25 or 30 hours.

Obviously, check the fuel pressure. Other possible causes are a ruptured diaphragm in the fuel pressure regulator, an injector stuck open, or the computer getting some wrong info from a bad sensor, causing the engine to run rich. There is probably other causes, but I cannot think of then right now.

Download the GT-40 service manual from this site.

[engineerj13]

So I took the boat out this morning and when I started it up I noticed gas in the water when I was idling. The gas was clearly coming out of the exhaust area. I put it in gear and did a very short cruise to raise the engine temp to see if it would go away. When I returned to idle it was still doing the same thing. I was wondering if it would be a bad injector so I took the spark plugs out and they all seems to be ok except for one that has a little more black color than the rest.

There was no black smoke when running or idling, but there is some white smoke at idle that I haven't noticed before. I will need to check the impeller for that.

Any thoughts?

[jasper]

This site might help on the one bad spark plug:

http://www.spark-plugs.co.uk/pages/t.../diagnosis.htm

[DanielC]

Good clues. The engine uses bank fire on the injectors, that means four injectors fire simultaneously, and then the other four fire. If the computer was putting out the wrong info, it would effect all the injectors. If one fuel injector driver was bad, it would effect the four injectors on that bank. If you have a bad injector, it would only effect one cylinder.
I am not a big fan of aftermarket gasoline additives. In this case, I would try to run fuel injector cleaner in the engine and see of that helps.
Another option is to remove the bad injector and replace it, or clean it outside of the engine.

[engineerj13]

So after a day of testing and such I believe I have it narrowed down to the fuel injector. I listened to each injector and there was only one that I could barely here or maybe not even at all. After running the engine that same cylinder was the only one which had a wet spark plug which smelled like fuel.

[jjgag60]

injector

I just had my injector's cleaned and serviced. The shop was able to test them to make sure all of them were "spraying" the same amount. The test equipment allows the tech to test all the injectors at once, or individual. It was not expensive to have the injectors cleaned (under $30.00).