I have a 51B1 series D311H Generator set. It has had a slobbering/oil heavy exhaust issue for years. Based on some of the posts I found here and elsewhere, I thought it may be bad injector nozzles that were preventing good fuel atomization. I changed those and replaced the injector o-rings, fuel filter, air filter, ran the injectors through an ultrasonic cleaner. I also had the exhaust off and saw an extremely heavy build up of carbon in the manifold but I haven't taken the manifold off since it looks like you need to take the injector pump off first and I didn't want to risk messing up the timing or having it that far apart, at the time. I scraped out of the manifold what I could reach and get at the time. 

Basically, it still slobbers, very heavily. I *thought* it may have run cleaner when I first cranked it up for 15-20 seconds, but then it was right back to how it has been. Significant drip from the exhaust pipe. I have noticed that the fuel pressure gauge is reading bad, but I think it may be the gauge itself, I've already ordered a new one to put on. I'll see what it reads when it arrives and investigate from there.

When I replaced the old injector nozzles, it did have some trash in the screens of the nozzles upon close inspection. I don't know how long those had been there, this machine has been in my family for about 40 years and my dad did some work on it probably 25 years ago. But I know it wasn't a full rebuild. It was only used periodically for probably 8-15hr per year those last 25 years as a backup during hurricane season. Some years didn't get ran at all.

Fuel is fresh, and fed from an aluminum tank, so I don't think I have sediment/trash issues there.  

It's acting like the rings are just worn out by the amount of oil in the exhaust, but it doesn't seem to have significant blow by out the breather or when I open the oil filler neck. It does use oil - probably a quart every 4 to 5 hours or run time? Maybe 6? 

Generally speaking it does run good, I hear a little miss in it only every now and then.  Smoke is lighter colored. Does not seem to handle as much of an electrical load as it use to in years past, but I don't remember it slobbering back in the day like it has the last 10 years or so either. We could run whole house A/C system, air compressor, etc. It'll about stall out if you do that now, which makes me think fuel issue, but? If my air filter is fresh and I have a good set of hot batteries in it, I can get it to crank and run without ether, but otherwise a small squirt usually gets it to fire right up.

My question is I guess, before I unhook it and pull it into the shop and tear it all the way down and try to do a ring/liner/piston job in it, is there anything else fuel related I should check or try?

Thanks for the good description of your problem.
You have what happens to stand by generators when they are not ran on a load.
If you can come up with a load bank you might try running it with a big load for a while and get the motor hot.
Otherwise pull the head and have it cleaned out and the valves checked.
The best suggestion I can come up with.
Good luck
Bob

Thank you for the reply. If you had to estimate how much of a load was necessary to achieve that - what would you say? 15kw? more? It's a 30kw unit. We've been running the whole house, and well pump when it's on. Things such as hot water heater, stove, microwave, obviously lights/fans/tv/wifi, dryer (last year) even, although probably not all at one time, but quite a little overlap.

I do remember years ago being able to power the central AC unit and the air compressor, but I tried to kick on the compressor last year and about stalled the generator.

We'd had a lot of overheating issues until the radiator came off and got cleaned out including snaking each one of the individual cooling tubes in the radiator (If I posted pictures of what the top of the radiator looked like after the top tank was off, you would not believe me it cooled at all), so now it runs about 170-180 on the water temp, and I've watched the tempt climb, thermostat open, and then it drop back down.

Should I just run it as normal for 8hr or something and see if it clears up? It sure does make a mess

When the tractors start doing the slobbering thing, the recommendation is always put a big load on it for 4 hours minimum, longer is better. So in this case I would say 8 or 10 would be good. I would say keep adding load until in wants to lug down then back off just a little. As bluox put it a big load. If it has a gauge for electric out put get close to the 30kw. 😉 But not knowing much about generators, I don't know how rating and what it is safe to put out really is. But running a light load is what caused your current situation.

Your comment on how little oil it is using points back to carbon and unburned fuel is what is coming out the stack not oil.

that engine will be much happier at 190-195. there information out there about changing the thermostat to a 190 for the factory one.

I'm thinking a gallon of oil a day is a bit excessive for a D311 motor.
This motor is only a 4x5 4cylinder at 1800 RPMs?
The regulator that is in it is what is called for.
As for your fuel system did you mean nozzles were cleaned not injection pumps?
One of the best suggestions I've ever got from an injection shop was use Stanadyne injector cleaner.
I would get enough to fill the fuel filter.
If you have a hand primer fill the pump and let it set a day before you start the motor.
let the motor run 30 minutes and run it the next day under half load.
This may clean up the miss and will cut the gummies.
One more thing I thought of does that motor have an oil cooler?
Good luck
Bob
 

Re: Higher temp thermostat - I also saw mentions of that here. I have not saw a part # for an alternative one in my parts book, but I'm willing to try that if anyone has any details or cross over model to try that from. I've not taken mine out and put in the pan with water/thermometer, but I've watched the gauge in the cluster get right up to about 180 before it opens and then seems to close around 165-168 and start climbing back up again when I've ran it and watched it close.

On the fuel system: I installed new in package OEM cat nozzles (capsule), part #8n5986. Which is what was on the ones that came out. The injector bodies, and the lines were put in an ultrasonic cleaner. I then installed the new nozzles with new o-rings at the bottom of the nut that locks the injector body into the precombustion chamber, and also the one that goes under the injector line nut/top of the injector body. Those are 6f1069 and 5b3718 but got a superceded part # for each I don't recall off the top of my head what they were but I could go back and look if that's relevant. I haven't had any visible leaks there since reinstalling everything although if it slobbers a few more hours of running it may be hard to tell again...

I did not touch the injection pump itself other than taking the injector lines themselves off while replaces the nozzles/removing the injector bodies.

A new fuel filter was installed before running with the new nozzles.

I feel fairly confident that the new nozzles, bodies, and lines are clean and clear unless there was trash between the fuel filter housing and them that just immediately clogged them back up, which I guess is a possibility.

No oil cooler on it.

     

The black parts you call injectors are nozzle bodies.
The injector cleaner suggestion is for the injection pumps which are in pump housing as they may be sticky.
Your regulator is not behaving correctly so you might check it out.
When was the last time you changed oil and what weight oil are you using?
Running the motor hotter would run the oil hotter making it thinner .
Bob

I not smart enough to tell you about them but from the pics you must have a late D311 as it's got the scroll style injection pump. I do believe they work with oil pressure or need oil presser to start. if it not seeing the right oil presser it may not be giving full fuel? witch would make you down on power. just guessing hear.