Runs rough and black smoke on initial start

[incorporatedbyinference]

Today I pulled my Mep 802 a out of the garage for a little exercise. My start procedure was a couple 5 second cranks using the dead crank. Then primed for 45 seconds. When I turned to start, it fired up running rough w black smoke. After about a minute I shut it down. Right away gave it another start, idle was much better but still rough. After shutting it off and starting again it ran smooth. I read through tm 9-6115-641-24. Chapter 3 didn’t address my issue. Filters are all new w fresh fuel. The generator is an 09 w 650hrs. Has anyone had a similar issue before?

 

[Icesythe7]

Today I pulled my Mep 802 a out of the garage for a little exercise. My start procedure was a couple 5 second cranks using the dead crank. Then primed for 45 seconds. When I turned to start, it fired up running rough w black smoke. After about a minute I shut it down. Right away gave it another start, idle was much better but still rough. After shutting it off and starting again it ran smooth. I read through tm 9-6115-641-24. Chapter 3 didn’t address my issue. Filters are all new w fresh fuel. The generator is an 09 w 650hrs. Has anyone had a similar issue before?

Just sounds like it was cold is all, black smoke is unburnt fuel most diesels do this at startup especially after not running for a bit or when in cold temperatures until it warms up a bit, all my gensets do it when cold (MEP-803a, MEP-831a, MEP-016d) as does my truck (11 6.7 powerstroke), generally do to feeding it fuel to get it up to speed yet the speed isn't coming up as fast (due to thick oil/not enough air etc) so the unburned fuel has to go somewhere.

 

[Light in the Dark]

Its possible one of your injectors is a bit leaky and some fuel puddled during the time while sitting.

 

[incorporatedbyinference]

I’ll check into that. It just seemed odd that turning it off and then restarting 3 times would clear the issue. The idle didn’t change at all while warming up all be it was less than 2 min.

 

[Icesythe7]

Its possible one of your injectors is a bit leaky and some fuel puddled during the time while sitting.

Also a valid point for sure and likely what it was

 

[Ray70]

I'd agree with LITD that you could have a slight leak in 1 of the injectors or possibly also could be a leak in one of the metering pumps allowing a little fuel to drain back creating an air pocket in the injector line.
This can cause the "Good" cylinder to struggle a little and smoke until the air is completely worked out of the offending cylinder.
Either way the good news is that it clear itself quickly.
I would just keep an eye on things next time you run it.
Out of curiosity, how long had it sat since you ran it last?

 

[incorporatedbyinference]

Maybe 5-6 weeks. The generator was bought at auction 3-4 months ago. I replaced all the fuel lines and filters. Started up and load tested. There was some noticeable dark smoke at near 100% load. I ran some sea foam through it with a good 3 hour run. The smoke at full load went away.

 

[incorporatedbyinference]

I just checked 24p the slight leak would be from the sealing washer or part number 5 in the diagram? Or internal to the injector itself?

 

[Ray70]

Only a leak in the injector pintle / nozzle itself can cause fuel to drip into the cylinder when shut down.
It may not cause any noticeable issue while running after heated up, but definitely isn't the best scenario for your engine.
A leak at the copper washer would cause a very slight loss of compression pressure, but won't cause fuel to drip while shut down and the compression loss is virtually undetectable except for possible some bubbling around the injector if it's wet with water or any fuel.

If the issue continues I would remove the exhaust manifold so you can see which cylinder is smoking.
Swap the injectors and see if the problem follows the injector or not.

 

[incorporatedbyinference]

what is the consensus opinion on the best place to source oem injectors? Is it possible to source parts to rebuild origional injector? For the sake of minimal downtime id like to replace both injectors. but then rebuild the problem injector for my own education. The rubber lines off the rail had cracked and I replaced both 4” hoses securing with hose clamps. Could this affect the leak I’m experiencing? Thanks for any input.

 

[Light in the Dark]

Anything Lister you can get from the UK based dealer Sleeman and Hawken https://www.sleeman-hawken.com/.

Cracked lines will just hemmorage fuel, as they are pressurized from the fuel pump. Lines aren't the issue here.

You may be able to rebuild, a question for the dealer. Will need to have a shop pop test them.

 

[Ray70]

The injectors can be disassembled and cleaned. One test would be to remove the injectors and turn the hard lines off to the side and reattach the injectors.
Crank the motor and look at the spray patterns. there should be 4 fine sprays coming out radially from the tip of the injector.
If it isn't a super fine spray mist and more of a squirt or a drip, the injector is bad.
If there aren't 4 sprays coming out, the injector is bad.
The bad thing is that other than cleaning, rebuilding isn't that practical.
I've never found a good source for replacement nozzles / needles and the pop pressure is adjusted using thin shims inside the injector to alter spring pressure.
Not exactly the most user friendly design.
I've used the cheap Chinese injectors before. They worked in a pinch, but not one of them ever had the pop pressure set exactly to spec. they were always a few hundred PSI too low.
I'd test yours first, then clean or replace with OEM if a problem is noticed.
Try testing using the machine's metering pumps.
If you want to pop test them I can do it if you can't find a local shop to test for you.

 

[incorporatedbyinference]

Pulled the 802 out of the garage to start and run again. Inspected the high pressure lines for anyt loose connections no finding any. With it being a week since the initial run. Same procedure a couple 5 sec turnovers at the deadcrank. 30 sec of prime then ignition started up just slightly rough. Tried to let her warm up and smooth out for a couple minutes. Wasn’t happening. Turned it off. Waited 15 sec. Then it started up smooth. Ran it for 4-5 hours switching between 3 4 and 5 kw loads. I ran hotshots secret diesel extreme in the fuel. There was a light rain and while switching between voltage readings the needle went to zero. I was still operational. Switched the dial position several times gauge still not working I gave it a flick w my finger and it started reading again. When visually looking over things I noticed a difference in appearance w the 2 injectors one had minuscule disturbance of the engine paint that was applied to the engine. The other one had more paint missing with a little diesel grime. Could this be my problem injector.

 

[Ray70]

Could you post up pictures of the injectors?

 

[incorporatedbyinference]

I’ll post the photos this evening. When I purchased this unit at auction it was pouring fuel out of the return fuel lines at the injectors. I replaced the lines.

 

[Strike Fighter]

Sure Sounds like a faulty injector to me , That may be why i recommend everyone have a back up complete engine for parts or replacement of entire engine , Parts from Onan no matter which country you order them from are SKY HIGH . I have 7 REBUILT ENGINES IN CRATES . Just saying .....

 

[incorporatedbyinference]

 

[incorporatedbyinference]

 

[incorporatedbyinference]

1st picture is possible problem injector. 2 nd photo not the best due to parts in the way. I’m just wondering to the trained eye is the difference relevant?

 

[Strike Fighter]

View attachment 913042

Hi , I have a trained eye for 802-A and 803-A Gensets , My question would be , I see the fuel saturation on top of the head around injector nut most likely from leaky fuel injection return lines in the past . I see the hard line connected to the injector and the new return lines . What do you see ?