blowing carbon/soot out of a Onan/Cummins

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My Onan/Cummins QD3200 is still puffing some smoke under load so I thought I's see if I can blow some soot out of the muffler and spark arrestor. The manual shows only one plug on the bottom of the muffler but as you can see I have two, anyone know if they are both intended for soot cleanout? (I already removed one plug and as you can see there is some soot accumulation) Attached ImagesMiller Challenger 172Miller Thunderbolt AC/DC 225/150Miller Maxstar 150 STLVictor 100CVictor JourneymanOxweld OAHarris O/ASmith O/A little torchNo, that's not my car.
Reply:If the engine is in good shape it sounds like you have an over rich fuel problem or an intake restriction.Ol' Stonebreaker  "Experience is the name everyone gives to their mistakes"Hobart G-213 portableMiller 175 migMiller thunderbolt ac/dc stick Victor O/A setupMakita chop saw
Reply:If the plug comes out easy, why not take it out? Might be worth putting some Seafoam in the fuel to help loosen carbon and soot deposits.
Reply:Start it up a and run some spray Sea Foam through it. It will clean the valves, piston and muffler Stay up wind as it can get very smoky. Keep the engine well revved up. Instructions are on the spray can.ChrisAuction Addict
Reply:Originally Posted by Welder DaveIf the plug comes out easy, why not take it out? Might be worth putting some Seafoam in the fuel to help loosen carbon and soot deposits.
Reply:Originally Posted by milomiloStart it up a and run some spray Sea Foam through it. It will clean the valves, piston and muffler Stay up wind as it can get very smoky. Keep the engine well revved up. Instructions are on the spray can.
Reply:Originally Posted by bigbIt draws fuel from the motorhome tank and I'm not sure I want to put Seafoam in a DPF equipped Sprinter.
Reply:Originally Posted by mla2ofusIf the engine is in good shape it sounds like you have an over rich fuel problem or an intake restriction.
Reply:I don't think the seafoam is a terrible idea, the key is a very controlled quantity at a time, I would use the non aerosol and introduce it through the air intake, another option is to mist water into the intake with it running, used to be pretty common on gas engines. Being a diesel you'll have to control the amount of fuel(seafoam) to prevent runaway.Last edited by CAVEMANN; 07-01-2021 at 08:34 PM.IMPEACH BIDEN!NRA LIFE MEMBERUNITWELD 175 AMP 3 IN1 DCMIDSTATES 300 AMP AC MACHINEGOD HELP AMERICA!“Freedom is never more than one generation away from extinction.We didn’t pass it to our children in the bloodstream".RONALD REAGAN
Reply:Originally Posted by CAVEMANNI don't think the seafoam is a terrible idea, the key is a very controlled quantity at a time, I would use the non aerosol and introduce it through the air intake, another option is to mist water into the intake with it running, used to be pretty common on gas engines. Being a diesel you'll have to control the amount of fuel(seafoam) to prevent runaway.
Reply:Diesel generators do not really like running unloaded for extended time, although I can't imagine having any issue after only 10 hours. I typically like to see 80% load or better otherwise it can coke up and/or wet stack. I'd add some plug in electric heaters to get your load up to near 100% and see how it does. Run it hard for about an hour. When Kohler came out and load banked my standby genset I expected some fancy load testing machine. Nope, just a big box fan with a lot of switchable resistance elements. They toggled the elements to reach the 130% peak power maximum. It was kinda nice, middle of the winter, dumping 27kW worth of heat. Everyone was warm and toasty.I'm not sure about the plugs. I'd pull them and see. Most standy machines have a weep hole that drains any rain that may get in. One year my stack dumped some pretty tar looking soot during high winds/rain. I now make a point to make sure I don't go all year without running the machine hard at least once if the power doesn't go out. Clearly exercising was sooting up everything pretty bad.
Reply:Originally Posted by forhireDiesel generators do not really like running unloaded for extended time, although I can't imagine having any issue after only 10 hours. I typically like to see 80% load or better otherwise it can coke up and/or wet stack. I'd add some plug in electric heaters to get your load up to near 100% and see how it does. Run it hard for about an hour. When Kohler came out and load banked my standby genset I expected some fancy load testing machine. Nope, just a big box fan with a lot of switchable resistance elements. They toggled the elements to reach the 130% peak power maximum. It was kinda nice, middle of the winter, dumping 27kW worth of heat. Everyone was warm and toasty.I'm not sure about the plugs. I'd pull them and see. Most standy machines have a weep hole that drains any rain that may get in. One year my stack dumped some pretty tar looking soot during high winds/rain. I now make a point to make sure I don't go all year without running the machine hard at least once if the power doesn't go out. Clearly exercising was sooting up everything pretty bad.
Reply:Originally Posted by bigbThanks, I've only had it for 10 hours and those 10 hours have been run hard. The PO had it for 10 years and 180 hours so I suspect it was not run hard during his ownership.