generator - black soot out exhaust (diesel)

The soot is normal. Change to a straight exhaust tip and you won't see the soot on the ground anymore, it will still be there but it will no longer show up.

I wouldn't point mine to the ground because they get hot enough to start a grass fire. A running generator at 90 degrees pulling 2 ACs can get up around 1200 degrees. Carbon is the result of burning diesel fuel and the old time trucks would put out a cloud of it. Look at some tractor trailers going down the road and you'll see lots of carbon at the top of a box trailer.

On Onan diesels generators there is a plug on the exhaust that needs to be removed periodically.
Allow the generator to run for about 30 mins. after it warms up remove the blow out plug and run under full load for about 10 to 15 mins. Doing this will blow out the accumulated soot that has collected in the exhaust. It will eliminate the soot condition, your experiencing, and allow the generator to run more efficient.
Also maintain a good air filter.
Sometimes the plug is hard to see/get to.
A 3/8 Drive extension works well in removal. hint when doing this, first loosen the plug while unit is cool(after loosening keep the plug in until ready for removal)Doing so will keep your arm/hand from getting a nasty burn trying to loosen it up when hot
If it's a front mounted unit(as on DPs)then care should be exercised in running the generator while driving in the rain, as this can lead to sucking in water through the air filter.
Good luck and if you resolve it please post the outcome

Mine does and every other diesel powered generator that I've seen does the same thing.

Assuming no intake issues, how many hours of use in the above picture? What size generator and what all are your powering?

mdamerell wrote:
If the fuel mix is too rich it will blow soot. Make sure your air filter is clean. That's my guess.

X2 on the air cleaner. Also check the air intake for birds and bees nests. Something is causing your generator to run rich.

I will check the air filter.

Two other Diesels in the group and neither are leaving black on the ground like mine... but they do have a straight exhaust tip where mine is pointed at the ground.



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my996duc1 wrote:

it would appear to be a soot and I am not sure what I need to do to fix it. any ideas ?

Pretty much normal..

these generators are not new technology eco friendly engines.

If the fuel mix is too rich it will blow soot. Make sure your air filter is clean. That's my guess.