generator - black soot out exhaust (diesel)

JimM68 wrote:

mabynack wrote:

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.

Guys, this is a diesel. There is no rich, only "more fuel = more power"

What you see is perfectly normal.

While what you see IS within normal operating parameters for most diesel engines, it is not necessarily 'normal'. More fuel = bigger bang, BUT if your fuel doesnt completely combust in the chamber, it will soot out like that. Typically, this is caused by excessive fuel being supplied to the engine. It doesnt take alot of excess fuel to start a diesel smoking, and the older it is, the more likely that its actually running just fine. Newer diesel engines (even small engines like generators) run much more clean and complete their combustion cycle, reducing the soot you see.

Best advice is to clean spark arrester, adjust your exhaust pipe (not to reduce soot, but for safety), as was said, at the very least its a fire hazard.

Rollnhome wrote:

Tip don't be under plug when you pull it out. Thought I would never get that stuff off my face.

Isn't it funny how the best lessons we learn are learned the hard way?

BobGed,
FYI. My 8KW Onan says clean every 150 hrs or once a year. I just did mine today so was reading up on how to do it, easy job actually. Two years would work.
Tip don't be under plug when you pull it out. Thought I would never get that stuff off my face.

It is NOT normal for a generator to continually emit black smoke or soot. If the spark arrestor hasn't been cleaned since the coach was new, I would bet that's your problem as it should be done every two years.

Rollnhome wrote:

Roman Duck wrote:
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

The spark arrestor collects soot and needs to be purged. However my Onan owners manual (8KW) says to remove the plug. Start engine and let run 5 minutes or longer. Shut off engine let muffler cool then replace plug.

This clears the soot out of the muffler/spark arrestor. May solve you problem.

X2 That's what I said, just in a lot less words

Roman Duck wrote:
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

The spark arrestor collects soot and needs to be purged. However my Onan owners manual (8KW) says to remove the plug. Start engine and let run 5 minutes or longer. Shut off engine let muffler cool then replace plug.

This clears the soot out of the muffler/spark arrestor. May solve you problem.

Retired JSO wrote:
Diesel smoke color

Good article. Thanks

That's all well and good, but when the diesel generator I was diagnosing would not run full RPM and pouring out acrid blue smoke on a cool day, I found the air filter had disintegrated due to being wet and was clogging the intake. Not enough air to burn the fuel being delivered.

Maybe, if it had run long enough to reach operating temperature the smoke would have turned black.

Having dealt with chipped diesel pickups and watching the black smoke roll when the extra fuel was being burned to create MO POWER, black smoke is indicative of a lot of fuel being burned.

Soot will always be a by-product of burning diesel fuel.

If the air filter is clogged, the generator will most likely not reach full RPM and the exhaust will be belching BLUE smoke.

mabynack wrote:

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.

Guys, this is a diesel. There is no rich, only "more fuel = more power"

What you see is perfectly normal.