Onan Generator Carbon Knock

Mark Ruset · 12-31-2011, 09:57 PM

I believe I have developed a carbon knock in my Onan Emerald 4000 generator. Has anyone else had a similiar experience and if so is there an easy remedy?

Chuck Westcott · 01-01-2012, 09:33 AM

Onan makes a carbon remover in a spray can I believe. I remember removing the heads on a 4.0 and scraping the carbon off. Ran like new.That was a pain for sure.

Dave Tincher · 01-01-2012, 12:25 PM

Quote:

Originally Posted by Chuck Westcott

Onan makes a carbon remover in a spray can I believe. I remember removing the heads on a 4.0 and scraping the carbon off. Ran like new.That was a pain for sure.

You wont have much luck with the carbon spray. Its more for maintanance, Removing the head is a pain but its the only real fix.

DIAPERMAN · 01-01-2012, 02:03 PM

After you fix if you run some Lucas fuel treatment in every few tanks of gas this will help.I have a lot of rv buddies that swear by it. Just an idea

Mark Ruset · 01-01-2012, 02:27 PM

I was hoping that I wouldn't have to pull the head, however that seems the concensous. I thought there may be a way to inject throught the intake some sort of liquid to breakup the carbon, like GM Top Engine Cleaner.

Dave Steltz · 01-01-2012, 05:49 PM

Mark I had the same thing with my previous MH...tried a few different spays, gas treatments...didnt work...Had to pull the generator out and pull the heads off...PIA for sure...also I dunno if you can do it in the MH, it was easier for me just to pull it out....

brett3533 · 01-02-2012, 04:09 PM

Mark, You might try some sea foam from napa. Start gen, and pour it into carb and stall out the gen. Alloy to set for between 20 and 30 minutes then restart. It will smoke alot but may loosen up and clean out your carbon deposits.

dennis dunlap · 01-02-2012, 05:24 PM

Mark ,I,ve used the GM upper cyl lube for many years ,worked for us. Sprayed it in an let it set , i used a long flexable hose to get in further.
Spin it over spray, let it set, repeat .I always had the headgaskets but never did pull the heads .Running generater with no load on it seems to be the enimey.....

Mark Ruset · 01-02-2012, 07:59 PM

Thanks to all who replied, I'm going to try the GM Top Engine Cleaner. I let you all know how it went

Darrin Christen · 01-03-2012, 10:24 PM

I had the same problem. I thought is was a bad rod bearing or broken piston. When I took the heads off I found a smashed chunk of carbon on top of one of the pistons. I probably could have sprayed something through the spark plug hole to dissolve it but I already had the generator out and apart. I would try some carbon cleaner before taking it apart. You can try a marine dealer who sells outboard engines. They carry several different types of carbon cleaners you spray into the engine while running.

12-31-2011, 09:57 PM	#1
Mark Ruset Member Join Date: May 2006 Location: Southwest Florida Posts: 250 Likes: 23 Liked 34 Times in 24 Posts	Onan Generator Carbon Knock I believe I have developed a carbon knock in my Onan Emerald 4000 generator. Has anyone else had a similiar experience and if so is there an easy remedy? __________________ Mark Ruset 2048 STK

01-01-2012, 09:33 AM	#2
Chuck Westcott Member Join Date: Dec 2003 Location: Brownsburg,Indiana Posts: 326 Likes: 0 Liked 0 Times in 0 Posts	Re: Onan Generator Carbon Knock Onan makes a carbon remover in a spray can I believe. I remember removing the heads on a 4.0 and scraping the carbon off. Ran like new.That was a pain for sure. __________________ Chuck Westcott- S/C -S/G 225

01-01-2012, 02:03 PM	#4
DIAPERMAN Senior Member Join Date: Apr 2007 Location: ILLINIOS Posts: 715 Likes: 2 Liked 21 Times in 6 Posts	Re: Onan Generator Carbon Knock After you fix if you run some Lucas fuel treatment in every few tanks of gas this will help.I have a lot of rv buddies that swear by it. Just an idea

01-01-2012, 02:27 PM	#5
Mark Ruset Member Join Date: May 2006 Location: Southwest Florida Posts: 250 Likes: 23 Liked 34 Times in 24 Posts	Re: Onan Generator Carbon Knock I was hoping that I wouldn't have to pull the head, however that seems the concensous. I thought there may be a way to inject throught the intake some sort of liquid to breakup the carbon, like GM Top Engine Cleaner. __________________ Mark Ruset 2048 STK

01-01-2012, 05:49 PM	#6
Dave Steltz Member Join Date: Nov 2003 Posts: 323 Likes: 0 Liked 0 Times in 0 Posts	Re: Onan Generator Carbon Knock Mark I had the same thing with my previous MH...tried a few different spays, gas treatments...didnt work...Had to pull the generator out and pull the heads off...PIA for sure...also I dunno if you can do it in the MH, it was easier for me just to pull it out.... __________________ Dave Steltz 135G SG/SP/SST BIAECH Racing Team

01-02-2012, 04:09 PM	#7
brett3533 Member Join Date: Jan 2007 Location: maysville Posts: 109 Likes: 15 Liked 33 Times in 9 Posts	Re: Onan Generator Carbon Knock Mark, You might try some sea foam from napa. Start gen, and pour it into carb and stall out the gen. Alloy to set for between 20 and 30 minutes then restart. It will smoke alot but may loosen up and clean out your carbon deposits. __________________ Brett McFarland A/S

01-02-2012, 05:24 PM	#8
dennis dunlap Member Join Date: Sep 2011 Posts: 221 Likes: 0 Liked 1 Time in 1 Post	Re: Onan Generator Carbon Knock Mark ,I,ve used the GM upper cyl lube for many years ,worked for us. Sprayed it in an let it set , i used a long flexable hose to get in further. Spin it over spray, let it set, repeat .I always had the headgaskets but never did pull the heads .Running generater with no load on it seems to be the enimey.....

01-02-2012, 07:59 PM	#9
Mark Ruset Member Join Date: May 2006 Location: Southwest Florida Posts: 250 Likes: 23 Liked 34 Times in 24 Posts	Re: Onan Generator Carbon Knock Thanks to all who replied, I'm going to try the GM Top Engine Cleaner. I let you all know how it went __________________ Mark Ruset 2048 STK

01-03-2012, 10:24 PM	#10
Darrin Christen Member Join Date: Mar 2007 Location: Des Allemands, LA Posts: 365 Likes: 8 Liked 1 Time in 1 Post	Re: Onan Generator Carbon Knock I had the same problem. I thought is was a bad rod bearing or broken piston. When I took the heads off I found a smashed chunk of carbon on top of one of the pistons. I probably could have sprayed something through the spark plug hole to dissolve it but I already had the generator out and apart. I would try some carbon cleaner before taking it apart. You can try a marine dealer who sells outboard engines. They carry several different types of carbon cleaners you spray into the engine while running. __________________ 4878 SS/GA 66CHEVY II

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