Home » Public Forums » GMCnet » Onan exhaust smell
| Onan exhaust smell [message #172077] |
Mon, 04 June 2012 23:07  |
bhayes
Messages: 263
Registered: March 2010
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Do our Onans typically have a strong-smelling exhaust? I was able to run my Onan for about an hour tonight with one of the roof A/Cs and water heater running (a new record perhaps). But even after warming up, the exhaust smell was fairly strong.
I gapped the plugs and points over the weekend to 0.20 per the manual. The points and condenser look new, and the plugs look good.
I'm comparing it to my Onan Microlite 2800, which seems to have hardly any exhaust smell.
Thanks!
Bryan Hayes
'76 Eleganza II
Salt Lake City, Utah
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| Re: [GMCnet] Onan exhaust smell [message #172141 is a reply to message #172077] |
Tue, 05 June 2012 13:17  |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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You're comparing apples to waterfowl. The only thing common to the two gensets is they're both green - or at leasst they started out th sanme color. The 6000 is a flathead opposed twin engine which runs at 1800 RPM. The Microlite is a single cylinder OHV engine which runs 3600 RPM. This the generators are different as well, one 4 pole and one 2 pole. Anyway I got both here and there, and the exhaust from the old ones does have greater odor. There's more of it, and flat head engines do not run as efficiently as OHV engines. There's more unburnt gas in the old one's exhaust. Stinks. My experience has been, the 1800 RPM twins are far more reliable than the Microlites.
--johnny
'76 23' transmode Norris
'76 palm beach
From: Bryan Hayes <hayesnet1@gmail.com>
To: gmclist@temp.gmcnet.org
Sent: Tuesday, June 5, 2012 12:07 AM
Subject: [GMCnet] Onan exhaust smell
Do our Onans typically have a strong-smelling exhaust? I was able to run my Onan for about an hour tonight with one of the roof A/Cs and water heater running (a new record perhaps). But even after warming up, the exhaust smell was fairly strong.
I gapped the plugs and points over the weekend to 0.20 per the manual. The points and condenser look new, and the plugs look good.
I'm comparing it to my Onan Microlite 2800, which seems to have hardly any exhaust smell.
Thanks!
--
Bryan Hayes
'76 Eleganza II
Salt Lake City, Utah
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Onan exhaust smell [message #172148 is a reply to message #172143] |
Tue, 05 June 2012 14:13 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Probably. It certainly would be a bit more reliable. Would it make the stink go away? Probably not. However. Next rally you go to, ask folks who has Pertronix and who has box stock Onan. Let each run for twenty minutes or so to gwet warm, load each, and give 'em the sniff test. Then you know for sure for free.
--johnny
'76 transmode norris
'76 palm beach
From: Larry Davick <ljdavick@comcast.net>
To: "gmclist@temp.gmcnet.org" <gmclist@temp.gmcnet.org>
Sent: Tuesday, June 5, 2012 2:33 PM
Subject: Re: [GMCnet] Onan exhaust smell
Would the Pertronix electronic ignition set to about 27 degrees more completely burn the fuel?
Larry Davick
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Onan exhaust smell [message #172149 is a reply to message #172148] |
Tue, 05 June 2012 14:18 |
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ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
Karma: -3
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My thinking is that for a flathead engine advancing the spark might be a good idea.
Larry Davick
On Jun 5, 2012, at 12:13 PM, Johnny Bridges <jhbridges@ymail.com> wrote:
> Probably. It certainly would be a bit more reliable. Would it make the stink go away? Probably not. However. Next rally you go to, ask folks who has Pertronix and who has box stock Onan. Let each run for twenty minutes or so to gwet warm, load each, and give 'em the sniff test. Then you know for sure for free.
>
> --johnny
> '76 transmode norris
> '76 palm beach
>
> From: Larry Davick <ljdavick@comcast.net>
> To: "gmclist@temp.gmcnet.org" <gmclist@temp.gmcnet.org>
> Sent: Tuesday, June 5, 2012 2:33 PM
> Subject: Re: [GMCnet] Onan exhaust smell
>
> Would the Pertronix electronic ignition set to about 27 degrees more completely burn the fuel?
>
> Larry Davick
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Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
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| Re: Onan exhaust smell [message #172152 is a reply to message #172077] |
Tue, 05 June 2012 14:54 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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| bhayes wrote on Mon, 04 June 2012 21:07 |
Do our Onans typically have a strong-smelling exhaust? I was able to run my Onan for about an hour tonight with one of the roof A/Cs and water heater running (a new record perhaps). But even after warming up, the exhaust smell was fairly strong.
I gapped the plugs and points over the weekend to 0.20 per the manual. The points and condenser look new, and the plugs look good.
I'm comparing it to my Onan Microlite 2800, which seems to have hardly any exhaust smell.
Thanks!
|
Bryan,
Did you also adjust the main jet screw on your carburetor? It will not get rid of the smell, but it might minimize it if you set it to 'lean best mixture". Turn the screw at the base of the carburetor, that faces toward the front of the coach, in, until the engine starts to stumble. Then back it out until it runs smoothly again. Watch what the throttle is doing as you do this. If the carb is set too rich, it will smell worse. Do all this when the gnerator is nice and hot.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: [GMCnet] Onan exhaust smell [message #172173 is a reply to message #172152] |
Tue, 05 June 2012 18:10 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Carl,
Do you think Bryan should have the Onan under max load (roof air on, water
heater on, microwave on) when he adjusts the jet?
Regards,
Rob M.
-----Original Message-----
From: Carl Stouffer
Bryan,
Did you also adjust the main jet screw on your carburetor? It will not get
rid of the smell, but it might minimize it if you set it to 'lean best
mixture". Turn the screw at the base of the carburetor, that faces toward
the front of the coach, in, until the engine starts to stumble. Then back
it out until it runs smoothly again. Watch what the throttle is doing as
you do this. If the carb is set too rich, it will smell worse. Do all this
when the gnerator is nice and hot.
--
Carl
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Onan exhaust smell [message #172196 is a reply to message #172173] |
Tue, 05 June 2012 20:52 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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Senior Member |
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| Robert Mueller wrote on Tue, 05 June 2012 16:10 |
Carl,
Do you think Bryan should have the Onan under max load (roof air on, water
heater on, microwave on) when he adjusts the jet?
Regards,
Rob M.
-----Original Message-----
From: Carl Stouffer
Bryan,
Did you also adjust the main jet screw on your carburetor? It will not get
rid of the smell, but it might minimize it if you set it to 'lean best
mixture". Turn the screw at the base of the carburetor, that faces toward
the front of the coach, in, until the engine starts to stumble. Then back
it out until it runs smoothly again. Watch what the throttle is doing as
you do this. If the carb is set too rich, it will smell worse. Do all this
when the gnerator is nice and hot.
--
Carl
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Rob,
I do put mine under load. Not necessarily max load. My advice was probably superfluous anyway. I got to thinking, after I made the post, that if Bryan is capable of making the other adjustments, I suspect he knows how to adjust a carburetor.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: Onan exhaust smell [message #172202 is a reply to message #172077] |
Tue, 05 June 2012 21:27 |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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Bryan,
Our Onan had not been run in years -- and the first few hours of run time it had a rather strong/sharp odor. Now seems to have lessened. That or I have come to accept it... I attributed it to "re-seasoning" the muffler. I have, however, pulled the heads and decarboned them -- although they were not bad.
Dennis
| bhayes wrote on Mon, 04 June 2012 23:07 |
Do our Onans typically have a strong-smelling exhaust? I was able to run my Onan for about an hour tonight with one of the roof A/Cs and water heater running (a new record perhaps). But even after warming up, the exhaust smell was fairly strong.
I gapped the plugs and points over the weekend to 0.20 per the manual. The points and condenser look new, and the plugs look good.
I'm comparing it to my Onan Microlite 2800, which seems to have hardly any exhaust smell.
Thanks!
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Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: [GMCnet] Onan exhaust smell [message #172212 is a reply to message #172173] |
Tue, 05 June 2012 23:28 |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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Senior Member |
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| Robert Mueller wrote on Tue, 05 June 2012 16:10 |
Carl,
Do you think Bryan should have the Onan under max load (roof air on, water
heater on, microwave on) when he adjusts the jet?
Regards,
Rob M.
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One thing to test when adjusting is how well the engine does when a sudden load is put on the engine. Most engines will run fairly lean when running at a steady speed but will balk when the throttle is opened suddenly. In car-truck engine carbs the accelerator pump kicks in the extra gas to keep this from happening. On smaller older engines there is no compensation.
So, before I slid it in after adjustment I would let it run with no load and turn on the air. If it coughs before it speeds up it is too lean. This is a warm test.
The final test will be if it does this well when it is "half warm". Sometimes we are impatient and throw on a load when the Onan is really just getting started. The choke helps but probably turns off fairly quickly.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: Onan exhaust smell [message #172239 is a reply to message #172077] |
Wed, 06 June 2012 09:57 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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That final fine adjustment will have a lot to do with emmisions. The old beast will "run" in a fairly wide band of tolerability, but if someone has a CO sniffer you can really dial it in. But as they are air cooled they run hot in the hot and cool in the cold. So some tweeking will be required seasonally and elevation wise. The 455/403 as setup from the factory has a coolant thermostat and an intake air thermostat in the AC Autothermac. This helps to set an engine temp around 185 and air intake temp around 115F. This gives a more level range for them to setup the carb to. Of course modern EFI is constantly looking at this stuff and correcting. That's why I still have my preheat air hooked up on the 455. At WOT it goes to all cold anyway so in my opinion is doesn't cut down on the 'go-faster' and lessens emissions. JMHO.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Onan exhaust smell [message #172260 is a reply to message #172256] |
Wed, 06 June 2012 12:55 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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Senior Member |
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| bhayes wrote on Wed, 06 June 2012 10:24 |
Carl, you give me too much credit. Whenever I need to work on a carb, we'll both just sit there and glare at each other, the carb baring its venturis, just daring me to try to adjust it, rebuild it, whatever. If I get too close with even the slightest hint of a screwdriver, the carb hisses at me and spits gas at my face, and then scurries off and hides behind a valve cover.
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Ha Ha!  Trust me, you can do this! Just take note of the position of the screw, and if the generator dies during the adjustment process, return the screw to it's original position and it should start back up. Then try, try again 
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: [GMCnet] Onan exhaust smell [message #172261 is a reply to message #172260] |
Wed, 06 June 2012 13:25 |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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Bryan, Carl,
Recently I had to change the o ring on the adjusting screw -- it seems to have deteriorated in just a couple of years.
Either the affects of the fuel or the quality of the o rings I have purchased. Sourced mine from Ace Hardware.
Dennis
| Carl S. wrote on Wed, 06 June 2012 12:55 |
| bhayes wrote on Wed, 06 June 2012 10:24 |
Carl, you give me too much credit. Whenever I need to work on a carb, we'll both just sit there and glare at each other, the carb baring its venturis, just daring me to try to adjust it, rebuild it, whatever. If I get too close with even the slightest hint of a screwdriver, the carb hisses at me and spits gas at my face, and then scurries off and hides behind a valve cover.
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Ha Ha! Trust me, you can do this! Just take note of the position of the screw, and if the generator dies during the adjustment process, return the screw to it's original position and it should start back up. Then try, try again
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Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: Onan exhaust smell [message #172283 is a reply to message #172077] |
Wed, 06 June 2012 17:22 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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| bhayes wrote on Mon, 04 June 2012 22:07 |
Do our Onans typically have a strong-smelling exhaust? I was able to run my Onan for about an hour tonight with one of the roof A/Cs and water heater running (a new record perhaps). But even after warming up, the exhaust smell was fairly strong.
I gapped the plugs and points over the weekend to 0.20 per the manual. The points and condenser look new, and the plugs look good.
I'm comparing it to my Onan Microlite 2800, which seems to have hardly any exhaust smell.
Thanks!
|
These old Onans run best a bit rich so that they can handle high loads and transitions without faltering. I have noticed the same thing. You can lean it out a bit but performance will fall off a bit. The newer engines have better combustion chambers, electronic ignition and better carburetors so that they can run just fine at a leaner mixture.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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