Home » Public Forums » GMCnet » Onan runs like Sheet: Episode II, the Onan still runs like sheet!
| Onan runs like Sheet: Episode II, the Onan still runs like sheet! [message #80080] |
Sat, 10 April 2010 23:15  |
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ok, Im really starting to become more then slightly annoyed with my onan. I got the carb kit last week and rebuilt the carb, I also put the old low pressure fuel pump back on, but no dice, she still sputters, pops, and runs like crap! she has new plugs, points, condenser, and just started running like this all out of the blue one day.
the carb seems to ice the manifold and it gets cold sweats which seems to me like it may be spraying a bit too much fuel into it? I'm still thinking this is a carbureator issue.
I have a video I will be uploading to youtube in a bit so you guys can see what I am talking about. perhaps someone has had a similar exprience and can offer their advice how to restore my onan to proper operating condition...
here is the youtube link
http://www.youtube.com/watch?v=aIqNyNS7I4g
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
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| Re: Onan runs like Sheet: Episode II, the Onan still runs like sheet! [message #80083 is a reply to message #80080] |
Sun, 11 April 2010 00:03  |
jtblank
Messages: 237
Registered: June 2007
Location: Tulare, CA
Karma: 1
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Senior Member |
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Duce,
Have you pulled the heads and checked carbon build up and looked at valves for coloration? How about compression check? and leak-down?
The icing of the carb could be normal depending on temperature and dew point as the venturi effect reduces temp of carb, that's why airplanes have carb heaters switched on during landing to prevent icing and assure engine performance.
just a thought, keep us in the loop.
John Blankenship
'76 Palm Beach
Tulare, CA
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| Re: [GMCnet] Onan runs like Sheet: Episode II, the Onan still runs like sheet! [message #80084 is a reply to message #80080] |
Sun, 11 April 2010 00:12 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Shan,
OK, I watched the video and notice that the coil looks like the original.
I looked back through the old series of messages re your Onan and at one
time you felt that the coil was the problem, have you checked it or has it
been replaced?
Are there any fellow GMCer's in your area that could lend you one for
troubleshooting purposes.
If I was in the USA I'd send you the spare one I keep in Double Trouble.
Regards,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Shan Rose
Sent: Sunday, 11 April 2010 2:15 PM
To: gmclist@temp.gmcnet.org
Subject: [GMCnet] Onan runs like Sheet: Episode II,the Onan still runs like
sheet!
ok, Im really starting to become more then slightly annoyed with my onan. I
got the carb kit last week and rebuilt the carb, I also put the old low
pressure fuel pump back on, but no dice, she still sputters, pops, and runs
like crap! she has new plugs, points, condenser, and just started running
like this all out of the blue one day.
the carb seems to ice the manifold and it gets cold sweats which seems to me
like it may be spraying a bit too much fuel into it? I'm still thinking this
is a carbureator issue.
I have a video I will be uploading to youtube in a bit so you guys can see
what I am talking about. perhaps someone has had a similar exprience and can
offer their advice how to restore my onan to proper operating condition...
here is the youtube link
http://www.youtube.com/watch?v=aIqNyNS7I4g
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
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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: Onan runs like Sheet: Episode II, the Onan still runs like sheet! [message #80085 is a reply to message #80080] |
Sun, 11 April 2010 00:49 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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De-carbonize the heads and set the spark plug gaps EXACTLY the same on both plugs. AFTER DECARBONIZING try adjusting the carb again.
You are not running rich, there is no black smoke coming out of the exhaust.
Any chance that you have something loose in the muffler that plugged it up?
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Onan runs like Sheet: Episode II, the Onan still runs like sheet! [message #80089 is a reply to message #80080] |
Sun, 11 April 2010 01:36 |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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Senior Member |
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| Duce Apocalypse wrote on Sat, 10 April 2010 21:15 |
ok, Im really starting to become more then slightly annoyed with my onan.
the carb seems to ice the manifold and it gets cold sweats which seems to me like it may be spraying a bit too much fuel into it? I'm still thinking this is a carbureator issue.
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The suggestion of checking the coil is excellent. They break down in heat.
But, I am going to go with the icing.
I believe it is sputtering because it is lean. Load made it sputter more. But not because of fuel or jet adjustment. Ice.
When it started it had puff of black smoke from the choke. Plenty of gas. Then it ran fine and the choke would be opening. Ice begins to form and in essence, it is sputtering because the gas is not vaporizing fast enough.
A test would be to move the choke a bit and see if it cleans up.
The fix? I see no provision for heating the intake other than reflective heat. So I am going with the "PVC" tube that enters the hose between the air filter and the carb. I am guessing that it provide warm air from the crankcase that helps warm the carb. If it is clogged, 1) why and 2) how to unclog it without getting junk in the crankcase.
Here is an quote from a VW guy:
As to the Vw bug...the factory design was that the intake manifold had a pre heat pipe that was connected to the muffler allowing exhaust gas to circulate keeping the intake portion below the carb fom icing up. Many old Intake manifolds were carboned up (plugged up) and you would see some sweating below the carb or if touching the area it would be ICE cold. A knowledged VW mechanic could ROTO Rooler out the carbon and make it functional again...but many did not know or just got another one from a wrecking yard. This was more common with the old 36 HP and 40 Hp engines from the late 50's thru the mid 60's. I cut my teeth on the 36 Hp starting in 1968 thru till 1996. Have seen it all. Steve
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: Onan runs like Sheet: Episode II, the Onan still runs like sheet! [message #80092 is a reply to message #80089] |
Sun, 11 April 2010 02:01 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Carb icing only occurs when the intake air is a few degrees above freezing and the intake air relative humidity 90% or more. If it is above 40 degrees F., you do not have carb ice.
Someone use to offer a heat deflector for the Onan for cool weather use to prevent carb icing. Ragusa maybe.
De-carbonize the heads.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Onan runs like Sheet: Episode II, the Onan still runs like sheet! [message #80104 is a reply to message #80089] |
Sun, 11 April 2010 07:53 |
Steven Ferguson
Messages: 3447
Registered: May 2006
Karma: 0
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Senior Member |
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There is always a puff of black smoke on a restart of the Onan because
the shut off only kills the ignition, fuel keeps entering the manifold
as long as there is vacuum. It does not seem to like load though so
maybe it is time to decarbon the heads.
Shan, have you put a timing light on it and watched it while it's
running? My Onan kicked Duane Simmon's butt at GMCMI SD and when I
got home and got to play with it for a whle, it turned out to be that
the timing would slip while it was running. Tough to trouble shoot.
On Sat, Apr 10, 2010 at 11:36 PM, George Beckman <gbeckman@pggp.com> wrote:
>
>
> Duce Apocalypse wrote on Sat, 10 April 2010 21:15
>> ok, Im really starting to become more then slightly annoyed with my onan.
>> the carb seems to ice the manifold and it gets cold sweats which seems to me like it may be spraying a bit too much fuel into it? I'm still thinking this is a carbureator issue.
>
>
> The suggestion of checking the coil is excellent. They break down in heat.
>
> But, I am going to go with the icing.
>
> I believe it is sputtering because it is lean. Load made it sputter more. But not because of fuel or jet adjustment. Ice.
>
> When it started it had puff of black smoke from the choke. Plenty of gas. Then it ran fine and the choke would be opening. Ice begins to form and in essence, it is sputtering because the gas is not vaporizing fast enough.
>
> A test would be to move the choke a bit and see if it cleans up.
>
> The fix? I see no provision for heating the intake other than reflective heat. So I am going with the "PVC" tube that enters the hose between the air filter and the carb. I am guessing that it provide warm air from the crankcase that helps warm the carb. If it is clogged, 1) why and 2) how to unclog it without getting junk in the crankcase.
>
> Here is an quote from a VW guy:
>
> As to the Vw bug...the factory design was that the intake manifold had a pre heat pipe that was connected to the muffler allowing exhaust gas to circulate keeping the intake portion below the carb fom icing up. Many old Intake manifolds were carboned up (plugged up) and you would see some sweating below the carb or if touching the area it would be ICE cold. A knowledged VW mechanic could ROTO Rooler out the carbon and make it functional again...but many did not know or just got another one from a wrecking yard. This was more common with the old 36 HP and 40 Hp engines from the late 50's thru the mid 60's. I cut my teeth on the 36 Hp starting in 1968 thru till 1996. Have seen it all. Steve
>
> --
> '74 Eleganza SE
>
>
> Best Wishes,
>
> George
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Steve Ferguson
'76 EII
Sierra Vista, AZ
Urethane bushing source
www.bdub.net/ferguson/
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| Re: [GMCnet] Onan runs like Sheet: Episode II, the Onan still runs like sheet! [message #80150 is a reply to message #80101] |
Sun, 11 April 2010 11:45 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| emerystora wrote on Sun, 11 April 2010 07:24 |
On Apr 11, 2010, at 1:01 AM, Ken Burton <n9cv@comcast.net> wrote:
>
>
> Carb icing only occurs when the intake air is a few degrees above
> freezing and the intake air relative humidity 90% or more. If it is
> above 40 degrees F., you do not have carb ice.
>
> Someone use to offer a heat deflector for the Onan for cool weather
> use to prevent carb icing. Ragusa maybe.
>
That was Darren Paget (TZE) but he no longer makes them.
Emery Stora
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Thanks Emery
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Onan runs like Sheet: Episode II, the Onan still runs like sheet! [message #80151 is a reply to message #80080] |
Sun, 11 April 2010 11:49 |
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Ok, first off thanks for the imput guys, I'm still leaning to a carb/ignition problem however. I dont think the heads are carbonized really that much, reason being when I pulled the plugs for a plug reading they were a nice light tan, not sooty black, and I have had the onan run for many hours and it always ran like a clock, only with an occational sumble, and I would load the SOB down with up to a good 30 amps of load, and it would always chug away with no problems, now it skips under no load and stumbles under the lightest load. A couple weeks ago it just started acting like that, and then wouldnt start. so I thought fuel pump, so I replaced that, also the fuel mixture smells richer then it should be, and there is not an occational backfire, the report something akin to a 1911 .45 ACP, which is real fun when you dont have your ears on. while working on the onan I take my rig to a commercial/industrial area as to not get the attention of the police looking for someone discharging a firearm within city limits.
Also ther still the odd EM feild which seems to like to screw with sensitive digital equipment. It was causing the display screen on my expensive sony HD handy cam to jump around when my GF got to cloose to the genset running.
As for Carb Icing, well its more of a clod sweat, the air temp yesterday was about 68 degrees when I was making that video. but you can see the sweat on the intake. its like the cooling effect seen with top fuel or nitrous injection. so this is what is making me think perhaps the onan is inhailing a denser mix of fuel then it should. it would seem its not atomizing correctly for some reason. and for what ever reason, walbro does not include a new power nozzle with the rebuild kit for their carb.
now as to what makes me think it could be ignition related is the strange EM feild which I never witnessed in my onan. it also screws with my digital timing light, something which it never did before.
basically what I need is someone who can loan me a working old coil or spare carb to troubleshoot both of these systems. I'd take care of the shipping and return. I need to get this onan running right, I do a lot of dry camping and need my AC 120 to effectively do stuff...
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
[Updated on: Sun, 11 April 2010 11:52] Report message to a moderator |
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| Re: [GMCnet] Onan runs like Sheet: Episode II, the Onan still runs like sheet! [message #80179 is a reply to message #80151] |
Sun, 11 April 2010 15:36 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Shan,
If you put your location in your signature there might be a fellow GMCer
nearby that can help you.
Don't be surprised if someone offers to loan you a coil but wants a deposit
up front.
There have been a number of people who have loaned tools, parts, manuals to
people on the net only to get burned!
Regards,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Shan Rose
Sent: Monday, 12 April 2010 2:49 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Onan runs like Sheet: Episode II,the Onan still runs
like sheet!
Ok, first off thanks for the imput guys, I'm stil leaning to a carb/ignition
problem however. I dont think the heads are carbonized really tha much,
reason being when I pulledthe plugs for a plug reading they were a nice
light tan, not sooty black, and I have had the onan run for many hours and
it always ran like a clock, only with an occational sumble, and I would load
the SOB down with a good 30 amps of load, and it would chug away with no
problems.
then one day it just started acting like that, and then wouldnt start. also
the fuel mixture smells richer then it should be, and there is not an
occational backfire, the report something akin to a 1911 .45 ACP, which is
real fun when you dont have your ears on. while working on the onan I take
my rig to a commercial/industrial area as to not get the attention of the
police looking for someone discharging a firearm within city limits.
Also ther still the odd EM feild whcih seems to like to screw with sensitive
digital equipment. it was causing the display screen on my expensive sony HD
handy cam to jump around when my GF got to cloose to the genset running.
As for Carb Icing, well its more of a clod sweat, the air temp yesterday was
about 68 degrees when I was making that video. but you can see the sweat on
the intake. its like the cooling effect seen with top fuel or nitrous
injection. so this is what is making me think perhaps the onan is inhailing
a denser mix of fuel then it should. it would seem its not atomizing
correctly for some reason. and for what ever reason, walbro does not include
a new power nozzle with the rebuild kit for their carb.
now as to what makes me think it could be ignition related is the strange EM
feild which I never witnessed in my onan. it also screws with my digital
timing light, something which it never did before.
basically what I need is someone who can loan me a working old coil or spare
carb to troubleshoot both of these systems. I'd take care of the shipping
and return. I need to get this onan running right, I do a lot of dry camping
and need my AC 120 to effectively do stuff...
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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 runs like Sheet: Episode II, the Onan still runs like sheet! [message #80183 is a reply to message #80179] |
Sun, 11 April 2010 15:55 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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De-carbonize the heads and piston. It will only take you 45 minutes. You can reuse the old head gaskets with no problem.
The moisture you see on the outside of the carb / intake is normal. I have seen it many times on my and other Onans when they were running perfectly.
De-carbonize the heads, Check the spark plug gap on BOTH plugs and make then exactly the same. Then readjust the carb mixture screw when it is running.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Onan runs like Sheet: Episode II, the Onan still runs like sheet! [message #80203 is a reply to message #80183] |
Sun, 11 April 2010 17:12 |
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ok Ken, I'll try that, the plugs are new and gapped exactly the same, both have less then an hour on them.
I do think its an ignition problem because of the strange EM field never before encountered....
Robert, i'm in Los Angeles California for what its worth. and yeah I would have a problem leaving someone a depost on a loaner. I rented a tool off the net before and left the deposit which was refunded when I returned the item...
| Ken Burton wrote on Sun, 11 April 2010 15:55 |
De-carbonize the heads and piston. It will only take you 45 minutes. You can reuse the old head gaskets with no problem.
The moisture you see on the outside of the carb / intake is normal. I have seen it many times on my and other Onans when they were running perfectly.
De-carbonize the heads, Check the spark plug gap on BOTH plugs and make then exactly the same. Then readjust the carb mixture screw when it is running.
|
73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
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| Re: [GMCnet] Onan runs like Sheet: Episode II, the Onan still runs like sheet! [message #80218 is a reply to message #80203] |
Sun, 11 April 2010 18:23 |
bhayes
Messages: 263
Registered: March 2010
Karma: 1
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Senior Member |
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Perhaps the strange EM field is being caused by the ignition system.
Bryan Hayes
GMCless in Salt Lake City, UT
On Sun, Apr 11, 2010 at 4:12 PM, Shan Rose <defconfx@gmail.com> wrote:
>
>
> ok Ken, I'll try that, the plugs are new and gapped exactly the same, both
> have less then an hour on them.
>
> I do think its an ignition problem because of the strange EM field never
> before encountered....
>
> Robert, i'm in Los Angeles California for what its worth. and yeah I would
> have a problem leaving someone a depost on a loaner. I rented a tool off the
> net before and left the deposit which was refunded when I returned the
> item...
>
> Ken Burton wrote on Sun, 11 April 2010 15:55
> > De-carbonize the heads and piston. It will only take you 45 minutes.
> You can reuse the old head gaskets with no problem.
> >
> > The moisture you see on the outside of the carb / intake is normal. I
> have seen it many times on my and other Onans when they were running
> perfectly.
> >
> > De-carbonize the heads, Check the spark plug gap on BOTH plugs and make
> then exactly the same. Then readjust the carb mixture screw when it is
> running.
>
>
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
_______________________________________________
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List Information and Subscription Options:
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Bryan Hayes
'76 Eleganza II
Salt Lake City, Utah
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| Re: Onan runs like Sheet: Episode II, the Onan still runs like sheet! [message #80247 is a reply to message #80151] |
Sun, 11 April 2010 20:27 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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| Duce Apocalypse wrote on Sun, 11 April 2010 12:49 |
<snip> . . . and there is not an occasional backfire, the report something akin to a 1911 .45 ACP, which is real fun when you don't have your ears on. <snip>
|
Duce,
If when you wrote this you indicated that there was a backfire issue, then we have a much bigger problem. . . Backfire actually means back through the carburetor.
Not That - Good
So -
If what you were actually talking about was an exhaust system report (big bang from the muffler and tail pipe), that indicates unburned charge was pumped into the muffler and ignited by a subsequent exhaust flame. That leans WAY toward an ignition problem.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: Onan runs like Sheet: Episode II, the Onan still runs like sheet! [message #80265 is a reply to message #80080] |
Sun, 11 April 2010 22:27 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Heres a LOOOONG shot. That oil filter looks like it is the original (kidding) or very old. Could it be cloged and tripping the low oil pressure switch. The switch could be "flickering" in the fail mode like Ford brake light switches were famous for. As for icing, I'm with Emery on that one--- it only happens under a very specific set of conditions and not with you wearing a short sleave shirt nor in that short a run time.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Onan runs like Sheet: Episode II, the Onan still runs like sheet! [message #80304 is a reply to message #80265] |
Mon, 12 April 2010 12:22 |
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Yeah I'm planning an oil change though the oil actually looks really clean. Iirc when you do the 5-9 jumper doesn't that bypass the LOP? Cause I still have the same issue with the jumper installed. I'm more interested in the source of EM that I'm getting...
| JohnL455 wrote on Sun, 11 April 2010 22:27 |
Heres a LOOOONG shot. That oil filter looks like it is the original (kidding) or very old. Could it be cloged and tripping the low oil pressure switch. The switch could be "flickering" in the fail mode like Ford brake light switches were famous for. As for icing, I'm with Emery on that one--- it only happens under a very specific set of conditions and not with you wearing a short sleave shirt nor in that short a run time.
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73 Canyon Lands, (a.k.a. The Yellow Submarine) West Los Angeles CA
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