Home » Public Forums » GMCnet » [GMCnet] Onan Question
| [GMCnet] Onan Question [message #24179] |
Fri, 10 October 2008 20:37  |
Bruce Tara
Messages: 3
Registered: August 2008
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Has anyone had experience with Blow By in the Onan? I took our "New" coach out of storage today for the first time in about 4 months. The coach has had nothing done to it since we acquired it. I started the Onan for the first time and had a horrendous experience. The P.O., or someone had replaced the oil filler cap with one that did not have "wings" on it that would hold it in. The result was an oil geyser that covered the Onan, me, coach and part of the driveway. There was no shutting down the Onan engine with either the switch on the Onan or the remote switch on the interior. The unit sounded good and ran well until I pulled the plug wires to shut it down.
My question is: Is this amount of Blowby normal? The shut down switch in another problem that I will address when the engine dry's out.
Bruce & Elizabeth Tara
'78 Royale Center Galley
"Bank Buster"
Our Next Project
Gilbert, AZ
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| Re: [GMCnet] Onan Question [message #24185 is a reply to message #24179] |
Fri, 10 October 2008 21:06  |
Walt Taylor
Messages: 3
Registered: February 2004
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on 10/10/08 8:37 PM, Bruce Tara at bnetara@aceweb.com wrote:
>
> Has anyone had experience with Blow By in the Onan? I took our "New" coach out
> of storage today for the first time in about 4 months. The coach has had
> nothing done to it since we acquired it. I started the Onan for the first time
> and had a horrendous experience. The P.O., or someone had replaced the oil
> filler cap with one that did not have "wings" on it that would hold it in. The
> result was an oil geyser that covered the Onan, me, coach and part of the
> driveway.
Ummm, yes. Welcome to the "gusher" club, Bruce. You may be the only innocent
member I know of. Some of us were unintelligent enough to pull the
cap/dipstick while it was running.
Since it's a two-cylinder, opposed engine, both pistons go out at the same
time. Then, they turn around and come in at the same time, pumping the total
displacement amount of air into the crankcase.
When I loosened the cap, it ricocheted off the drip rail, but still stayed
airborne for several seconds.
Walt Taylor
Elroy, TX
'75 Eleganza, '75 Transmode
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| Re: [GMCnet] Onan Question [message #24194 is a reply to message #24192] |
Fri, 10 October 2008 22:43 |
Walt Taylor
Messages: 3
Registered: February 2004
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I always thought they called them "boxers", 'cuz they imitated the motion of
a boxer striking gloves together in front of his chest. But Col Cracker, if
they moved in the same direction simultaneously, I think the engine would
imitate a schizophrenic frog, leaping forward and backward from the
stop-start of both pistons summing, rather than opposing.
Only an intellectual exercise to us rotor-heads (Wankel), though.
Walt
on 10/10/08 10:06 PM, Ken Henderson at ken0henderson@gmail.com wrote:
> Ooops! Pardon my Boo-Boo! Walt's right: the pistons move in opposite
> directions. I don't know why I had it in my mind that it was a single
> throw crank, making them move in the same direction. Took me a while to
> find an illustration of the 2-throw crank to convince me too.
>
> That makes the reason for the oil geyser even more acute. And that
> tremendous pressure variation explains why I had to repair the oil pan
> on my old 4KH -- it had cracked for several inches along one of the
> creases in the bottom.
>
> Ken Henderson
> Americus, GA
> www.gmcwipersetc.com
> '76 X-Birchaven
> '76 X-Palm Beach
>
>
> Walt Taylor wrote:
>> on 10/10/08 8:37 PM, Bruce Tara at bnetara@aceweb.com wrote:
>>> Has anyone had experience with Blow By in the Onan? ...
>
>> ...Since it's a two-cylinder, opposed engine, both pistons go out at the same
>> time. Then, they turn around and come in at the same time, pumping the total
>> displacement amount of air into the crankcase...
>
> _______________________________________________
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> Gmclist@temp.gmcnet.org
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| Re: [GMCnet] Onan Question [message #24197 is a reply to message #24179] |
Fri, 10 October 2008 23:02 |
Bruce Tara
Messages: 3
Registered: August 2008
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Thanks all for the information. I am not worried now about this "problem", that turns out to be normal. Now the answer is to get a proper crankcase filler cap. Autozone, Checker or Napa should have something. Although I was covered in oil along with the coach and Onan, thank goodness for Gunk and the fact that the oil was fairly clean the mess is cleaned up. Having hosed down the engine I will let it bake in the sun until Sunday before I try again to fire the brute up again. That will give me tomorrow to look for a cap.
Thanks again.
Bruce & Elizabeth Tara
'78 Royale Center Galley
"Bank Buster"
Our Next Project
Gilbert, AZ
------- Original Message -------
From : Ken Henderson[mailto:ken0henderson@gmail.com]
Sent : 10/10/2008 6:46:39 PM
To : gmclist@temp.gmcnet.org
Cc :
Subject : RE: Re: [GMCnet] Onan Question
Bruce,
I think what you experienced is the normal crankcase pressure variation
many of us have experienced when we innocently pulled the oil cap with
the engine running. Remember that the two pistons always move in the
same direction, moving a big bolus of air back and forth with them.
That air would rather escape through the filler pipe than move back and
forth. And does when we give it a chance.
Ken Henderson
Americus, GA
www.gmcwipersetc.com
'76 X-Birchaven
'76 X-Palm Beach
Bruce Tara wrote:
> ...I started the
> Onan for the first time and had a horrendous experience. The P.O., or
> someone had replaced the oil filler cap with one that did not have
> "wings" on it that would hold it in. The result was an oil geyser
> that covered the Onan, me, coach and part of the driveway...
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| Re: [GMCnet] Onan Question [message #24200 is a reply to message #24192] |
Sat, 11 October 2008 00:07 |
Tin Gerbil
Messages: 236
Registered: October 2006
Location: Vancouver Island, B.C.
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Ken;
Wouldn't a non-boxer be a bear to balance? Just think a 200 lb flywheel
on a 400 lb engine.
Gordon
Ken Henderson wrote:
> Ooops! Pardon my Boo-Boo! Walt's right: the pistons move in opposite
> directions. I don't know why I had it in my mind that it was a single
> throw crank, making them move in the same direction. Took me a while to
> find an illustration of the 2-throw crank to convince me too.
>
> That makes the reason for the oil geyser even more acute. And that
> tremendous pressure variation explains why I had to repair the oil pan
> on my old 4KH -- it had cracked for several inches along one of the
> creases in the bottom.
>
> Ken Henderson
> Americus, GA
>
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Gordon
'74 Canyon Lands "Tin Gerbil"
Vancouver Island, B.C.
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| Re: [GMCnet] Onan Question [message #24201 is a reply to message #24179] |
Sat, 11 October 2008 00:24 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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""Has anyone had experience with Blow By in the Onan? I took our "New" coach out of storage today for the first time in about 4 months. The coach has had nothing done to it since we acquired it. I started the Onan for the first time and had a horrendous experience. The P.O., or someone had replaced the oil filler cap with one that did not have "wings" on it that would hold it in. The result was an oil geyser that covered the Onan, me, coach and part of the driveway. There was no shutting down the Onan engine with either the switch on the Onan or the remote switch on the interior. The unit sounded good and ran well until I pulled the plug wires to shut it down.
My question is: Is this amount of Blowby normal? The shut down switch in another problem that I will address when the engine dry's out.""
Hi Bruce--although I don't like it, it seems to be typical of these old Onans. Mine did it before and after I rebuilt it about 10 years ago. It runs perfectly and uses just a bit of oil while running 24/7 for days out here in AZ
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Onan question [message #97205 is a reply to message #24179] |
Wed, 25 August 2010 17:10 |
i.d.garza
Messages: 1
Registered: April 2004
Karma: 0
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Junior Member |
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Check the electric fuel pump on the Onan. It is probably getting stuck and not pumping fuel when hot. You can run a short wire to it to power it direct. You will more than likely find that it will not vibrate when hot. You can dismental the pump and clean the plunger with fine sand paper and that may fix your problem.
LOL
Dan
---------- Original Message ----------
From: Larry Davick <ljdavick@comcast.net>
To: "gmclist@temp.gmcnet.org" <gmclist@temp.gmcnet.org>
Subject: Re: [GMCnet] Onan question
Date: Mon, 23 Aug 2010 19:42:05 -0700
Fuel filter?
Ljdavick at comcast.net
On Aug 23, 2010, at 2:05 PM, Bryan Hayes <bhayes@byu.net> wrote:
> We've been having an issue with the Onan in our newly purchased '76
> Eleganza. It will run under load for about 30-60 minutes, then
> stumble and
> stall. No amount of cranking will get it to start again until at
> least 30+
> minutes have passed. I suspect a fuel delivery issue or that it is
> overheating, and was wondering if there is a thermal shutdown switch
> somewhere that shuts it down to prevent overheating. The problem
> seems to
> occur more often if the outside temperature is above 85 degrees, and
> it
> occurs even when the fuel tank is full. It also has plenty of oil,
> so I
> don't think it's the low oil switch.
>
> Bryan Hayes
> '76 Eleganza II
> Salt Lake City, Utah
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