Home » Public Forums » GMCnet » [GMCnet] Running the Onan now, and then isn't as good as you might think
| [GMCnet] Running the Onan now, and then isn't as good as you might think [message #317729] |
Thu, 18 May 2017 08:42  |
BobDunahugh
Messages: 2465
Registered: October 2010
Location: Cedar Rapids, IA
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I've heard of owners starting the Onan every two weeks, or once a month. And thinking that the practice is good for the unit. Think of it this way. Every time you start it. You fill the carb with gas. Then you shut it off with a carb filled with gas. Then the lights evaporate out of the carb. Leaving the heavier material to build up in the carb as deposits in the carb. I only run my Onan when I need to use it. If your GMC sits for a very long time. Drain your tanks. Put in fresh gas. Disconnect the gas line to the carb of the generator. Turn the electric fuel pump on with your prime button. Or a jumper switch to get fresh gas from the tank to the carb. Reconnect the gas line to the carb. And start. This is the same situation for your engine in the GMC. Bob Dunahugh Member GMCMI
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| Re: [GMCnet] Running the Onan now, and then isn't as good as you might think [message #317733 is a reply to message #317729] |
Thu, 18 May 2017 09:16  |
Richard Denney
Messages: 920
Registered: April 2010
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Seems to me, stuff lasts longer when it is used, if for no other reason
that faults are detected and corrected earlier rather than later. I've
determined to take my coach out once a month, if at all possible, for a
drive around the area of at least 50 miles. I have not been doing that, and
it is part of the reason I'm now correcting many items of my own neglect.
That 600 miles a year isn't going to wear it out, but it will keep the fuel
recycled and minimize the formation of corrosion in moving parts. It will
heat up the engine enough to boil off condensation. Yes, I will run the
generator or after that exercise. I'm betting that the relatively frequent
use will do more good than the increased possibility of varnish building up
in the carb. Finally, it will remind me that the coach works, and can be
used any time, which we sometimes forget and allow ourselves to get nervous.
Rick "maybe I'm wrong" Denney
On Thu, May 18, 2017 at 9:42 AM, Bob Dunahugh wrote:
> I've heard of owners starting the Onan every two weeks, or once a month.
> And thinking that the practice is good for the unit. Think of it this way.
> Every time you start it. You fill the carb with gas. Then you shut it off
> with a carb filled with gas. Then the lights evaporate out of the carb.
> Leaving the heavier material to build up in the carb as deposits in the
> carb. I only run my Onan when I need to use it. If your GMC sits for a very
> long time. Drain your tanks. Put in fresh gas. Disconnect the gas line to
> the carb of the generator. Turn the electric fuel pump on with your prime
> button. Or a jumper switch to get fresh gas from the tank to the carb.
> Reconnect the gas line to the carb. And start. This is the same situation
> for your engine in the GMC. Bob Dunahugh Member GMCMI
>
--
'73 X-Glacier 230 "Jaws"
Northern Virginia
Offlist email: rick at rickdenney dot com
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| Re: [GMCnet] Running the Onan now, and then isn't as good as you might think [message #317735 is a reply to message #317732] |
Thu, 18 May 2017 09:52 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Mr ERFisher wrote on Thu, 18 May 2017 09:57On Thu, May 18, 2017 at 6:50 AM gene Fisher wrote:
> Or go to propane 😀😀
>
Read here
http://gmc49ers.blogspot.com/2015/09/onan-gmc-propane-conversion.html
Gene Fisher -- 74-23,77PB/ore/ca
"Give a man a fish; you have fed him for today --- give him a URL and
Gene,
As simple as this might sound to you, do you realize that one has to purchase a new propane tank to do this right. I used to have two pieces of LP fueled equipment. Either side of both weeks of Michigan summer they were true PITAs. If you pull gas out of the LP tank, the tank sub-cools and the flow stops. When I changed to a forkup trunk tank with a liquid withdrawal and a vaporizer, at least I could use the equipment in the spring when we needed it.
I don't need to go through that again. We use the coach in both the spring and fall. (Outside of winter, that is what most of the time that is not winter in Michigan.)
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: [GMCnet] Running the Onan now, and then isn't as good as you might think [message #317736 is a reply to message #317733] |
Thu, 18 May 2017 09:50 |
richshoop
Messages: 190
Registered: April 2017
Karma: 0
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Standard practice for standby generators of all sizes is either bi- weekly or monthly exercise running. For our own generator, I run it once a month for about 15 minutes, I shut off the gas supply and allow the generator to burn off all of the gas in the carb as it quits running. I also use synthetic oil of the recommended grade.
----- Original Message -----
From: "Richard Denney"
To: "gmclist"
Sent: Thursday, May 18, 2017 7:16:12 AM
Subject: Re: [GMCnet] Running the Onan now, and then isn't as good as you might think
Seems to me, stuff lasts longer when it is used, if for no other reason
that faults are detected and corrected earlier rather than later. I've
determined to take my coach out once a month, if at all possible, for a
drive around the area of at least 50 miles. I have not been doing that, and
it is part of the reason I'm now correcting many items of my own neglect.
That 600 miles a year isn't going to wear it out, but it will keep the fuel
recycled and minimize the formation of corrosion in moving parts. It will
heat up the engine enough to boil off condensation. Yes, I will run the
generator or after that exercise. I'm betting that the relatively frequent
use will do more good than the increased possibility of varnish building up
in the carb. Finally, it will remind me that the coach works, and can be
used any time, which we sometimes forget and allow ourselves to get nervous.
Rick "maybe I'm wrong" Denney
On Thu, May 18, 2017 at 9:42 AM, Bob Dunahugh wrote:
> I've heard of owners starting the Onan every two weeks, or once a month.
> And thinking that the practice is good for the unit. Think of it this way.
> Every time you start it. You fill the carb with gas. Then you shut it off
> with a carb filled with gas. Then the lights evaporate out of the carb.
> Leaving the heavier material to build up in the carb as deposits in the
> carb. I only run my Onan when I need to use it. If your GMC sits for a very
> long time. Drain your tanks. Put in fresh gas. Disconnect the gas line to
> the carb of the generator. Turn the electric fuel pump on with your prime
> button. Or a jumper switch to get fresh gas from the tank to the carb.
> Reconnect the gas line to the carb. And start. This is the same situation
> for your engine in the GMC. Bob Dunahugh Member GMCMI
>
--
'73 X-Glacier 230 "Jaws"
Northern Virginia
Offlist email: rick at rickdenney dot com
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| Re: [GMCnet] Running the Onan now, and then isn't as good as you might think [message #317741 is a reply to message #317736] |
Thu, 18 May 2017 10:17 |
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Dutch Marc
Messages: 101
Registered: March 2017
Location: Full TIme Nomad
Karma: 1
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Senior Member |
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[quote title=
Seems to me, stuff lasts longer when it is used, if for no other reason
that faults are detected and corrected earlier rather than later. I've
determined to take my coach out once a month, if at all possible, for a
drive around the area of at least 50 miles. I have not been doing that, and
it is part of the reason I'm now correcting many items of my own neglect.
That 600 miles a year isn't going to wear it out, but it will keep the fuel
recycled and minimize the formation of corrosion in moving parts. It will
heat up the engine enough to boil off condensation. Yes, I will run the
generator or after that exercise. I'm betting that the relatively frequent
use will do more good than the increased possibility of varnish building up
in the carb. Finally, it will remind me that the coach works, and can be
used any time, which we sometimes forget and allow ourselves to get nervous.
[/quote]
Seems to make sense to me. I am thinking about trying to do the same thing.
Thanks Dutch Marc
1973 26' Canyon Land (Mello Yello) (TZE063v101302)
Full Time GMC Nomad ('98 NL 2 USA)
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| Re: [GMCnet] Running the Onan now, and then isn't as good as you might think [message #317758 is a reply to message #317736] |
Thu, 18 May 2017 11:39 |
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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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This is an interesting thread, and everybody is both some right and sone wrong and all at the same time.
Start with Rich Schoop
There are BIG differences between standby units and ours.
Standby units (all the good ones) are heated. Both the coolant and lube oil are maintained at just below operating temperatures all the time. (This is also true of all capital engines.) This vastly mitigates the thermal cycle issues. These engines are also carefully maintained.
Now To Rick Denny, Who is not really wrong, the simple answer is that things work better when they are not ignored. Maintenance is the real key here. I you shove a machine aside for months and expect it ot operate as it should when you want it next is just plain foolish. (I see this in marinas all the time.)
Bob Dunahugh is also right about getting the fuel out of the float bowl, but with our Onans it is way easier than he makes it out to be. It does take two steps to do it real right. The first to disconnect the fuel pump while the engine is running, when it quits, step two is to loose n the float bowl (takes a 7/16 box) and drain the float bowl because the main jet is there.
On to significant generalities that I have learned over nearly six decades (yes, I stated at 12) of taking care of other peoples engines and later doing literally millions of hours (simultaneous not sequential) of engine testing.
There are two things that internal engine are not happy about.
First is corrosion. This is easy with all open loop engines. If you are going to leave any engine unattended for an unkonwn or a known long time, fog it. OK, fogging is a simple operation of blowing oil vapor into the intake just before it gets shut down. This is best done warm. It will coat all that bare metal with a film that will discourage corrosion. If done carefully, and engine can sit alone a long time and suffer no damage. I personally can vouch for a decade. This may damage and O2 sensor, and don't do it to a diesel as the engine may run away on the oil vapor.
Second, but really not very far behind is thermal cycles. This is so profound that the aircraft industry counts engine cycles more than hours on their engines. All of the Detroit Oes now have cold cycle testing as a part of their validation. Everytime and engine is heated and cooled, the parts move. One of the worst of these is the cylinder head gasket joint. I have actually seen head and manifold gaskets get worn out from this movement.
Then there is the basic issue of "nothing good happens to an engnie at idle". I have seen the all of the years I have been an "engine guy".
Now is a time for another of Matthew's Pet Peaves...
"Run a generator unit at some load regularly to keep the moisture out of the windings."
The coil varnish that was this moisture sensitive was obsoleted before the Second World War. Personally, I believe that Onan keeps this myth alive because they sell parts. There can be no other reason that I can imagine.
If you take care of an Onan just a little, it should outlast any of us. I have seen NH engines with over eight thousand hours on them. One was still just fine, but one was tired and needed an overhaul. (Just for reference, 8760 is a year - remember, I did durability.)
As a side note, if you pop the heads off to de-carbon, don't buy gaskets. The OE were copper with asbestos fill, and if they are undamaged, they will seal even better the second time and each successive, just don't over tension (torque) the fasteners.
While composing this thesis on the way to visit Blain and Diane, we passed John Shotwell and John Pryzbylek. We have two stops to make on the way. One more for fuel and another for a Museum of Miniature Houses.
Matt - typing and taking pictures while Mary drives
richshoop wrote on Thu, 18 May 2017 10:50Standard practice for standby generators of all sizes is either bi- weekly or monthly exercise running. For our own generator, I run it once a month for about 15 minutes, I shut off the gas supply and allow the generator to burn off all of the gas in the carb as it quits running. I also use synthetic oil of the recommended grade.
----- Original Message -----
From: "Richard Denney"
To: "gmclist"
Sent: Thursday, May 18, 2017 7:16:12 AM
Subject: Re: [GMCnet] Running the Onan now, and then isn't as good as you might think
Seems to me, stuff lasts longer when it is used, if for no other reason that faults are detected and corrected earlier rather than later. I've determined to take my coach out once a month, if at all possible, for a drive around the area of at least 50 miles. I have not been doing that, and it is part of the reason I'm now correcting many items of my own neglect. That 600 miles a year isn't going to wear it out, but it will keep the fuel recycled and minimize the formation of corrosion in moving parts. I'll heat up the engine enough to boil off condensation. Yes, I will run the
generator or after that exercise. I'm betting that the relatively frequent use will do more good than the increased possibility of varnish building up in the carb. Finally, it will remind me that the coach works, and can be used any time, which we sometimes forget and allow ourselves to get nervous.
Rick "maybe I'm wrong" Denney
On Thu, May 18, 2017 at 9:42 AM, Bob Dunahugh wrote:
I've heard of owners starting the Onan every two weeks, or once a month.
And thinking that the practice is good for the unit. Think of it this way.
Every time you start it. You fill the carb with gas. Then you shut it off with a carb filled with gas. Then the lights evaporate out of the carb. Leaving the heavier material to build up in the carb as deposits in the carb. I only run my Onan when I need to use it. If your GMC sits for a very long time. Drain your tanks. Put in fresh gas. Disconnect the gas line to the carb of the generator. Turn the electric fuel pump on with your prime button. Or a jumper switch to get fresh gas from the tank to the carb. Reconnect the gas line to the carb. And start. This is the same situation for your engine in the GMC.
Bob Dunahugh Member GMCMI
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: [GMCnet] Running the Onan now, and then isn't as good as you might think [message #317759 is a reply to message #317739] |
Thu, 18 May 2017 11:53 |
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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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Marc,
With a virtual antique as our Onans are, you will be hard pressed to get a lube oil that not effective. A problem with any small engine is that the cooling of the lubricating oil is problematic at best. So, all my small engines use a 10W30 synthetic. Recently, that has been Mobil 1 because of a wonderful casual evening dinner at an SAE conference years ago. Other may have caught up with Mobil, but I don't have freinds in the business anymore. (The luck of those I did have are retired.) One thing of value that I found out then was that while the oil may continue to lubricate a much longer time, the anti-corrosion additives do loose effectiveness due to oxidation. That can't be prevented. They las ta bit longer than a year. So, I don't bother tracking hours onmy small engines (the Onan I do for fuel use) I just date the engine cowl with a china marker.
Matt - still reading while Mary drives.
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: [GMCnet] Running the Onan now, and then isn't as good as you might think [message #317765 is a reply to message #317759] |
Thu, 18 May 2017 13:12 |
Richard Denney
Messages: 920
Registered: April 2010
Karma: 9
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Senior Member |
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To some extent, I wonder if worrying about byproducts of evaporation in the
float bowl is working at the margins.
Backup generators are only kept warm in certain situations--the typical
home backup or commercial lighting generator, even expensive ones that are
permanently installed, are not. One of the radio clubs I play with has a
30-KW diesel Kohler that came off the roof of a shopping center--it's role
was to provide lighting for safety in case of a power failure. It certainly
was never kept to operating temperature. But it was still subject to
periodic testing, mostly for the purpose of making sure it worked.
Thermal cycles are what they are. I drive my Ford every day of the year. I
traded the previous one in with 170,000 miles on it to avoid having to
spend a lot to repair a transmission that was certainly not failing because
of thermal cycles. That drivetrain went through 300-400 complete thermal
cycles a year, maybe more, for eight years--maybe 2500-3000 over its life.
My Honda lawn mower (to choose an example from the other end of the scale),
which has certainly not received diligent maintenance, has been used about
20 times a year for 18 years, for a total of 350-400 thermal cycles. It
needs a new recoil starter, which is on order, but otherwise still runs
great. Run once a month, an engine capable of only 400 thermal cycles can
go over 33 years. If the engine can survive ten times that number with no
loss of function, then it's a non-issue. So, it seems to me that thermal
cycles are a marginal issue at best in the consideration of monthly
exercise, though I don't doubt their real effects.
And the things we might do to prepare for long-term storage are
interesting, but nobody's going to do them. Fogging the engine with oil
vapor? Not a chance. Pulling the plugs, squirting oil in the cylinders, and
then cranking the engine to distribute the oil? Nope. Maybe if I owned a
backup engine being stored for later use, but not in a vehicle I can drive.
So, how to we prevent the damage of corrosion, which seems to me worse than
the effects of evaporated fuel in the float bowl? Use it. A monthly drive
(not just sitting in the driveway idling, of course--but the Onan, which
runs at 1800 RPMs, never really idles) heats everything up, boils off
condensation, distributes oil and coolant, exercises tires (which are
constructed to stay softer when exercised, which I learned I think from
Emery about 15 years ago), knocks the dust off, chases off the mice, and
reinforces our confidence that the machine works well enough to be used on
a whim. The more we use it, the more use we get out of it.
The problems I had with my Onan were not related to varnish in the carb.
They were related to three things: 1.) Unreliable electrical control
system, 2.) the spray of oil it produced when running (which was not any of
the easy things to fix--I tried them all), and 3.) a cracked exhaust riser,
which could have burned the coach up--it was jetting right onto the plywood
enclosure. People are still fighting the control system, and yes I could
have overhauled the motor to fix the other two issues. None of these were
related to varnish. The oil spray might have been related to corrosion--in
the cylinders and affecting the seals I did not replace. The exhaust leak
might have been related to thermal cycling, but I suspect it was corrosion
in that threaded connection that provided a crack path. And corrosion in
the control board was part of its problem, too.
Rust never sleeps (I think I heard that somewhere) and that is the real
enemy, it seems to me. I'll restate what I suggested in my first message in
this thread: The risk of varnish formation seems to be much less than the
risk of things getting too used to not being used, and becoming unusable.
I'm certainly not saying Bob is wrong, but I would rather address the issue
by contriving to *need* the generator once a month--that way, I'm not just
running it without need.
Rick "trying to keep things in practical perspective" Denney
On Thu, May 18, 2017 at 12:53 PM, Matt Colie wrote:
> Marc,
>
> With a virtual antique as our Onans are, you will be hard pressed to get a
> lube oil that not effective. A problem with any small engine is that the
> cooling of the lubricating oil is problematic at best. So, all my small
> engines use a 10W30 synthetic. Recently, that has been Mobil 1 because of a
> wonderful casual evening dinner at an SAE conference years ago. Other may
> have caught up with Mobil, but I don't have freinds in the business
> anymore. (The luck of those I did have are retired.) One thing of value
> that I found out then was that while the oil may continue to lubricate a
> much
> longer time, the anti-corrosion additives do loose effectiveness due to
> oxidation. That can't be prevented. They las ta bit longer than a year.
> So,
> I don't bother tracking hours onmy small engines (the Onan I do for fuel
> use) I just date the engine cowl with a china marker.
>
> Matt - still reading while Mary drives.
> --
> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Still Loving OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
'73 X-Glacier 230 "Jaws"
Northern Virginia
Offlist email: rick at rickdenney dot com
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| Re: [GMCnet] Running the Onan now, and then isn't as good as you might think [message #317772 is a reply to message #317729] |
Thu, 18 May 2017 15:47 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Our big sets were all 'hospital' rated, which means they will take rated load within seven seconds of a start command. We used them because the transmitters would withstand a seven second power loss and run immediately instead of going through the entire start sequence. Which in a Top Ten market equates to money. A Cummins 'Big Cam' engine will not take load when the block is twenty degrees Fahrenheit, things will break. So part of the package is a block heater which keeps the set ready to run. They ran with load thirty minutes a week. This routine did in fact fail one engine to a leak in a cylinder liner, but it took 25 years of service to do it. The set was still running, but poorly and getting hot. We put an Onan rebuilt short block in it and kept going. That was ten years ago, the set is still working fine. Which brings up a couple of truisms. Like the coaches, they respond better to use than to sitting; and if you don't run them regularly there's no guarantee they'll run when you need them.
--johnny
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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