Onan generator what to do

davidlive

davidlive

Member
Nov 19, 2011
216
27
18
Simi Valley, California
What advice / things should I check or replace before attempting to start the Onan generator that's been sitting for over 8 years ?

I might work for on it this weekend Fri or sat. Or it might wait till next erek.

Thanks David
--
1974 G-M-C Painted Desert #136
"Oversteer is when you hit the wall with the rear of the car, understeer is when you hit the wall with the front of the car. Hp is how fast you hit
the wall, and torque is how far you take the wall with you when you hit it."
 
I think I would definitely change the oil.

Then I would take a short jumper with alligator clips and connect pin 5 to pin 9 on the control board for about 30 seconds. You should heard he fuel
pump running and after it fills the carb with gas the pump should slow down.

Then remove the jumper and try to start it and see what happens. It might surprise you and run. If it does run smoothly, I would run it for 5
minutes or so, and then add some load to it like the air condition. Run it with load for an additional 5 minutes.

TURN OFF THE LOAD first and then shut down the Onan.

If it does not start and run smoothly then come back here and tell us what happened. We will give you additional help.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
> What advice / things should I check or replace before attempting to start the Onan generator that's been sitting for over 8 years?
>
> I might work on it this weekend Fri or Sat. Or it might wait till next week.
>
> Thanks David
Before you do what Ken Burton said, turn off the AC circuit breaker at the Onan to make sure it doesn't try to come on under load.

Don't be surprised if the fuel pump doesn't work. Mine was seized up with shellac from the gas that had evaporated from it. I had to turn it upside
down and soak it in acetone for a week to get it loose. And the acetone ruined the rubber seal at the bottom cap, so take that out if you need to soak
the pump with acetone.

If the fuel pump is seized up, rig up something like a lawnmower tank to gravity feed it for testing purposes. Or buy a low pressure electric gas pump
from the auto parts store. IIRC, Mr. Gasket is a popular brand for this application. There are several models available, get the lowest pressure model
you can find. 3.5 PSI or lower.

My experience with gas engines is, if it was running when it was abandoned, it will run again as soon as it gets turning with gas in the cylinder(s).
The carburetor float might be stuck and let too much gas in and flood it, but it should fire a few times before it drowns.
--
73 23' Sequoia 4 Sale
73 23' CanyonLands Parts Unit 4 Sale
Upper Alabama
"When I grow up I am going to be a curmudgeon."
 
David

Go here, scroll down to Waking a Sleeping Giant

http://bdub.net/gmcmotorhome.info/generator.html

Good luck,
Dennis

> What advice / things should I check or replace before attempting to start the Onan generator that's been sitting for over 8 years ?
>
> I might work for on it this weekend Fri or sat. Or it might wait till next erek.
>
>
> Thanks David

--
Dennis S
73 Painted Desert 230
Memphis TN Metro
 
> > ***SNIP***
> >
> > Thanks David
> Before you do what Ken Burton said, turn off the AC circuit breaker at the Onan to make sure it doesn't try to come on under load.
>
>
> ***SNIP***

That is a good thought. Rather than trip the CB you can also just leave it unplugged in the outside electrical cabinet. Then prior to plugging the
coah into the Onan you can check the no load voltage if desired at the receiptical inside the cabinet.

I have had the float stick open in the carb after sitting as little as 6 months. If it sticks open you will have gas overflowing everywhere around
the carb air cleaner and also inside the engine. So when you initially install the 5-9 jumper without it running look at the carb, the air cleaner
and around the carb for any indication of gas overflow.

Keep a fire extinguisher close at hand just in case. Preferably bot a dry powder type.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
When i change the oil, what oil should be used ? i've found 2 new onan filters left by the previous owner

Thanks David
--
1974 G-M-C Painted Desert #136
"Oversteer is when you hit the wall with the rear of the car, understeer is when you hit the wall with the front of the car. Hp is how fast you hit
the wall, and torque is how far you take the wall with you when you hit it."
 
> When i change the oil, what oil should be used ? i've found 2 new onan filters left by the previous owner
>
>
> Thanks David

David,

Were I you, (I try never to say this, because there is a lot about you are your situation that I do not know) I would drain and refill with anything
handy that ends in 30. I would try not to use one that starts with a 0 or a 5. That engine is just too old. The reason that the manuals all have
the "Pick a Weight" chart is that oils were not as good then as they are now.

The oil in the engine is old and the anti-wear additives have aged out. So Yes, drain that. Put back in something new as above. That oil will
probably get abused while getting the thing to light and stay lit. By that I mean it will get overly contaminated with both wet fuel and combustion
by-products. So, get that sweat old thing humming again, then change the filter and put in the good oil you want to keep in it.

I happen to run Mobil 1 10W40 (the one Costco does not sell) in all my small engines (4) because air cooled engines are hard on the oil as that oil
does more of the cooling and gets less cooling in the lube oil path.

Matt
--
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
 
> When i change the oil, what oil should be used ? I've found 2 new Onan filters left by the previous owner
> Thanks David
I respectfully disagree with Matt. In SoCal it doesn't get cold enough to need multi-viscosity oil in the Onan. Put straight 30 weight oil in it,
especially for the initial start and run where you are. The viscosity enhancers in multi-viscosity oil will break down fast in the Onan, and you would
need to change the oil more often than the manual recommends.

If you are going to use it a lot in temperatures below freezing, then you would consider 10W30.

Matt is in Michigan, and runs snowblowers and snowmobiles and what-not. You may have never seen either one.
--
73 23' Sequoia 4 Sale
73 23' CanyonLands Parts Unit 4 Sale
Upper Alabama
"When I grow up I am going to be a curmudgeon."
 
My Onan has always been happy running what I use in the engine. In my case this was 5-40 rotella for a short time but mostly 15-50 Mobil one both
synthetic . It never leaked or burned any oil that I can recall in the 29 years that I owned it. It has lived its life in Southern California and
Nevada. I always figured since it is air cooled synthetic oil can take more heat then Dino oil and 15-50 would be a good thing in the hot south west
deserts.
--
Roy Keen
Minden,NV
76 X Glenbrook
 
Oil preference is like any other preference. Autos, Sports Teams, Women,
BBQ, Politics, you name it. It does not matter much whether or not one is
better than the other, it comes down to preference. Reason, heck there
isn't a reason, it's company policy. There used to be a small re-refinery
in Salem, long since driven out of business by stringent air quality
regulations, that collected used engine oils and re-refined them. They had
10 wt., 20 wt., 30 wt., 40 wt., in both detergent and non detergent.
Bottled it in white plastic containers. Pride of Oregon brand, then it
changed to Proco Oil, then went away entirely. People either swore by it or
at it, depending upon their preference. I personally did not use it, but
only because I got my major brand oil for free because I worked in a full
service gas station that did more than hand you a receipt after you had
pumped your own gas. That was in addition to my full time day job. Owner
helped sponsor our race car, and I helped him out by working evenings and
weekends to pay for my racing habit. Stuff was different, back in the 50's
and 60's.
Jim Hupy
Salem, OR
78 GMC Royale 403

> My Onan has always been happy running what I use in the engine. In my case
> this was 5-40 rotella for a short time but mostly 15-50 Mobil one both
> synthetic . It never leaked or burned any oil that I can recall in the 29
> years that I owned it. It has lived its life in Southern California and
> Nevada. I always figured since it is air cooled synthetic oil can take
> more heat then Dino oil and 15-50 would be a good thing in the hot south
> west
> deserts.
> --
> Roy Keen
> Minden,NV
> 76 X Glenbrook
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
It's interesting to note that Back When, a lot of the Unlimited air racers ran rerefined oil in their engines. It's been refined twice, which means
fewer of the large molecules are left - it's slicker than new stuff. In the racer, it's coming out after the race, so the lack of many of the
additives for longevity isn't a problem.
The onset of synthetic oils seems to have done away with rerefining old oil, I haven't seen any in a long time. Always used it in the race car
engines, again it's coming out after the race. Use it in a street car, you probably ought to add some decent aftermarket stuff to make up for what's
missing. On the farm, used oil goes into the two stroke gasoline and the cutter bar oiler on the chainsaw. Waste nothing.

--johnny
--
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" - ol Andy, paraphrased
 
Thank you all, I think this answers my questions, hopefully i'll be able to get to this next weekend, this weekend i'm changing the fuel lines in the
coach, and thought of this while at it.

Thanks David
--
1974 G-M-C Painted Desert #136
"Oversteer is when you hit the wall with the rear of the car, understeer is when you hit the wall with the front of the car. Hp is how fast you hit
the wall, and torque is how far you take the wall with you when you hit it."
 
I have quite a bit of experience on air cooled engines which is what most aircraft use. The first rule of thumb is NEVER use a synthetic oil. The
second rules is to use a multi-weight oil that is higher weight than what you would use in a water cooled engine in the same outside air temperature
environment.

Air cooled engines are built with greater tolerances and they all (burn) some oil to some extent. The reason they are built with wider gaps is they
run at various temperatures depending on the outside air temperatures and loads applied to the engine. A water cooled engine runs at the temperature
of the installed thermostat. Usually this is 180 or 195. Air cooled engines do not.

Because they do burn some oil, the residue left from oil burning accumulates inside the cylinders. This is why we remove and clean plugs every 50 or
100 hours on aircraft air cooled engines. On aircraft engines we also use an FAA approved Ashless Dispersant oil to reduce this cylinder buildup.
Usually we use a 50W oil except in cold weather start up or initial engine break-in conditions. These days the preferred oil is a 15W50 oil for
easier starting and good lubrication at extreme conditions.

What we NEVER use is a synthetic oil. This is because when synthetic oil burns it leaves rock hard deposits inside the engine cylinders that is
almost impossible to remove. We had one guy that used a Synthetic oil in his airplane, When we pulled the engine apart due to low compression
readings we ended up throwing away all 4 of his cylinders because of the synthetic oil deposits. We tried everything to remove the deposits. We
eventually sent them to the cylinder rebuild shop where they were officially declared junk. At the time new cylinders were around $1200 each.

So, based on all of this, I recommend that you use a 15W40 non-synthetic oil in your Onan engine. Shell Rotella T4 (non-synthetic) is a good one but
others will also work. You might also look at 10W40 or 20W50 non-synthetic oil.

That said, NEVER use an Aircraft oil in your non-aircraft air cooled engine. It is a poor lubricant on things like cams but that is a different
topic.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
> I have quite a bit of experience on air cooled engines which is what most aircraft use. The first rule of thumb is NEVER use a synthetic oil.
> The second rules is to use a multi-weight oil that is higher weight than what you would use in a water cooled engine in the same outside air
> temperature environment.
>
> Air cooled engines are built with greater tolerances and they all (burn) some oil to some extent. The reason they are built with wider gaps is
> they run at various temperatures depending on the outside air temperatures and loads applied to the engine. A water cooled engine runs at the
> temperature of the installed thermostat. Usually this is 180 or 195. Air cooled engines do not.
>
> Because they do burn some oil, the residue left from oil burning accumulates inside the cylinders. This is why we remove and clean plugs every 50
> or 100 hours on aircraft air cooled engines. On aircraft engines we also use an FAA approved Ashless Dispersant oil to reduce this cylinder
> buildup. Usually we use a 50W oil except in cold weather start up or initial engine break-in conditions. These days the preferred oil is a 15W50
> oil for easier starting and good lubrication at extreme conditions.
>
> What we NEVER use is a synthetic oil. This is because when synthetic oil burns it leaves rock hard deposits inside the engine cylinders that is
> almost impossible to remove. We had one guy that used a Synthetic oil in his airplane, When we pulled the engine apart due to low compression
> readings we ended up throwing away all 4 of his cylinders because of the synthetic oil deposits. We tried everything to remove the deposits. We
> eventually sent them to the cylinder rebuild shop where they were officially declared junk. At the time new cylinders were around $1200 each.
>
> So, based on all of this, I recommend that you use a 15W40 non-synthetic oil in your Onan engine. Shell Rotella T4 (non-synthetic) is a good one
> but others will also work. You might also look at 10W40 or 20W50 non-synthetic oil.
>
> That said, NEVER use an Aircraft oil in your non-aircraft air cooled engine. It is a poor lubricant on things like cams but that is a different
> topic.

Ken,

I have also seen the hard deposits left in the combustion space, but then, I actually helped create them. But, I would not try to tag that as all air
cooled engines. Aircraft motors are designed to both run at much higher BMEP and to consume more lube oil than other engines. This is a value
judgement on their part and it makes sense when you look at the service. By that same token, if one has any engine that is consuming a significant
amount of lube oil, I would not recommend any synthetic. There is apparently a silicon component that cooks up real nicely and fuses with hot metal
surfaces. Quartz is silicon dioxide.

The operation band of little air cooled engines is very different. Their specific power output is WAY down. That's the difference between 0.4
and 0.7 (Both are rounded by a lot.) But, those little engines have no means to cool the oil that has cooled the piston other than let is sit
in the pan. I have been watching, and have not seen the hard deposits in my Onan and I also have never seen them in the personal Kohler fleet.

Matt

--
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
 
well i cleaned up the generator, from the rat nest, rat crap, power washed it, and I will need new plugs, wires, battery cables, some other wire
repairs (rat chew) and clean what i think is the control board, hopefully it's alright, i could always salvage the one off my other unit too if
needed...

http://s3.photobucket.com/user/DavidLive/media/1978%20GMC%20motorhome/IMG_20170310_165254_zpsqwsczuem.jpg.html
http://s3.photobucket.com/user/DavidLive/media/1978%20GMC%20motorhome/IMG_20170310_165308_zpsccewrcpi.jpg.html
http://s3.photobucket.com/user/DavidLive/media/1978%20GMC%20motorhome/IMG_20170310_165317_zpssujfeq3q.jpg.html
http://s3.photobucket.com/user/DavidLive/media/1978%20GMC%20motorhome/IMG_20170310_165504_zpsa66cdlxm.jpg.html

Thanks David
--
78 Royal #749
74 #136
Oversteer is when you hit the wall with the rear of the car, understeer is when you hit the wall with the front of the car. Hp is how fast you hit the
wall, and torque is how far you take the wall with you when you hit it.
 
Matt, I was just trying to give some background on my recommendation of not using Synthetic. The problem is not just limited to air cooled engines as
we saw on Arch's 455 years ago when it was burning oil. I was trying to point out that it happens more frequently in air cooled engines do to their
looser tolerances. I never run Synthetic in my Onan, my motorcycles, and my airplane 4 cycle air cooled engines.

A few years back one of the oil companies came out with a synthetic oil for piston engine aircraft. After they had to replace many damaged engines,
the oil was pulled off of the market.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
> ...power washed it...
You are joking, right?

You don't ever want water near the Onan.
--
73 23' Sequoia 4 Sale
73 23' CanyonLands Parts Unit 4 Sale
Upper Alabama
"When I grow up I am going to be a curmudgeon."
 
Duane Simmons the Onan Expert said to NEVER power wash the onan generator!

J.R. Wright
GMC GreatLaker
Newsletter Editor/Publisher
Tech Editor
78 Buskirk 30' Stretch
75 Avion Under Reconstruction
Michigan

>

>> ...power washed it...
> You are joking, right?
>
> You don't ever want water near the Onan.
> --
> 73 23' Sequoia 4 Sale
> 73 23' CanyonLands Parts Unit 4 Sale
> Upper Alabama
> "When I grow up I am going to be a curmudgeon."
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
> Duane Simmons the Onan Expert said to NEVER power wash the onan generator!


Water near the generator section is a bad situation due to the aluminum wiring that was used to wind both the armature and the field coils. I expect that many of the fields that I’ve repaired have failed primarily due to water incursion. The usual failure mode is one or more of the coil windings (usually the one on the bottom of the field) having turned to white powder - aluminum oxide - at the location where it winds around a pole piece. When I repair a field assembly I impregnate the coils with motor epoxy and then wrap them with polyester tape before installing them back over the pole pieces; hopefully this will help to prevent stress concentrations at the locations in question.

It would be OK, however, to wash the generator with some dehydrated water…unobtanium oxide.

Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH
 
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