Running the onan in hot weather

[RJW]

> Richard,
>
> You might consider adding a supplemental fan like Johnny's been promoting
> or like this one of mine (since permanently mounted):
>
> http://www.gmcmhphotos.com/photos/troybilt-generator-installation/p31703-140-cdddooling-fan-temporarily-mounted.html
>
> That one works very well supplying air to the ToryBilt I've been running,
> with NO problems, since 2009.
>
> With such a fan rigged to run with the Onan shut down (perhaps on a
> thermostat or a timer?), you might easily alleviate your vapor lock problem.
>
> Oh yeah, it's installed to blow INTO the compartment.
>
> Ken H.

That could work. I wonder if there is enough room for a fan with the Onan installed.

When I first read about the fans, I assumed it was for use with the APU running. I did not realize it was for cooling after shutdown.

--
Richard
76 Palm Beach
SE Michigan
www.PalmBeachGMC.com


Coop Roller Cam 455, Howell TBI + EBL, 3.42 FD, Quadra Bag, Macerator, Manny Tranny etc.

 

[Ken H.]

RIchard,

I really don't know whether there'd be room for a supply fan with the
Onan. The one I have installed runs only with the TroyBilt, but it I don't
have a post-run heating problem like yours.

Ken H.

> That could work. I wonder if there is enough room for a fan with the Onan
> installed.
>
> When I first read about the fans, I assumed it was for use with the APU
> running. I did not realize it was for cooling after shutdown.
>
>

 

[jim miller]

> I did not try sliding it out during gas stops. In retrospect, it seems like that would help cool it during a fuel stop. Good tip!

Unless the gas pump behavior police are patrolling the area when you stop to fuel up - or you have a seriously compromised fuel tank vent system on your coach - I do not understand why you would shut the Onan down.

Your main tanks are vented with an elaborate system that releases tank air up through the fill nozzle during fueling and captures the rest in a charcoal canister once the fill port is capped. If you overfill a bit then a check valve in the driver side wheel well will prevent liquid fuel from getting to the canister and escaping.

IMO the area most at risk during fueling is at the fill nozzle rather than 20' away at the Onan. Do you smell gas fumes at the back of the coach while the nozzle up front is filling the tanks?

If you are going to shut down the Onan while fueling the vehicle then open the Onan hatch as soon as possible and leave it open during the entire fuel stop. Convection will naturally scavenge the heat from the compartment; the heated air in the vicinity of the manifold will rise up and away from the coach through the open hatch - and as it leaves it will naturally draw in cooler air from the back of the compartment.

I have documented the temperatures inside the Onan compartment after a 30 minute full-load run by using thermocouples throughout the enclosure. On an 85F day _with the hatch closed the whole time_ the temperature directly above the exhaust manifold after shutdown reached a peak of 220F and then immediately begins to decrease. If the hatch is open then the situation is much better since the hot air can directly escape through natural flow.

I do not think pulling the Onan out on its slides during the stop will appreciably reduce the cool down time compared to simply opening the hatch and frankly I think it increases the risk of a fire or some other problem. There’s a fuel hose and some electrical wiring in the bottom of the drawer that has to flex when the drawer comes out - and is at risk of getting pinched or cut when the drawer goes back in.

If you are having severe problems with “vapor lock” then investigate a reflective barrier between the manifolds and the carb as well as the other insulating techniques that Ken and others have already pointed out.

—Jim

Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH

 

[Jim Hupy]

Like I always say: "Fuel up first thing in the morning, travel as early in
the day as possible." Hot fueling is asking for trouble, particularly in
Spring and Early Summer when winter blend fuel is still present in the
supply chain. But, what the heck, last time I checked, this is still a free
country. Make your choices, live with the results.
Jim Hupy
Salem, Or (88° farenheit today)
78 GMC ROYALE 403

>
> > I did not try sliding it out during gas stops. In retrospect, it seems
> like that would help cool it during a fuel stop. Good tip!
>
> Unless the gas pump behavior police are patrolling the area when you stop
> to fuel up - or you have a seriously compromised fuel tank vent system on
> your coach - I do not understand why you would shut the Onan down.
>
> Your main tanks are vented with an elaborate system that releases tank air
> up through the fill nozzle during fueling and captures the rest in a
> charcoal canister once the fill port is capped. If you overfill a bit then
> a check valve in the driver side wheel well will prevent liquid fuel from
> getting to the canister and escaping.
>
> IMO the area most at risk during fueling is at the fill nozzle rather than
> 20' away at the Onan. Do you smell gas fumes at the back of the coach while
> the nozzle up front is filling the tanks?
>
> If you are going to shut down the Onan while fueling the vehicle then open
> the Onan hatch as soon as possible and leave it open during the entire fuel
> stop. Convection will naturally scavenge the heat from the compartment; the
> heated air in the vicinity of the manifold will rise up and away from the
> coach through the open hatch - and as it leaves it will naturally draw in
> cooler air from the back of the compartment.
>
> I have documented the temperatures inside the Onan compartment after a 30
> minute full-load run by using thermocouples throughout the enclosure. On an
> 85F day _with the hatch closed the whole time_ the temperature directly
> above the exhaust manifold after shutdown reached a peak of 220F and then
> immediately begins to decrease. If the hatch is open then the situation is
> much better since the hot air can directly escape through natural flow.
>
> I do not think pulling the Onan out on its slides during the stop will
> appreciably reduce the cool down time compared to simply opening the hatch
> and frankly I think it increases the risk of a fire or some other problem.
> There’s a fuel hose and some electrical wiring in the bottom of the drawer
> that has to flex when the drawer comes out - and is at risk of getting
> pinched or cut when the drawer goes back in.
>
> If you are having severe problems with “vapor lock” then investigate a
> reflective barrier between the manifolds and the carb as well as the other
> insulating techniques that Ken and others have already pointed out.
>
> —Jim
>
> Jim Miller
> 1977 Eleganza
> 1977 Royale
> Hamilton, OH
>
>
>
>
> _______________________________________________
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> Unsubscribe or Change List Options:
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>

 

[RJW]

> Like I always say: "Fuel up first thing in the morning, travel as early in
> the day as possible." Hot fueling is asking for trouble, particularly in
> Spring and Early Summer when winter blend fuel is still present in the
> supply chain. But, what the heck, last time I checked, this is still a free
> country. Make your choices, live with the results.
> Jim Hupy
> Salem, Or (88° farenheit today)
> 78 GMC ROYALE 403

Sure, in a perfect world that makes perfect sense. However, since I still work for a living and could only budget 2 weeks for a 3,000 mile (with a
week at the destination) trip, I had 7 days for travel. That forced me to drive 2 600 mile days, 2 500 mile days and the rest ~250-300 mile days. That
forced me to stop for gas 1 to 2 times a day since I can only comfortably go ~250 miles between fillups. The alternative would have been to fly (costs
more than the GMC gas) down and stay in motels/hotels. No thanks, I would rather drive the GMC.
--
Richard
76 Palm Beach
SE Michigan
www.PalmBeachGMC.com


Coop Roller Cam 455, Howell TBI + EBL, 3.42 FD, Quadra Bag, Macerator, Manny Tranny etc.

 

[RJW]

> If you are having severe problems with "vapor lock" then investigate a reflective barrier between the manifolds and the carb as well as the other
> insulating techniques that Ken and others have already pointed out.
>
> Jim Miller
> 1977 Eleganza
> 1977 Royale
> Hamilton, OH

Normally, I do not have problems with the Onan vapor lock issue since I rarely get outside of the Midwest US and Canada. If I go to the Southeast,
it's in the spring when temps there are still relatively cool. The trip to Texas was the first time in 19 years (over 110,000 miles) of owning my GMC
that I had been exposed to 95-100+ degree temps when traveling in the motorhome. I only did that because of a wedding we needed to attend.

Since I plan on keeping my GMC, I (like most everyone else on this list) like to continually make improvements that help to improve driveability and
comfort.

--
Richard
76 Palm Beach
SE Michigan
www.PalmBeachGMC.com


Coop Roller Cam 455, Howell TBI + EBL, 3.42 FD, Quadra Bag, Macerator, Manny Tranny etc.

 

[Jim Hupy]

The ONE POINT I was trying to make, was this: There is nothing wrong with
your coach, or for that matter, your ONAN. Trying to fix a non problem, has
little probability of success.
The PROBLEM IS THE FUEL and the additives it doesn't contain at all
temperatures. Unless your name is ExxonMobil or Standard Oil or Arco you
are probably not in an area of decision making that would allow you to
influence this problem to any great degree.
That leaves all of us in the same boat. Trying "Band-Aid" fixes to an
injury that needs advanced life support.
I'm just saying that you can minimize the effects of alcohol laced
gasoline, but not eliminate them completely, especially in the heat of the
day. Believe me, I hate it just as much as you do.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

> > If you are having severe problems with "vapor lock" then investigate a
> reflective barrier between the manifolds and the carb as well as the other
> > insulating techniques that Ken and others have already pointed out.
> >
> > Jim Miller
> > 1977 Eleganza
> > 1977 Royale
> > Hamilton, OH
>
>
> Normally, I do not have problems with the Onan vapor lock issue since I
> rarely get outside of the Midwest US and Canada. If I go to the Southeast,
> it's in the spring when temps there are still relatively cool. The trip
> to Texas was the first time in 19 years (over 110,000 miles) of owning my
> GMC
> that I had been exposed to 95-100+ degree temps when traveling in the
> motorhome. I only did that because of a wedding we needed to attend.
>
> Since I plan on keeping my GMC, I (like most everyone else on this list)
> like to continually make improvements that help to improve driveability and
> comfort.
>
> --
> Richard
> 76 Palm Beach
> SE Michigan
> www.PalmBeachGMC.com
>
>
> Coop Roller Cam 455, Howell TBI + EBL, 3.42 FD, Quadra Bag, Macerator,
> Manny Tranny etc.
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[johnny]

I always ran the carbureted coach and its genset on non alcohol fuel and once I got the coach cooling system sorted, had no problem with vapor lock
even in the Florida and Georgia summers. The current coach runs on alcohol gas if asked, I try not to ask it more for the Onan than the coach itself.
The fuel system is fairly tight, doesn't leak or smell at fillup, so I let the Onan putter away. When I go to Orlando or Salem or the like, I start
very early but there's gonna be the occasional fuel stop on the trip.

--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

 

[Ken B]

> The ONE POINT I was trying to make, was this: There is nothing wrong with
> your coach, or for that matter, your ONAN. Trying to fix a non problem, has
> little probability of success.
> The PROBLEM IS THE FUEL and the additives it doesn't contain at all
> temperatures. Unless your name is ExxonMobil or Standard Oil or Arco you
> are probably not in an area of decision making that would allow you to
> influence this problem to any great degree.
> That leaves all of us in the same boat. Trying "Band-Aid" fixes to an
> injury that needs advanced life support.
> I'm just saying that you can minimize the effects of alcohol laced
> gasoline, but not eliminate them completely, especially in the heat of the
> day. Believe me, I hate it just as much as you do.
> Jim Hupy
> Salem, Or
> 78 GMC ROYALE 403

To backup Jim's posting, here is what the EPA dictates the Reid Vapor Pressure of the fuel is during the summer months which is usually May 1 through
Sept 15. Look up you state and county to see the number. Higher is worser.

https://www.epa.gov/gasoline-standards/gasoline-reid-vapor-pressure

The problem NOT SHOWN in the chart is there is a second rule allowing alcohol blends of 9% or 10%, a waiver of one point. So if you are already at
9.0, what you are usually getting is at he pump is 10.0. As a side note, aviation gasoline is 7.0 year round in the US and no ethanol is allowed.
They do not want vapor lock problems in aircraft.

This one point is not a major problem for most of the driving public because all modern vehicles are fuel injected and they use higher pressure in
tank pumps which usually keeps the fuel from vaporizing in the lines.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[jim kanomata1]

On the generator, there are times a vapor loc will happen, so always use a
1/4" hose.

> The ONE POINT I was trying to make, was this: There is nothing wrong with
> your coach, or for that matter, your ONAN. Trying to fix a non problem, has
> little probability of success.
> The PROBLEM IS THE FUEL and the additives it doesn't contain at all
> temperatures. Unless your name is ExxonMobil or Standard Oil or Arco you
> are probably not in an area of decision making that would allow you to
> influence this problem to any great degree.
> That leaves all of us in the same boat. Trying "Band-Aid" fixes to an
> injury that needs advanced life support.
> I'm just saying that you can minimize the effects of alcohol laced
> gasoline, but not eliminate them completely, especially in the heat of the
> day. Believe me, I hate it just as much as you do.
> Jim Hupy
> Salem, Or
> 78 GMC ROYALE 403
>

>

> > > If you are having severe problems with "vapor lock" then investigate a
> > reflective barrier between the manifolds and the carb as well as the
> other
> > > insulating techniques that Ken and others have already pointed out.
> > >
> > > Jim Miller
> > > 1977 Eleganza
> > > 1977 Royale
> > > Hamilton, OH
> >
> >
> > Normally, I do not have problems with the Onan vapor lock issue since I
> > rarely get outside of the Midwest US and Canada. If I go to the
> Southeast,
> > it's in the spring when temps there are still relatively cool. The trip
> > to Texas was the first time in 19 years (over 110,000 miles) of owning my
> > GMC
> > that I had been exposed to 95-100+ degree temps when traveling in the
> > motorhome. I only did that because of a wedding we needed to attend.
> >
> > Since I plan on keeping my GMC, I (like most everyone else on this list)
> > like to continually make improvements that help to improve driveability
> and
> > comfort.
> >
> > --
> > Richard
> > 76 Palm Beach
> > SE Michigan
> > www.PalmBeachGMC.com
> >
> >
> > Coop Roller Cam 455, Howell TBI + EBL, 3.42 FD, Quadra Bag, Macerator,
> > Manny Tranny etc.
> >
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502