Home » Public Forums » GMCnet » [GMCnet] how the dual gas tanks work?
| [GMCnet] how the dual gas tanks work? [message #301976] |
Fri, 10 June 2016 17:26  |
Ek_Lektro
Messages: 167
Registered: March 2011
Karma: 2
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hey, long time since i’ve visited the forum here!
(with the facebook group seeming to grab most attention lately.. from the photo side of things).
well my question is a little technical, and hopefully answered somewhere in the archives.. so nobody has to type out a long explanation :) (please let me know if there’s a link somewhere)
Its been a while since i’ve had to wrap my head around how
the 2 gas tanks work, in terms of main tank and reserve tank.
i know that they’re both 25 gallons, and i recall that if you just ran with the switch in the main tank position, til things ran dry, that you’d have a reserve of 6 gallons in tank #2.
(Is that right?)
well after an attempted fix of the long-standing “breathing” problem in the ’76 Birchhaven, (whereas i could only fill a few gallons of gas at a time, regardless of letting air out of the bags, etc), OK, now the gas fills rapidly, great! however, now we’ve got the opposite problem: Apparently the output line from tank #1 sometimes gets restricted, and we’ll stall out. but with the switch in the aux tank position, everything works just fine.
Yes! This was one of the super cheap repairs i got done down in Mexico while we were getting our paintjob (literally, one guy was working on the fuel lines, while other guys were doing bodywork), and i’m planning on driving back down to get another round of work done, sometime soon... including fixing this probable crimped line;
but in the meantime, my question:
Can i keep running off tank #2 (switch to the aux tank position) and presume to have 25 gallons available? I think the downside is that i’d have to fill up completely in order to achieve 25 gallons in tank #2, because i recall that tank 2 only fills once tank #1 is fully filled?
again, if there’s a link that explains all this, that’d be great!
I’d like to take some road-trips in the next couple weeks, but want to know how much fuel range i have available to play with.. before i get time to fix the problem once and for all.
many thanks!
Greg
los angeles
’76 Birchhaven custom cut-down 21’ (finally painted!)
’78 Eleganza II w/1000 watt solar array
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| Re: [GMCnet] how the dual gas tanks work? [message #301977 is a reply to message #301976] |
Fri, 10 June 2016 17:49  |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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Greg,
Give me a call and I'll go over it with you.
On Fri, Jun 10, 2016 at 3:26 PM, Ek_Lektro wrote:
> hey, long time since i’ve visited the forum here!
> (with the facebook group seeming to grab most attention lately.. from the
> photo side of things).
> well my question is a little technical, and hopefully answered somewhere
> in the archives.. so nobody has to type out a long explanation :) (please
> let me know if there’s a link somewhere)
>
> Its been a while since i’ve had to wrap my head around how
> the 2 gas tanks work, in terms of main tank and reserve tank.
> i know that they’re both 25 gallons, and i recall that if you just ran
> with the switch in the main tank position, til things ran dry, that you’d
> have a reserve of 6 gallons in tank #2.
> (Is that right?)
>
> well after an attempted fix of the long-standing “breathing” problem in
> the ’76 Birchhaven, (whereas i could only fill a few gallons of gas at a
> time, regardless of letting air out of the bags, etc), OK, now the gas
> fills rapidly, great! however, now we’ve got the opposite problem:
> Apparently the output line from tank #1 sometimes gets restricted, and
> we’ll stall out. but with the switch in the aux tank position, everything
> works just fine.
>
> Yes! This was one of the super cheap repairs i got done down in Mexico
> while we were getting our paintjob (literally, one guy was working on the
> fuel lines, while other guys were doing bodywork), and i’m planning on
> driving back down to get another round of work done, sometime soon...
> including fixing this probable crimped line;
> but in the meantime, my question:
>
> Can i keep running off tank #2 (switch to the aux tank position) and
> presume to have 25 gallons available? I think the downside is that i’d
> have to fill up completely in order to achieve 25 gallons in tank #2,
> because i recall that tank 2 only fills once tank #1 is fully filled?
>
> again, if there’s a link that explains all this, that’d be great!
> I’d like to take some road-trips in the next couple weeks, but want to
> know how much fuel range i have available to play with.. before i get time
> to fix the problem once and for all.
>
> many thanks!
> Greg
> los angeles
> ’76 Birchhaven custom cut-down 21’ (finally painted!)
> ’78 Eleganza II w/1000 watt solar array
>
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] how the dual gas tanks work? [message #301978 is a reply to message #301976] |
Fri, 10 June 2016 17:59 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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If you ran on tank #2 (the reserve), you will have exactly the same amount of fuel available as if you ran on tank #1. You can run tank#2 to empty and then would have 6 to 7 gallons left in the unused remaining tank.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] how the dual gas tanks work? [message #301981 is a reply to message #301976] |
Fri, 10 June 2016 18:21 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Somebody (Colie?) pointed out the dynamics of the fuel running to the rear in the fill line and then being bounced back by the tank unbuckling restriced flow into the aux tank. Rear tank is the end of the fill line, aux is essentially off to the side. Both of mine fell slowly. If there's a line at the pumps I set the nozzle on slow and walk back and tell the guy behind me 'you might want to get in another line....'
--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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| Re: [GMCnet] how the dual gas tanks work? [message #301983 is a reply to message #301976] |
Fri, 10 June 2016 18:35 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Since Cinnabar re did mine about 10 yrs back they fill full speed. Still as you get near full, best to go to one click as the "stop" shock wave reflects back and will regurgitate.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] how the dual gas tanks work? [message #301989 is a reply to message #301980] |
Fri, 10 June 2016 22:27 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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I do not have an explanation because the two tanks are connected together by the 1" or 1-1/4 " fill line. After 7 gallons are in each tank then they balance out through the fill tube.
They could be slow to balance out if one of the air vents on the top of the tanks were plugged / restricted. I would assume that you would see the same fill problems no matter which tank is emptied first. Even with the air vent completely plugged the tank with the most fuel would get air through the fuel fill tube once for the lower tank once goes below 7 gallons.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] how the dual gas tanks work? [message #301994 is a reply to message #301976] |
Sat, 11 June 2016 00:20 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Senior Member |
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Be aware if you get low on fuel running on the auxiliary tank and you try to climb a steep hill the little fuel that is in it will mostly transfer to the main tank.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] how the dual gas tanks work? [message #302004 is a reply to message #301994] |
Sat, 11 June 2016 09:33 |
kstockwell
Messages: 367
Registered: May 2016
Location: Putney VT
Karma: 4
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Senior Member |
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So, to clarify what's obvious in the drawing/info in the link
Fill it up like any other vehicle, both tanks fill with the link between tanks
Keep the selector switch to "main" which is the rear tank as a default setting
when fuel gets low or if you're going down hills with a lower level of fuel switch to Aux
going up hill with a lower level of fuel be sure you're on main
did i get it?
there's no pump between tanks, it's just at the mercy of gravity.
kelly
1978 Kingsley
Putney VT
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| Re: [GMCnet] how the dual gas tanks work? [message #302024 is a reply to message #301976] |
Sat, 11 June 2016 19:36 |
Ek_Lektro
Messages: 167
Registered: March 2011
Karma: 2
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Senior Member |
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Sorry for the late response (i’m on the digest version of the list)
and thanks to everybody for contributing info!
Also many thanks to Jim K / Applied GMC for volunteering the after-hours phonecall
yesterday, with the verbal explanation, confirming my hopes that
if i keep the switch on “aux”, i should get 30-some gallons of driving from a 50-gallon fill
(that’s what i needed to hear)
at least until i can get the suspected crimped line fixed!
Also thanks for that link Bruce….
I’ve got some reading to do…
More commentary after i catch up on the reading..
cheers!
> On Jun 10, 2016, at 3:49 PM, gmclist-request@list.gmcnet.org wrote:
>
> From: Jim Kanomata
> To: gmclist@list.gmcnet.org
> Subject: Re: [GMCnet] how the dual gas tanks work?
>
> Greg,
> Give me a call and I'll go over it with you.
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. How did they ever think you could fill one of these with all the bends/twists in the fill lines?