Home » Public Forums » GMCnet » Fuel Vent Mod
| Fuel Vent Mod [message #242791] |
Sat, 08 March 2014 17:28  |
Jon payne
Messages: 495
Registered: May 2008
Karma: 1
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Hi everyone,
First week in April I hope to drop my fuel tanks and begin the restoration of the system. I have been planning on doing the below fuel vent mod but I have some doubts on how effective it is. Just thinking that the extra line will not do to much since both lines will still connect to the one going to the filler neck negating the effect of the extra line. Am I wrong?
http://www.gmcmhphotos.com/photos/data/5908/Fuel_Tank_Vent_Mod.JPG
Jon Payne
76 Palm Beach
Westfield,IN
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| Re: Fuel Vent Mod [message #242797 is a reply to message #242791] |
Sat, 08 March 2014 18:22  |
corleyw
Messages: 130
Registered: June 2007
Location: Battle Ground, WA
Karma: 0
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Has anyone tried moving the filler pipe back into the area of the tanks? Seems like shortening those two lines would be very advantageous, if it is possible to do this. Also, the filler pipe could be arranged to enter at an angle, instead of straight up and down. I am always running into pump nozzles that don't work well on the GMC. I never really understood why he filler pipe is up front anyway...
As to your question, I am sorry to report I have no idea of the effectiveness of that "fix", it just seems to me that there is a better option.
Corley
'76 Glenbrook
29 other vehicles
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| Re: [GMCnet] Fuel Vent Mod [message #242805 is a reply to message #242791] |
Sat, 08 March 2014 19:00 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Jon,
I modified that drawing because it was reported here that this mod is effective; however, I did not know about it when I dropped the
tanks in Double Trouble and replaced all the lines. I have problems with burping when I fill up.
IIRC when this mod was published it was noted that the vent lines get gasoline in them which restricts venting when filling. I have
NO idea if that is correct or not.
I have all the parts necessary to drop the tanks again and install in tank pumps using Poly Armour tubing, I will run two vent lines
as close to the vent attached to the fill tube as possible.
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
-----Original Message-----
From: Jon Payne
Hi everyone,
First week in April I hope to drop my fuel tanks and begin the restoration of the system. I have been planning on doing the below
fuel vent mod but I have some doubts on how effective it is. Just thinking that the extra line will not do to much since both lines
will still connect to the one going to the filler neck negating the effect of the extra line. Am I wrong?
http://www.gmcmhphotos.com/photos/data/5908/Fuel_Tank_Vent_Mod.JPG
Jon
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Fuel Vent Mod [message #242806 is a reply to message #242797] |
Sat, 08 March 2014 19:05 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Manny moved his because he installed a door on the driver side he could get out of along with a slide out:
http://www.gmcmhphotos.com/photos/2004-southern-oregon-mini-rally/p8508.html
MarcH also moved the fill on his diesel:
http://www.gmcmhphotos.com/photos/restoration-and-diesel-conversion/p8699.html
As far as why GMC put it where they did one must look back at the 1970's when service stations had pump attendents, you could stay
in the drivers seat and hand the payment out the small window.
When I was in NJ with Double Trouble that's exactly what I did!
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
-----Original Message-----
From: Corley Wooldridge
Has anyone tried moving the filler pipe back into the area of the tanks? Seems like shortening those two lines would be very
advantageous, if it is possible to do this. Also, the filler pipe could be arranged to enter at an angle, instead of straight up and
down. I am always running into pump nozzles that don't work well on the GMC. I never really understood why he filler pipe is up
front anyway...
As to your question, I am sorry to report I have no idea of the effectiveness of that "fix", it just seems to me that there is a
better option.
--
Corley
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Fuel Vent Mod [message #242817 is a reply to message #242805] |
Sat, 08 March 2014 19:40 |
Jon payne
Messages: 495
Registered: May 2008
Karma: 1
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Thanks Rob for your input!. That is my plan as well, that is, installing in-tank fuel pumps and Poly Armour steel lines. I too thought about running two vent lines as close as possible to the filler but that would mean they would terminate in the engine compartment and I have some concerns with fuel vapors in that area. Not sure if that is what you had in mine.
Anyway, I have been trying to think of how to terminate the vent lines to the outside, maybe in the driver wheel well?. Any ideas??
Jon
Jon Payne
76 Palm Beach
Westfield,IN
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| Re: [GMCnet] Fuel Vent Mod [message #242823 is a reply to message #242817] |
Sat, 08 March 2014 20:10 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Jon,
The existing vents tee together back near the front tank and are connected to the vent line connected to the filler neck.
http://www.gmcmhphotos.com/photos/misc/p51371-type-1-fuel-vent-line.html
Run two lines as far forward and as close vent line connected to the filler neck.
http://www.gmcmhphotos.com/photos/random-photos/p51372-fuel-tank-vent-mod.html
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org [mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Jon Payne
Thanks Rob for your input!. That is my plan as well, that is, installing in-tank fuel pumps and Poly Armour steel lines. I too
thought about running two vent lines as close as possible to the filler but that would mean they would terminate in the engine
compartment and I have some concerns with fuel vapors in that area. Not sure if that is what you had in mine.
Anyway, I have been trying to think of how to terminate the vent lines to the outside, maybe in the driver wheel well?. Any ideas??
Jon
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: Fuel Vent Mod [message #242824 is a reply to message #242791] |
Sat, 08 March 2014 20:13 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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I'm considering Dave Lenzi's vent mod. 1/2" vent lines to a common vent through the roof and one of those weather vane caps. Remove all the charcoal canisters and associated 'stuff'.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: [GMCnet] Fuel Vent Mod [message #242851 is a reply to message #242824] |
Sun, 09 March 2014 01:59 |
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ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
Karma: -3
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For what benefit?
Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, CA
> On Mar 8, 2014, at 6:13 PM, Kerry Pinkerton <Pinkertonk@MCHSI.com> wrote:
>
>
>
> I'm considering Dave Lenzi's vent mod. 1/2" vent lines to a common vent through the roof and one of those weather vane caps. Remove all the charcoal canisters and associated 'stuff'.
> --
> Kerry Pinkerton
>
> North Alabama, near Huntsville,
>
> 77 Eleganza II, "The Lady", 403CI, also a 76 Eleganza being re-bodied as an Art Deco car hauler
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
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| Re: [GMCnet] Fuel Vent Mod [message #242852 is a reply to message #242817] |
Sun, 09 March 2014 03:12 |
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ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
Karma: -3
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Maybe I've been insulated by my checkbook. When I needed to replace the fuel lines I took the coach to Jim K who brought it back to factory specs. I fill at full speed and have no issues though I use a foam donut for the California nozzles. I conclude from my experience that the GM design works.
Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, CA
> On Mar 8, 2014, at 5:40 PM, Jon Payne <embrep@sbcglobal.net> wrote:
>
>
>
> Thanks Rob for your input!. That is my plan as well, that is, installing in-tank fuel pumps and Poly Armour steel lines. I too thought about running two vent lines as close as possible to the filler but that would mean they would terminate in the engine compartment and I have some concerns with fuel vapors in that area. Not sure if that is what you had in mine.
>
> Anyway, I have been trying to think of how to terminate the vent lines to the outside, maybe in the driver wheel well?. Any ideas??
>
> Jon
> --
> Jon Payne
> 76 Palm Beach
> Westfield,IN
> _______________________________________________
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Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
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| Re: Fuel Vent Mod [message #242860 is a reply to message #242797] |
Sun, 09 March 2014 08:12 |
peter bailey
Messages: 367
Registered: March 2009
Location: Gawler, South Australia
Karma: 0
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Some one up in Canada had moved their filler pipe to just above the tanks. I saw this conversion when we attended the international rally in Pueblo which ofcourse they attended also.
Peter Bailey
from Ozy (Aussie)
[Updated on: Sun, 09 March 2014 08:13] Report message to a moderator |
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| Re: [GMCnet] Fuel Vent Mod [message #242869 is a reply to message #242824] |
Sun, 09 March 2014 09:37 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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where is this mod described?
erf
On Sat, Mar 8, 2014 at 6:13 PM, Kerry Pinkerton <Pinkertonk@mchsi.com>wrote:
>
>
> I'm considering Dave Lenzi's vent mod. 1/2" vent lines to a common vent
> through the roof and one of those weather vane caps. Remove all the
> charcoal canisters and associated 'stuff'.
> --
> Kerry Pinkerton
>
> North Alabama, near Huntsville,
>
> 77 Eleganza II, "The Lady", 403CI, also a 76 Eleganza being re-bodied as
> an Art Deco car hauler
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Gene Fisher -- 74-23,77PB/ore/ca
"Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html
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| Re: [GMCnet] Fuel Vent Mod [message #242881 is a reply to message #242869] |
Mon, 10 March 2014 04:20 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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| Mr ERFisher wrote on Sun, 09 March 2014 09:37 |
where is this mod described?
erf
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Eugene, if memory serves, it was described during a bench racing session while sitting on the outside far bench on the KOA supplied picnic table in Dave's spot at the top of the hill in Branson during the GMCMI fall rally, 2013. There were other people present but can't recall who.
To my knowledge, it wasn't written down.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: [GMCnet] Fuel Vent Mod [message #242886 is a reply to message #242881] |
Mon, 10 March 2014 05:19 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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arrrgggggg
erf
On Mon, Mar 10, 2014 at 2:20 AM, Kerry Pinkerton <Pinkertonk@mchsi.com>wrote:
>
>
> Mr ERFisher wrote on Sun, 09 March 2014 09:37
> > where is this mod described?
> > erf
>
>
> Eugene, if memory serves, it was described during a bench racing session
> while sitting on the outside far bench on the KOA supplied picnic table in
> Dave's spot at the top of the hill in Branson during the GMCMI fall rally,
> 2013. There were other people present but can't recall who.
>
> To my knowledge, it wasn't written down.
> --
> Kerry Pinkerton
>
> North Alabama, near Huntsville,
>
> 77 Eleganza II, "The Lady", 403CI, also a 76 Eleganza being re-bodied as
> an Art Deco car hauler
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Gene Fisher -- 74-23,77PB/ore/ca
"Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html
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| Re: [GMCnet] Fuel Vent Mod [message #242903 is a reply to message #242852] |
Mon, 10 March 2014 09:20 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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| ljdavick wrote on Sun, 09 March 2014 04:12 |
Maybe I've been insulated by my checkbook. When I needed to replace the fuel lines I took the coach to Jim K who brought it back to factory specs. I fill at full speed and have no issues though I use a foam donut for the California nozzles. I conclude from my experience that the GM design works.
Larry Davick
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Larry and others,
There is a little known EPA (c1998) that motorfuel (gasoline) dispenser pumps cannot pump faster than 10 GPM. 16 states have laws in place that require testing and, the dispenser manufactures use this as a design criteria. Then comes California. With their vapor recovery rules, few can meet the 10gpm. I am told that most are closer to 5 (which explains why there are so often lines at CA fuel pumps).
The CFD that I ran on the fuel system so many years ago pointed out that the vent system was a problem and I did not include foaming fuel.
Some one was leery of venting to the engine room, and that is also something that I would never do, but if you run both of the fill vent lines as far forward as you can without jumping though any flaming hoops, you will end up with the T just under the cab floor. The T feeds both fill vents into the existing vent that goes up to the fill neck. I can promise you that this works and works very well. I know this because with bubbly alcohol laced winter fuel, I can still run the pump at WOT. There is a station just over the MI/OH line that I use a lot only because everything is more expensive in MI. I don't know what the actual rate is, but last time there, I took on 46+ gallons in just over 4 minutes.
If you don't have the vent connected to the fill neck, (I have been told) many California pumps will shut down. If they don't get some vapor volume return, they figure you must have rigged the system to put fuel in an older car.
I suspect (and will ask) that Dave has run the vapor vent to the roof line. This would make sense as the stupid little ping-pong ball valve is a POS at best. I do not know if the JimK version is more reliable.
I know that foaming is a big issue because I just had to buy another can of gas for my tractor. It was like trying to pour a warm coke. With any luck, I won't have to fill a Gerry can again until I have to mow grass.
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: Fuel Vent Mod [message #242932 is a reply to message #242791] |
Mon, 10 March 2014 14:39 |
bwevers
Messages: 597
Registered: October 2010
Location: San Jose
Karma: 5
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Senior Member |
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I just filled up at the Costco. 30 gallons at $3.699.
I shut it off early because of fuel foaming, it was
taking too long and there was a line behind me.
The summer gas seems to top-off faster.
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose
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| Re: [GMCnet] Fuel Vent Mod [message #242970 is a reply to message #242948] |
Mon, 10 March 2014 19:21 |
corleyw
Messages: 130
Registered: June 2007
Location: Battle Ground, WA
Karma: 0
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The only reason I can think of for not having the fuel filler pipe back by the tanks is that on many models, the furnace exhaust is back there. (Can you say kerblewy?) I'm pretty sure the attendant could have walked the 10 feet from the window to the filler. (And in Oregon, he/she still can. As it is, I have to get out and listen for the inevitable sloshing and burping issue anyway.  )
I'm reasonably sure that moving the filler back above the tanks would solve most of the fill / vent issues. AND, oh yeah, I don't have the furnace exhaust back there any longer! Hummm... 
Corley
'76 Glenbrook
29 other vehicles
[Updated on: Mon, 10 March 2014 19:23] Report message to a moderator |
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| Re: [GMCnet] Fuel Vent Mod [message #242993 is a reply to message #242948] |
Mon, 10 March 2014 23:59 |
Jim Rountree
Messages: 47
Registered: July 2010
Location: San Antonio, TX
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Jon & TOM
The vent system stops working when it starts filling with raw gas during tank filling. This happens because one tank is higher than the other because we are not parked completely level. when the low tank over fills and belches into the vent lines then both are contaminated and also may be below the tank tops with no way for the fuel now trapped to escape.
Jon, the dual system you are looking at will work if the tee is above the tank top level since one line cannot block the other and venting can continue. It also helps if there are no low spots from the tanks forward to let fuel be trapped.
Someone in CA has a three tank system and this is where the idea came from.
Tom, from your pictures the tee looks to be below tank top and there is also some traps. you may want to look at that
JMHO
Jim Rountree
San Antonio,TX
76 PB,
76 Royale RB
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