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[GMCnet] External feel lines [message #303748] Mon, 18 July 2016 08:42 Go to next message
Lawrence Schmitt is currently offline  Lawrence Schmitt   United States
Messages: 4
Registered: August 2010
Location: Memphis Tn
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Junior Member
Hope this works as this is my first post.
I am trying to address my GMC's terminal vapor lock. I have added a return line from a fuel pressure regulator, added an inline fuel pump,changed all the filters. Still have problems when temps are in the high 90's and the engine is hot. No issues with overheating.
I bought a roll of aluminum fuel line and am planning to move the external pump to the outside of the frame and run the al fuel line.

My question is this: is there any issues in running the fuel line across the front in the air flow instead of across the rear of the engine bay. Seems that it might help keep the temp down. Q

Lawrence Schmitt
76 Glenbrook
455
Drummonds TN
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Re: [GMCnet] External feel lines [message #303752 is a reply to message #303748] Mon, 18 July 2016 09:33 Go to previous messageGo to next message
JohnL455 is currently offline  JohnL455   United States
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
Senior Member
Factory is steel line down the left frame then crossing over forward of the engine. Short rubber line ( must now be barrier rubber line due to E10) to mechanical pump front right. All steel line up to carb. Hard to say exactly what mods your system has. The proven solution is a low pressure elec pump in front of left forward wheel as close as practical to the selector valve. The AUX switch wire feeds the valve and is 12V only in AUX. T off that wire to a weatherproof relay for signal source. Feed the 12V actual power from ign switched point on fuse box. When you switch to AUX on the dash the pump comes on and VP clears in under 2 sec. There have been tons of theorys and failed attemps at fixing VL but this one works. Remember old style rubber fuel line is obsolete due to E10. It breaks down in a few short years snd starts weeping fuel. All hoses should be type such as Gates Barrier by now or you have a fire hazzard.

John Lebetski
Woodstock, IL
77 Eleganza II
Re: [GMCnet] External feel lines [message #303755 is a reply to message #303748] Mon, 18 July 2016 09:49 Go to previous messageGo to next message
jhbridges is currently offline  jhbridges   United States
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
Senior Member
If you have the stock selector valve, it is suspect due to alcohol deterioration of the seals. Second cure - two electric pumps with check valves, one for each tank, powere through a relay which the slector energizes for aux. My 23' just went to a rally and back in 100 degree temps without problems. Engine and trans temp 175+ -, no 'vapor lock' at all.

--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
Re: [GMCnet] External feel lines [message #303760 is a reply to message #303748] Mon, 18 July 2016 10:36 Go to previous messageGo to next message
armandminnie is currently offline  armandminnie   United States
Messages: 864
Registered: May 2009
Location: Marana, AZ
Karma: 2
Senior Member
A big cause of hot fuel issues is the exhaust crossover under the
carburetor. Blocking that crossover was the single biggest improvement for
hot fuel on my coach. The problem is really aggravated if one of your
mufflers has a problem - forces hot exhaust to balance via the intake path
- really hot.

On Mon, Jul 18, 2016 at 6:42 AM, Lawrence Schmitt
wrote:

> Hope this works as this is my first post.
> I am trying to address my GMC's terminal vapor lock. I have added a return
> line from a fuel pressure regulator, added an inline fuel pump,changed all
> the filters. Still have problems when temps are in the high 90's and the
> engine is hot. No issues with overheating.
> I bought a roll of aluminum fuel line and am planning to move the external
> pump to the outside of the frame and run the al fuel line.
>
> My question is this: is there any issues in running the fuel line across
> the front in the air flow instead of across the rear of the engine bay.
> Seems that it might help keep the temp down. Q
>
> Lawrence Schmitt
> 76 Glenbrook
> 455
> Drummonds TN
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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Armand Minnie
Marana, AZ
'76 Eleganza II TZE166V103202
visit my gmc blog
click here to visit gmcws.org
Re: [GMCnet] External feel lines [message #303761 is a reply to message #303748] Mon, 18 July 2016 10:47 Go to previous messageGo to next message
jhbridges is currently offline  jhbridges   United States
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
Senior Member
Mine's unblocked - stock choke and stove. Blocking was on the list, just haven't got to it. And haven't needed it.

--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
Re: [GMCnet] External feel lines [message #303762 is a reply to message #303748] Mon, 18 July 2016 11:06 Go to previous messageGo to next message
roy1 is currently offline  roy1   United States
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
Senior Member
A number of things can add to the vapor lock problem. I haven't had it since I replaced the fuel lines . Removed the selector valve by using 2 carter electric pumps outside the frame rails insulated the fuel lines and ran the line up the rear of the engine to the carb eleminating the mechanical pump. I also put deflectors between the tanks and the exhaust pipe. My intake manifold was filled at an earlier time.

Roy Keen Minden,NV 76 X Glenbrook
Re: [GMCnet] External feel lines [message #303770 is a reply to message #303760] Mon, 18 July 2016 14:40 Go to previous message
jimk is currently offline  jimk   United States
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
Senior Member
We are finding that small things as the location of aux. pump and distance
from tank ,etc. makes difference.
If the coach has not been rehosed in the last few years, you must as the
ethanal has attacked the old rupper..

On Mon, Jul 18, 2016 at 8:36 AM, Armand Minnie wrote:

> A big cause of hot fuel issues is the exhaust crossover under the
> carburetor. Blocking that crossover was the single biggest improvement for
> hot fuel on my coach. The problem is really aggravated if one of your
> mufflers has a problem - forces hot exhaust to balance via the intake path
> - really hot.
>
> On Mon, Jul 18, 2016 at 6:42 AM, Lawrence Schmitt
> wrote:
>
>> Hope this works as this is my first post.
>> I am trying to address my GMC's terminal vapor lock. I have added a
> return
>> line from a fuel pressure regulator, added an inline fuel pump,changed
> all
>> the filters. Still have problems when temps are in the high 90's and the
>> engine is hot. No issues with overheating.
>> I bought a roll of aluminum fuel line and am planning to move the
> external
>> pump to the outside of the frame and run the al fuel line.
>>
>> My question is this: is there any issues in running the fuel line across
>> the front in the air flow instead of across the rear of the engine bay.
>> Seems that it might help keep the temp down. Q
>>
>> Lawrence Schmitt
>> 76 Glenbrook
>> 455
>> Drummonds TN
>> _______________________________________________
>> 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, 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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