Home » Public Forums » GMCnet » [GMCnet] Gas Cap
| [GMCnet] Gas Cap [message #135803] |
Sun, 24 July 2011 09:55  |
Ray Erspamer
Messages: 1707
Registered: May 2007
Location: Milwaukee Wisconsin
Karma: -3
|
Senior Member |
|
|
Do we use Vented or Non-Vented?
Sent via BlackBerry by AT&T
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Ray Erspamer
78 GMC Royale Center Kitchen
403, 3.70 Final Drive
Holley Sniper Quadrajet EFI System,
Holley Hyperspark Ignition System
414-484-9431
|
|
|
|
| Re: [GMCnet] Gas Cap [message #135807 is a reply to message #135803] |
Sun, 24 July 2011 10:08  |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
|
Senior Member |
|
|
| Ray Erspamer wrote on Sun, 24 July 2011 09:55 |
Do we use Vented or Non-Vented?
|
Ray called me. I gave him the Stant number from the GMCMI parts exchange book. At the time he was standing in front of the Stant display in a farm and barn store.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
|
|
|
|
| Re: [GMCnet] Gas Cap [message #135811 is a reply to message #135803] |
Sun, 24 July 2011 10:30 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
|
Senior Member |
|
|
Ray, the correct gas cap for the GMC is a semi vented one. It allows
atmospheric air to be drawn into the tanks as they are emptied, but holds a
certain pressure in the tanks, I believe it to be around 2 psi or so, so
that the fumes from evaporation will go to the charcoal cannister and
eventually to the intake manifold where they can be burned. The correct cap,
of which there are 4 part numbers, depends on what series coach you have.
There are early and late series, locking and non locking. The part numbers
are GM 413755 (w/rpo NA9), 6263474 prior to 1975, and 790899 effective
w/1975 & later. The Stant Early # is 31722, NAPA 703-1049, Locking is
703-1167. Stant Late is 11807, and Locking is G-807. Hope that clarifies
rather than confuses the issue. If you use an incorrect gas cap that is not
vented, I suppose that it could cause vaporlock.
On Sun, Jul 24, 2011 at 7:55 AM, Ray Erspamer <78gmc-royale@att.net> wrote:
> Do we use Vented or Non-Vented?
> Sent via BlackBerry by AT&T
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
| Re: [GMCnet] Gas Cap [message #135840 is a reply to message #135811] |
Sun, 24 July 2011 15:08 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
|
Senior Member |
|
|
Jim,
That's close 'nuff to my empirical data:
http://www.gmcmhphotos.com/photos/showgallery.php?cat=5123
But for the last statement about non-vented causing vapor lock, my
experience, and that I've heard of, indicates just the opposite should
be true: I've never heard any evidence of vacuum in the tanks but
have several times experienced pressure -- which SHOULD force liquid
gasoline toward the engine & minimize vapor lock -- IMHO.
Ken H.
On Sun, Jul 24, 2011 at 11:30 AM, James Hupy <jamesh1296@gmail.com> wrote:
> Ray, the correct gas cap for the GMC is a semi vented one. It allows
> atmospheric air to be drawn into the tanks as they are emptied, but holds a
> certain pressure in the tanks, I believe it to be around 2 psi or so, so
> that the fumes from evaporation will go to the charcoal cannister and
> eventually to the intake manifold where they can be burned. The correct cap,
> of which there are 4 part numbers, depends on what series coach you have.
> There are early and late series, locking and non locking. The part numbers
> are GM 413755 (w/rpo NA9), 6263474 prior to 1975, and 790899 effective
> w/1975 & later. The Stant Early # is 31722, NAPA 703-1049, Locking is
> 703-1167. Stant Late is 11807, and Locking is G-807. Hope that clarifies
> rather than confuses the issue. If you use an incorrect gas cap that is not
> vented, I suppose that it could cause vaporlock.
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
|
|
|
|
|
|
| Re: [GMCnet] Gas Cap [message #135853 is a reply to message #135846] |
Sun, 24 July 2011 16:10 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
|
Senior Member |
|
|
On Sun, Jul 24, 2011 at 4:41 PM, Emery Stora wrote:
>
> On Jul 24, 2011, at 2:08 PM, Ken Henderson wrote:
>...
>> But for the last statement about non-vented causing vapor lock, my
>> experience, and that I've heard of, indicates just the opposite should
>> be true: I've never heard any evidence of vacuum in the tanks but
>> have several times experienced pressure -- which SHOULD force liquid
>> gasoline toward the engine & minimize vapor lock -- IMHO.
>>
>> Ken H.
>>
>
>
> That pressure is usually caused by hot fuel. But to force fuel to the engine it has to pass through the fuel pump. When the fuel pump operates it pulls a vacuum on the fuel tank and then the hot fuel will start to vaporize which is what contributes to vapor lock.
>
Agreed, but the positive pressure in the tank will compensate, psi for
psi, for the suction of the fuel pump, thereby reducing the tendency
for the fuel to vaporize.
Ken H.
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
|
|
|
|
| Re: [GMCnet] Gas Cap [message #135857 is a reply to message #135840] |
Sun, 24 July 2011 16:33 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
|
Senior Member |
|
|
Vacuum or pressure? Aren't they both shades of grey? When I went to Bosch
Fuel Injection technical classes at Rivera Motors in Portland, the
instructor, Hulmut Gomez, born in Germany of German mother and Hispanic G.I.
Father, and educated at the Factory, refused to discuss vacuum. He said that
everything in a closed system, not exposed to atmospheric pressure, could be
described from a total absence of pressure, to the maximum that the system
could produce. One bar being the accepted standard for atmospheric pressure
at 70 degrees F at sea level and he also gave the specific gravity. Every
example that he gave was in bar or percentage of bar. It works well for
Bosch and most people fluent in the metric system, and I had to force myself
to become intimate with it. My thinking when it relates to supplying fuel to
the fuel mixing device(s) is that you want nothing impeding the flow of
fuel, or heating it up. Either will cause problems in fuel delivery systems.
On those systems that are belching fuel back out the filler neck when fuel
is being added do not make sense to me. If there is all that space in the
tanks for more fuel, what is the fuel doing in the filler neck? I personally
have never experienced that phenomenon except with gas cans that were
allowed to sit in the sun and become pressurized from the expansion. If the
tank venting system is doing it's intended job, there should not be enough
pressure in the tanks for that to happen. I would drop the tanks and check
the venting system from the tanks, through the liquid/vapor separator to the
charcoal cannister, paying special attention to the last few feet of vent
hose before the charcoal cannister. I have found plugged lines more than
once in that area.
Jim Hupy
Salem, OR
78 GMC Royale 403
On Sun, Jul 24, 2011 at 1:08 PM, Ken Henderson <hend4800@bellsouth.net>wrote:
> Jim,
>
> That's close 'nuff to my empirical data:
>
> http://www.gmcmhphotos.com/photos/showgallery.php?cat=5123
>
> But for the last statement about non-vented causing vapor lock, my
> experience, and that I've heard of, indicates just the opposite should
> be true: I've never heard any evidence of vacuum in the tanks but
> have several times experienced pressure -- which SHOULD force liquid
> gasoline toward the engine & minimize vapor lock -- IMHO.
>
> Ken H.
>
>
> On Sun, Jul 24, 2011 at 11:30 AM, James Hupy <jamesh1296@gmail.com> wrote:
>
> > Ray, the correct gas cap for the GMC is a semi vented one. It allows
> > atmospheric air to be drawn into the tanks as they are emptied, but holds
> a
> > certain pressure in the tanks, I believe it to be around 2 psi or so, so
>
> > that the fumes from evaporation will go to the charcoal cannister and
> > eventually to the intake manifold where they can be burned. The correct
> cap,
> > of which there are 4 part numbers, depends on what series coach you have.
> > There are early and late series, locking and non locking. The part
> numbers
> > are GM 413755 (w/rpo NA9), 6263474 prior to 1975, and 790899 effective
> > w/1975 & later. The Stant Early # is 31722, NAPA 703-1049, Locking is
> > 703-1167. Stant Late is 11807, and Locking is G-807. Hope that clarifies
> > rather than confuses the issue. If you use an incorrect gas cap that is
> not
> > vented, I suppose that it could cause vaporlock.
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
| Re: [GMCnet] Gas Cap [message #135858 is a reply to message #135853] |
Sun, 24 July 2011 16:37 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
|
Senior Member |
|
|
On Jul 24, 2011, at 3:10 PM, Ken Henderson wrote:
> On Sun, Jul 24, 2011 at 4:41 PM, Emery Stora wrote:
>>
>> On Jul 24, 2011, at 2:08 PM, Ken Henderson wrote:
>> ...
>>> But for the last statement about non-vented causing vapor lock, my
>>> experience, and that I've heard of, indicates just the opposite should
>>> be true: I've never heard any evidence of vacuum in the tanks but
>>> have several times experienced pressure -- which SHOULD force liquid
>>> gasoline toward the engine & minimize vapor lock -- IMHO.
>>>
>>> Ken H.
>>>
>>
>>
>> That pressure is usually caused by hot fuel. But to force fuel to the engine it has to pass through the fuel pump. When the fuel pump operates it pulls a vacuum on the fuel tank and then the hot fuel will start to vaporize which is what contributes to vapor lock.
>>
>
> Agreed, but the positive pressure in the tank will compensate, psi for
> psi, for the suction of the fuel pump, thereby reducing the tendency
> for the fuel to vaporize.
>
> Ken H.
But Ken,
that pressure you see in the tank is only temporary. Once you open the fuel tank cap it quickly equalizes to atmospheric pressure. The same holds when you start the fuel pump. The little advantage of any pressure i the tank is quickly gone.
Emery Stora
77 Kingsley
Santa Fe, NM
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
| Re: [GMCnet] Gas Cap [message #135860 is a reply to message #135858] |
Sun, 24 July 2011 17:30 |
 |
Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
|
Senior Member |
|
|
| Emery and Ken discussed fuel pressure/ vapor lock |
On Jul 24, 2011, at 3:10 PM, Ken Henderson wrote:
But for the last statement about non-vented causing vapor lock, my experience, and that I've heard of, indicates just the opposite should >>> be true: I've never heard any evidence of vacuum in the tanks but >>> have several times experienced pressure -- which SHOULD force liquid gasoline toward the engine & minimize vapor lock -- IMHO.
Ken H.
On Sun, Jul 24, 2011 at 4:41 PM, Emery Stora wrote:
That pressure is usually caused by hot fuel. But to force fuel to the engine it has to pass through the fuel pump. When the fuel pump operates it pulls a vacuum on the fuel tank and then the hot fuel will start to vaporize which is what contributes to vapor lock.
On Jul 24, 2011, at 2:08 PM, Ken Henderson wrote:
Agreed, but the positive pressure in the tank will compensate, psi for psi, for the suction of the fuel pump, thereby reducing the tendency for the fuel to vaporize.
Ken H.
emerystora wrote on Sun, 24 July 2011 17:37
But Ken,
That pressure you see in the tank is only temporary. Once you open the fuel tank cap it quickly equalizes to atmospheric pressure. The same holds when you start the fuel pump. The little advantage of any pressure in the tank is quickly gone.
Emery Stora
|
No offense intended guys, but this sounds like the three blind men trying to separately describe am elephant based on the single part that each has hands on. You are both correct, but you are talking about different things.
You are both correct except:
The fuel tank should relieve any pressure though the carbon canister (but they sure don’t seem to).
If the coach is underway, nobody is going to open the fuel fill cap to relieve the pressure.
Any pressure in the tank will be of value to mitigate vapor lock up to fuel rates as required for a land speed record attempt.
Respectfully submitted;
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
|
|
|
|
|
|
| Re: [GMCnet] Gas Cap [message #135862 is a reply to message #135860] |
Sun, 24 July 2011 17:46 |
|
|
I love it when you guys "talk dirty"!
Educational, too.
Now, someone splain what is going on at higher altitudes. There's less
pressure somewhere. Or, does a fuel delivery system not like the air at
high altitudes while working much like a few guys I know my age?
Byron
-----Original Message-----
From: Matt Colie <matt7323tze@gmail.com>
Organization: GMCnet
Reply-To: <gmclist@temp.gmcnet.org>
Date: Sun, 24 Jul 2011 17:30:34 -0500
To: <gmclist@temp.gmcnet.org>
Subject: Re: [GMCnet] Gas Cap
>
>
>Emery and Ken discussed fuel pressure/ vapor lock
>> On Jul 24, 2011, at 3:10 PM, Ken Henderson wrote:
>> But for the last statement about non-vented causing vapor lock, my
>>experience, and that I've heard of, indicates just the opposite should
>>>>> be true: I've never heard any evidence of vacuum in the tanks but
>>>>>>>> have several times experienced pressure -- which SHOULD force
>>>>>>>>liquid gasoline toward the engine & minimize vapor lock -- IMHO.
>> Ken H.
>>
>> On Sun, Jul 24, 2011 at 4:41 PM, Emery Stora wrote:
>> That pressure is usually caused by hot fuel. But to force fuel to the
>>engine it has to pass through the fuel pump. When the fuel pump
>>operates it pulls a vacuum on the fuel tank and then the hot fuel will
>>start to vaporize which is what contributes to vapor lock.
>>
>> On Jul 24, 2011, at 2:08 PM, Ken Henderson wrote:
>> Agreed, but the positive pressure in the tank will compensate, psi for
>>psi, for the suction of the fuel pump, thereby reducing the tendency for
>>the fuel to vaporize.
>> Ken H.
>>
>> emerystora wrote on Sun, 24 July 2011 17:37
>> But Ken,
>> That pressure you see in the tank is only temporary. Once you open the
>>fuel tank cap it quickly equalizes to atmospheric pressure. The same
>>holds when you start the fuel pump. The little advantage of any
>>pressure in the tank is quickly gone.
>> Emery Stora
>
>No offense intended guys, but this sounds like the three blind men trying
>to separately describe am elephant based on the single part that each has
>hands on. You are both correct, but you are talking about different
>things.
>
>You are both correct except:
>The fuel tank should relieve any pressure though the carbon canister (but
>they sure don’t seem to).
>If the coach is underway, nobody is going to open the fuel fill cap to
>relieve the pressure.
>Any pressure in the tank will be of value to mitigate vapor lock up to
>fuel rates as required for a land speed record attempt.
>
>Respectfully submitted;
>Matt
>--
>Matt & Mary Colie
>'73 Glacier 23 Chaumiere (say show-me-air) Just about as stock as you
>will find
>SE Michigan - Twixt A2 and Detroit
>_______________________________________________
>GMCnet mailing list
>Unsubscribe or Change List Options:
>http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
--
Byron Songer
Full-timing to enjoy the USA
Former owner but still an admirer
GMC paint schemes at -
http://www.songerconsulting.net
|
|
|
|
| Re: [GMCnet] Gas Cap [message #135863 is a reply to message #135858] |
Sun, 24 July 2011 17:52 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
|
Senior Member |
|
|
Matt,
VBG!!! You're right about the 3 blind men & the elephant -- though I
don't think any one of us has less than 20-20 vision -- maybe we're
feeling the elephant under a big canvas?
One point I will readily concede: I haven't checked for tank pressure
with the engine even idling, much less climbing a mountain. There may
not be pressure in either of those cases. But, considering the volume
of vapor (& sometimes liquid) I've seen escape after parking and
immediately removing the cap to refuel, I suspect there IS pressure
any time the vent system is plugged during hot weather.
I've said all I know to say on the subject. :-)
Except maybe to report when I've worked on my liquid/vapor separator
again, since I had some tank pressure when I last filled up. :-(
Ken H.
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
|
|
|
|
|
|
| Re: [GMCnet] Gas Cap [message #135872 is a reply to message #135861] |
Sun, 24 July 2011 19:30 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
|
Senior Member |
|
|
A wiser man than I am is credited with the following quote" None is so blind
as he who will not see!" I don't know who that was but suspect it might have
been Confucious or Anon. I am not intending any disrespect towards Either of
the other distinguished gentlemen included in the three blind mice saga. For
gasoline to be forcibly ejected from an empty fuel tank, there has to be a
pressure differential between the tank and the atmosphere, with the tank
being the greater of the two. In order for that to occur, the tank must have
been sealed, something that can not happen if the venting/vapour recovery
system is working correctly. Another possibility is that the gas cap is the
incorrect one for the application AND the venting has failed at the same
time. That being said, if the tanks are nearly full, and the contents are
heated to the boiling point of oxygenated fuel and are under pressure, if
the gas cap is opened and the pressure is reduced on the contents, boiling
could concievably occur at that point. If the tank contents expand enough,
the fuel could be forcibly ejected from the filler neck. I propose that this
might be an explanation as to the filler neck regurgitation. Just a
Scientific wild A** Guess on my part.
Jim Hupy
Salem, OR
78 GMC Royale 403
On Sun, Jul 24, 2011 at 3:41 PM, Hardie Johnson <hardie.j@gmail.com> wrote:
>
>
> mcolie wrote on Sun, 24 July 2011 18:30
> > No offense intended guys, but this sounds like the three blind men trying
> to separately describe am elephant <>
>
> Matt, thank you for the title to my next novel.
> "3 Blind Men in Search of an Elephant"
>
> --
> Hardie Johnson "Crashj"
> 1973 26 foot Glacier, White Thing
> Raleigh NC
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
| Re: [GMCnet] Gas Cap [message #135879 is a reply to message #135862] |
Sun, 24 July 2011 20:03 |
|
Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
|
Senior Member |
|
|
| Byron Songer wrote on Sun, 24 July 2011 18:46 |
I love it when you guys "talk dirty"!
Educational, too.
Now, someone splain what is going on at higher altitudes. There's less pressure somewhere. Or, does a fuel delivery system not like the air at high altitudes while working much like a few guys I know my age?
Byron
|
Byron,
As far as naturally aspirated (not supercharged) engines go, there is nothing good that happens with increasing altitude (aka decreasing absolute pressure).
Technical Brief:
Absolute pressure is the pressure referenced from zero instead of from local atmospheric pressure. A simple pressure gauge reads the inlet pressure relative to local atmospheric pressure (~14.7psi). You typical vacuum gauge is the same way.
Engine engineers (and some strange little airplane pilots) never talk about manifold vacuum, they always talk in terms of Manifold Absolute Pressure (MAP). A MAP instrument reads local barometer with the engine shut down. This reading decreases as when the engine is running and increases with increasing power. But, lets start with the fuel delivery system since that is the current subject line.
The modern motor fuels all use a Reid Vapor Pressure model of 7psi. That is to say that if you put the fuel you just bought in a can with an absolute pressure gauge and removed the air, the gauge would read 7psi at 68*F. At even slightly elevated temperatures, this pressure will rise rapidly with the increasing temperature. The EPA put limits on how high in can rise by geographic location. This all went out the window with the addition of ethanol. As the "oxygenated" fuels can never meet the original specifications, waivers up to 11psi were originally issued, and the temperature curve was also pitched out the window.
So, since local atmospheric pressure decrease by about 1inHg (~0.5psi) per thousand feet of altitude, your local pressure is now only about 11psi. If you are in Albuquerque (~6000ft) and it is hot (this has been known to happen), there is not much left to hold the gasoline in the tank or keep it from boiling in the hot fuel lines. This gets to be a real big problem if you have a mechanical fuel pump and a carburetor. When the fuel pump tries to suck fuel out of the tank, the pressure at the pump inlet has to go down to get the fuel to go in. Usually you count on the pressure in the tank to help you out here, but if the pressure at the pump inlet is so low and the fuel so volatile that it turns to vapor - TADA - VAPOR LOCK CITY... The pump can't suck unless it has liquid to work with.
Now lets look at the poor old carburetor. He was born when the alphabet soup that is gasoline had about 26 fewer letters. Take a sea level calibration and reduce the density of the air by about 20%, add fuel that does not behave any thing like what it was supposed to and that poor old thing doesn't stand a chance.
First off, the float bowl is vented to the intake just before everything else happens. So, some of that evaporating fuel is pouring into the inlet airstream with no control at all. This can really screw up a high altitude idle on an hot day. And, we aren't even trying to make horsepower yet.
Now, if you went to engineering school in the 60's, you were taught that a venturi based carburetor (like ours) is a mass flow device and as such, it should not be drastically effected by the reduced density with increasing altitude. That may be what the math says, but for some reason it does not reflect reality. It has turned out that they are much more velocity differential devices with much less sensitivity to actual mass flow than is either expected or desired. So, just when you really don't need it, the thing is pouring more fuel into the engine than the engine can manage in the thin air - Way Too Rich. It still burns, but there are so many things wrong that I cannot begin to tell you all of them.
So, now you know why Emery was one of the early adopters of a closed loop computer controlled fuel delivery system.
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
|
|
|
|
| Re: [GMCnet] Gas Cap [message #135883 is a reply to message #135803] |
Sun, 24 July 2011 20:35 |
PettyVTX
Messages: 363
Registered: April 2011
Location: Winder Ga.
Karma: 1
|
Senior Member |
|
|
As Foghorn Leghorn Says "Dems figures boy can't argue with figures"
Ted
Ex Avion now looking for a 23'
Jeep Wrangler Towd
|
|
|
|
| Re: [GMCnet] Gas Cap [message #135885 is a reply to message #135872] |
Sun, 24 July 2011 20:48 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
|
Senior Member |
|
|
Huh? Where's the controversy? Perhaps this blind man has lost sight
of it? I thought we were trying to decide whether pressurized fuel
tanks would aid or inhibit vapor lock. Now it sounds like we're
trying to determine how fuel can escape when the cap's removed from an
"empty" tank. So let me clarify my opinions on that:
1. Even when I've been beside the road because I've run out of gas,
the fuel tanks have never been "empty" since I poured the first ounce
of gasoline into them after re-installing them.
2. Even when I drained the tanks by removing the plugs from them, the
"burp" line and the vent lines to the liquid/vapor separator still
contained liquid.
3. None of my comments in this thread have addressed a fuel system
which had a correctly operating vent system, including a functional
liquid/vapor separator and a properly venting charcoal cannister. In
such a system, there should be no pressure build up, nullifying the
entire discussion.
4. Even with the assumption in 3., preceding, the pressure in the
tanks should be limited by the 2 psi vent setting of the fuel cap --
to the extent that small orifice can pass vapor faster than it is
generated. So I've always assumed a maximum of 2 psi of trapped
pressure.
5. While removal of a cap has never been, IMHO, a part of the
discussion, the loss of liquid along with escaping pressure is
certainly to be expected due to the residual fuel in the burp line
(see 2., preceding). Upon the opening of the gas cap it's inevitable
that the pressure at the tank end of that line will be higher than
that at the cap end. We could
calculate the likely volume of vapor at 2 psi, the cross sectional
areas of the burp line and the fill tube, the volume of the burp line,
and produce a reasonable estimate of how much fuel could possibly be
ejected. I'll lay dollars to donuts it would be enough to saturate a
shirt cuff. But, I'm satisfied with the empirical evidence without
bothering with the calculations.
Just as I'm convinced that the rising fuel level in tanks, while
they're being filled, expels enough air to overcome both the venting
capability of the liquid/vapor separator and the flow resistance of
any fuel trapped in the burp line. Both MUST be true for automatic
shutoff nozzles to work.
Again, I'm not upset, nor in an argument with anyone; I just don't
understand the direction the discussion has taken... But if, as so
often happens here, we want to wander off into some other esoteric
discussion, great! See 1.-5., preceding. :-)
Heck, it's not even necessary for 'Maters' twin and me to agree to the
source of vapor lock; it's still going to be a problem.
Ken H.
On Sun, Jul 24, 2011 at 8:30 PM, James Hupy wrote:
> A wiser man than I am is credited with the following quote" None is so blind
> as he who will not see!" I don't know who that was but suspect it might have
> been Confucious or Anon. I am not intending any disrespect towards Either of
> the other distinguished gentlemen included in the three blind mice saga. For
> gasoline to be forcibly ejected from an empty fuel tank, there has to be a
> pressure differential between the tank and the atmosphere, with the tank
> being the greater of the two. In order for that to occur, the tank must have
> been sealed, something that can not happen if the venting/vapour recovery
> system is working correctly. Another possibility is that the gas cap is the
> incorrect one for the application AND the venting has failed at the same
> time. That being said, if the tanks are nearly full, and the contents are
> heated to the boiling point of oxygenated fuel and are under pressure, if
> the gas cap is opened and the pressure is reduced on the contents, boiling
> could concievably occur at that point. If the tank contents expand enough,
> the fuel could be forcibly ejected from the filler neck. I propose that this
> might be an explanation as to the filler neck regurgitation. Just a
> Scientific wild A** Guess on my part.
> Jim Hupy
> Salem, OR
> 78 GMC Royale 403
>
> On Sun, Jul 24, 2011 at 3:41 PM, Hardie Johnson <hardie.j@gmail.com> wrote:
>
>>
>>
>> mcolie wrote on Sun, 24 July 2011 18:30
>> > No offense intended guys, but this sounds like the three blind men trying
>> to separately describe am elephant <>
>>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
|
|
|
|
|
|
|
|
|
|
Goto Forum:
Current Time: Tue Sep 24 20:38:48 CDT 2024
Total time taken to generate the page: 0.04945 seconds
|
GMCforum
Search
Help
Register
Login
Home
