Home » Public Forums » GMCnet » Stupid Vapor separator
| Stupid Vapor separator [message #283529] |
Thu, 30 July 2015 09:52  |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
Karma: 0
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My fuel / Vapor separator is leaking ( again ) stinking up the coach.
do any of the normal parts houses carry that thing?
I want to use it this weekend.
I see the corvette supplies have is as does Jim K, but thats too late.
I suppose I could glue it up again, but it didn't work so well last time
Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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| Re: Stupid Vapor separator [message #283532 is a reply to message #283529] |
Thu, 30 July 2015 10:43  |
habbyguy
Messages: 896
Registered: May 2012
Location: Mesa, AZ
Karma: 3
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Senior Member |
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My separator had been replaced by the PO, but cracked and would leak when I got my tanks overly full (which of course, happens when you fill up since there's no way to know when the tanks are "just right"). I think it's just a poorly designed part, as is the recovery canister that goes with it.
If the entire purpose of this system is to vent air / gas fumes only when filling the tanks, it seems that there would have to be better options, like running a vent well above the level of the tanks, maybe with a one-way valve. Yes, I know that the result is that the Earth will burst into flames 20 years from now, but I'll just drive the GMC north to escape all that. 
Mark Hickey
Mesa, AZ
1978 Royale Center Kitchen
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| Re: [GMCnet] Stupid Vapor separator [message #283538 is a reply to message #283532] |
Thu, 30 July 2015 12:20 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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These are parts you'll need to acquire from a GMC shop.
On Thu, Jul 30, 2015 at 8:43 AM, Mark wrote:
> My separator had been replaced by the PO, but cracked and would leak when
> I got my tanks overly full (which of course, happens when you fill up since
> there's no way to know when the tanks are "just right"). I think it's
> just a poorly designed part, as is the recovery canister that goes with it.
>
> If the entire purpose of this system is to vent air / gas fumes only when
> filling the tanks, it seems that there would have to be better options, like
> running a vent well above the level of the tanks, maybe with a one-way
> valve. Yes, I know that the result is that the Earth will burst into
> flames 20
> years from now, but I'll just drive the GMC north to escape all that. ;)
> --
> Mark Hickey
> Mesa, AZ
> 1978 Royale Center Kitchen
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Stupid Vapor separator [message #283546 is a reply to message #283538] |
Thu, 30 July 2015 14:13 |
habbyguy
Messages: 896
Registered: May 2012
Location: Mesa, AZ
Karma: 3
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Senior Member |
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jimk wrote on Thu, 30 July 2015 10:20These are parts you'll need to acquire from a GMC shop.
Jim, the one that broke is identical to the one I just bought from you to replace it. The failure mode on the old one was that the plastic seam on the bottom separated, allowing fuel to dribble out, which it would do for a long, long time if the tanks were really full.
Mark Hickey
Mesa, AZ
1978 Royale Center Kitchen
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| Re: Stupid Vapor separator [message #283588 is a reply to message #283532] |
Thu, 30 July 2015 23:54 |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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habbyguy wrote on Thu, 30 July 2015 08:43My separator had been replaced by the PO, but cracked and would leak when I got my tanks overly full (which of course, happens when you fill up since there's no way to know when the tanks are "just right"). I think it's just a poorly designed part, as is the recovery canister that goes with it.
If the entire purpose of this system is to vent air / gas fumes only when filling the tanks, it seems that there would have to be better options, like running a vent well above the level of the tanks, maybe with a one-way valve. Yes, I know that the result is that the Earth will burst into flames 20 years from now, but I'll just drive the GMC north to escape all that.
If I am not mistaken the vent system for filling has a tube that goes to the filler neck. The separator circuit is for expansion on a hot day and also can let air back into an emptying tank as it cools in the night... one of the reasons for a filter on the bottom of the canister.
I did get one of the newer designs that I first saw at Jeff Sirum's. It seemed pretty well made. But, yes, when we fill too full the separator closes and doesn't do anything until some gas is used. This can cause pressure to build in filled tanks on a hot day.
I have never figured out what is up with filling. We have had two GMCs and had new hoses on both. Our former '78 burped and spit, gurgled and wheezed. Our '74 allows me to put the pump on fast (in CA) or medium in the midwest and when it clicks off the first time it is full.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: Stupid Vapor separator [message #283590 is a reply to message #283530] |
Fri, 31 July 2015 01:09 |
Rick Staples
Messages: 126
Registered: May 2014
Location: Johnstown, Colorado, USA
Karma: -1
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Senior Member |
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The system is SUPPOSED to work like this:
1 When filling the tanks, the displaced air/vapor is supposed to flow freely through the large vent hoses back up to the filler neck. (In California and many other states, the vapor recovery pump nozzle will capture that vapor and store it in the gas station's underground tanks, where time and cooling will condense much of it an they can sell it again. It's only a couple teaspoonfuls.) On the GMC, since we have two big flat tanks spread out over 6 or 8 feet, and a mostly level filler tube that approaches 10' - 12', sometimes air is trapped in the tanks, making it "kick back" fuel before tanks are full. My only suggestion is to be sure there are no low or high spots or clogs in the fill vent line. Your vapor separator has little or nothing to do with filling the tanks.
2 Once you've filled up and put the cap on, the tanks are vented via the gas cap, which will release vapor IF the pressure gets dangerously high OR will allow air to enter the tanks with little resistance to replace the fuel you burn up on a cool day. Of course in warm/hot weather, or with winter blend fuel (more volatile), or at high altitudes, the fuel vapor pressure is going to mildly pressurize the tanks, as evidenced by the "whoosh" when you remove the gas cap. Actually this is a good thing, as it helps combat vapor lock. Any vapor above a certain pressure, is routed to the vapor separator, where any bubbles or drops of fuel are supposed be removed and drained back to the tanks. The remaining excess vapor goes to the carbon canister(s), where it is adsorbed and kept from the atmosphere. When we drive along, the purge valve opens and that excess vapor is drawn into the engine and burned. The vapor canister filter is to let fresh air be drawn through the canister to "sweep" it clean at this time. (It's not really to vent the tanks.)
Now that you know more than you ever wanted to about vapor recovery, I can say that as a TEMPORARY fix, I'd just bypass the valve by joining all its hoses together, but be sure NOT to fill the tanks all the way, lest you damage your charcoal canister and/or drip gas from it (behind right front wheel).
HTH
Rick Staples, '75 Eleganza, Johnstown, CO
"Advice is a dangerous gift, even from the Wise to the Wise, and all paths may run ill." -Tolkien
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| Re: [GMCnet] Stupid Vapor separator [message #283594 is a reply to message #283590] |
Fri, 31 July 2015 05:16 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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Senior Member |
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Read here to help visualize this problem
http://www.gmcmhphotos.com/photos/data/4634/TANK_VENTS1.pdf
Erf
On Thursday, July 30, 2015, Richard H Staples
wrote:
> The system is SUPPOSED to work like this:
> 1 When filling the tanks, the displaced air/vapor is supposed to flow
> freely through the large vent hoses back up to the filler neck. (In
> California
> and many other states, the vapor recovery pump nozzle will capture that
> vapor and store it in the gas station's underground tanks, where time and
> cooling will condense much of it an they can sell it again. It's only a
> couple teaspoonfuls.) On the GMC, since we have two big flat tanks spread
> out over 6 or 8 feet, and a mostly level filler tube that approaches 10' -
> 12', sometimes air is trapped in the tanks, making it "kick back" fuel
> before tanks are full. My only suggestion is to be sure there are no low
> or high spots or clogs in the fill vent line. Your vapor separator has
> little or nothing to do with filling the tanks.
>
> 2 Once you've filled up and put the cap on, the tanks are vented via the
> gas cap, which will release vapor IF the pressure gets dangerously high OR
> will allow air to enter the tanks with little resistance to replace the
> fuel you burn up on a cool day. Of course in warm/hot weather, or with
> winter
> blend fuel (more volatile), or at high altitudes, the fuel vapor pressure
> is going to mildly pressurize the tanks, as evidenced by the "whoosh" when
> you remove the gas cap. Actually this is a good thing, as it helps combat
> vapor lock. Any vapor above a certain pressure, is routed to the vapor
> separator, where any bubbles or drops of fuel are supposed be removed and
> drained back to the tanks. The remaining excess vapor goes to the carbon
> canister(s), where it is adsorbed and kept from the atmosphere. When we
> drive along, the purge valve opens and that excess vapor is drawn into the
> engine and burned. The vapor canister filter is to let fresh air be drawn
> through the canister to "sweep" it clean at this time. (It's not really to
> vent the tanks.)
>
> Now that you know more than you ever wanted to about vapor recovery, I can
> say that as a TEMPORARY fix, I'd just bypass the valve by joining all its
> hoses together, but be sure NOT to fill the tanks all the way, lest you
> damage your charcoal canister and/or drip gas from it (behind right front
> wheel).
>
> HTH
> --
> Rick Staples, '75 Eleganza, Louisville, CO
>
> "Advice is a dangerous gift, even from the Wise to the Wise, and all paths
> may run ill." -Tolkien
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
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] Stupid Vapor separator [message #283600 is a reply to message #283594] |
Fri, 31 July 2015 09:20 |
Arthur Mansfield
Messages: 290
Registered: April 2010
Karma: 0
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Senior Member |
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I am confused by the diagram. My tank has a fill line. Has a lines to the separator which I had to have resolder as they were both broken, a line to the generator from one tank, a line to the fuel pump from both tanks and a connection between tanks. It does not have a vent line to the filler from the tank that I know of. There is a vent coming up from the fill line but it does nothing to help fill the tanks.
I had my tanks out the clean the connection to the gauges. There is only a single line coming from the top of the tanks were the gauge sensor is located. If some have two lines attached to the the gauge and fuel line I need two of those. Then I might be able to fill my thank without having go so slow.
I have been thinking of connecting the line going to the separator to vent to the vent line going to the filler line.
My cap to the fill line does not seal air tight the tank. It came with the RV when I got it. My tank will not pressurize.
I am going to have to drop the tanks again this winter as the gauges have almost quit again. I read ¾ of a tank when near empty. The last time I checked the sensor and found they worked. If they still work then I will clean the connection and seal the connections the keep them from corroding.
Art
On Jul 31, 2015, at 5:16 AM, gene Fisher wrote:
> Read here to help visualize this problem
> http://www.gmcmhphotos.com/photos/data/4634/TANK_VENTS1.pdf
>
> Erf
>
> On Thursday, July 30, 2015, Richard H Staples
> wrote:
>
>> The system is SUPPOSED to work like this:
>> 1 When filling the tanks, the displaced air/vapor is supposed to flow
>> freely through the large vent hoses back up to the filler neck. (In
>> California
>> and many other states, the vapor recovery pump nozzle will capture that
>> vapor and store it in the gas station's underground tanks, where time and
>> cooling will condense much of it an they can sell it again. It's only a
>> couple teaspoonfuls.) On the GMC, since we have two big flat tanks spread
>> out over 6 or 8 feet, and a mostly level filler tube that approaches 10' -
>> 12', sometimes air is trapped in the tanks, making it "kick back" fuel
>> before tanks are full. My only suggestion is to be sure there are no low
>> or high spots or clogs in the fill vent line. Your vapor separator has
>> little or nothing to do with filling the tanks.
>>
>> 2 Once you've filled up and put the cap on, the tanks are vented via the
>> gas cap, which will release vapor IF the pressure gets dangerously high OR
>> will allow air to enter the tanks with little resistance to replace the
>> fuel you burn up on a cool day. Of course in warm/hot weather, or with
>> winter
>> blend fuel (more volatile), or at high altitudes, the fuel vapor pressure
>> is going to mildly pressurize the tanks, as evidenced by the "whoosh" when
>> you remove the gas cap. Actually this is a good thing, as it helps combat
>> vapor lock. Any vapor above a certain pressure, is routed to the vapor
>> separator, where any bubbles or drops of fuel are supposed be removed and
>> drained back to the tanks. The remaining excess vapor goes to the carbon
>> canister(s), where it is adsorbed and kept from the atmosphere. When we
>> drive along, the purge valve opens and that excess vapor is drawn into the
>> engine and burned. The vapor canister filter is to let fresh air be drawn
>> through the canister to "sweep" it clean at this time. (It's not really to
>> vent the tanks.)
>>
>> Now that you know more than you ever wanted to about vapor recovery, I can
>> say that as a TEMPORARY fix, I'd just bypass the valve by joining all its
>> hoses together, but be sure NOT to fill the tanks all the way, lest you
>> damage your charcoal canister and/or drip gas from it (behind right front
>> wheel).
>>
>> HTH
>> --
>> Rick Staples, '75 Eleganza, Louisville, CO
>>
>> "Advice is a dangerous gift, even from the Wise to the Wise, and all paths
>> may run ill." -Tolkien
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
>
>
> --
> 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
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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| Re: [GMCnet] Stupid Vapor separator [message #283616 is a reply to message #283600] |
Fri, 31 July 2015 14:25 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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Art,
Unless your current sending units are dramatically non-stock, there are two lines there. One is the draw tube that may still have a sock on it and the other barely penetrates the cover. That one is a fill vent to allow air/vapor in the tank to escape during filling. Those are typically Teed at near but above the fill T. That line that goes up to the fill neck has everything to do with filling the tanks.
If you want to be able to refill the tanks from empty to full in 5 minutes (no joke), move the T for the fill vent to just under the cab floor. Higher might be better, but you have to get behind the side panel.
Matt
Arthur Mansfield wrote on Fri, 31 July 2015 10:20I am confused by the diagram. My tank has a fill line. Has a lines to the separator which I had to have resolder as they were both broken, a line to the generator from one tank, a line to the fuel pump from both tanks and a connection between tanks. It does not have a vent line to the filler from the tank that I know of. There is a vent coming up from the fill line but it does nothing to help fill the tanks.
I had my tanks out the clean the connection to the gauges. There is only a single line coming from the top of the tanks were the gauge sensor is located. If some have two lines attached to the the gauge and fuel line I need two of those. Then I might be able to fill my thank without having go so slow.
I have been thinking of connecting the line going to the separator to vent to the vent line going to the filler line.
My cap to the fill line does not seal air tight the tank. It came with the RV when I got it. My tank will not pressurize.
I am going to have to drop the tanks again this winter as the gauges have almost quit again. I read ¾ of a tank when near empty. The last time I checked the sensor and found they worked. If they still work then I will clean the connection and seal the connections the keep them from corroding.
Art
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: [GMCnet] Stupid Vapor separator [message #283639 is a reply to message #283635] |
Fri, 31 July 2015 23:44 |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
Karma: 0
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Senior Member |
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I put in 2, 3/8" ( or was it 1/2") vent lines all the way to the filler neck where they are teed into the vent there.
I still get burping.
I glued up the old separator with abs cement, we'll see how that holds. if not I'll buy a new one
Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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| Re: [GMCnet] Stupid Vapor separator [message #283655 is a reply to message #283639] |
Sat, 01 August 2015 09:25 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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Keith,
You will still get some burping with alcohol laced fuel.
But if you had not done that, you would be stuck at the low hook on the pump and a fuel stop would take 20 minutes for only a 40 gallon load.
Matt
Keith V wrote on Sat, 01 August 2015 00:44I put in 2, 3/8" ( or was it 1/2") vent lines all the way to the filler neck where they are teed into the vent there.
I still get burping.
I glued up the old separator with abs cement, we'll see how that holds. if not I'll buy a new one
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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