Home » Public Forums » GMCnet » [GMCnet] Vapor lock - lost the battle but not the war, or: Ethanol is for drinking
| [GMCnet] Vapor lock - lost the battle but not the war, or: Ethanol is for drinking [message #99782] |
Tue, 14 September 2010 17:43  |
Gary Casey
Messages: 448
Registered: September 2009
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I've read dozens of posts on vapor lock, the cause and the cure. My(previous)
thoughts: They must have been halfway smart back in the ole days of the GMC, so
stop complaining, just fix everything, put it back to stock and it will work.
Thoughts were wrong. I did that and headed out on the first trip. Lots of
vapor lock symptoms and very consistent. I checked everything I could and
replaced everything that has a moving part, all to no avail. So as a last ditch
effort I put an electric pump in the feed line from the rear tank, pumping
through the selector valve and powered in parallel to it. In that way the front
tank was fed exactly as standard so it was a good baseline. Went out today for
a test drive up and down some hills, elevation 6000 to 7000 feet. Got it hot,
pulled off to the side and let it idle for 2 minutes in drive. Accelerate out
and it would sag and almost die before getting to 20 mph. Turn on the pump and
it would stumble for a few seconds and off we go. Pull off again (electric pump
off) for longer and the idle speed would gradually drop, and then it would
hardly take Throttle at all. Turned on the electric pump and I could idle for 5
minutes with no variation in idle speed and it would accelerate away without
problem. Duplicated all the tests while running the electric pump and no
symptoms at all. I'm convinced. It's the ethanol. The only (okay, one of the
only) rational fuel system, I'm convinced, is one that was suggested some time
back: Throw away the fuel selector and mechanical pump install an electric pump
on the outlet of each tank with the outputs T'd together. No need for a valve
since the pumps have internal check valves. Install an oil pressure switch to
shut them off if the engine quits and then bypass that during cranking by
connecting to the starter solenoid terminal. A selector switch is used to
change tanks. Yes, they were smart back then, but they didn't have this fuel to
contend with.
Several people reported that they run premium fuel, look for the ethanol sticker
on the pump, find a no-ethanol source, etc. I just felt that approach to be not
reliable enough when on the road, so I think the fuel system has to work with
the fuel we have.
Just my opinion.
Gary Casey
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| Re: [GMCnet] Vapor lock - lost the battle but not the war, or: Ethanol is for drinking [message #99856 is a reply to message #99849] |
Wed, 15 September 2010 07:24  |
Jim Bounds
Messages: 842
Registered: January 2004
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The pump we use is made by Facet. They make them for Onan (low pressure one),
Purolator even the Mr. Gasket one has s triking resemblence! It has no check
valve in it, it's a small cube shape, is cheap (costs little) and seems to work
well in this application.
Jim Bounds
--------------------------
----- Original Message ----
From: Gary Casey <casey.gary@yahoo.com>
To: gmclist@temp.gmcnet.org
Sent: Wed, September 15, 2010 8:01:48 AM
Subject: Re: [GMCnet] Vapor lock - lost the battle but not the war, or: Ethanol
is for drinking
Yeah, it might not. In my frustration I went to the first parts store and
bought the only pump they had - a Holley. I checked, and it had a check valve.
I have no idea if that's the best or only one, but it worked.
Gary
I don't think the Carter pump has a check valve.
Roy
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| Re: [GMCnet] Vapor lock - lost the battle but not the war, or: Ethanol is for drinking [message #99857 is a reply to message #99849] |
Wed, 15 September 2010 07:24 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Holley is probably as good as they come and a lot of people swear by them.
But 5+ years ago I had one under the GMC literally melt down -- dripping
"asphalt" on the ground. I won't be installing another.
Carter 4070's have served me very well. I don't know whether they have
check valves, and don't care. When I installed two pumps in place of the
selector valve, I installed a pair of check valves to feed the line forward.
If I have to install another pump "beside the road" I still won't have to
worry about whether it has a check valve.
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI+ & EBL
www.gmcwipersetc.com
On Wed, Sep 15, 2010 at 8:01 AM, Gary Casey <casey.gary@yahoo.com> wrote:
> Yeah, it might not. In my frustration I went to the first parts store and
> bought the only pump they had - a Holley. I checked, and it had a check
> valve.
> I have no idea if that's the best or only one, but it worked.
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Vapor lock - lost the battle but not the war, or: Ethanol is for drinking [message #99928 is a reply to message #99874] |
Wed, 15 September 2010 14:16 |
 |
USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Gary,
Jim B had Jason fit one of the Facet pumps to Double Trouble. It is plumbed
in between the Aux tank and the selector valve. When you switch to Aux it
uses the power sent to the selector valve and pressurizes the mechanical
pump. It works great. The down side is that if there is a hole in the
mechanical pump diaphragm it will pump fuel into the crankcase. Having said
that if there was a hole in the mechanical fuel pump diaphragm it will
already probably be pumping fuel into the crankcase and you won't have to
worry about vapor lock for long! ;-)
I anticipate vapor lock (at a stop light - heavy traffic) and switch to Aux
and I don't have problems.
Regards,
Rob M.
USAussie
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Gary Casey
Sent: Wednesday, September 15, 2010 10:36 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Vapor lock - lost the battle but not the war,or:
Ethanol is for drinking
The Facet pump is used in a lot of aircraft applications. It's a
solenoid-driven piston pump, so I don't see how it could work unless it has
check valves in it. I certainly wouldn't be afraid to use it. The Holley
pump cost me $45 at Autozone - seemed expensive to me.
Gary
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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] Vapor lock - lost the battle but not the war, or: Ethanol is for drinking [message #99929 is a reply to message #99900] |
Wed, 15 September 2010 14:16 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Bruce,
One GMC'er did - he put his LPG tanks in a pod on the roof!
Regards,
Rob M.
USAussie
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Bruce Hislop
Sent: Wednesday, September 15, 2010 12:59 PM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Vapor lock - lost the battle but not the war,or:
Ethanol is for drinking
I've got the ideal solution...
Mount the tanks on the roof!... gravity feed, no problems :lol:
--
Bruce Hislop,
S. Ontario Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI and ESC.
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
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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] Vapor lock - lost the battle but not the war, or: Ethanol is for drinking [message #99954 is a reply to message #99782] |
Wed, 15 September 2010 16:57 |
Larry C
Messages: 1168
Registered: July 2004
Location: NE Illinois by the Illino...
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My(previous)thoughts: They must have been halfway smart back in the ole days of the GMC, so stop complaining, just fix everything, put it back to stock and it will work.
Thoughts were wrong.
____________________________________________________________
As with any investigation, you must have a solid starting point. In the case of the GMC, that would be the OEM design.
From that point you can work out to search for the cause.
Modified units can cause a different problem and wont be identical mechanically, to all the rest on the road with or without problems.
GOod report, another item to consider as a fix.
Gatsbys' CRUISER  08-18-04
74 GLACIER X, 260/455-APC-4 Bagg'r
Remflex Manifold gaskets
CampGrounds needed, Add yours to "PLACES" />
http://www.gmceast.com/travel
_
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| Re: [GMCnet] Vapor lock - lost the battle but not the war, or: Ethanol is for drinking [message #99965 is a reply to message #99782] |
Wed, 15 September 2010 19:32 |
Gary Casey
Messages: 448
Registered: September 2009
Karma: 0
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Senior Member |
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No, that's one of the frustrating things - the engine likes ethanol just fine.
Some race series have converted from methanol to ethanol so they can claim
"green" status. Ethanol has a very high octane rating, so the compression ratio
could be raised if running on ethanol. Problem is in all the systems around the
engine. It aggressively absorbs water, so the fuel system has to be carefully
vented. For the same reason it can't be mixed at the refinery and piped to
distribution - it has to be added at the last minute, increasing the cost. It
is corrosive and attacks metal and some types of rubber. It has very low vapor
pressure at low temperatures, so it has to be mixed with gasoline to enable cold
starts. But it has a very high vapor pressure at high temperature, causing
vapor lock in our carbureted engines. And to top it off it has only about 60%
as much energy per gallon as gasoline. It costs a little less, but only if you
take into account the federal subsidy. Even then it is still more expensive per
BTU output. You might have read between the lines to figure out I'm not a fan
of ethanol, but my taxes still go to pay for its production and use. :-(
Gary
My primary question would be, does the ethanol 'hurt' our engines?
--
CBWood
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| Re: [GMCnet] Vapor lock - lost the battle but not the war, or: Ethanol is for drinking [message #99995 is a reply to message #99782] |
Wed, 15 September 2010 22:51 |
GeorgeRud
Messages: 1380
Registered: February 2007
Location: Chicago, IL
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There's a move afoot to increase the ethanol content to 15% (E15) for newer cars. Though there are some countries that do well using ethanol (Brazil where sugar, not corn, is used to make the ethanol), it seems to be a political decision more than an engineered one.
As with others, I'm not a big fan of ethanol when all aspects of it's production costs, benefits and liabilities are included.
George Rudawsky
Chicago, IL
75 Palm Beach
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| Re: [GMCnet] Vapor lock - lost the battle but not the war, or: Ethanol is for drinking [message #100008 is a reply to message #99995] |
Thu, 16 September 2010 08:07 |
Dr. Detroit
Messages: 158
Registered: April 2010
Location: Novi, MI.
Karma: 0
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The vapor lock problem is two fold. First the ethanol component has a lower boiling point (typically) than plain old gasoline. Second, the specs on gasoline are pretty wide when it comes to boil point so when you buy a batch of gas with a low boil point and it has the ethanol in it making things worse, you get a nice low boil point.
While fuel is supposed to be blended for specific regions (hot versus cold) as I mentioned the spec to start with is pretty wide. Also just because the pump you are using does not have a "Contains 10% Ethanol" sign on it does not mean you are OK. You must check the fill sheets from the supplier with the attendant. That's the only way to know the E content in the fuel you are buying. Here in MIchigan all unleaded fuels at typical gas stations are 10%. No way around it other than AV gas or Turbo Blue race gas.
Thanks to our government and strong lobbying Ethanol is here to stay and is only going to go up in concentration to E15 in the near future.
All that said, the only way to solve vapor lock is to raise the boil point of the fuel. So far the only thing I've found that does this effectively is tetraethyl lead and the stuff is called Maxlead2000. A few of my friends use the stuff in old Vettes and Big Block Chevelles with success. The claim is that the stuff raises the boil point by 30 degrees. I have no data to back up the claim. If you are considering this product as a possible solution verify this claim before purchasing.
Now for the real and permanent solution. 
Has anyone ever wondered why new cars and trucks don't have a vapor lock problem with the new "fuels" like E10 and E85?
The solution is pressure in the fuel lines. As pressure is increased the boil point of the fuel goes up thus eliminating the boil off and subsequent vapor lock in the lines.
That said, our OEM system while good at the time our coaches were built is now outdated. The system only gets pressurized between the fuel pump on the engine and the carb. However the pressure is only 3-5 PSI usually for carbs. That's hardly enough to increase the boil off point of the fuel at one of the hottest places in it's path.
Howell TBI Fuel injection systems use an inline pump at 15 PSI and use a preset regulator at 11 PSI. Even though pressure is higher than a carb motor the 10 PSI difference will not significantly increase the boil point either. To make matters worse, the pump is an inline pump so the fuel in the line from the pickup to the pump is at 1 atmosphere anyhow so that's a prime place for the fuel to boil off.
Typical Multiport or MPI systems use high pressure pumps mounted in the fuel tank and the entire system (lines and all) operate between 36 psi and 43.5 psi. This solved a lot of problems with vapor lock as the increase in pressure raised the boil off point to well above what is needed.
Everything was fine until E85 came into play. To deal with the changes in the fuel the auto companies upped the pressure to 60 PSI. For example the 2005 Chevy Flex Fuel 5.3 liter engine uses 59 psi as it's spec. As a result it can run any of the E fuels without issue.
So knowing that this situation will only get worse with the intro of E15, my upgrade this winter is going to be 60 PSI pumps in my tanks with a new line pressurized all of the way up to just before the carb. Within just inches of the carb I plan to install a return style regulator and drop the pressure to a 3-5 psi that the float can deal with.
I expect to delete the mechanical pump and the fuel tank selector from the system. I will power each fuel pump with a DPDT relay which will allow me to switch them on or off allowing me to select between tanks.
By doing it this way the possibility of vapor lock will only be between the regulator and the base plate of the carb.
If all else fails, I'll do an engine swap to a modern powerplant such as a 5.3 or 6.0 Vortec.
Ken Wolkens
1973 GMC 23'
All Birch and Maple Interior Cabinetry. TZE033V100221
"The Honeycomb Hideout"
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| Re: [GMCnet] Vapor lock - lost the battle but not the war, or: Ethanol is for drinking [message #100013 is a reply to message #100008] |
Thu, 16 September 2010 09:00 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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Senior Member |
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Ken
Are you going to the GMCMI convention at DuQuoin?
The seminar I am presenting on In-Tank Fuel Pumps addresses exactly
what you have posted.
However you don't need a double pole double throw relay. A single pole
relay works well. The main tank pump connects to the normally closed
contact. The Aux tank pump connects to the normall open contact. The
wire that formerly actuates the fuel selector switch now actuates the
relay. The wire that went to the electric fuel pump now goes to the
other end of the contact that gets switched to each in tank fuel pump.
Emery Stora
77 Kingsley
Santa Fe
"with high pressure furl pumps in each tank"
On Sep 16, 2010, at 9:07 AM, Ken Wolkens <kwolkens@gmail.com> wrote:
>
>
> The vapor lock problem is two fold. First the ethanol component has
> a lower boiling point (typically) than plain old gasoline. Second,
> the specs on gasoline are pretty wide when it comes to boil point so
> when you buy a batch of gas with a low boil point and it has the
> ethanol in it making things worse, you get a nice low boil point.
>
> While fuel is supposed to be blended for specific regions (hot
> versus cold) as I mentioned the spec to start with is pretty wide.
> Also just because the pump you are using does not have a "Contains
> 10% Ethanol" sign on it does not mean you are OK. You must check
> the fill sheets from the supplier with the attendant. That's the
> only way to know the E content in the fuel you are buying. Here in
> MIchigan all unleaded fuels at typical gas stations are 10%. No way
> around it other than AV gas or Turbo Blue race gas.
>
> Thanks to our government and strong lobbying Ethanol is here to stay
> and is only going to go up in concentration to E15 in the near future.
>
> All that said, the only way to solve vapor lock is to raise the boil
> point of the fuel. So far the only thing I've found that does this
> effectively is tetraethyl lead and the stuff is called Maxlead2000.
> A few of my friends use the stuff in old Vettes and Big Block
> Chevelles with success. The claim is that the stuff raises the boil
> point by 30 degrees. I have no data to back up the claim. If you
> are considering this product as a possible solution verify this
> claim before purchasing.
>
> Now for the real and permanent solution. :d
>
> Has anyone ever wondered why new cars and trucks don't have a vapor
> lock problem with the new "fuels" like E10 and E85?
>
> The solution is pressure in the fuel lines. As pressure is
> increased the boil point of the fuel goes up thus eliminating the
> boil off and subsequent vapor lock in the lines.
>
> That said, our OEM system while good at the time our coaches were
> built is now outdated. The system only gets pressurized between the
> fuel pump on the engine and the carb. However the pressure is only
> 3-5 PSI usually for carbs. That's hardly enough to increase the
> boil off point of the fuel at one of the hottest places in it's path.
>
> Howell TBI Fuel injection systems use an inline pump at 15 PSI and
> use a preset regulator at 11 PSI. Even though pressure is higher
> than a carb motor the 10 PSI difference will not significantly
> increase the boil point either. To make matters worse, the pump is
> an inline pump so the fuel in the line from the pickup to the pump
> is at 1 atmosphere anyhow so that's a prime place for the fuel to
> boil off.
>
> Typical Multiport or MPI systems use high pressure pumps mounted in
> the fuel tank and the entire system (lines and all) operate between
> 36 psi and 43.5 psi. This solved a lot of problems with vapor lock
> as the increase in pressure raised the boil off point to well above
> what is needed.
>
> Everything was fine until E85 came into play. To deal with the
> changes in the fuel the auto companies upped the pressure to 60
> PSI. For example the 2005 Chevy Flex Fuel 5.3 liter engine uses 59
> psi as it's spec. As a result it can run any of the E fuels without
> issue.
>
> So knowing that this situation will only get worse with the intro of
> E15, my upgrade this winter is going to be 60 PSI pumps in my tanks
> with a new line pressurized all of the way up to just before the
> carb. Within just inches of the carb I plan to install a return
> style regulator and drop the pressure to a 3-5 psi that the float
> can deal with.
>
> I expect to delete the mechanical pump and the fuel tank selector
> from the system. I will power each fuel pump with a DPDT relay
> which will allow me to switch them on or off allowing me to select
> between tanks.
>
> By doing it this way the possibility of vapor lock will only be
> between the regulator and the base plate of the carb.
>
> If all else fails, I'll do an engine swap to a modern powerplant
> such as a 5.3 or 6.0 Vortec.
>
> Ken Wolkens
>
>
>
>
> --
> 1973 GMC 23'
> All Birch and Maple Interior Cabinetry. TZE033V100221
> "The Honeycomb Hideout"
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] Vapor lock - lost the battle but not the war, or: Ethanol is for drinking [message #100044 is a reply to message #100024] |
Thu, 16 September 2010 17:16 |
Dr. Detroit
Messages: 158
Registered: April 2010
Location: Novi, MI.
Karma: 0
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Senior Member |
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Yep, you guys are right a DPDT relay is not required. I should have said SPDT because they are the most common and what I really would have used anyhow.
Regarding the bypass regulator, yep if the bypass is used then the whole fuel system would be at the same fuel pressure of 3-5 psi. That's not ideal. I want at least 40 psi all the way to within a couple inches of the carb.
Thanks for catching the error.
I should have stated that the system needs to be a deadhead system. Also note that the pump selected would need to have a built in bypass valve so it does not stall its self and die. I've used Walbro's 255 before in a deadhead system and the pump was constantly on and not triggered by an ECU.
Ken Wolkens
1973 GMC 23'
All Birch and Maple Interior Cabinetry. TZE033V100221
"The Honeycomb Hideout"
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