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| [GMCnet] Vapor Lock Incidents [message #98406] |
Fri, 03 September 2010 18:21  |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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G'day,
We got caught in rush hour traffic heading south on US 1 between Miami and
Homestead and suffered a number of incidents of vapor lock. It was no big
deal as I had installed Jim B's fix.
A small fuel pump (3-6 psi outlet) is installed between the Aux tank outlet
and the selector valve. When vapor lock occurs you switch from Main to Aux
and the power that actuates the selector valve powers up the pump.
I discovered that it took about 15-30 seconds for the pump to "prime" the
mechanical pump.
After vapor lock occurred the third time I "anticipated" it happening and
would watch the traffic flow and switched over to Aux before applying gas to
start moving and voila - NO vapor lock!
Jim did note that there is a downside to this fix - if there is a hole /
tear in the diaphragm of the mechanical pump the electric pump could / would
pump gas into the engine.
Regards,
Rob M.
USAussie
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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 Incidents [message #98418 is a reply to message #98406] |
Fri, 03 September 2010 19:50  |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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Rob,
We will possibly start removing the mecanical pump and rely on the electric
pump at the rear.
On Fri, Sep 3, 2010 at 4:21 PM, Rob Mueller <robmueller@iinet.net.au> wrote:
> G'day,
>
> We got caught in rush hour traffic heading south on US 1 between Miami and
> Homestead and suffered a number of incidents of vapor lock. It was no big
> deal as I had installed Jim B's fix.
>
> A small fuel pump (3-6 psi outlet) is installed between the Aux tank outlet
> and the selector valve. When vapor lock occurs you switch from Main to Aux
> and the power that actuates the selector valve powers up the pump.
>
> I discovered that it took about 15-30 seconds for the pump to "prime" the
> mechanical pump.
>
> After vapor lock occurred the third time I "anticipated" it happening and
> would watch the traffic flow and switched over to Aux before applying gas
> to
> start moving and voila - NO vapor lock!
>
> Jim did note that there is a downside to this fix - if there is a hole /
> tear in the diaphragm of the mechanical pump the electric pump could /
> would
> pump gas into the engine.
>
> Regards,
> Rob M.
> USAussie
>
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
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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| Re: [GMCnet] Vapor Lock Incidents [message #98443 is a reply to message #98406] |
Fri, 03 September 2010 22:16 |
Charles
Messages: 455
Registered: January 2004
Karma: 0
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Senior Member |
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Rob,
your report is encouraging. I have not had time to check out
my modification of the system but I will be leaving for a 5000
mile trip around the 9th. I have eliminated the manual pump
and the fuel tank selector valve. I put a separate electric
fuel pump off of each fuel tank with one way valves in
lines just forward of the electric fuel pumps. Now when I switch
pumps I switch tanks so if switching tanks stopped the vapor
lock my switching pumps and tanks should work the same
(I can say this now but could while doing the task.) With
Ken Henderson's help with wiring "it was a simple
change". For me it was one of those one hour jobs that
ended up talking me six hours. Most of that was running
new wires. The first oil pressure switch I installed went out
the second time I turned the key on. After that one pump ran
all the time. Even with the key turned off.So it didn't take long
to find the bad oil pressure switch. I'm expect vapor lock will
be a major point of discussion at Du quoin. Hope to see
you there.
Charles
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Charles Wersal
Duncanville, Texas
26 foot 1975 Glenbrook
Pandora's Box
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| Re: [GMCnet] Vapor Lock Incidents [message #98489 is a reply to message #98418] |
Sat, 04 September 2010 09:03 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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""Rob,
We will possibly start removing the mecanical pump and rely on the electric
pump at the rear.
""
I thought about that but so far my mechanical pump has been more reliable than my electric pump.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Vapor Lock Incidents [message #98613 is a reply to message #98501] |
Sun, 05 September 2010 07:50 |
Steven Ferguson
Messages: 3447
Registered: May 2006
Karma: 0
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Senior Member |
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Gene,
That matches my results.
On Sat, Sep 4, 2010 at 7:51 AM, Mr.erf ERFisher <mr.erfisher@gmail.com> wrote:
>>
>> I thought about that but so far my mechanical pump has been more reliable
>> than my electric pump.
>> --
>>
> I continue to be amazed by this, I removed my mechanical pump almost 10
> years ago, and still on the same carter pump.
>
> I know of one mechanical pump that was moved through 3 engines, and
> destroyed all three.
>
> It just seems to me,
> *that since all the cars today use electrical pumps,
> *and we are having trouble with the new fuels,
> *and elabrate switching systems are a PITA , just to turn on electrics
> pumps.
>
> just bite the bullet and tear out all that excess wiring and plumbing and
> install an electric pump that runs all the time.
>
> JWID - cannot understand the resistance
>
> not sent from my iPhone
> gene
>
>
> --
> 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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--
Steve Ferguson
'76 EII
Sierra Vista, AZ
Urethane bushing source
www.bdub.net/ferguson/
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| Re: [GMCnet] Vapor Lock Incidents [message #98861 is a reply to message #98501] |
Tue, 07 September 2010 15:32 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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""I continue to be amazed by this, I removed my mechanical pump almost 10
years ago, and still on the same carter pump.
I know of one mechanical pump that was moved through 3 engines, and
destroyed all three""
I wouldn't call it resistance as much as bad luck with my Carter electric pump which I installed as a booster. So far my mechanical pump has done it's duty for about 20 years and just keeps on going--can't say that for a 2 year old carter.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Vapor Lock Incidents [message #98904 is a reply to message #98861] |
Tue, 07 September 2010 21:28 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Senior Member |
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I wounder has anyone that has switched to separate carter electric pumps for each tank that have removed the mechanical pump
upon encountering vapor lock, turned on both pumps simultaneously to minimize the vapor lock?? Or would it not matter if only 1 pump were operating?
Roy
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] Vapor Lock Incidents [message #98910 is a reply to message #98904] |
Tue, 07 September 2010 22:07 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Roy,
I've been running 2 Carter 4070's for several years -- don't even remember
how far back it was. I've never tried running both of them to overcome
vapor lock for 2 reasons: 1. I've got them wired to the tank selector
switch so I can only select one at a time. 2. I haven't experienced vapor
lock since installing them.
However, I would not expect running both simultaneously to have any effect
because they are pressure limited; the pressure should be the same even with
two feeding the same line. Since the carburetor is a pressure fed device
and doesn't "suck" the fuel, it cannot reduce the pressure in the line below
what the pumps provide.
Now, if one low volume pump was feeding a higher volume pump, adding an
additional supply pump might overcome "boiling" in the line between them.
It's the "sucking" mechanical pump that's apparently the most frequent
cause of vapor lock.
JMHO,
Ken H.
On Tue, Sep 7, 2010 at 10:28 PM, roy keen <roynpaula@charter.net> wrote:
>
> I wounder has anyone that has switched to separate carter electric pumps
> for each tank that have removed the mechanical pump
> upon encountering vapor lock, turned on both pumps simultaneously to
> minimize the vapor lock?? Or would it not matter if only 1 pump were
> operating?
>
>
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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 Incidents [message #98917 is a reply to message #98910] |
Tue, 07 September 2010 22:53 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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""Now, if one low volume pump was feeding a higher volume pump, adding an
additional supply pump might overcome "boiling" in the line between them.
It's the "sucking" mechanical pump that's apparently the most frequent
cause of vapor lock.
""
Now the real question is still why some people are having vapor lock and others aren't. Once I fixed my split suction line, I haven't had to turn on my carter pump at all even at altitude and 100+f temps. I'm not bragging, just more curious how some folks do and don't have the issue. Out here it is impossible to find non alcohol fuel so that isn't the issue.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Vapor Lock Incidents [message #98926 is a reply to message #98406] |
Wed, 08 September 2010 00:43 |
James Moore
Messages: 71
Registered: January 2004
Karma: 0
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Member |
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> Now the real question is still why some people are having vapor lock and
others aren't. Once I fixed my split suction line, I haven't had to turn on
my carter pump at all even at altitude and 100+f temps. I'm not bragging,
just more curious how some folks do and don't have the issue. Out here it
is impossible to find non alcohol fuel so that isn't the issue.
> --
> Bob de Kruyff
> 78 Eleganza
> Chandler, AZ
> _______________________________________________
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Bob,
I think the problem is caused by more than alcohol in the fuel and hot gas
tanks. People have reported vapor lock being corrected by running electric
fuel pumps. Others have reported an electric fuel pump had no effect.
People have reported vapor lock on hot days and others on cool days. One
person reported vapor lock when he drove more than 4 hrs. Some people have
vapor lock at high altitudes and others have no vapor lock at high
altitudes.
In my case I have never had what I consider an actual case of vapor lock in
the 10+ yrs I have owned my GMC. During that time I have had it above 9000
ft, operated it in 115F temperatures and don't know that I have ever burned
any gas that didn't have at least 10% alcohol in it.
I have had fuel starvation due to plugged carb filters and quite running
them within a week after I purchased it. I have suffered loss of power due
to a stuck centrifugal advance, But no vapor lock.
I think there is a long list of things that can cause a loss of power and a
rough running engine that have nothing to do with alcohol in the fuel or
the temperature of the fuel or the vapor pressure of the fuel which are
commonly blamed for vapor lock.
I don't think alcohol in fuel directly causes vapor lock but it may
indirectly cause what some call vapor lock. Recently I have rebuilt 2
quadrajet carbs. Both of them had sat for several months. Both carbs had
grayish deposits in the float bowl and other wetted parts. The power piston
was stuck down in both carbs. One of the carbs was on my Blazer with a
small block Chevy engine. The engine would misfire under load, bog down
when accelerating and spark knock at high loads. This sounds like what
people have described as vapor lock. The engine ran fine until I didn't
use it for about 6 months. After I cleaned the power piston and made sure
it was free, the engine ran fine. It pulls from 15 mph in 3rd gear (manual
tranny) with no misfires or bogging down and no spark knocking under load.
I think the stuck power piston was causing the engine to run lean. In this
case an electric fuel pump might have improved engine operation.
The second carb had a leaking needle valve and was running rich in addition
to the stuck power piston. Sometimes it would shut off at stop signs and
be difficult to restart and ran rough with poor acceleration and a loss of
power. It would also run fine for several days. Since I replaced the
needle valve and float, the engine is running fine. In this case an
electric fuel pump might have hurt engine operation.
I have a 1500 watt generator I use during extended power outages for
emergency power. Every fall I get it out and crank it up to make sure it
is running OK, fill it up with gas and put it in a wheel barrow so my wife
and move it to the house. Last fall it would not crank. Corrosion in the
carb had plugged the jet. After I got it running, I added Stabil to the
fuel and it started fine about 3 months later. I think moisture had gotten
into the fuel through the gas cap vent and created a corrosive mixture.
I encountered a similar problem with corrosion in the Onan carb after it
sat for a couple of years. After sitting over night in carb cleaner, it
runs fine.
On my trip from Battle Ground, WA to Pinehurst, GA, I lost power and had
difficulty maintaining 60 mph in the hills north of Atlanta. This was
caused by a stuck centrifugal advance in the distributor. It also caused
the engine to operate about 10 to 15 degrees hotter than normal. That is
why I checked the distributor instead of the carb.
During hot weather, I always start a hot engine with the gas pedal about
1/2 way to the floor and hold the engine speed around 1500 rpm until it
runs smoothly for a minute or so. This reduces the chances of the engine
flooding due to fuel boiling in the carb.
To me corrosion caused by moisture reacting with the alcohol in the fuel is
more like to cause poor engine performance than the alcohol in the fuel.
Alcohol in the fuel can also damage elastomers used in original fuel pumps,
carbs, selector valves and fuel hoses. Damaged elastomers can also cause
poor engine performance which is why I replaced all the hoses and the fuel
pump and rebuilt the carb shortly after I got the GMC. One of the hoses I
installed cracked and started leaking a couple of years. There has been no
problem with any of the other hoses so I guess it was not a fuel hose or
old stock.
My experience with vehicles has been that they sit idle for extended
periods of time, you can expect to have problems. Most GMC's aren't used
on a daily basis and sit idle most of the time so problems are to be
expected. Most people don't know how to check the power valve in a
quadrajet, or the centrifugal advance and just assume their poor engine
performance is due to boiling gasoline caused by alcohol in the fuel and
radiant heat from the pavement. When I was a kid, people put clothes pins
on the fuel lines of their flat head Ford engines to prevent vapor lock.
Now people insulate gas tanks and fuel lines to get rid of vapor lock. A
smart mechanic replaced my vacuum advance and told me to put the clothes
pins back in my Mother's basket.
Jim Moore in Battle Ground, WA
75 PB parked in Pinhurst, G
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