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| [GMCnet] In tank fuel temperatures [message #242996] |
Tue, 11 March 2014 00:30  |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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G'day,
I just provided a link to Chuck Garton's three fuel tank installations. I hadn't read this article in a LONG time! I discovered that
Chuck has temperature probes in all three of the tanks and here's what he notes regarding the temps he has seen:
http://www.gmcpc.org/archive/3rd_fuel_tank.pdf
Quote #1
I mounted the fuel pumps (again, one for each tank) outside of frame rails (picture 13). By mounting them this way, I was able to
get each pump closer to its tank (electric fuel pumps are better pushers than pullers). Also on 100°+ days the area outside the
frame rails is about 25° cooler than the fuel in the front tank.
Quote #2
Picture 14 shows the fuel tank temperature sensor installed. All three tanks have temperature sensors. When a fuel tank is selected
to pump from, the temperature sensor for that tank is also selected. The hottest temperature observed was 148° F in August 2005 on
I-15’s sixteen-mile climb just north of Baker, CA on the way to Las Vegas.
Quote #3
Last summer, during a trip to the east coast, I experienced vapor lock problems when forced to idle on 100°+ days for more than
three minutes. When I returned home, I abandoned the stock steel fuel line that ran inside the frame around the engine and ran a new
steel line outside the frame. When I finished this task, it was 105° in Ridgecrest and I drove to a large empty black asphalt
parking lot and idled for thirty minutes with no vapor lock problems.
Comments:
Quote #1 - I am of the opinion that this demonstrates that the tanks pickup heat from hot air flowing rearward from the engine and
radiated from the roadway.
Quote #2 - ONE HUNDRED AND FORTY EIGHT DEGREES! Holy crap!
Quote #3 - This is very interesting it might just be the main cause of vapor lock in OEM GMC's
I am going to send Chuck an off net email and ask him if he can provide some additional data.
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
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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] In tank fuel temperatures [message #243048 is a reply to message #242996] |
Tue, 11 March 2014 18:30  |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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G'day,
Chuck was kind enough to provide a response to my email below.
Regards,
Rob
From: Robert Mueller
Sent: Monday, March 10, 2014 10:50 PM
To: 'Garton Chuck & Dorris'
Subject: In tank fuel temperatures
G’day Chuck,
I just stumbled on to your article about three fuel tanks and noted some data regarding in tank fuel temperatures and sent the
following message into the GMCnet.
Have you recorded any additional temperatures?
I assume the front tank is always the hottest have you recorded any additional temperatures and OAT at the same time in sequence,
Tank 1, Tank 2, Tank 3, Ambient Temp?
You are probably the ONLY person that has EVER seen what the fuel temps reach other than the engineers that built the GMC!
Any additional information you can provide would be great. I’ve sent this message to you directly as I don’t know if you monitor the
GMCnet or not.
All the best,
Rob
From: Chuck Garton [mailto:ceg777@earthlink.net]
Sent: Wednesday, March 12, 2014 5:38 AM
To: Robert Mueller
Subject: Re: In tank fuel temperatures
Hi,
The displayed temp is the tank in use. The front tank (tank 1) run 5°-7° hotter than tanks 2 & 3 The mid tank (tank 2) and the rear
tank (tank 3) are usually the same temperature.
146° is still the hottest I’ve seen (tank 1). At that temp, the temp outside the frame rails is 25° cooler.
After 2 hours of travel, tanks 2 & 3 stabilize at about 40° over ambient. At normal temps (70°), the temp outside the frame stays at
about 15° cooler.
I have thought about in tank fuel pumps, but I like my fuel pumps cooler than the fuel.
Like a lot of the gauges I have installed, I watch them closely until I have established a normal reading. Then if things start to
go wrong......
Chuck
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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] In tank fuel temperatures [message #243092 is a reply to message #243048] |
Tue, 11 March 2014 21:55 |
corleyw
Messages: 130
Registered: June 2007
Location: Battle Ground, WA
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Makes a pretty good case for getting all the air that you can out the sides rather than under the coach. PLUS, getting the steel fuel line outside the frame rail. (Or replacing it with an insulated line, or something that doesn't transfer heat as well as steel. Like, tada, nylon lines.)
I've ordered in-tank pumps (17 lbs for TBI possibility in the future), nylon lines, quick disconnect fittings, and will use a return line (also nylon). I plan to try using it with the q-jet (for now), no regulator, just a 'T' at the carb. I think the fuel pressure should be low enough with the 5/16" return line, that it won't overflow the q-jets needle and seat, but if it does, I'll add a regulator.
Still chewing on moving the fill pipe... Maybe, Maybe not. Filling has not been all that bad except when the nozzle won't fit down far enough in Cal.
Now all I need is the spirit to move me to get under that sucker. Just what I'm doing, not recommending it to anyone else.
Corley
'76 Glenbrook
29 other vehicles
[Updated on: Tue, 11 March 2014 21:56] Report message to a moderator |
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| Re: [GMCnet] In tank fuel temperatures [message #243103 is a reply to message #243092] |
Tue, 11 March 2014 22:32 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Corley,
Please note that Chuck stated; "After 2 hours of travel, tanks 2 & 3 stabilize at about 40° over ambient."
As I've said earlier there are three sources of heat gain into the tanks:
1) conduction - from items that come into the fuel tanks
2) convection - from the hot air circulating under the coach
3) radiation - from the hot road surface
JimB painted a set of tanks with Lizard Skin AND insulated the rubber lines on a GMC that suffered vapor lock and it did not cure
the problem it only delayed the onset.
Another GMCer reported that he covered the tanks with diamond plate and I "THINK" he blocked off the airflow through the holes in
the cross members. I used the word "THINK" because I can't remember for sure. He noted that solved his vapor lock problems.
I am of the OPINION that since the fuel in the lines is flowing the amount of heat it gains for the amount time it is in the lines
would not make much of a difference and insulating them would not be worth it.
However, I agree that "getting all the air that you can out the sides rather than under the coach" and moving the fuel lines outside
the frame rails are good ideas.
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
-----Original Message-----
From: Corley Wooldridge
Makes a pretty good case for getting all the air that you can out the sides rather than under the coach. PLUS, getting the steel
fuel line outside the frame rail. (Or replacing it with an insulated line, or something that doesn't transfer heat as well as steel.
Like, tada, nylon lines.)
I've ordered in-tank pumps (17 lbs for TBI possibility in the future), nylon lines, quick disconnect fittings, and will use a return
line (also nylon). I plan to try using it with the q-jet (for now), no regulator, just a 'T' at the carb. I think the fuel
pressure should be low enough with the 5/16" return line, that it won't overflow the q-jets needle and seat, but if it does, I'll
add a regulator.
Still chewing on moving the fill pipe... Maybe, Maybe not. Filling has not been all that bad except when the nozzle won't fit down
far enough in Cal.
Now all I need is the spirit to move me to get under that sucker.
--
Corley
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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] In tank fuel temperatures [message #243140 is a reply to message #243103] |
Wed, 12 March 2014 08:33 |
corleyw
Messages: 130
Registered: June 2007
Location: Battle Ground, WA
Karma: 0
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| USAussie wrote on Tue, 11 March 2014 19:32 |
Corley,
Please note that Chuck stated; "After 2 hours of travel, tanks 2 & 3 stabilize at about 40° over ambient."
As I've said earlier there are three sources of heat gain into the tanks:
1) conduction - from items that come into the fuel tanks
2) convection - from the hot air circulating under the coach
3) radiation - from the hot road surface
JimB painted a set of tanks with Lizard Skin AND insulated the rubber lines on a GMC that suffered vapor lock and it did not cure
the problem it only delayed the onset.
Another GMCer reported that he covered the tanks with diamond plate and I "THINK" he blocked off the airflow through the holes in
the cross members. I used the word "THINK" because I can't remember for sure. He noted that solved his vapor lock problems.
I am of the OPINION that since the fuel in the lines is flowing the amount of heat it gains for the amount time it is in the lines
would not make much of a difference and insulating them would not be worth it.
However, I agree that "getting all the air that you can out the sides rather than under the coach" and moving the fuel lines outside
the frame rails are good ideas.
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
-----Original Message-----
From: Corley Wooldridge
Makes a pretty good case for getting all the air that you can out the sides rather than under the coach. PLUS, getting the steel
fuel line outside the frame rail. (Or replacing it with an insulated line, or something that doesn't transfer heat as well as steel.
Like, tada, nylon lines.)
I've ordered in-tank pumps (17 lbs for TBI possibility in the future), nylon lines, quick disconnect fittings, and will use a return
line (also nylon). I plan to try using it with the q-jet (for now), no regulator, just a 'T' at the carb. I think the fuel
pressure should be low enough with the 5/16" return line, that it won't overflow the q-jets needle and seat, but if it does, I'll
add a regulator.
Still chewing on moving the fill pipe... Maybe, Maybe not. Filling has not been all that bad except when the nozzle won't fit down
far enough in Cal.
Now all I need is the spirit to move me to get under that sucker.
--
Corley
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Well, after two hours to 55mph travel, I don't have any issues on flat land. When a hill comes along, and I start to pull hard, and then the fan kicks in, shortly after THAT is when the problems begin. We are probably looking more at the max temps in the tanks that he sees, not the 40 degrees above ambient he mentions. Slow down the vehicle and we get more heat from the road, slow the vehicle, and the heat from the engine does not dilute as much with other incoming 'cooler' air, slow the and work it hard and the fan is pushing a lot more really hot air under the coach. That's when the temps get hot enough to cause VP.
Now, when it stops, I pull over to the side of the same road, still blacktop so radiating the same, and wait 10 minutes, and presto, I can start and go for a little longer. My analysis of that is that Hot air from the engine is heating the fuel in the lines, and probably the mechanical pump is topping it off to a nice vapor.
I come from the old school, and have seen a lot of cars with tin foil around gas lines to stop vapor lock on hot days. Some cars came new with asbestos wraps for this problem. That solution has worked for years now. I'm pretty sure that a fuel line can pick up a LOT of heat is short order, when hot air, make that really hot air, is passing over it.
Of course I'm not talking about the hot soak VP when sitting still for a few minutes, that's a whole different thing, and frankly it lasts such a short time as to not be an issue for me so far, just a brief sputter in acceleration. It's the hill climbing on hot days, with low RVP fuel vapor lock, that is the killer.
But we can disagree on that if you like.
Corley
Corley
'76 Glenbrook
29 other vehicles
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| Re: [GMCnet] In tank fuel temperatures [message #243394 is a reply to message #243140] |
Thu, 13 March 2014 20:48 |
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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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Corley,
Comments below in CAPS, not shouting.
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
-----Original Message-----
From: Corley Wooldridge
Well, after two hours to 55mph travel, I don't have any issues on flat land. When a hill comes along, and I start to pull hard, and
then the fan kicks in, shortly after THAT is when the problems begin.
I DON'T UNDERSTAND WHY THAT HAPPENS. WHEN I'M UNDERWAY IN DOUBLE TROUBLE I DON'T HAVE PROBLEMS.
We are probably looking more at the max temps in the tanks that he sees, not the 40 degrees above ambient he mentions.
I DON'T UNDERSTAND WHY YOU SAY THIS; CHUCK HAS PROVIDED HARD DATA OF TEMPERATURE READINGS OF THE FUEL IN THE TANKS AND OUTSIDE THE
FRAME.
Slow down the vehicle and we get more heat from the road,
I'M SORRY BUT I'M GOING TO DISAGREE WITH THIS; IF THE ROADWAY TEMP REMAINS CONSTANT THE SPEED YOU TRAVEL OVER IT HAS NO EFFECT ON
THE AMOUNT OF HEAT RADIATED INTO THE FUEL TANKS.
slow the vehicle, and the heat from the engine does not dilute as much with other incoming 'cooler' air, slow the and work it hard
and the fan is pushing a lot more really hot air under the coach. That's when the temps get hot enough to cause VP.
AGREED
Now, when it stops, I pull over to the side of the same road, still blacktop so radiating the same, and wait 10 minutes, and presto,
I can start and go for a little longer.
IN DOUBLE TROUBLE THE OPPOSITE IS WHAT HAPPENS; WHEN I SIT AT A TRAFFIC LIGHT AND THEN TRY TO PULL AWAY IT VAPOR LOCKS AND I HAVE TO
SWITCH TO AUX WHICH STARTS THE FACET PUMP WHICH PUSHES FUEL TO THE MECHANICAL PUMP.
My analysis of that is that Hot air from the engine is heating the fuel in the lines, and probably the mechanical pump is topping it
off to a nice vapor.
AT IDLE THE FLOW THROUGH THE STEEL LINE ATTACHED TO THE FRONT CROSSMEMBER WOULD DECREASE SIGNIFICANTLY AND THE FUEL WOULD GET
HEATED. I'D GUESS THAT AT THE INLET TO THE MECHANICAL PUMP THERE WOULD BE A PRESSURE DROP WHICH COULD CAUSE THE VAPOR LOCK.
I come from the old school, and have seen a lot of cars with tin foil around gas lines to stop vapor lock on hot days. Some cars
came new with asbestos wraps for this problem. That solution has worked for years now. I'm pretty sure that a fuel line can pick up
a LOT of heat is short order, when hot air, make that really hot air, is passing over it.
AS I NOTED IN AN EARLIER EMAIL JIMB PAINTED THE TANKS WITH LIZARD SKIN AND INSULATED THE FUEL LINES WITH SOME KIND OF TUBULAR
INSULATION AND ALL IT DID WAS POSTPONE THE ONSET OF VAPOR LOCK.
Of course I'm not talking about the hot soak VP when sitting still for a few minutes, that's a whole different thing, and frankly it
lasts such a short time as to not be an issue for me so far, just a brief sputter in acceleration.
THAT'S WHAT HAPPENS TO DOUBLE TROUBLE CONSISTENTLY BUT THE ENGINE DIES IF I DON'T SWITCH TO AUX.
It's the hill climbing on hot days, with low RVP fuel vapor lock, that is the killer.
FRANKLY THE ONLY WAY TO REALLY DETERMINE WHERE THE FUEL PICKS UP HEAT IS TO PUT THERMOCOUPLES IN THE TANKS AND IN THE FUEL LINES:
A) AT THE EXIT OF THE FUEL TANKS
B) AT THE START OF THE METAL LINE THAT GOES ACROSS THE TOP OF THE FRONT CROSS MEMBER
C) AT THE INLET TO THE MECHANICAL
But we can disagree on that if you like.
Corley
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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] In tank fuel temperatures [message #243401 is a reply to message #243394] |
Thu, 13 March 2014 21:31 |
corleyw
Messages: 130
Registered: June 2007
Location: Battle Ground, WA
Karma: 0
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| USAussie wrote on Thu, 13 March 2014 17:48 |
Corley,
Comments below in CAPS, not shouting.
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
-----Original Message-----
From: Corley Wooldridge
Well, after two hours to 55mph travel, I don't have any issues on flat land. When a hill comes along, and I start to pull hard, and
then the fan kicks in, shortly after THAT is when the problems begin.
I DON'T UNDERSTAND WHY THAT HAPPENS. WHEN I'M UNDERWAY IN DOUBLE TROUBLE I DON'T HAVE PROBLEMS.
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Ron,
I'm glad that you finally admitted it!   Sounds like you are only looking at hot soak issues, whereas others (like me) are seeing vapor lock while underway, in hot, hard pulls. Two different animals, with possiibly, two different solutions.
But I'll give you this, you sure do like to defend your ideas / positions!
Corley
Corley
'76 Glenbrook
29 other vehicles
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| Re: [GMCnet] In tank fuel temperatures [message #243420 is a reply to message #242996] |
Fri, 14 March 2014 01:15 |
Luvn737s
Messages: 1106
Registered: June 2007
Karma: 2
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Senior Member |
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I live in AZ and am conscious of potential Vapor Lock conditions. I try to keep the tanks as full as possible when traveling over roads at slow or stop-and-go speeds. In cruise I rarely see a problem. A traffic light on a hill is a whole 'nuther matter. Pump works well, but more fuel takes longer to heat up. I also wrap the hard line from the mechanical pump to the carb with rubber hose and aviation fire sleeve to insulate it as well as possible.
Randy
1973 26' Painted Desert
Ahwatukee (Phoenix) AZ
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| Re: [GMCnet] In tank fuel temperatures [message #243467 is a reply to message #243394] |
Fri, 14 March 2014 11:03 |
Jp Benson
Messages: 649
Registered: October 2011
Location: Fla
Karma: 2
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Obviously there are numerous effects that can contribute to vapor lock.
In most cases, I would suspect multiple effects working together. In
tank fuel being 40 degrees above ambient temp is certainly a good
starting point for a problem. However, concerning fuel in transit from
the tank to the engine:
Fuel travels ~18 feet from the tank to the engine. At 60 mph with a 10
mpg fuel rate (0.1 gal/minute) it will take about 1 minute for fuel to
transit the lines. At 30 mph around 2 minutes. Even longer when the
engine is idling in traffic. If the fuel lines are all metal, there is
almost 2 sq. ft. of surface area for heat transfer to the fuel in the
3/8" tubes.
By no means am I discounting other effects but simply pointing out that
metal fuel lines (especially thin wall dark colored metal tubing) can
contribute to the problem of vapor lock. This is supported by the
reports of vapor lock while idling in traffic.
Another issue that I haven't seen mentioned is the retarding force in
the fuel lines during forward acceleration. A vehicle accelerating
uniformly from 0-30 mph in 15 sec will feel a retarding force of 0.2g.
It's not much but coupled with other effects could be the proverbial
straw that broke the camels back. For comparison, a vehicle parked on a
15 degree incline would feel a force of 0.26g.
Hopefully all my calculations are correct.
g-force calculator:
http://www.smartconversion.com/unit_calculation/Acceleration_calculator.aspx
JP
On 3/13/2014 9:48 PM, Robert Mueller wrote:
> Corley,
>
> Comments below in CAPS, not shouting.
>
> Regards,
> Rob M.
> Sydney, Australia
> AUS '75 Avion - The Blue Streak TZE365V100428
> USA '75 Avion - Double Trouble TZE365V100426
>
> -----Original Message-----
> From: Corley Wooldridge
>
> Well, after two hours to 55mph travel, I don't have any issues on flat land. When a hill comes along, and I start to pull hard, and
> then the fan kicks in, shortly after THAT is when the problems begin.
>
> I DON'T UNDERSTAND WHY THAT HAPPENS. WHEN I'M UNDERWAY IN DOUBLE TROUBLE I DON'T HAVE PROBLEMS.
>
> We are probably looking more at the max temps in the tanks that he sees, not the 40 degrees above ambient he mentions.
>
> I DON'T UNDERSTAND WHY YOU SAY THIS; CHUCK HAS PROVIDED HARD DATA OF TEMPERATURE READINGS OF THE FUEL IN THE TANKS AND OUTSIDE THE
> FRAME.
>
> Slow down the vehicle and we get more heat from the road,
>
> I'M SORRY BUT I'M GOING TO DISAGREE WITH THIS; IF THE ROADWAY TEMP REMAINS CONSTANT THE SPEED YOU TRAVEL OVER IT HAS NO EFFECT ON
> THE AMOUNT OF HEAT RADIATED INTO THE FUEL TANKS.
>
> slow the vehicle, and the heat from the engine does not dilute as much with other incoming 'cooler' air, slow the and work it hard
> and the fan is pushing a lot more really hot air under the coach. That's when the temps get hot enough to cause VP.
>
> AGREED
>
> Now, when it stops, I pull over to the side of the same road, still blacktop so radiating the same, and wait 10 minutes, and presto,
> I can start and go for a little longer.
>
> IN DOUBLE TROUBLE THE OPPOSITE IS WHAT HAPPENS; WHEN I SIT AT A TRAFFIC LIGHT AND THEN TRY TO PULL AWAY IT VAPOR LOCKS AND I HAVE TO
> SWITCH TO AUX WHICH STARTS THE FACET PUMP WHICH PUSHES FUEL TO THE MECHANICAL PUMP.
>
> My analysis of that is that Hot air from the engine is heating the fuel in the lines, and probably the mechanical pump is topping it
> off to a nice vapor.
>
> AT IDLE THE FLOW THROUGH THE STEEL LINE ATTACHED TO THE FRONT CROSSMEMBER WOULD DECREASE SIGNIFICANTLY AND THE FUEL WOULD GET
> HEATED. I'D GUESS THAT AT THE INLET TO THE MECHANICAL PUMP THERE WOULD BE A PRESSURE DROP WHICH COULD CAUSE THE VAPOR LOCK.
>
> I come from the old school, and have seen a lot of cars with tin foil around gas lines to stop vapor lock on hot days. Some cars
> came new with asbestos wraps for this problem. That solution has worked for years now. I'm pretty sure that a fuel line can pick up
> a LOT of heat is short order, when hot air, make that really hot air, is passing over it.
>
> AS I NOTED IN AN EARLIER EMAIL JIMB PAINTED THE TANKS WITH LIZARD SKIN AND INSULATED THE FUEL LINES WITH SOME KIND OF TUBULAR
> INSULATION AND ALL IT DID WAS POSTPONE THE ONSET OF VAPOR LOCK.
>
> Of course I'm not talking about the hot soak VP when sitting still for a few minutes, that's a whole different thing, and frankly it
> lasts such a short time as to not be an issue for me so far, just a brief sputter in acceleration.
>
> THAT'S WHAT HAPPENS TO DOUBLE TROUBLE CONSISTENTLY BUT THE ENGINE DIES IF I DON'T SWITCH TO AUX.
>
> It's the hill climbing on hot days, with low RVP fuel vapor lock, that is the killer.
>
> FRANKLY THE ONLY WAY TO REALLY DETERMINE WHERE THE FUEL PICKS UP HEAT IS TO PUT THERMOCOUPLES IN THE TANKS AND IN THE FUEL LINES:
>
> A) AT THE EXIT OF THE FUEL TANKS
> B) AT THE START OF THE METAL LINE THAT GOES ACROSS THE TOP OF THE FRONT CROSS MEMBER
> C) AT THE INLET TO THE MECHANICAL
>
> But we can disagree on that if you like.
>
> Corley
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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| Re: [GMCnet] In tank fuel temperatures [message #243472 is a reply to message #243467] |
Fri, 14 March 2014 12:09 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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I have difficulty understanding all the buzz about causes of vapor lock.
IMHO, it's foolish to do ANYTHING to an OEM system to alleviate vapor lock
unless the first, all important 2 steps have been taken:
1. Add a PUSHER pump. It's not possible to suck bubbles -- they just
get bigger & bigger the harder you try. Conversely, they can be pushed,
and then they get smaller the harder they're pushed -- and eventually
they're purged from the system, whether it be carburetor or EFI. Where the
pushing's done does matter -- the closer to the gasoline pool, the better;
i.e., in the tank is the ultimate -- but close to the tank should be
adequate in all but the worst cases.
2. Remove or bypass the mechanical pump. No matter what you do
toit, it's still sucking and thereby promoting enlarged bubbles. And
it will
always transfer heat from the engine to the fuel, again promoting bubbling.
Don't need it, why want it?
Until those two remedies have been implemented, all others are just a waste
of time, money, and good brain power. If they don't fix the problem, then
some other thoughts are justified -- but will probably be ineffective.
Antagonizing each other over all those dubious remedies is certainly
unjustified.
JMHO,
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI & EBL
www.gmcwipersetc.com
On Fri, Mar 14, 2014 at 12:03 PM, Jp Benson <chocomo99@yahoo.com> wrote:
> Obviously there are numerous effects that can contribute to vapor lock.
> In most cases, I would suspect multiple effects working together. In
> tank fuel being 40 degrees above ambient temp is certainly a good
> starting point for a problem. However, concerning fuel in transit from
> the tank to the engine:
> ...
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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] In tank fuel temperatures [message #243478 is a reply to message #243472] |
Fri, 14 March 2014 14:24 |
Jp Benson
Messages: 649
Registered: October 2011
Location: Fla
Karma: 2
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Senior Member |
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Ken,
Thanks. Prevention is the best cure. I've got my PUSHER pumps
installed. One for each tank. Therefore I was contemplating removal of
the now redundant mechanical pump. So, with your sage guidance, I can
conserve my brainpower and just take that SUCKER off. What you say
makes good sense. I already cut a billet to make the blockoff plate so
that effort won't be wasted either. Probably a spare pump is a good
idea too.
I don't believe that exercising my brain is wasteful but do agree that a
lot of time and money has been lost. But if you lose much sleep over
that, then sell your GMC motorhome and cut your losses.
It's not my intention to antagonize anyone. Certainly not over the
cause and/or cure of vapor lock. Nor do I feel the least bit
antagonized by those who have a different perspective than mine. I am
in the process of putting my fuel supply system together. Since this
was a topic of interest to me I wanted to take an analytic approach to
one portion of that system. Hopefully no ones feelings have been hurt
by that.
Sometimes it appears that folks on GMCnet take themselves and each other
way too seriously. Often over off topic issues. That too me is the
real waste here.
Thanks again for your insightful input.
JP
On 3/14/2014 1:09 PM, Ken Henderson wrote:
> ...
> IMHO, it's foolish to do ANYTHING to an OEM system to alleviate vapor lock
> unless the first, all important 2 steps have been taken:
>
> 1. Add a PUSHER pump...
>
> 2. Remove or bypass the mechanical pump...
>
> Until those two remedies have been implemented, all others are just a waste
> of time, money, and good brain power. If they don't fix the problem, then
> some other thoughts are justified -- but will probably be ineffective.
> Antagonizing each other over all those dubious remedies is certainly
> unjustified.
>
> JMHO,
>
> Ken H.
> Americus, GA
> '76 X-Birchaven w/Cad500/Howell EFI & EBL
> www.gmcwipersetc.com
>
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