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| [GMCnet] Heat, pumps, and the gas tanks. [message #332346] |
Sun, 20 May 2018 13:45  |
BobDunahugh
Messages: 2465
Registered: October 2010
Location: Cedar Rapids, IA
Karma: 11
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Heating of the gas is an issue that seems to come up a lot. So when I installed the Howell system. I thought of in tank pumps. So that the fuel is under pressure from inside the tanks. To the TB. This concept has true merit. But I've had too many pumps from China that failed. I wanted both tank pumps simple/quick to get too. So I put the two pumps for my EFI on the outside of the main steel frame. Plus. In an attempt to get away from engine heat that's more prevalent inboard of that steel frame. Plus back to the simplicity of the service concept. That did prove out way sooner then I ever expected. As one of the EFI pumps failed after only 6 blocks into my first test run of the EFI. The aux tank pump got me back home. Pump change took about 15 minutes. Now back to the heat. Most of the heat is coming from the engine. The extreme heat goes out the back by way of the tail pipe. Header displace a lot of the heat into the engine bay. That originally went out the tail pipe, back from the gas tanks. Thus headers acerbating the heating of the gas tanks. There are vents that can be put in the body, above the front wheels. These vents are about straight out board of the headers. This header heat leaves the engine bay by way of under the gas tanks. Our GMC doesn't have headers. Does still have the GM gas tank exhaust pipe heat shields. ( Did make mine taller. No surprise that I'd do that kind of thing.) Last year I was monitoring tank temps. I was very surprised as to how high tank temps got. Gas temps at the outboard pumps was at the tank temps. So no gas temp rise to the pumps.
Has anyone put gas tank heat shields bellow their gas tanks. Then a cool air duct to the outside of the tanks? Bob Dunahugh
________________________________
From: gmcmh-efi@googlegroups.com on behalf of Randy Van Winkle
Sent: Sunday, May 20, 201:58 AM
To: gmcmh-efi@googlegroups.com
Subject: Re: [GMCMH-EFI] Fuel Pump Questions
Seems like more complication than necessary. I would wait until you were ready to install the efi system (sounds like you are close to doing that anyway) then remove the sometimes troublesome fuel selector switch and intall two high pressure pumps as close to the tanks as possible or in the tanks if you are up to the extra work. To me the low pressure oump is just added complication.
If you need the low pressure electric for the carb to prevent vapor lock until you do the efi then install an inexpensive pump to feed the mechanical. Remove it when you go to efi. The goal is to keep fuel under pressure from tanks to engine.
Randy (liking simplicity)
'77 Eleganza II "403"
On Sat, May 19, 2018, 8:51 PM Ty Hardiman wrote:
Thanks all. I've gotten some useful information to think about. I realize there are many ways to lay out the fuel supply system. But my takeaway is this:
Q: What are the opinions about using a low-pressure external pump to feed the high-pressure external pump.
A. It's a hedge against vapor lock. And if you installed a bypass loop with a check valve on the low-pressure pump, the high-pressure pump would work with or without the low pressure pump operating.
On Saturday, May 19, 2018 at 7:17:39 PM UTC-5, Larry Davick wrote:
Unless you have an urgent need to replace the mechanical fuel pump, I would wait. I don’t see a good reason to put an electric pump in place when it’s really not needed. I did this and regretted it. My tired old carb was not happy with the pump and despite some fiddling I was not ever happy I’d replaced the pump. It finally worked perfectly, but it did not improve the stock set-up in any way for me.
Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, CA
Howell EFI + EBL + Electronic Distributor
On May 18, 2018, at 8:01 PM, Ty Hardiman wrote:
Fair enough. Let me expand my question:
I would like to install electric fuel pumps on my coach, with my q-jet. Upgrading later to a Rochester TBI. I can put in a pair of 4070s now, but would that be wasted money if I'm just going to go to an Airtex + EFI in a few months? Or would it be beneficial to feed the dual 4070's into an Airtex?
On Friday, May 18, 2018 at 9:41:49 PM UTC-5, Ty Hardiman wrote:
Hello all, first post. What a great resource this forum is! I have spent a lot of time over the past month reading the forum posts and the related resources, working on understanding EFI for the GMCMH.
I'm in the "learning, thinking, & planning" phase and I'll try to ask concise and specific questions. I'm doing some fuel pump planning right now.
Q: What are opinions on using a Carter 4070 to supply an Airtex 8094 - is this required, not required but beneficial, or completely unnecessary?
Thanks in advance,
Ty
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| Re: [GMCnet] Heat, pumps, and the gas tanks. [message #332349 is a reply to message #332346] |
Sun, 20 May 2018 15:17  |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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G'day,
I have seen photos of fuel tanks "covered" with diamond plate attached to the main frame with short spacers unfortunately I can't
seem to remember where I saw the photos.
On a hot sunny summers day the amount of heat radiated from the road surface would not provide any "cool" air. It might be a bit
cooler than what flows down from the engine compartment but it's not going to solve the issue. I don't know how you'd duct it from
outside the frame rails without reducing the road clearance of the frame. Sooner or later the gas tank will reach the OAT plus what
heat it picks up radiated from the road surface.
Having said that I'm going to put plates on the Kingsley in the USA and the Avion in Australia, the cost is negligible and its not
much work so what the hell.
Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808
-----Original Message-----
From: Gmclist [mailto:gmclist-bounces@list.gmcnet.org] On Behalf Of Bob Dunahugh
Sent: Sunday, May 20, 2018 1:45 PM
To: gmclist@list.gmcnet.org
Subject: [GMCnet] Heat, pumps, and the gas tanks.
Heating of the gas is an issue that seems to come up a lot. So when I installed the Howell system. I thought of in tank pumps. So
that the fuel is under pressure from inside the tanks. To the TB. This concept has true merit. But I've had too many pumps from
China that failed. I wanted both tank pumps simple/quick to get too. So I put the two pumps for my EFI on the outside of the main
steel frame. Plus. In an attempt to get away from engine heat that's more prevalent inboard of that steel frame. Plus back to the
simplicity of the service concept. That did prove out way sooner then I ever expected. As one of the EFI pumps failed after only 6
blocks into my first test run of the EFI. The aux tank pump got me back home. Pump change took about 15 minutes. Now back to the
heat. Most of the heat is coming from the engine. The extreme heat goes out the back by way of the tail pipe. Header displace a
lot of the heat into the engine bay. That originally went out the tail pipe, back from the gas tanks. Thus headers acerbating the
heating of the gas tanks. There are vents that can be put in the body, above the front wheels. These vents are about straight out
board of the headers. This header heat leaves the engine bay by way of under the gas tanks. Our GMC doesn't have headers. Does still
have the GM gas tank exhaust pipe heat shields. ( Did make mine taller. No surprise that I'd do that kind of thing.) Last year I
was monitoring tank temps. I was very surprised as to how high tank temps got. Gas temps at the outboard pumps was at the tank
temps. So no gas temp rise to the pumps.
Has anyone put gas tank heat shields bellow their gas tanks. Then a cool air duct to the outside of the tanks? Bob Dunahugh
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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] Heat, pumps, and the gas tanks. [message #332360 is a reply to message #332349] |
Mon, 21 May 2018 09:41 |
Bill Van Vlack
Messages: 419
Registered: September 2015
Location: Guemes Island, Washington
Karma: 14
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Senior Member |
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I'm considering the installation of a fuel cooler in the EFI return line. Shell and tube heat exchanger, about 8" long with AC evap discharge in the tube and fuel in the shell. Got one from a Mercedes on Ebay. The more fuel that bypasses, the cooler the fuel in the tank. Good for stop/go traffic and oversized fuel pumps. Location is an issue - route the AC to the fuel line or vice versa or somewhere in between?
Reducing heat gain in the tanks makes sense in that arrangement.
At least I'll get some benefit from that '76 dash air system.
Bill Van Vlack
'76 Royale; Guemes Island, Washington; Twin bed, full (DS) side bath, Brazilian Redwood counter and settee tops,455, 6KW generator; new owner a/o mid November 2015.
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| Re: [GMCnet] Heat, pumps, and the gas tanks. [message #332361 is a reply to message #332346] |
Mon, 21 May 2018 09:59 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Bob what about ducts sourced from the rear flooding the tanks. Sourced just below the tail lights where body curves and air wraps around. This should give a more ambiant source away from the road heat. Or just above the bumper or using the bumper itself that "scoops" air as you drive anyway. Or get stylish with a NACA or Testarosa styled inlet. I'm sure with your racing experience you have lots of ideas. You would have to use some oval or flat duct to bring it forward but if you boxed in the tanks you could then have an area pressurized with only this cooler source. Maybe.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Heat, pumps, and the gas tanks. [message #332364 is a reply to message #332360] |
Mon, 21 May 2018 10:03 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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I have one of those Mercedes fuel coolers, and it looks like a fairly
effective way to cool the fuel. Just have some A/C hoses the right length,
ditto fuel lines, and it should do the trick. Mercedes has been using them
for about 30 years, so it is proven technology. I just got mine this
weekend, so I haven't done anything with it yet, but, I will.
Jim Hupy
Salem, Or
78 GMC ROYALE 403
On Mon, May 21, 2018, 7:42 AM Bill Van Vlack
wrote:
> I'm considering the installation of a fuel cooler in the EFI return line.
> Shell and tube heat exchanger, about 8" long with AC evap discharge in the
> tube and fuel in the shell. Got one from a Mercedes on Ebay. The more fuel
> that bypasses, the cooler the fuel in the tank. Good for stop/go traffic
> and oversized fuel pumps. Location is an issue - route the AC to the fuel
> line or vice versa or somewhere in between?
>
> Reducing heat gain in the tanks makes sense in that arrangement.
>
> At least I'll get some benefit from that '76 dash air system.
> --
> Bill Van Vlack
> '76 Royale; Guemes Island, Washington; Twin bed, full (DS) side bath,
> Brazilian Redwood counter and settee tops,455, 6KW generator; new owner a/o
> mid
> November 2015.
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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>
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| Re: [GMCnet] Heat, pumps, and the gas tanks. [message #332366 is a reply to message #332346] |
Mon, 21 May 2018 11:05 |
lw8000
Messages: 201
Registered: July 2012
Location: S.E. Michigan
Karma: 1
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Senior Member |
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I was really close to installing the aluminum panels under the tanks as well. I'm not a fan of the high amount of pressure that builds up in the tanks on hot days. This write-up was one that I found very interesting:
http://minniebiz.com/gmcmotorhome/2017/02/25/insulating-the-fuel-tanks/
I'm particularly interested in it due to the fact it seemed to help with the tank pressure issue that we see often.
I too have seen pics of the diamond plate aluminum, similar fashion to above, but cannot find it.
I researched reflective coatings, but did not find anything that seemed promising or proven to actually work. I found that some had tried to coat the tanks with thermal coatings (including Jim B) but the conclusions seem to indicate it did not help.
I also tinkered with the idea of installing a deflector to direct the hot engine air down below the tanks but so far have not revisited. That would be much easier to install but would probably not help the issue with road heat. We did install the side air vents from JimK to vent the engine box, and so far I'm convinced those are well worth it. I figure getting any hot air out of that area can only help.
Chris S. -
77 Kingsley, 3.70 FD, mostly OEM -
S.E. Michigan
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| Re: [GMCnet] Heat, pumps, and the gas tanks. [message #332367 is a reply to message #332346] |
Mon, 21 May 2018 11:07 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Bob -
My coach has shields on the front tank, made of aluminum checkerplate. Vertical from the floor down to the horizontal one which runs horizontal the length and width of the tank. And exhaust pipe shields. Tank seems to stay cool, at least n o pressure when opened at a gas stop on a hot day.
I'll get you a picture or two when we reconnect, I had the coach towed to Chuck's place - closest around - because yet again it looks as if I've lunched yet another transmission. If I'm lucky, it lost a governor gear. I don't think that's the case but that's first check Wednesday when I get back up there to figure out the problem.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Heat, pumps, and the gas tanks. [message #332372 is a reply to message #332346] |
Mon, 21 May 2018 13:02 |
Rick Staples
Messages: 126
Registered: May 2014
Location: Johnstown, Colorado, USA
Karma: -1
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Senior Member |
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Just a couple of thoughts here. A couple of pounds pressure in the fuel tanks is a GOOD thing on a hot day. It raises the boiling point of the gas and helps prevent vapor lock. Almost any modern car will exhibit a slight whoosh when the gas cap is removed (when hot) as this how they are designed. (OTOH, if you perceive any suction when opening the gas cap, there's a problem.) The difficulty is making almost a seventy feet of pipes, tubes, hoses and fittings tight enough to sustain a little pressure. I'm still trying, with some success.
For what it's worth, here's my anti-vapor-lock saga on a limited budget '75 GMC with stock carburetor at 5500'+ altitude:
1 - Insulated the steel fuel lines where they run alongside of the engine near the left exhaust manifold and near the radiator by encasing them in several layers of rubber fuel and heater hose. Seemed to help.
2 - Added homemade heat shields to the exhaust pipe where it passes the fuel tanks. Made from surplus stove pipe, mine cover both the side and top of the pipe. Seems to help.
3 - Added an auxiliary (Carter) electric fuel pump just in front of the tanks. Mine is plumbed into the auxiliary tank line, and comes on when "Auxiliary" fuel is selected. Also has a momentary switch to allow priming the carburetor. Helps a lot.
4 - Replaced the stock fuel pump with an Oldsmobile "A/C" pump with a vapor return fitting to circulate some fuel, and hopefully vapor bubbles, back to the tanks. Helps less than I hoped.
5 - Replaced every darned piece of hose in the fuel system with steel tubing or SAE30R9 fuel injection grade hose. Replaced tank pickup O'rings. Don't know how much it helps, but at least I can build a little pressure (see above) and not belch fuel on the ground when filling the tanks.
JWID, HTH
Rick Staples
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] Heat, pumps, and the gas tanks. [message #332374 is a reply to message #332372] |
Mon, 21 May 2018 13:11 |
Emery Stora
Messages: 959
Registered: January 2011
Karma: 4
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Senior Member |
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Hi Rick
Its not the slight pressure that is the problem. At times the tanks get so hot that when one removes the fuel cap there is a geyser of gasoline which can shoot up a foot or so. Then the gasoline boils for a while and copious amounts fo fuel continue to come out of the fill spout. This happened to me a couple of times in the past. I had to wait about 10 minutes before I could put any fuel into the tank.
Emery Stora
77 Kingsley
Frederick, CO
> On May 21, 2018, at 12:02 PM, Richard H Staples wrote:
>
> Just a couple of thoughts here. A couple of pounds pressure in the fuel tanks is a GOOD thing on a hot day. It raises the boiling point of the gas
> and helps prevent vapor lock. Almost any modern car will exhibit a slight whoosh when the gas cap is removed (when hot) as this how they are
> designed. (OTOH, if you perceive any suction when opening the gas cap, there's a problem.) The difficulty is making almost a seventy feet of pipes,
> tubes, hoses and fittings tight enough to sustain a little pressure. I'm still trying, with some success.
>
> For what it's worth, here's my anti-vapor-lock saga on a limited budget '75 GMC with stock carburetor at 5500'+ altitude:
>
> 1 - Insulated the steel fuel lines where they run alongside of the engine near the left exhaust manifold and near the radiator by encasing them in
> several layers of rubber fuel and heater hose. Seemed to help.
> 2 - Added homemade heat shields to the exhaust pipe where it passes the fuel tanks. Made from surplus stove pipe, mine cover both the side and top of
> the pipe. Seems to help.
> 3 - Added an auxiliary (Carter) electric fuel pump just in front of the tanks. Mine is plumbed into the auxiliary tank line, and comes on when
> "Auxiliary" fuel is selected. Also has a momentary switch to allow priming the carburetor. Helps a lot.
> 4 - Replaced the stock fuel pump with an Oldsmobile "A/C" pump with a vapor return fitting to circulate some fuel, and hopefully vapor bubbles, back
> to the tanks. Helps less than I hoped.
> 5 - Replaced every darned piece of hose in the fuel system with steel tubing or SAE30R9 fuel injection grade hose. Replaced tank pickup O'rings.
> Don't know how much it helps, but at least I can build a little pressure (see above) and not belch fuel on the ground when filling the tanks.
>
> JWID, HTH
> Rick Staples
>
> --
> 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] Heat, pumps, and the gas tanks. [message #332378 is a reply to message #332376] |
Mon, 21 May 2018 16:09 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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The problem is not the tanks, lines, or pumps. It is the Reformulated
Gasoline. First of all, the viscosity is correct for engines that have high
pressure supply systems and fuel injectors. Not carbs.
So consider using more fuel pressure between the tank and the carb
inlet. But not in the carb itself. The float inlet valve will not handle
much more than 4 psi. If you continue to use a carb, expect vapor lock.
Drive as much as possible in the cool part of the day, fuel up in the early
morning, make sure there are no leaks in the supply lines. A low pressure
fuel pump, like the Carter 4070 helps a great deal in the supply line as
well. Fuel injection helps too. But, don't blame the coach, blame the
gasoline. And the folks that insist that alcohol is good for blending into
it. Just how it is.
Jim Hupy
Salem, Or
78 GMC ROYALE 403
On May 21, 2018 1:48 PM, "Jack Christensen" wrote:
Armand Minnie Insulated his tanks not long before he sold his beautiful
unit using ceramic insulating blankets and metal roofing panels. Here's a
link to his presentation.
http://minniebiz.com/gmcmotorhome/2017/02/25/insulating-the-fuel-tank
--
Jack Christensen - K6ROW,
'76 Glenbrook/Clasco - "The Silver Bullet",
Sebastopol, CA
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| Re: [GMCnet] Heat, pumps, and the gas tanks. [message #332394 is a reply to message #332346] |
Tue, 22 May 2018 07:20 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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I drove all over the southeast in july and august after putting the electric pumps in the 23' without any vapor lock problems. On just the mechanical punmp, don't slow down. I ran it on no alcohol gas, especially in the summertime. Alcohol laced gas is going to lock it up when it's hot and carbureted.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Heat, pumps, and the gas tanks. [message #332458 is a reply to message #332372] |
Wed, 23 May 2018 15:09 |
lw8000
Messages: 201
Registered: July 2012
Location: S.E. Michigan
Karma: 1
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Senior Member |
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[SNIP]
Rick Staples wrote on Mon, 21 May 2018 13:02
3 - Added an auxiliary (Carter) electric fuel pump just in front of the tanks. Mine is plumbed into the auxiliary tank line, and comes on when "Auxiliary" fuel is selected. Also has a momentary switch to allow priming the carburetor. Helps a lot.
[SNIP]
I second this workaround. I too have done many things to the coach to try and work around vapor lock, and this is the only one I know for sure works, and it's simple to install. I talked to JimB (@ Co-Op) extensively about vapor lock in June 2016 while we were in Florida as we had severe vapor lock while down there. At the time this low pressure inline aux pump was the known workaround that is tried and true. His guys installed it to the aux line/switch in under an hour, and our vapor lock problems were instantly resolved. Jim's instructions were: When the engine starts to sputter after sitting or taking off in hot weather, just flip the switch to aux and let everything return to normal (usually takes 10-20 seconds). At that point, flip the switch back to main and use the mechanical pump which will keep you going. It's not perfect, but it works every time.
And, the additional benefit is it really does help to prime the carb after sitting for an extended period of time. Flip the switch, start the engine (usually goes after 1 - 2 tries), and flip it back once it's started up.
Chris S. -
77 Kingsley, 3.70 FD, mostly OEM -
S.E. Michigan
[Updated on: Wed, 23 May 2018 15:12] Report message to a moderator |
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