Home » Public Forums » GMCnet » Fuel/Carb question (Leaking Carb and gas tank pressure)
| Fuel/Carb question [message #338207] |
Tue, 30 October 2018 05:46  |
Eleganza2 Newbie
Messages: 9
Registered: October 2018
Location: Boone, NC USA
Karma: 0
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Junior Member |
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Greetings all. I am a newbie to the GMC motorhome club. I have a 1976 Eleganza II. I purchased it to make some great memories with my wife and children.
Here's what is going on. It seems to be flooding as I drive, especially on hills and curvy roads. I replaced the needle valve and seat in the carb, and checked the float and it still floods on occasion. Once while it was flooding badly and the fuel was boiling in the carb someone suggested I loosen the gas cap. When I did, gas and gas-vapor shot out. So I have begun running it with the cap loose. Even then the engine will occasionally stall (which I assume is due to flooding still). I wait about 5 minutes and put the gas pedal to the floor and it will eventually start.
Here are my questions:
1. Does this sound like the carb is in trouble? If so, who works on these quadrajets? I have talked to 4 mechanics in the area and nobody wants to deal with it. I found one who suggested to put a Edelbrock on it since it's simpler....Any suggestions?
2. Assuming that my vent tubes are clogging somewhere I feel like I should drop the tanks and go ahead and replace all the vent lines. Or perhaps there is an easier fix, maybe just replacing the canister up front. Where can I buy a new canister and do I need to replace the vapor separator at the rear tire?
I would appreciate any advice in tackling this.
Thanks
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| Re: [GMCnet] Fuel/Carb question [message #338209 is a reply to message #338207] |
Tue, 30 October 2018 06:24  |
Richard Denney
Messages: 920
Registered: April 2010
Karma: 9
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Senior Member |
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Good morning—welcome to GMCnet. My name is Rick—what’s yours?
Anyway, first, does your coach have an electric fuel pump? If so, it may be
putting out excessive pressure. The QJ is happywith 4-5 psi only.
If it still has the mechanical pump and no electric booster, then that
won’t be the problem, but there are many other possible problems.
Second, our coaches use vented fuel caps that will relieve excess pressure.
Also, we have a ventilation system that runs vapors through a liquid
separator in the left rear wheel well and from there to a charcoal canister
behind the front right wheel well that is evacuated by engine vacuum, at
least from the factory. These systems should keep fuel tank pressure from
building, but an overheated tank might still blow out, mostly through the
fill vent lines. Modern fuels are more prone to that than the real gas used
in the 70’s.
Any time one buys a coach, Step 1 is replacing all the rubber hose in the
fuel system from filler to carb. It’s work but it’s necessary for safety.
Many coaches have some original parts in that system, and they will be
dried out, hard, and cracked. Use barrier hose designed for alcohol—SAE
30R9 if I recall.
All those bits can be located by studying the GMC Maintenance Manual, which
can be found here:
http://www.bdub.net/factory-manuals.html
While I’m on Billy’s site, look here:
http://www.bdub.net/GMCLinks.html
It is a one-stop shop for information. The suppliers are linked there, and
on that page you’ll find a link to Dick Paterson of Springfield Ignition,
who rebuilds Quadrajets for our application, as long as you have a proper
core (which may be a problem if your carb was ever replaced).
You’ll also find Applied GMC, run by Jim Kanomata. He sells everything,
including the workable alternatives to the Quadrajet. Hint: no other carb
will please you. Forget replacing the Qjet with an Edelbrock or a
Holley—many waves have crashed on that rocky shore. The replacement that
works is throttle-body fuel injection, of which there are several types.
Rick “replace brake lines, too, if you can document when it was last done”
Denney
On Tue, Oct 30, 2018 at 6:47 AM wrote:
> Greetings all. I am a newbie to the GMC motorhome club. I have a 1976
> Eleganza II. I purchased it to make some great memories with my wife and
> children.
>
> Here's what is going on. It seems to be flooding as I drive, especially on
> hills and curvy roads. I replaced the needle valve and seat in the carb,
> and checked the float and it still floods on occasion. Once while it was
> flooding badly and the fuel was boiling in the carb someone suggested I
> loosen the gas cap. When I did, gas and gas-vapor shot out. So I have
> begun running it with the cap loose. Even then the engine will occasionally
> stall (which I assume is due to flooding still). I wait about 5 minutes
> and put the gas pedal to the floor and it will eventually start.
>
> Here are my questions:
> 1. Does this sound like the carb is in trouble? If so, who works on these
> quadrajets? I have talked to 4 mechanics in the area and nobody wants to
> deal with it. I found one who suggested to put a Edelbrock on it since
> it's simpler....Any suggestions?
>
> 2. Assuming that my vent tubes are clogging somewhere I feel like I should
> drop the tanks and go ahead and replace all the vent lines. Or perhaps
> there is an easier fix, maybe just replacing the canister up front. Where
> can I buy a new canister and do I need to replace the vapor separator at the
> rear tire?
>
> I would appreciate any advice in tackling this.
>
> Thanks
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Rick Denney
73 x-Glacier 230 "Jaws"
Off-list email to rick at rickdenney dot com
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| Re: [GMCnet] Fuel/Carb question [message #338211 is a reply to message #338209] |
Tue, 30 October 2018 06:37 |
Bruce Hart
Messages: 1501
Registered: October 2011
Location: La Grange, Wyoming
Karma: 5
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Senior Member |
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If the carb has been over torqued and the top cover is bowed, Dick
Patterson will not rebuild the unit.
Kanomata has in the past been able to rebuild these units.
On Tue, Oct 30, 2018 at 5:25 AM Richard Denney wrote:
> Good morning—welcome to GMCnet. My name is Rick—what’s yours?
>
> Anyway, first, does your coach have an electric fuel pump? If so, it may be
> putting out excessive pressure. The QJ is happywith 4-5 psi only.
>
> If it still has the mechanical pump and no electric booster, then that
> won’t be the problem, but there are many other possible problems.
>
> Second, our coaches use vented fuel caps that will relieve excess pressure.
> Also, we have a ventilation system that runs vapors through a liquid
> separator in the left rear wheel well and from there to a charcoal canister
> behind the front right wheel well that is evacuated by engine vacuum, at
> least from the factory. These systems should keep fuel tank pressure from
> building, but an overheated tank might still blow out, mostly through the
> fill vent lines. Modern fuels are more prone to that than the real gas used
> in the 70’s.
>
> Any time one buys a coach, Step 1 is replacing all the rubber hose in the
> fuel system from filler to carb. It’s work but it’s necessary for safety.
> Many coaches have some original parts in that system, and they will be
> dried out, hard, and cracked. Use barrier hose designed for alcohol—SAE
> 30R9 if I recall.
>
> All those bits can be located by studying the GMC Maintenance Manual, which
> can be found here:
>
> http://www.bdub.net/factory-manuals.html
>
> While I’m on Billy’s site, look here:
>
> http://www.bdub.net/GMCLinks.html
>
> It is a one-stop shop for information. The suppliers are linked there, and
> on that page you’ll find a link to Dick Paterson of Springfield Ignition,
> who rebuilds Quadrajets for our application, as long as you have a proper
> core (which may be a problem if your carb was ever replaced).
>
> You’ll also find Applied GMC, run by Jim Kanomata. He sells everything,
> including the workable alternatives to the Quadrajet. Hint: no other carb
> will please you. Forget replacing the Qjet with an Edelbrock or a
> Holley—many waves have crashed on that rocky shore. The replacement that
> works is throttle-body fuel injection, of which there are several types.
>
> Rick “replace brake lines, too, if you can document when it was last done”
> Denney
>
> On Tue, Oct 30, 2018 at 6:47 AM wrote:
>
>> Greetings all. I am a newbie to the GMC motorhome club. I have a 1976
>> Eleganza II. I purchased it to make some great memories with my wife and
>> children.
>>
>> Here's what is going on. It seems to be flooding as I drive, especially
> on
>> hills and curvy roads. I replaced the needle valve and seat in the carb,
>> and checked the float and it still floods on occasion. Once while it was
>> flooding badly and the fuel was boiling in the carb someone suggested I
>> loosen the gas cap. When I did, gas and gas-vapor shot out. So I have
>> begun running it with the cap loose. Even then the engine will
> occasionally
>> stall (which I assume is due to flooding still). I wait about 5 minutes
>> and put the gas pedal to the floor and it will eventually start.
>>
>> Here are my questions:
>> 1. Does this sound like the carb is in trouble? If so, who works on these
>> quadrajets? I have talked to 4 mechanics in the area and nobody wants to
>> deal with it. I found one who suggested to put a Edelbrock on it since
>> it's simpler....Any suggestions?
>>
>> 2. Assuming that my vent tubes are clogging somewhere I feel like I
> should
>> drop the tanks and go ahead and replace all the vent lines. Or perhaps
>> there is an easier fix, maybe just replacing the canister up front. Where
>> can I buy a new canister and do I need to replace the vapor separator at
> the
>> rear tire?
>>
>> I would appreciate any advice in tackling this.
>>
>> Thanks
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> --
> Rick Denney
> 73 x-Glacier 230 "Jaws"
> Off-list email to rick at rickdenney dot com
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Bruce Hart
1976 Palm Beach
Milliken, Co
GMC=Got More Class
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Bruce Hart
1976 Palm Beach
1977 28' Kingsley
La Grange, Wyoming
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| Re: Fuel/Carb question [message #338212 is a reply to message #338207] |
Tue, 30 October 2018 06:46 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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Senior Member |
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My guess, is you are not dealing with flooding. I would believe you are dealing with fuel delivery problems, such as vapor lock.
Start by looking for fuel filters and get them all changed. careful on the one for front of carb on cross threading.
you can always get a boat gas tank, and feed the fuel pump on the engine direct from that, and should let you know if you have carb problems, or gas tank problems.
the end all- is to replace the fuel lines. Gates Barricade is what you want that meets the SAE 30R14 spec. Then you know what you have, how it was done, and when it was done. Normally you do not have to worry about changing the charcoal canister,and can re-use the vapor seperator. Just check the vapor separator on it's operation, and if you are concerned, then change that too. I can't think of someone that has changed the charcoal canister.
Other things you should make sure you do, is install at minimum a Aux electric fuel pump. So you have some electric pusher pump, that you can kick in to help starts, or overcome vapor lock. All depends on where you live and what temps you drive in.
https://lqqkatjon.blogspot.com/search?q=fuel+lines
as far as the carb, you need to look around. There are carb shops out there, but make sure you find one that is really comfortable with the quadrajet, and that they understand that there is differences between quadrajets that they need to pay attention to, so it is still set for our coaches. the best way, is just to send it to dick patterson- he is been doing GMC carbs and distributors for decades.
bookmark this site:
http://www.bdub.net/GMCLinks.html
then scroll down to find suppliers:
http://www.gmcmotorhomemarketplace.com/
and you will find Dick Paterson:
http://www.springfield-ignition.com/
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: [GMCnet] Fuel/Carb question [message #338213 is a reply to message #338212] |
Tue, 30 October 2018 07:17 |
Bruce Hart
Messages: 1501
Registered: October 2011
Location: La Grange, Wyoming
Karma: 5
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Senior Member |
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There is a replaceable filter on the bottom end of the vapor canister.
After forty years it might be a little hard to
replace because of dirt and rust issues.
Dick Patterson, Jim Kanomata, and Jim Bounds all have rebuilt our carbs.
On Tue, Oct 30, 2018 at 5:47 AM Jon Roche wrote:
> My guess, is you are not dealing with flooding. I would believe you are
> dealing with fuel delivery problems, such as vapor lock.
>
> Start by looking for fuel filters and get them all changed. careful on
> the one for front of carb on cross threading.
> you can always get a boat gas tank, and feed the fuel pump on the engine
> direct from that, and should let you know if you have carb problems, or gas
> tank problems.
>
>
>
> the end all- is to replace the fuel lines. Gates Barricade is what you
> want that meets the SAE 30R14 spec. Then you know what you have, how it
> was
> done, and when it was done. Normally you do not have to worry about
> changing the charcoal canister,and can re-use the vapor seperator. Just
> check
> the vapor separator on it's operation, and if you are concerned, then
> change that too. I can't think of someone that has changed the charcoal
> canister.
>
> Other things you should make sure you do, is install at minimum a Aux
> electric fuel pump. So you have some electric pusher pump, that you can
> kick in
> to help starts, or overcome vapor lock. All depends on where you live
> and what temps you drive in.
>
> https://lqqkatjon.blogspot.com/search?q=fuel+lines
>
>
> as far as the carb, you need to look around. There are carb shops out
> there, but make sure you find one that is really comfortable with the
> quadrajet, and that they understand that there is differences between
> quadrajets that they need to pay attention to, so it is still set for our
> coaches. the best way, is just to send it to dick patterson- he is been
> doing GMC carbs and distributors for decades.
>
> bookmark this site:
> http://www.bdub.net/GMCLinks.html
>
> then scroll down to find suppliers:
> http://www.gmcmotorhomemarketplace.com/
>
> and you will find Dick Paterson:
> http://www.springfield-ignition.com/
>
>
>
>
>
>
>
> --
> Jon Roche
> 75 palm beach
> St. Cloud, MN
> http://lqqkatjon.blogspot.com/
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Bruce Hart
1976 Palm Beach
Milliken, Co
GMC=Got More Class
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
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Bruce Hart
1976 Palm Beach
1977 28' Kingsley
La Grange, Wyoming
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| Re: Fuel/Carb question [message #338214 is a reply to message #338207] |
Tue, 30 October 2018 08:06 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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It's new to you. Drop the tanks and replace EVERY bit of rubber hose that doesn't have the proper stuff stamped on it with new barrier hose. Even if like me you only use non-alcohol gas when you can find it. This includes the hose going to the vapor canister - or canisters if it's a CA coach it has two in series and the fill hoses connecting the tanks to the fill line. Replace ALL the vacuum hoses and be sure they're properly connected according to the book diagram.
My first coach had a carb, once I got the system working properly and the cooling system working and a pair of low pressure pumps installed, it pulled Culowee Mountain regularly with my Kia Soul in tow in July and August without com[plaint. A pair of electric pumps back by the tanks will pretty much preclude vapor lock, which is what you're describing when you sit a bit and then it fires up. It worked better than my current injected coach (which in all fairness I haven't sorted out quite yet).
Here's a picture or two of how I mounted a pair of Mr Gasket low pressure pumps. Don't use the supplied filters, get a pair of the Wix replacements which don't leak air after a while.
http://www.gmcmhphotos.com/photos/g6198-cane-9-creek-rv-park-heflin-2c-al.html
Note I blank - flanged the mechanical pump mounting rather than leave it. Also note the barbed fitting screwed into the original pump outlet fitting. You can revert to OEM stock in 30 minutes roadside if you had to. I never had to.
--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: Fuel/Carb question [message #338217 is a reply to message #338207] |
Tue, 30 October 2018 09:27 |
Chris Tyler
Messages: 458
Registered: September 2013
Location: Odessa FL
Karma: 7
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Senior Member |
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If you are flooding It will probably have a different ''feel' if you have carberated driving experience. Also the exhaust will often be black unless it is so severe it shuts off cleanly. In that case you will probaly smell gas.
Excessive fuel pressure will definitely cause Q jet flooding. So will a maladjusted or sticking float. Also, the foats can absorb fuel, especially if damaged, and lose buoyancy.
Something in the needle and seat would cause constant flooding
76 Glenbrook
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| Re: Fuel/Carb question [message #338227 is a reply to message #338207] |
Tue, 30 October 2018 14:58 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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Eleganza2 Newbie
Welcome to the group, family, cult, asylum...
You are welcome here even if you don't have a name, but with the number of Eleganzas there is bound to be confusion.
If the vent valve in the left wheel well is working, it should be tough to have pressure in the fuel tanks. If you need to know more, it is all available to you.
It looks like you are working the forum and not the e-mail side, so I suggest that you go to the <Control Panel/Account Settings> and scroll down to the place that you can fill in a sigfile. Please include your real name, maybe the spouse too, a bit about the coach (You did post '76-E2) so people don't have to keep looking it up and a geographic reference. Right now all we have is a Canadian flag and that is a big area. There are reasons why we like this.
When you meet other owners, they might like to recognize that they already know you.
Changes in years and models matter, and so do major mods.
Where you are matters because this is a helping and supportive community, and you may have a brand new old friend nearby.
You can change your alias (screen name) without changing your logon.
You should also go to: http://www.gmcmhregistry.com/ and register the coach. This allows the community to keep track of where coaches are and how the owners are doing. When you register, you can ask John for the prior owners if you do not know who that was. If you do know, say so here because we will be glad to know his coach is being cared for.
This is a community like very few others. These are supportive people that all want to see to it that you and yours get to enjoy your coach and what it can do for you as much as we all know that it can and will if you take care of her. We have some amazing stories here, and most of us know that we can count on others here.
The other community that I know personally is that of the watermen that are my world. For that reason, I like to welcome new owners here much as a new owner or vessel is welcomed there. So,
May the Good Lord bless this coach and all those that set forth within her.
Welcome EleganzaII, spouse and progeny (Hope we have some names soon.)
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: Fuel/Carb question [message #338233 is a reply to message #338207] |
Tue, 30 October 2018 17:51 |
Tilerpep
Messages: 404
Registered: June 2013
Location: Raleigh, NC
Karma: 7
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Senior Member |
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I had lots of fuel and running issues, including pressurized tanks (Sirum optimistically said "proves no leaks!"). Despite having checked everything over and over, and the vapor seperator checked good, he said i should change it. Pricey for a plastic ball valve...but it changed everything. Genny now runs all day (used to cut off about 30 minutes into trip) and motor only stumbles in heat at stop lights from vapor lock, solved by electric fuel pump. Keep learning and read all the good replies in addition to mine. It can be fixed.
1975 Glenbrook, 1978 Royale rear bath
Raleigh, NC
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| Re: Fuel/Carb question [message #338251 is a reply to message #338207] |
Wed, 31 October 2018 19:45 |
Eleganza2 Newbie
Messages: 9
Registered: October 2018
Location: Boone, NC USA
Karma: 0
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Junior Member |
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Greetings all and thanks for the many replies. Great to have an amazing group of knowledgable and helpful people as I navigate these new waters.
So my coach has a aux fuel pump after between the tanks and the motor pump. The previous owner had put in a new motor pump and a stainless steel fuel line to the carb. Unfortunately it is tough to get that SS line in and out to check the fuel filter near the carb. So on one little roadside challenge I opted to eliminate it all together. In its place I put a fuel filter after the aux pump. So my coach now has two fuel filters, one before the aux electric pump, and the other after it.
So I will plan to drop the tanks and replace the rubber fuel lines.
Here are a few questions (you all will have to be patient with me as I am no mechanic and certainly ignorant with these coaches):
1. Why do I need the Aux pump? I only use it when doing a cold start to get some gas into the carb, but shut it off immediately because, as mentioned I thought I was dealing with flooding. If the motor runs without the aux pump then why bother having it?
2. How do I test the separator in the left wheel well or the charcoal canister to see if they need to be replaced?
3. Several people mentioned that it is likely not a carb issue, but a fuel supply issue, How can I check that? Do I need to buy a gizmo to check my fuel pressure? How can I know if it is vapor lock, pressurized tanks, or flooding?
I realize these may be simple questions, but as I said, I'm new to this stuff.
Michael
PS. Don't know why I have a Canadian flag, I live in Boone NC with my wife and three kids ages 9, 15 and 17.
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| Re: [GMCnet] Fuel/Carb question [message #338252 is a reply to message #338251] |
Wed, 31 October 2018 20:46 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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You can change the carb filter by simply undoing the 4 bolts after breaking
loose the fitting and the filter housing, then slide the carb back.
I feel a filter in the carb is best as particulars from hose and fittings
will flake off.
On Wed, Oct 31, 2018 at 5:46 PM Michael Stevens
wrote:
> Greetings all and thanks for the many replies. Great to have an amazing
> group of knowledgable and helpful people as I navigate these new waters.
>
> So my coach has a aux fuel pump after between the tanks and the motor
> pump. The previous owner had put in a new motor pump and a stainless steel
> fuel
> line to the carb. Unfortunately it is tough to get that SS line in and out
> to check the fuel filter near the carb. So on one little roadside challenge
> I opted to eliminate it all together. In its place I put a fuel filter
> after the aux pump. So my coach now has two fuel filters, one before the aux
> electric pump, and the other after it.
>
> So I will plan to drop the tanks and replace the rubber fuel lines.
>
> Here are a few questions (you all will have to be patient with me as I am
> no mechanic and certainly ignorant with these coaches):
>
> 1. Why do I need the Aux pump? I only use it when doing a cold start to
> get some gas into the carb, but shut it off immediately because, as
> mentioned
> I thought I was dealing with flooding. If the motor runs without the aux
> pump then why bother having it?
>
> 2. How do I test the separator in the left wheel well or the charcoal
> canister to see if they need to be replaced?
>
> 3. Several people mentioned that it is likely not a carb issue, but a fuel
> supply issue, How can I check that? Do I need to buy a gizmo to check my
> fuel pressure? How can I know if it is vapor lock, pressurized tanks, or
> flooding?
>
> I realize these may be simple questions, but as I said, I'm new to this
> stuff.
>
> Michael
>
> PS. Don't know why I have a Canadian flag, I live in Boone NC with my wife
> and three kids ages 9, 15 and 17.
>
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,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: Fuel/Carb question [message #338253 is a reply to message #338207] |
Wed, 31 October 2018 20:57 |
Tilerpep
Messages: 404
Registered: June 2013
Location: Raleigh, NC
Karma: 7
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Senior Member |
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I was in Boone last week...
1. you need the aux pump when it is hot. the long fuel run and high heat load under the low to the ground coach gets it too high with modern fuel. the aux pump provides a push which solves this in most cases. I use mechanical all the time, and aux only when it acts up.
2. low air pressure (like you blowing through it, not a compressor). mine would test fine, but apparently when actual gas would hit it and it would close it would stick closed. you need to test the lines that run all the way forward to the charcoal canister. rubber except metal across the frame rail under the front seats. one of mine was rusted full and required a metal coat hanger reaming
3. if the coach is new to you all those things are worth considering, but you already know you have pressurized tanks and need to fix that, so I'd start there. mine would not vapor lock in current Boone temps, so I doubt it is that right now.
1975 Glenbrook, 1978 Royale rear bath
Raleigh, NC
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| Re: [GMCnet] Fuel/Carb question [message #338254 is a reply to message #338252] |
Wed, 31 October 2018 20:55 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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This message is for Michael, and it is safety related. If you have any
rubber hose or inline aftermarket fuel filters between the carb and
mechanical fuel pump, my advice would be to remove it, and go back to a 1
piece steel fuel line. Fuel leaks and Fire is the reason.
Jim Hupy
Salem, Or
78 GMC ROYALE 403
On Wed, Oct 31, 2018, 6:46 PM Jim Kanomata wrote:
> You can change the carb filter by simply undoing the 4 bolts after breaking
> loose the fitting and the filter housing, then slide the carb back.
> I feel a filter in the carb is best as particulars from hose and fittings
> will flake off.
>
> On Wed, Oct 31, 2018 at 5:46 PM Michael Stevens
> wrote:
>
>> Greetings all and thanks for the many replies. Great to have an amazing
>> group of knowledgable and helpful people as I navigate these new waters.
>>
>> So my coach has a aux fuel pump after between the tanks and the motor
>> pump. The previous owner had put in a new motor pump and a stainless
> steel
>> fuel
>> line to the carb. Unfortunately it is tough to get that SS line in and
> out
>> to check the fuel filter near the carb. So on one little roadside
> challenge
>> I opted to eliminate it all together. In its place I put a fuel filter
>> after the aux pump. So my coach now has two fuel filters, one before the
> aux
>> electric pump, and the other after it.
>>
>> So I will plan to drop the tanks and replace the rubber fuel lines.
>>
>> Here are a few questions (you all will have to be patient with me as I am
>> no mechanic and certainly ignorant with these coaches):
>>
>> 1. Why do I need the Aux pump? I only use it when doing a cold start to
>> get some gas into the carb, but shut it off immediately because, as
>> mentioned
>> I thought I was dealing with flooding. If the motor runs without the aux
>> pump then why bother having it?
>>
>> 2. How do I test the separator in the left wheel well or the charcoal
>> canister to see if they need to be replaced?
>>
>> 3. Several people mentioned that it is likely not a carb issue, but a
> fuel
>> supply issue, How can I check that? Do I need to buy a gizmo to check my
>> fuel pressure? How can I know if it is vapor lock, pressurized tanks, or
>> flooding?
>>
>> I realize these may be simple questions, but as I said, I'm new to this
>> stuff.
>>
>> Michael
>>
>> PS. Don't know why I have a Canadian flag, I live in Boone NC with my
> wife
>> and three kids ages 9, 15 and 17.
>>
>>
>>
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> --
> Jim Kanomata
> Applied/GMC, Newark,CA
> jimk@appliedairfilters.com
> http://www.appliedgmc.com
> 1-800-752-7502
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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| Re: Fuel/Carb question [message #338262 is a reply to message #338251] |
Thu, 01 November 2018 08:37 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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Senior Member |
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1. the aux pump is a fairly inexpensive back up system for vapor lock. sucking fuel causes vacuum, and that lowers the boiling point of fuel. aux pump will push the fuel, and cause a little pressure to raise the point. but the science behind it really does not matter. owners have found vapor lock to be a problem. I personally have installed new fuel lines, and it is when it is 90 degrees + out, and I come off the highway and end up stuck in some traffic. Go to hit the gas and the coach stumbles big time. turning on the aux fuel pump instantly pushes fuel up to the carb and away I go. I also use it to prime the carb, so when I start up, it starts quick. I still feel a mechanical pump is the most reliable thing out there, other then the occasional fact it is trying to suck gas 25-30 feet and has that vapor lock problem. MN we are stuck with 10% ethonal gas.
2. I can't say on the charcoal container. but the separator is just a ball in it that will float up and stop gas flow when it floats. so you can shake it to make sure it rattles, and you can blow into it to see that it will stop gas flow.
3. Like my original post. get a good fuel filter in the carb. (pull the bolts off the intake to take the carb loose to remove the line/filter housing). You can use a boat tank, and some fuel line. put the boat tank on the passenger seat, run the fuel line out the toll window, and into the wheel well, where you can easily hook that up to the mechanical fuel pump. That will easily let you know if it is from the fuel pump to the carb. or if you have a fuel delivery issue.
http://www.gmcmhphotos.com/photos/mike-27s-gmc-stable/p38034-boattank2.html
you do not need an electric fuel pump to run the GMC this way. It can help, if you think there is a problem with the mechanical fuel pump.
The last thing that could possible be part of the problem, is sometimes the body pads are squished, and you can have pinched off fuel lines or vent lines in the system. so just keep that in mind as you inspect/replace the fuel system.
Eleganza2 Newbie wrote on Wed, 31 October 2018 19:45Greetings all and thanks for the many replies. Great to have an amazing group of knowledgable and helpful people as I navigate these new waters.
So my coach has a aux fuel pump after between the tanks and the motor pump. The previous owner had put in a new motor pump and a stainless steel fuel line to the carb. Unfortunately it is tough to get that SS line in and out to check the fuel filter near the carb. So on one little roadside challenge I opted to eliminate it all together. In its place I put a fuel filter after the aux pump. So my coach now has two fuel filters, one before the aux electric pump, and the other after it.
So I will plan to drop the tanks and replace the rubber fuel lines.
Here are a few questions (you all will have to be patient with me as I am no mechanic and certainly ignorant with these coaches):
1. Why do I need the Aux pump? I only use it when doing a cold start to get some gas into the carb, but shut it off immediately because, as mentioned I thought I was dealing with flooding. If the motor runs without the aux pump then why bother having it?
2. How do I test the separator in the left wheel well or the charcoal canister to see if they need to be replaced?
3. Several people mentioned that it is likely not a carb issue, but a fuel supply issue, How can I check that? Do I need to buy a gizmo to check my fuel pressure? How can I know if it is vapor lock, pressurized tanks, or flooding?
I realize these may be simple questions, but as I said, I'm new to this stuff.
Michael
PS. Don't know why I have a Canadian flag, I live in Boone NC with my wife and three kids ages 9, 15 and 17.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
[Updated on: Thu, 01 November 2018 08:38] Report message to a moderator |
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| Re: [GMCnet] Fuel/Carb question [message #338295 is a reply to message #338254] |
Fri, 02 November 2018 12:57 |
NextGenGMC
Messages: 146
Registered: December 2017
Location: Washington State
Karma: -1
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Senior Member |
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James Hupy wrote on Wed, 31 October 2018 18:55This message is for Michael, and it is safety related. If you have any
rubber hose or inline aftermarket fuel filters between the carb and
mechanical fuel pump, my advice would be to remove it, and go back to a 1
piece steel fuel line. Fuel leaks and Fire is the reason.
Jim Hupy
Salem, Or
78 GMC ROYALE 403
I've installed a nylon braided hose with AN connectors (and a couple of appropriate adapters) between mechanical fuel pump and carburetor. This setup still has the final in-carb fuel filter as well. I feel this is a very good and safe setup. It allow me to route the hose away from any moving parts or belts, the hose is designed for modern fuels (low risk of unintended degradation) and it can handle even high pressures for EFI setups. Being a flexible hose, it is much easier to properly align the hose and carburetor and not risk stripping the thread in the QuradraJet.
Vadim Jitkov
'76 Glenbrook 26'
Pullman, WA
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| Re: [GMCnet] Fuel/Carb question [message #338301 is a reply to message #338295] |
Fri, 02 November 2018 15:17 |
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pjburt
Messages: 436
Registered: February 2016
Location: Fresno, California
Karma: 1
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Senior Member |
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I got mine from JimK at Applied. He has them ready made. Sure makes life easier when changing the filter and you don't have to loosen the carb bolts.
NextGenGMC wrote on Fri, 02 November 2018 10:57
I've installed a nylon braided hose with AN connectors (and a couple of appropriate adapters) between mechanical fuel pump and carburetor. This setup still has the final in-carb fuel filter as well. I feel this is a very good and safe setup. It allow me to route the hose away from any moving parts or belts, the hose is designed for modern fuels (low risk of unintended degradation) and it can handle even high pressures for EFI setups. Being a flexible hose, it is much easier to properly align the hose and carburetor and not risk stripping the thread in the QuradraJet.
Jerry Burt Fresno, CA.
73 Gmc 26' Canyon Lands
Members: FMCA - GMCMI - GMCWS
A truly happy person is one who can enjoy the scenery on a detour.
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