Fuel Pump or Carburetor?

B

Balaboys

Member
Jun 21, 2021
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We have recently purchased a 76 Glenbrook with 455 and 76,000 miles on it.  It was refurbished in 2009 with new paint, interior and other upgrades I have yet to experience.  The coach has been stored indoors and was used very little for GMC Rallies, as the owner also had a Prevost for long trips.  It has been sitting for the last five years, but was started and moved in and out of it's indoor storage for various reasons.  I was told it is hard to start if it sits for any period and requires Quick Start or gas poured into the carb.  f it sits for a week, it starts and runs perfectly, but if it sits for anything longer, this time it was 3 weeks and I poured a few ounces of gasoline, six times before it fired up and kept on running.I did not check if the primers were squirting out, but I also could not smell gas or hear them.I have been pre-occupied with a cottage reno project since buying the coach, but will be addressing a few issues in the next month.Thank you,
Eric RoellAurora, Ontario76 Glenbrook "Safari" 76,000 miles,Alcoa, Continental Kit, Stainless Exhaust, Macerator, Ragusa Step
 
Gravity.

You could do a massive carb rebuild. And new pump. And hope that problem goes away.

I would install(or check if it is already done that way?). Electry fuel pump on the aux fuel tank.

Then you switch the dash to aux fuel. Listen to that pump do it’s job and start coach right up. Your starter and battery will thank you.
Then back to main and drive away.
--
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
 
Eric,
You will get better advice than mine here regarding the benefits of various fuel pump configurations. Take that advice.

My story was the similar. I have a rebuilt carb, barrier fuel hose and a new mechanical fuel pump. I've not (yet) had any problems with vapor lock,
but I did have a problem after a long sit with cranking for what I deemed to be injurious to the starter. I simply bought an electric fuel pump (5 TO
7lbs pressure) installed it in the fuel line post selector valve and put it on a switch at the dash. It serves only to prime the quadrajet after a
long sit and (maybe) to help with vapor lock should I see it. Now, after a 2 month sit I hit the prime switch till the pump slows down and hit the
starter. Starting is within 1-2 seconds as the q-jet has gas. Just be sure not to get a pump exceeding 5-7 lbs pressure as more will overwhelm the
q-jet. It's about as simple a mod as I've done and solved the problem. JWID
--
Douglas & Virginia Smith,
dsmithy18 at gmail,
Lincoln Nebraska,
’73 “Sequoia” since ‘95: "Wanabizo";
Quadrabag/6 wheel disks/3:70 final/Paterson QuadraJet/Thorley’s/Alloy wheels/Sundry other
 
If that original pump is over 7 -8 years oil, replace it as the rubber
diaphram is cracked and the ethanal is eating it.
Aux electric pump is always an option.
Also replace ALL the rubber now.
Call me and I will assist you.

> Eric,
> You will get better advice than mine here regarding the benefits of
> various fuel pump configurations. Take that advice.
>
> My story was the similar. I have a rebuilt carb, barrier fuel hose and a
> new mechanical fuel pump. I've not (yet) had any problems with vapor lock,
> but I did have a problem after a long sit with cranking for what I deemed
> to be injurious to the starter. I simply bought an electric fuel pump (5 TO
> 7lbs pressure) installed it in the fuel line post selector valve and put
> it on a switch at the dash. It serves only to prime the quadrajet after a
> long sit and (maybe) to help with vapor lock should I see it. Now, after a
> 2 month sit I hit the prime switch till the pump slows down and hit the
> starter. Starting is within 1-2 seconds as the q-jet has gas. Just be sure
> not to get a pump exceeding 5-7 lbs pressure as more will overwhelm the
> q-jet. It's about as simple a mod as I've done and solved the problem. JWID
> --
> Douglas & Virginia Smith,
> dsmithy18 at gmail,
> Lincoln Nebraska,
> ’73 “Sequoia” since ‘95: "Wanabizo";
> Quadrabag/6 wheel disks/3:70 final/Paterson QuadraJet/Thorley’s/Alloy
> wheels/Sundry other
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>

--
Jim Kanomata ASE
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
Thank you Jim, since it has not been driven in 5 yrs and little use prior to that, I would suspect the fuel pump is more than 8 yrs old.I will try that route first.
Eric Roell, Aurora, Ontario76 Glenbrook "Safari" 76,000 miles,Alcoa, Continental Kit, Fender Flares, Stainless Exhaust, Macerator, Ragusa Step

On Monday, July 26, 2021, 11:27:33 p.m. EDT, Jim Kanomata wrote:

If that original pump is over 7 -8 years oil, replace it as the rubber
diaphram is cracked and the ethanal is eating it.
Aux electric pump is always an option.
Also replace ALL the rubber now.
Call me and I will assist you.

> Eric,
> You will get better advice than mine here regarding the benefits of
> various fuel pump configurations. Take that advice.
>
> My story was the similar. I have a rebuilt carb, barrier fuel hose and a
> new mechanical fuel pump. I've not (yet) had any problems with vapor lock,
> but I did have a problem after a long sit with cranking for what I deemed
> to be injurious to the starter. I simply bought an electric fuel pump (5 TO
> 7lbs pressure) installed it in the fuel line post selector valve and put
> it on a switch at the dash. It serves only to prime the quadrajet after a
> long sit and (maybe) to help with vapor lock should I see it. Now, after a
> 2 month sit I hit the prime switch till the pump slows down and hit the
> starter. Starting is within 1-2 seconds as the q-jet has gas. Just be sure
> not to get a pump exceeding 5-7 lbs pressure as more will overwhelm the
> q-jet. It's about as simple a mod as I've done and solved the problem. JWID
> --
> Douglas & Virginia Smith,
> dsmithy18 at gmail,
> Lincoln Nebraska,
> ’73 “Sequoia” since ‘95: "Wanabizo";
> Quadrabag/6 wheel disks/3:70 final/Paterson QuadraJet/Thorley’s/Alloy
> wheels/Sundry other
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>

--
Jim Kanomata ASE
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
 
Thank you Douglas,The fuel pump seems to be the common denominator on this fix and an electric fuel pump has come up as an economical upgrade. 
Eric Roell, Aurora, Ontario76 Glenbrook "Safari" 76,000 miles,Alcoa, Continental Kit, Fender Flares, Stainless Exhaust, Macerator, Ragusa Step

On Monday, July 26, 2021, 11:00:12 p.m. EDT, Douglas Smith wrote:

Eric,
You will get better advice than mine here regarding the benefits of various fuel pump configurations. Take that advice.

My story was the similar. I have a rebuilt carb, barrier fuel hose and a new mechanical fuel pump. I've not (yet) had any problems with vapor lock,
but I did have a problem after a long sit with cranking for what I deemed to be injurious to the starter. I simply bought an electric fuel pump (5 TO
7lbs pressure) installed it in the fuel line post selector valve and put it on a switch at the dash. It serves only to prime the quadrajet after a
long sit and (maybe) to help with vapor lock should I see it. Now, after a 2 month sit I hit the prime switch till the pump slows down and hit the
starter. Starting is within 1-2 seconds as the q-jet has gas. Just be sure not to get a pump exceeding 5-7 lbs pressure as more will overwhelm the
q-jet. It's about as simple a mod as I've done and solved the problem. JWID
--
Douglas & Virginia Smith,
dsmithy18 at gmail,
Lincoln Nebraska,
’73 “Sequoia” since ‘95: "Wanabizo";
Quadrabag/6 wheel disks/3:70 final/Paterson QuadraJet/Thorley’s/Alloy wheels/Sundry other
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
 
One of the things that happens to an engine while sitting between outings is that gravity allows oil to drain off of our bearing surfaces into the oil
pan. So, IMO, after a period of time sitting, it is a good thing for the starter to turn the engine over for a period of time without immediate
start. That allows the oil pump to build oil pressure and to put oil on bearing surfaces reducing dry run damage. IMO, if you need to use the
electric fuel pump to prime the carb for start, allow the engine to turn over without start for 15 seconds or so, then prime the carb for start.
Replacing a starter is a lot easier and cheaper than replacing an engine. JWIT
--
Larry
78 Royale w/500 Caddy
Menomonie, WI.
 
Part of it may be operator error. Starting a 70s carbureted vehicle
is completely different process than starting a newer computer controlled vehicle. Procedures are in owners manual to read for cold and hot starts.
If it has been sitting a long long time, carb should fill and engine start under 10 seconds on a stock setup if everything is correct. .
You may have a combination of issues
1) leaking carb bowl well plugs
2) weak accelerator pump in carb
3) gummed or misadjusted choke
4) incorrect starting procedure.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
One of the weaknesses of the quadrajet Carburetor is the fact that it has a
small internal reservoir of fuel, and is subject to heat soak on the
motorhome because of the lowered placement of the carb to allow for hood
clearance. This places the carb base very close to the exhaust crossover
passage in the manifold. Result being that the small fuel reserve in the
float bowl evaporates, leaving no fuel in the carb to start the engine.
Fix? Three ways that I know work are, an auxiliary electric fuel pump in
the supply fuel line, that can be run before starting the engine to fill
the float bowl, and/or blocking off the crossover passages to reduce
heating of the Carburetor, and third, convert the coach to fuel injection.
That gets rid of the Carburetor, mechanical fuel pump, etc. $$$$ but
effective, and perhaps a good choice for younger drivers who can't seem to
grasp all the "oddities" of 40+ year old engines.
Jim Hupy
Salem, Oregon

On Tue, Jul 27, 2021, 6:41 AM John R. Lebetski
wrote:

> Part of it may be operator error. Starting a 70s carbureted vehicle
> is completely different process than starting a newer computer
> controlled vehicle. Procedures are in owners manual to read for cold and
> hot starts.
> If it has been sitting a long long time, carb should fill and engine
> start under 10 seconds on a stock setup if everything is correct. .
> You may have a combination of issues
> 1) leaking carb bowl well plugs
> 2) weak accelerator pump in carb
> 3) gummed or misadjusted choke
> 4) incorrect starting procedure.
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
 
Hello Jim,Thanks for the detailed response and suggestions, all very valuable and noted.Although I am younger than most GMC owners, I did grow up in the seventies with the anguish of older carbureted motorcycles, boats and of course V8 cars, I still own a 73 Mustang and an older carbureted V8 boat.I will start working on the coach next month to get it road worthy and make a few small trips around town to establish my priority ($$$) list.  EFI does sound intriging to me.
Eric Roell, Aurora, Ontario76 Glenbrook "Safari" 76,000 miles,Alcoa, Continental Kit, Fender Flares, Stainless Exhaust, Macerator, Ragusa Step

On Tuesday, July 27, 2021, 10:09:43 a.m. EDT, James Hupy wrote:

One of the weaknesses of the quadrajet Carburetor is the fact that it has a
small internal reservoir of fuel, and is subject to heat soak on the
motorhome because of the lowered placement of the carb to allow for hood
clearance. This places the carb base very close to the exhaust crossover
passage in the manifold. Result being that the small fuel reserve in the
float bowl evaporates, leaving no fuel in the carb to start the engine.
Fix? Three ways that I know work are,  an auxiliary electric fuel pump in
the supply fuel line, that can be run before starting the engine to fill
the float bowl, and/or blocking off the crossover passages to reduce
heating of the Carburetor, and third, convert the coach to fuel injection.
That gets rid of the Carburetor, mechanical fuel pump, etc. $$$$ but
effective, and perhaps a good choice for younger drivers who can't seem to
grasp all the "oddities" of 40+ year old engines.
Jim Hupy
Salem, Oregon

On Tue, Jul 27, 2021, 6:41 AM John R. Lebetski
wrote:

> Part of it may be operator error.  Starting a 70s carbureted vehicle
>  is completely different  process than starting a newer computer
> controlled vehicle.  Procedures are in owners manual to read for cold and
> hot starts.
>  If it has been sitting a long long time, carb should fill and engine
> start under 10 seconds on a stock setup if everything is correct. .
> You may have a combination of issues
> 1) leaking carb bowl well plugs
> 2) weak accelerator pump in carb
> 3) gummed or misadjusted choke
> 4) incorrect starting procedure.
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
 
Eric, I was young once and leaned from tons of older guys and asked lot of
questions and had them saying that for an Engineer your wanting to learn,
not like the rest.
Feel free to call me with any questions.

> Hello Jim,Thanks for the detailed response and suggestions, all very
> valuable and noted.Although I am younger than most GMC owners, I did grow
> up in the seventies with the anguish of older carbureted motorcycles, boats
> and of course V8 cars, I still own a 73 Mustang and an older carbureted V8
> boat.I will start working on the coach next month to get it road worthy and
> make a few small trips around town to establish my priority ($$$) list.
> EFI does sound intriging to me.
> Eric Roell, Aurora, Ontario76 Glenbrook "Safari" 76,000 miles,Alcoa,
> Continental Kit, Fender Flares, Stainless Exhaust, Macerator, Ragusa Step
>
> On Tuesday, July 27, 2021, 10:09:43 a.m. EDT, James Hupy <

>
> One of the weaknesses of the quadrajet Carburetor is the fact that it has
> a
> small internal reservoir of fuel, and is subject to heat soak on the
> motorhome because of the lowered placement of the carb to allow for hood
> clearance. This places the carb base very close to the exhaust crossover
> passage in the manifold. Result being that the small fuel reserve in the
> float bowl evaporates, leaving no fuel in the carb to start the engine.
> Fix? Three ways that I know work are, an auxiliary electric fuel pump in
> the supply fuel line, that can be run before starting the engine to fill
> the float bowl, and/or blocking off the crossover passages to reduce
> heating of the Carburetor, and third, convert the coach to fuel injection.
> That gets rid of the Carburetor, mechanical fuel pump, etc. $$$$ but
> effective, and perhaps a good choice for younger drivers who can't seem to
> grasp all the "oddities" of 40+ year old engines.
> Jim Hupy
> Salem, Oregon
>
> On Tue, Jul 27, 2021, 6:41 AM John R. Lebetski

>
> > Part of it may be operator error. Starting a 70s carbureted vehicle
> > is completely different process than starting a newer computer
> > controlled vehicle. Procedures are in owners manual to read for cold and
> > hot starts.
> > If it has been sitting a long long time, carb should fill and engine
> > start under 10 seconds on a stock setup if everything is correct. .
> > You may have a combination of issues
> > 1) leaking carb bowl well plugs
> > 2) weak accelerator pump in carb
> > 3) gummed or misadjusted choke
> > 4) incorrect starting procedure.
> > --
> > John Lebetski
> > Woodstock, IL
> > 77 Eleganza II
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>

--
Jim Kanomata ASE
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
I appreciate the offer Jim.  Once I delve in the coach further, I will know more about the problems I am dealing with.
Eric Roell, Aurora, Ontario76 Glenbrook "Safari" 76,000 miles,Alcoa, Continental Kit, Fender Flares, Stainless Exhaust, Macerator, Ragusa Step

On Tuesday, July 27, 2021, 02:36:18 p.m. EDT, Jim Kanomata wrote:

Eric, I was young once and leaned from tons of older guys and asked lot of
questions and had them saying that for an Engineer your wanting to learn,
not like the rest.
Feel free to call me with any questions.

> Hello Jim, Thanks for the detailed response and suggestions, all very
> valuable and noted. Although I am younger than most GMC owners, I did grow
> up in the seventies with the anguish of older carbureted motorcycles, boats
> and of course V8 cars, I still own a 73 Mustang and an older carbureted V8
> boat. I will start working on the coach next month to get it road worthy and
> make a few small trips around town to establish my priority ($$$) list.
> EFI does sound intriging to me.
> Eric Roell, Aurora, Ontario76 Glenbrook "Safari" 76,000 miles, Alcoa,
> Continental Kit, Fender Flares, Stainless Exhaust, Macerator, Ragusa Step
>
>    On Tuesday, July 27, 2021, 10:09:43 a.m. EDT, James Hupy <

>
>  One of the weaknesses of the quadrajet Carburetor is the fact that it has
> a
> small internal reservoir of fuel, and is subject to heat soak on the
> motorhome because of the lowered placement of the carb to allow for hood
> clearance. This places the carb base very close to the exhaust crossover
> passage in the manifold. Result being that the small fuel reserve in the
> float bowl evaporates, leaving no fuel in the carb to start the engine.
> Fix? Three ways that I know work are,  an auxiliary electric fuel pump in
> the supply fuel line, that can be run before starting the engine to fill
> the float bowl, and/or blocking off the crossover passages to reduce
> heating of the Carburetor, and third, convert the coach to fuel injection.
> That gets rid of the Carburetor, mechanical fuel pump, etc. $$$$ but
> effective, and perhaps a good choice for younger drivers who can't seem to
> grasp all the "oddities" of 40+ year old engines.
> Jim Hupy
> Salem, Oregon
>
> On Tue, Jul 27, 2021, 6:41 AM John R. Lebetski

>
> > Part of it may be operator error.  Starting a 70s carbureted vehicle
> >  is completely different  process than starting a newer computer
> > controlled vehicle.  Procedures are in owners manual to read for cold and
> > hot starts.
> >  If it has been sitting a long long time, carb should fill and engine
> > start under 10 seconds on a stock setup if everything is correct. .
> > You may have a combination of issues
> > 1) leaking carb bowl well plugs
> > 2) weak accelerator pump in carb
> > 3) gummed or misadjusted choke
> > 4) incorrect starting procedure.
> > --
> > John Lebetski
> > Woodstock, IL
> > 77 Eleganza II
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>

--
Jim Kanomata ASE
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
 
Thank you for the reminder Larry. I do turn it over a bit before hitting the prime switch.
--
Douglas & Virginia Smith,
dsmithy18 at gmail,
Lincoln Nebraska,
’73 “Sequoia” since ‘95: "Wanabizo";
Quadrabag/6 wheel disks/3:70 final/Paterson QuadraJet/Thorley’s/Alloy wheels/Sundry other
 
Had my carb rebuilt by Canadian carb in bc and my ignition by Patterson's in Ontario. Both smart upgrades. Electric fuel pump on the secondary tank. Also block offs on the intake and manual choke. Works great.

Sent from Yahoo Mail on Android

On Tue., 27 Jul. 2021 at 12:44 p.m., Douglas Smith wrote: Thank you for the reminder Larry. I do turn it over a bit before hitting the prime switch.
--
Douglas & Virginia Smith,
dsmithy18 at gmail,
Lincoln Nebraska,
’73 “Sequoia” since ‘95: "Wanabizo";
Quadrabag/6 wheel disks/3:70 final/Paterson QuadraJet/Thorley’s/Alloy wheels/Sundry other
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Unsubscribe or Change List Options:
 
Great feedback, thank you.PS - nice to have some Canadian content!
Eric Roell, Aurora, Ontario76 Glenbrook "Safari" 76,000 miles,Alcoa, Continental Kit, Fender Flares, Stainless Exhaust, Macerator, Ragusa Step

On Wednesday, July 28, 2021, 09:42:50 p.m. EDT, delbert lecky via Gmclist wrote:

Had my carb rebuilt by Canadian carb in bc and my ignition by Patterson's in Ontario. Both smart upgrades. Electric fuel pump on the secondary tank. Also block offs on the intake and manual choke. Works great.

Sent from Yahoo Mail on Android

  On Tue., 27 Jul. 2021 at 12:44 p.m., Douglas Smith wrote:  Thank you for the reminder Larry. I do turn it over a bit before hitting the prime switch.
--
Douglas & Virginia Smith,
dsmithy18 at gmail,
Lincoln Nebraska,
’73 “Sequoia” since ‘95: "Wanabizo";
Quadrabag/6 wheel disks/3:70 final/Paterson QuadraJet/Thorley’s/Alloy wheels/Sundry other
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Unsubscribe or Change List Options:
 
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