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Next Noob Question- secondary's not opening

DS
dave silva
Mon, Jul 19, 2021 5:10 PM

The coach starts easy and runs smooth, takes off nicely but  when i put my foot in it very little happens-

I ran it with the cover off and watched the carb- secondary not opening.    I poked around a bit and i understand it has something to with the choke
being fully open.

And there's a vacuum diaphragm in front that does something?

If someone could explain what normal operation looks like i can probably form a more intelligent question.

Dave & Ellen Silva
Hertford, NC

76  Birchaven, 1-ton and other stuff

Currently planning the Great american Road Trip Summer 2021

It's gonna take a lot of Adderall to get this thing right.

The coach starts easy and runs smooth, takes off nicely but when i put my foot in it very little happens- I ran it with the cover off and watched the carb- secondary not opening. I poked around a bit and i understand it has something to with the choke being fully open. And there's a vacuum diaphragm in front that does something? If someone could explain what normal operation looks like i can probably form a more intelligent question. -- Dave & Ellen Silva Hertford, NC 76 Birchaven, 1-ton and other stuff Currently planning the Great american Road Trip Summer 2021 It's gonna take a lot of Adderall to get this thing right.
JR
Jon Roche
Mon, Jul 19, 2021 8:56 PM
  1. Some q-jets have a little tag on far passenger side of choke that blocks the secondary from opening.  When choke is fully open that should push
    the tang in and allow the secondary to open.  Try opening the secondary by pushing open with screwdriver.  You should see how that works.

  2. Secondarys open when vacuum is low.  Basically a vacuum
    Plunger holds them
    Closed.  As you hammer
    The has vacuum drops and the plunger no longer has ability to hold them closed.  Think opposite of how your cruise
    Control
    Works.

Having a vacuum gauge to diagnose is helpful.  They rarely open in normal driving.  You have to be smashing the throttle down.  Just putzing normally
you may not see them
Open.

Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/

1. Some q-jets have a little tag on far passenger side of choke that blocks the secondary from opening. When choke is fully open that should push the tang in and allow the secondary to open. Try opening the secondary by pushing open with screwdriver. You should see how that works. 2. Secondarys open when vacuum is low. Basically a vacuum Plunger holds them Closed. As you hammer The has vacuum drops and the plunger no longer has ability to hold them closed. Think opposite of how your cruise Control Works. Having a vacuum gauge to diagnose is helpful. They rarely open in normal driving. You have to be smashing the throttle down. Just putzing normally you may not see them Open. -- Jon Roche 75 palm beach EBL EFI, manny headers, Micro Level, rebuilt most of coach now. St. Cloud, MN http://lqqkatjon.blogspot.com/
JR
John R. Lebetski
Tue, Jul 20, 2021 1:34 AM

If the choke is fully open, the lockout tab clear and they still don’t open try this test.  Push down on the larger rear part with your finger and
the air valves should not touch or scrape the air horn. If they do, just loosen the air valve screws about 3/4 turn and recenter the air valve plates
on the shaft so they do not touch anything, then resnug the 2 screws on each. Do not loosen more than a turn or you risk dropping them into the carb
and engine. The screws are thinner than the holes in plates to  allow adjustment.

John Lebetski
Woodstock, IL
77 Eleganza II

If the choke is fully open, the lockout tab clear and they still don’t open try this test. Push down on the larger rear part with your finger and the air valves should not touch or scrape the air horn. If they do, just loosen the air valve screws about 3/4 turn and recenter the air valve plates on the shaft so they do not touch anything, then resnug the 2 screws on each. Do not loosen more than a turn or you risk dropping them into the carb and engine. The screws are thinner than the holes in plates to allow adjustment. -- John Lebetski Woodstock, IL 77 Eleganza II
DS
dave silva
Fri, Jul 23, 2021 10:00 PM

Ok, i figured out how it's supposed to  work and everything seems to be doing what it's supposed to.

The choke opens completely, allowing everything else to open.

When i hit the throttle I see large amounts of fuel spraying into the intake, everything looks fine.

But on the road when I do that it bogs down and loses power.

Timing? i put a light on it but the timing mark is not visible. Lots of surface rust.

But i can tell with my timing light that it is advancing.

It have NEW HEI

Dave & Ellen Silva
Hertford, NC

76  Birchaven, 1-ton and other stuff

Currently planning the Great american Road Trip Summer 2021

It's gonna take a lot of Adderall to get this thing right.

Ok, i figured out how it's supposed to work and everything seems to be doing what it's supposed to. The choke opens completely, allowing everything else to open. When i hit the throttle I see large amounts of fuel spraying into the intake, everything looks fine. But on the road when I do that it bogs down and loses power. Timing? i put a light on it but the timing mark is not visible. Lots of surface rust. But i can tell with my timing light that it is advancing. It have NEW HEI -- Dave & Ellen Silva Hertford, NC 76 Birchaven, 1-ton and other stuff Currently planning the Great american Road Trip Summer 2021 It's gonna take a lot of Adderall to get this thing right.
JR
John R. Lebetski
Fri, Jul 23, 2021 10:26 PM

When you rev it in park the secondary air valve should only slightly open visually.  If it is flopping wide open the front dash pot is bad, vac hose
to it is bad or spring on air valve set too lose.  The front dashpot has a less than pin hole orifice to hold back the opening time after the vacuum
to the pot drops. It should open gradually in gear under load as you floor it.  Fuel is heavy compared to air an takes time to match the more rapidly
accelerating air. If air valve opens too soon you get bog. If the front dashpot and hose to it are good, you can increase spring wind up tension on
the air valve.  You hold the flat blade scrre with a small driver, loosen the locking allen and slightly turn the screw for more tension, then tighten
allen lock screw.

John Lebetski
Woodstock, IL
77 Eleganza II

When you rev it in park the secondary air valve should only slightly open visually. If it is flopping wide open the front dash pot is bad, vac hose to it is bad or spring on air valve set too lose. The front dashpot has a less than pin hole orifice to hold back the opening time after the vacuum to the pot drops. It should open gradually in gear under load as you floor it. Fuel is heavy compared to air an takes time to match the more rapidly accelerating air. If air valve opens too soon you get bog. If the front dashpot and hose to it are good, you can increase spring wind up tension on the air valve. You hold the flat blade scrre with a small driver, loosen the locking allen and slightly turn the screw for more tension, then tighten allen lock screw. -- John Lebetski Woodstock, IL 77 Eleganza II
JH
James Hupy
Fri, Jul 23, 2021 11:01 PM

Also, if you "Stomp" the accelerator clean to the floor at too low of an
RPM, it will bog. Feed the throttle in gradually. If that works, then the
problem is not in the Carb, but in your foot. If it still bogs, then you
have a problem with too weak of a spring on the secondaries. There are
various springs for different applications on GM vehicles. Lastly, If you
are still running the 3:07 to 1 differential ratio, a solution might be to
go to a 3:55 or 3:70 to 1 final drive ratio.
Jim Hupy
Salem, Oregon

On Fri, Jul 23, 2021 at 3:26 PM John R. Lebetski gransport7087@gmail.com
wrote:

When you rev it in park the secondary air valve should only slightly open
visually.  If it is flopping wide open the front dash pot is bad, vac hose
to it is bad or spring on air valve set too lose.  The front dashpot has a
less than pin hole orifice to hold back the opening time after the vacuum
to the pot drops. It should open gradually in gear under load as you floor
it.  Fuel is heavy compared to air an takes time to match the more rapidly
accelerating air. If air valve opens too soon you get bog. If the front
dashpot and hose to it are good, you can increase spring wind up tension on
the air valve.  You hold the flat blade scrre with a small driver, loosen
the locking allen and slightly turn the screw for more tension, then tighten
allen lock screw.

John Lebetski
Woodstock, IL
77 Eleganza II


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Also, if you "Stomp" the accelerator clean to the floor at too low of an RPM, it will bog. Feed the throttle in gradually. If that works, then the problem is not in the Carb, but in your foot. If it still bogs, then you have a problem with too weak of a spring on the secondaries. There are various springs for different applications on GM vehicles. Lastly, If you are still running the 3:07 to 1 differential ratio, a solution might be to go to a 3:55 or 3:70 to 1 final drive ratio. Jim Hupy Salem, Oregon On Fri, Jul 23, 2021 at 3:26 PM John R. Lebetski <gransport7087@gmail.com> wrote: > When you rev it in park the secondary air valve should only slightly open > visually. If it is flopping wide open the front dash pot is bad, vac hose > to it is bad or spring on air valve set too lose. The front dashpot has a > less than pin hole orifice to hold back the opening time after the vacuum > to the pot drops. It should open gradually in gear under load as you floor > it. Fuel is heavy compared to air an takes time to match the more rapidly > accelerating air. If air valve opens too soon you get bog. If the front > dashpot and hose to it are good, you can increase spring wind up tension on > the air valve. You hold the flat blade scrre with a small driver, loosen > the locking allen and slightly turn the screw for more tension, then tighten > allen lock screw. > -- > John Lebetski > Woodstock, IL > 77 Eleganza II > _______________________________________________ > GMCnet mailing list > Unsubscribe or Change List Options: >
DS
dave silva
Sun, Jul 25, 2021 11:43 AM

James Hupy wrote on Fri, 23 July 2021 18:01

Also, if you "Stomp" the accelerator clean to the floor at too low of an
RPM, it will bog. Feed the throttle in gradually. If that works, then the
problem is not in the Carb, but in your foot. If it still bogs, then you
have a problem with too weak of a spring on the secondaries.

I've taken a few test drives to articulate this problem.

From a dead stop it takes off very smoothly with a light touch on the throttle, if i leave my foot in the  same spot it will very slowly accelerate to
45 mph or so, but if i give it any more gas it bogs no matter how gently i feather it.

This problem came on over  a short period of time.

The coach had been completely gone over in 2013 with a new/rebuilt carb, distributor, wiring etc.  It drove up here here to NC from the COOP and ran
fine. Then it sat until 2020.

When i first  took it on  there was a lot of cranking and pouring gas down it's throat  before  it sparked.  Then i got it running pretty good with
fresh fuel.

At that point it behaved  like the muscle car it is. When i stomped on the throttle it roared and launched like a 10,000 lb missile.

Then it started having a power loss under load. I changed several dirty fuel filters but that seemed to have little effect.  It was getting harder to
start and had less power.

Then it lost spark.  I diagnosed the HEI, installed new components and it ran great, it starts instantly and idles smoothly but this power problem has
not gone away.

So it appears the ignition problem masked or imitated an intermittant fuel problem but when i got the spark right the fuel problem is still there.

I think i've ruled out issues related to dirty fuel, clogged filter, bad pump, etc.

--
Dave & Ellen Silva
Hertford, NC

76  Birchaven, 1-ton and other stuff

Currently planning the Great american Road Trip Summer 2021

It's gonna take a lot of Adderall to get this thing right.

James Hupy wrote on Fri, 23 July 2021 18:01 > Also, if you "Stomp" the accelerator clean to the floor at too low of an > RPM, it will bog. Feed the throttle in gradually. If that works, then the > problem is not in the Carb, but in your foot. If it still bogs, then you > have a problem with too weak of a spring on the secondaries. I've taken a few test drives to articulate this problem. From a dead stop it takes off very smoothly with a light touch on the throttle, if i leave my foot in the same spot it will very slowly accelerate to 45 mph or so, but if i give it any more gas it bogs no matter how gently i feather it. This problem came on over a short period of time. The coach had been completely gone over in 2013 with a new/rebuilt carb, distributor, wiring etc. It drove up here here to NC from the COOP and ran fine. Then it sat until 2020. When i first took it on there was a lot of cranking and pouring gas down it's throat before it sparked. Then i got it running pretty good with fresh fuel. At that point it behaved like the muscle car it is. When i stomped on the throttle it roared and launched like a 10,000 lb missile. Then it started having a power loss under load. I changed several dirty fuel filters but that seemed to have little effect. It was getting harder to start and had less power. Then it lost spark. I diagnosed the HEI, installed new components and it ran great, it starts instantly and idles smoothly but this power problem has not gone away. So it appears the ignition problem masked or imitated an intermittant fuel problem but when i got the spark right the fuel problem is still there. I think i've ruled out issues related to dirty fuel, clogged filter, bad pump, etc. -- Dave & Ellen Silva Hertford, NC 76 Birchaven, 1-ton and other stuff Currently planning the Great american Road Trip Summer 2021 It's gonna take a lot of Adderall to get this thing right.
DC
D C _Mac_ Macdonald
Sun, Jul 25, 2021 10:20 PM

Is your distributor advance working properly?
Or is it frozen in place with corrosion?

D C "Mac" Macdonald
Amateur Radio K2GKK
Since 30 November '53
USAF and FAA, Retired
Member GMCMI & Classics
Oklahoma City, OK
"The Money Pit"
TZE166V101966
'76 ex-Palm Beach
k2gkk + hotmail dot com


From: dave silva admin@oldrv.net
Sent: Sunday, July 25, 2021 06:43
To: gmclist@list.gmcnet.org gmclist@list.gmcnet.org
Subject: [GMCnet] Re: - secondary's not opening - more info

James Hupy wrote on Fri, 23 July 2021 18:01

Also, if you "Stomp" the accelerator clean to the floor at too low of an
RPM, it will bog. Feed the throttle in gradually. If that works, then the
problem is not in the Carb, but in your foot. If it still bogs, then you
have a problem with too weak of a spring on the secondaries.

I've taken a few test drives to articulate this problem.

From a dead stop it takes off very smoothly with a light touch on the throttle, if i leave my foot in the  same spot it will very slowly accelerate to
45 mph or so, but if i give it any more gas it bogs no matter how gently i feather it.

This problem came on over  a short period of time.

The coach had been completely gone over in 2013 with a new/rebuilt carb, distributor, wiring etc.  It drove up here here to NC from the COOP and ran
fine. Then it sat until 2020.

When i first  took it on  there was a lot of cranking and pouring gas down it's throat  before  it sparked.  Then i got it running pretty good with
fresh fuel.

At that point it behaved  like the muscle car it is. When i stomped on the throttle it roared and launched like a 10,000 lb missile.

Then it started having a power loss under load. I changed several dirty fuel filters but that seemed to have little effect.  It was getting harder to
start and had less power.

Then it lost spark.  I diagnosed the HEI, installed new components and it ran great, it starts instantly and idles smoothly but this power problem has
not gone away.

So it appears the ignition problem masked or imitated an intermittant fuel problem but when i got the spark right the fuel problem is still there.

I think i've ruled out issues related to dirty fuel, clogged filter, bad pump, etc.

--
Dave & Ellen Silva
Hertford, NC

76  Birchaven, 1-ton and other stuff

Currently planning the Great american Road Trip Summer 2021

It's gonna take a lot of Adderall to get this thing right.


GMCnet mailing list
Unsubscribe or Change List Options:

Is your distributor advance working properly? Or is it frozen in place with corrosion? D C "Mac" Macdonald Amateur Radio K2GKK Since 30 November '53 USAF and FAA, Retired Member GMCMI & Classics Oklahoma City, OK "The Money Pit" TZE166V101966 '76 ex-Palm Beach k2gkk + hotmail dot com ________________________________ From: dave silva <admin@oldrv.net> Sent: Sunday, July 25, 2021 06:43 To: gmclist@list.gmcnet.org <gmclist@list.gmcnet.org> Subject: [GMCnet] Re: - secondary's not opening - more info James Hupy wrote on Fri, 23 July 2021 18:01 > Also, if you "Stomp" the accelerator clean to the floor at too low of an > RPM, it will bog. Feed the throttle in gradually. If that works, then the > problem is not in the Carb, but in your foot. If it still bogs, then you > have a problem with too weak of a spring on the secondaries. I've taken a few test drives to articulate this problem. From a dead stop it takes off very smoothly with a light touch on the throttle, if i leave my foot in the same spot it will very slowly accelerate to 45 mph or so, but if i give it any more gas it bogs no matter how gently i feather it. This problem came on over a short period of time. The coach had been completely gone over in 2013 with a new/rebuilt carb, distributor, wiring etc. It drove up here here to NC from the COOP and ran fine. Then it sat until 2020. When i first took it on there was a lot of cranking and pouring gas down it's throat before it sparked. Then i got it running pretty good with fresh fuel. At that point it behaved like the muscle car it is. When i stomped on the throttle it roared and launched like a 10,000 lb missile. Then it started having a power loss under load. I changed several dirty fuel filters but that seemed to have little effect. It was getting harder to start and had less power. Then it lost spark. I diagnosed the HEI, installed new components and it ran great, it starts instantly and idles smoothly but this power problem has not gone away. So it appears the ignition problem masked or imitated an intermittant fuel problem but when i got the spark right the fuel problem is still there. I think i've ruled out issues related to dirty fuel, clogged filter, bad pump, etc. -- Dave & Ellen Silva Hertford, NC 76 Birchaven, 1-ton and other stuff Currently planning the Great american Road Trip Summer 2021 It's gonna take a lot of Adderall to get this thing right. _______________________________________________ GMCnet mailing list Unsubscribe or Change List Options:
NW
Nelson Wright
Sun, Jul 25, 2021 10:32 PM

Maybe check for blockage in the exhaust system .

Sent from my iPhone
Nelson Wright

Orlando Fl.

On Jul 25, 2021, at 6:20 PM, D C Mac Macdonald k2gkk@hotmail.com wrote:

Is your distributor advance working properly?
Or is it frozen in place with corrosion?

D C "Mac" Macdonald
Amateur Radio K2GKK
Since 30 November '53
USAF and FAA, Retired
Member GMCMI & Classics
Oklahoma City, OK
"The Money Pit"
TZE166V101966
'76 ex-Palm Beach
k2gkk + hotmail dot com


From: dave silva admin@oldrv.net
Sent: Sunday, July 25, 2021 06:43
To: gmclist@list.gmcnet.org gmclist@list.gmcnet.org
Subject: [GMCnet] Re: - secondary's not opening - more info

James Hupy wrote on Fri, 23 July 2021 18:01

Also, if you "Stomp" the accelerator clean to the floor at too low of an
RPM, it will bog. Feed the throttle in gradually. If that works, then the
problem is not in the Carb, but in your foot. If it still bogs, then you
have a problem with too weak of a spring on the secondaries.

I've taken a few test drives to articulate this problem.

From a dead stop it takes off very smoothly with a light touch on the throttle, if i leave my foot in the  same spot it will very slowly accelerate to
45 mph or so, but if i give it any more gas it bogs no matter how gently i feather it.

This problem came on over  a short period of time.

The coach had been completely gone over in 2013 with a new/rebuilt carb, distributor, wiring etc.  It drove up here here to NC from the COOP and ran
fine. Then it sat until 2020.

When i first  took it on  there was a lot of cranking and pouring gas down it's throat  before  it sparked.  Then i got it running pretty good with
fresh fuel.

At that point it behaved  like the muscle car it is. When i stomped on the throttle it roared and launched like a 10,000 lb missile.

Then it started having a power loss under load. I changed several dirty fuel filters but that seemed to have little effect.  It was getting harder to
start and had less power.

Then it lost spark.  I diagnosed the HEI, installed new components and it ran great, it starts instantly and idles smoothly but this power problem has
not gone away.

So it appears the ignition problem masked or imitated an intermittant fuel problem but when i got the spark right the fuel problem is still there.

I think i've ruled out issues related to dirty fuel, clogged filter, bad pump, etc.

--
Dave & Ellen Silva
Hertford, NC

76  Birchaven, 1-ton and other stuff

Currently planning the Great american Road Trip Summer 2021

It's gonna take a lot of Adderall to get this thing right.


GMCnet mailing list
Unsubscribe or Change List Options:


GMCnet mailing list
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Maybe check for blockage in the exhaust system . Sent from my iPhone Nelson Wright Orlando Fl. > On Jul 25, 2021, at 6:20 PM, D C _Mac_ Macdonald <k2gkk@hotmail.com> wrote: > > Is your distributor advance working properly? > Or is it frozen in place with corrosion? > > D C "Mac" Macdonald > Amateur Radio K2GKK > Since 30 November '53 > USAF and FAA, Retired > Member GMCMI & Classics > Oklahoma City, OK > "The Money Pit" > TZE166V101966 > '76 ex-Palm Beach > k2gkk + hotmail dot com > ________________________________ > From: dave silva <admin@oldrv.net> > Sent: Sunday, July 25, 2021 06:43 > To: gmclist@list.gmcnet.org <gmclist@list.gmcnet.org> > Subject: [GMCnet] Re: - secondary's not opening - more info > > James Hupy wrote on Fri, 23 July 2021 18:01 >> Also, if you "Stomp" the accelerator clean to the floor at too low of an >> RPM, it will bog. Feed the throttle in gradually. If that works, then the >> problem is not in the Carb, but in your foot. If it still bogs, then you >> have a problem with too weak of a spring on the secondaries. > > > I've taken a few test drives to articulate this problem. > > From a dead stop it takes off very smoothly with a light touch on the throttle, if i leave my foot in the same spot it will very slowly accelerate to > 45 mph or so, but if i give it any more gas it bogs no matter how gently i feather it. > > This problem came on over a short period of time. > > The coach had been completely gone over in 2013 with a new/rebuilt carb, distributor, wiring etc. It drove up here here to NC from the COOP and ran > fine. Then it sat until 2020. > > When i first took it on there was a lot of cranking and pouring gas down it's throat before it sparked. Then i got it running pretty good with > fresh fuel. > > At that point it behaved like the muscle car it is. When i stomped on the throttle it roared and launched like a 10,000 lb missile. > > Then it started having a power loss under load. I changed several dirty fuel filters but that seemed to have little effect. It was getting harder to > start and had less power. > > Then it lost spark. I diagnosed the HEI, installed new components and it ran great, it starts instantly and idles smoothly but this power problem has > not gone away. > > So it appears the ignition problem masked or imitated an intermittant fuel problem but when i got the spark right the fuel problem is still there. > > I think i've ruled out issues related to dirty fuel, clogged filter, bad pump, etc. > > > > > > > > -- > Dave & Ellen Silva > Hertford, NC > > 76 Birchaven, 1-ton and other stuff > > Currently planning the Great american Road Trip Summer 2021 > > It's gonna take a lot of Adderall to get this thing right. > > _______________________________________________ > GMCnet mailing list > Unsubscribe or Change List Options: > _______________________________________________ > GMCnet mailing list > Unsubscribe or Change List Options:
JR
Jon Roche
Mon, Jul 26, 2021 1:44 AM

Recent experience(july)

Coach showed up in my neck of the woods.  Guy revived a coach, fixed a few things(fuel filters, put cherry bomb mufflers on because old ones were
blown, few other things including new batteries)

Took off from Pennsylvania and drove to mn. Had many other issues but ran strong and good power.

Then while here in MN for a week, he had power issues.    Seemed like fuel.  Replaced fuel filters again,  and they were dirty already.    Full
tune up.  No improvement.

We swapped on a spare carb and that fixed it.

So from what your story is,  i am leaning toward carb has some issues that are now shown up from bad gas.

Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/

Recent experience(july) Coach showed up in my neck of the woods. Guy revived a coach, fixed a few things(fuel filters, put cherry bomb mufflers on because old ones were blown, few other things including new batteries) Took off from Pennsylvania and drove to mn. Had many other issues but ran strong and good power. Then while here in MN for a week, he had power issues. Seemed like fuel. Replaced fuel filters again, and they were dirty already. Full tune up. No improvement. We swapped on a spare carb and that fixed it. So from what your story is, i am leaning toward carb has some issues that are now shown up from bad gas. -- Jon Roche 75 palm beach EBL EFI, manny headers, Micro Level, rebuilt most of coach now. St. Cloud, MN http://lqqkatjon.blogspot.com/