Quadrajet acting up when cold. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

skokie · 02-12-2005, 02:37 AM

When I first go to start the truck I give the pedal a one stab and it wont fire up. I went out popped the hood, remove the air cleaner and low and behold the choke is almost fully closed. So I go back to the truck hit the gas pedal 3-4 more times and it fires up. Go's to a fast idle of 1200-1300 and its fine. I can drive it for hours and shut up down and it will fire back up. The truck is setup with 5/16 lines and I have a 3/8 L metal line ( about 4-5 inches long) going down to a rubber fuel line which is 4 inches to a metal 5/16 line which is running to the pump and the line to the tank is 5/16. Not sure if that info s needed but hey who knows

Any thought on what is causing this? Carb just got rebuilt so I am pretty sure thats not it.

Thanks

4x4Poet · 02-12-2005, 02:55 AM

Since you say the carb (& engine) run fine once warm, I would suspect the choke circuit. My first check would be whether the choke, when closed, is still slightly open to factory specs. Second check would be...uh,,,umm. Hmm. I don't have a second check.

Actually, I think my second check needs to be electric, rod-to-intake-mounted coil, or manual choke specific. Which do you have? (Hopefully, someone else will be my second.

)

Float bowl draining could also be involved, but I'm not up on step-by-step solutions.

skokie · 02-12-2005, 03:07 AM

It's a divorced style choke.

GMC AMI · 02-12-2005, 08:23 AM

When cold with a flashlight look in carb. with choke open and pump the gas a couple of squirts. You should be able to see if the accel. pump is working. If no gas is visable it may well mean the float bowl is draining back. I have seen quadra bogs do this before. When they work right they are great carbs.

neonlarry · 02-12-2005, 08:54 AM

Do the above check, it sounds like you might have leaking fuel bowl plugs (a common problem w\QJets). Somewhat easy fix just have to take carb apart.

skokie · 02-13-2005, 01:26 AM

Ok i popped off the aircleaner and pumped the throttle rod. That carb is getting gas no prob. Here is a pic from above of my qjet after one press of the gas pedal.

*chevytruckfan* · 02-15-2005, 08:17 PM

Quote:

Originally Posted by skokie

Ok i popped off the aircleaner and pumped the throttle rod. That carb is getting gas no prob. Here is a pic from above of my qjet after one press of the gas pedal.

Ok in that pic your choke plates are only slightly open when cold. Mine are fully open with the engine cold. Should the choke plates be open or closed when cold?

**smitty62** · 02-15-2005, 09:38 PM

Should closed or very nearly so.
GM's recomended way of starting a Quad "when cold" is: press the accelerator to the floor once-release--then start. Twice is ok, but more than that and it's not adjusted right. If it's set a few days and needs severe pumping--the fuel is leaking off somewhere and you're actually refilling the float bowl. A traditional Quadrajet failing.
Some people even put an electric pump in tandem with the mechanical--running the electric for a few seconds before starting to fill the bowl, then letting the mechanical take over.

skokie · 02-13-2005, 01:40 AM

Something else I just thought of. My airclearner has the snorkel with the little door on the inside of it. If that is shut could that cause a prob? Also should that choke be closed anymore than it is?

cheyenne10 · 02-13-2005, 01:48 AM

The way I was taught to set choke when cold was to depress pedal all the way to the floor and let it up real slow (1-2 seconds). This should set choke for cold start and high idle. Maybe this helps or not.

GMC AMI · 02-13-2005, 12:12 PM

Quote:

Originally Posted by skokie

Something else I just thought of. My airclearner has the snorkel with the little door on the inside of it. If that is shut could that cause a prob? Also should that choke be closed anymore than it is?

Hi Brad, to me that choke if cold outside is open too much. That would explain why you needed more pumps to fire up. Mike

**VetteVet** · 02-14-2005, 01:47 AM

Quote:

Originally Posted by skokie

Something else I just thought of. My airclearner has the snorkel with the little door on the inside of it. If that is shut could that cause a prob? Also should that choke be closed anymore than it is?

This item is called the heat stove and it's purpose is to direct heated air from the exhaust manifold to the air intake via a flexible tube to the snorkel.
I expect you have probably removed this feature. The little baffle plate in the snorkel is operated by vacuum from the intake manifold or other vacuum source. The primary purpose of this little gem is to assure that the carburetor intake does not ice up in cold, high humidity weather.
Since you live in Cal. it isn't a factor. You can disregard it as long as the vacuum line that feeds it is disconnected and the source is plugged.

Vettevet

**smitty62** · 02-14-2005, 05:31 PM

If the truck was truely cold when you took the pic, it's not closed enough. It should be closed all the way when cold and the engine vacuum will pull it open slightly immediately when it starts. The choke just needs adjusting slightly and it doesn't need gaskets, new parts etc! Buy a Quadrajet book--you'll need it later anyway if you're going to keep the truck.

hotrodtroy · 02-14-2005, 06:00 PM

Try this it has a lot of good info

Quadra Jets

*chevytruckfan* · 02-13-2005, 02:33 AM

If you have the divorce style choke. Pump the pedal and turn it over then check the choke pulloff and make sure it has sucked back into the diapharam. I had the same problem, chock pulloff not working right made it had to start but once the spring warmed up no problem. Once I got mine fixed it started right up just had to adjust the fast idle ajustment.

skokie · 02-13-2005, 03:03 AM

chevytruckfan I am not following you. Is the choke pulloff the white piece on the left in the pic?
thanks

72 CustomCamper · 02-13-2005, 03:09 AM

This is the choke pulloff...

Chuck

skokie · 02-13-2005, 03:25 AM

If you mean this one circled in blue then ys ot does go back into the diapharam after I push the pedal.

*chevytruckfan* · 02-13-2005, 02:07 PM

Quote:

Originally Posted by skokie

If you mean this one circled in blue then ys ot does go back into the diapharam after I push the pedal.

No it is the thin flat metal piece to the right of it. It should be pulled into the diaphram (white plastic piece) when vacuum is applied once you first crank the engine over.

skokie · 02-13-2005, 04:45 PM

Quote:

Originally Posted by chevytruckfan

No it is the thin flat metal piece to the right of it. It should be pulled into the diaphram (white plastic piece) when vacuum is applied once you first crank the engine over.

Update :
I cranked the truck and it was pulled into the diaphram.

What else can I check?

*rage'nrat638* · 02-13-2005, 08:30 PM

your on the right track my brother.....the devorced choke coil should pull the choke closed all the way......

the pull off will open it ....to the correct amount....if adjusted correctly....

mine has a little stumble....filling the power brake booster that bleeds off
after sitting a long time......

bend the rod....with it cold to pull choke plate closed all the way.....

*rage'nrat638* · 02-13-2005, 08:36 PM

in fact after looking at your picture i see your using a very thin mounting gasket.....
i like the stock gasket you get at the auto parts store about 1/4 thick...
put one of those in and that will adjust the rod for you...might even give you a better seal....

check out the one in my picture.....this gasket has plastic barrels where the bolts go thru....to keep from over tighting

skokie · 02-13-2005, 02:01 PM

Thanks Mike. Guess its back to adjusting the choke rod. Should I make it longer or shorter?

Thanks

skokie · 02-13-2005, 10:38 PM

I will shorten the rod and see what happens.

skokie · 02-14-2005, 10:52 PM

I am going to adjust the rod and post back. I will try making it shorter and see if that does it.

02-12-2005, 02:37 AM	#1
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,342	Quadrajet acting up when cold. When I first go to start the truck I give the pedal a one stab and it wont fire up. I went out popped the hood, remove the air cleaner and low and behold the choke is almost fully closed. So I go back to the truck hit the gas pedal 3-4 more times and it fires up. Go's to a fast idle of 1200-1300 and its fine. I can drive it for hours and shut up down and it will fire back up. The truck is setup with 5/16 lines and I have a 3/8 L metal line ( about 4-5 inches long) going down to a rubber fuel line which is 4 inches to a metal 5/16 line which is running to the pump and the line to the tank is 5/16. Not sure if that info s needed but hey who knows Any thought on what is causing this? Carb just got rebuilt so I am pretty sure thats not it. Thanks __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

02-12-2005, 02:55 AM	#2
4x4Poet Registered User Join Date: Nov 2004 Location: "Under Montana skies." Posts: 1,836	Since you say the carb (& engine) run fine once warm, I would suspect the choke circuit. My first check would be whether the choke, when closed, is still slightly open to factory specs. Second check would be...uh,,,umm. Hmm. I don't have a second check. Actually, I think my second check needs to be electric, rod-to-intake-mounted coil, or manual choke specific. Which do you have? (Hopefully, someone else will be my second.) Float bowl draining could also be involved, but I'm not up on step-by-step solutions. __________________ '71 GMC K20 Suburban, '71 GMC K10 Suburban, '72 Chevy C10 CST Suburban, '72 Chevy K20 clunker pickup. Last edited by 4x4Poet; 02-12-2005 at 02:58 AM.

02-12-2005, 03:07 AM	#3
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,342	It's a divorced style choke. __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

02-12-2005, 08:23 AM	#4
GMC AMI Registered User Join Date: Apr 2004 Location: The Other Maine! Posts: 2,236	When cold with a flashlight look in carb. with choke open and pump the gas a couple of squirts. You should be able to see if the accel. pump is working. If no gas is visable it may well mean the float bowl is draining back. I have seen quadra bogs do this before. When they work right they are great carbs. __________________ 1968 Chevy 4x4 307 4 speed

02-12-2005, 08:54 AM	#5
neonlarry Registered User Join Date: Feb 2002 Location: Vacaville, CA Posts: 2,746	Do the above check, it sounds like you might have leaking fuel bowl plugs (a common problem w\QJets). Somewhat easy fix just have to take carb apart. __________________ 70 C/10 Light Red 350/TH350, HEI, Duals w/40 series Flows, 91 seat, LED taillights 99 Pontiac S/C GTP, SLP Ram Air hood, GMPP Konis & springs 95 Neon ACR, MP PCM, AFX UDP, 3.0 CAI

02-13-2005, 01:26 AM	#6
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,342	Ok i popped off the aircleaner and pumped the throttle rod. That carb is getting gas no prob. Here is a pic from above of my qjet after one press of the gas pedal. Attached Images __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

02-15-2005, 09:38 PM	#8
smitty62 Registered User Join Date: May 2002 Location: North Carolina Posts: 1,234	Should closed or very nearly so. GM's recomended way of starting a Quad "when cold" is: press the accelerator to the floor once-release--then start. Twice is ok, but more than that and it's not adjusted right. If it's set a few days and needs severe pumping--the fuel is leaking off somewhere and you're actually refilling the float bowl. A traditional Quadrajet failing. Some people even put an electric pump in tandem with the mechanical--running the electric for a few seconds before starting to fill the bowl, then letting the mechanical take over. __________________ Stepsides look like real trucks! Smitty

02-13-2005, 01:40 AM	#9
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,342	Something else I just thought of. My airclearner has the snorkel with the little door on the inside of it. If that is shut could that cause a prob? Also should that choke be closed anymore than it is? __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

02-13-2005, 01:48 AM	#10
cheyenne10 Senior Member Join Date: Apr 2000 Location: Oregon Posts: 2,512	setting choke The way I was taught to set choke when cold was to depress pedal all the way to the floor and let it up real slow (1-2 seconds). This should set choke for cold start and high idle. Maybe this helps or not. __________________ Bob

02-14-2005, 05:31 PM	#13
smitty62 Registered User Join Date: May 2002 Location: North Carolina Posts: 1,234	If the truck was truely cold when you took the pic, it's not closed enough. It should be closed all the way when cold and the engine vacuum will pull it open slightly immediately when it starts. The choke just needs adjusting slightly and it doesn't need gaskets, new parts etc! Buy a Quadrajet book--you'll need it later anyway if you're going to keep the truck. __________________ Stepsides look like real trucks! Smitty Last edited by smitty62; 02-14-2005 at 05:33 PM.

02-14-2005, 06:00 PM	#14
hotrodtroy Registered User Join Date: Feb 2004 Location: Colorado Springs, CO Posts: 138	Try this it has a lot of good info Quadra Jets __________________ '72 C-10 w/ '68 Large Journal 327cu.in. "It's o.k. to dream about what you want to do, until you start doing what you are meant to do." Line from "The Rookie"

02-13-2005, 02:33 AM	#15
chevytruckfan Account Suspended Join Date: May 2004 Location: Lake Placid, Florida Posts: 930	If you have the divorce style choke. Pump the pedal and turn it over then check the choke pulloff and make sure it has sucked back into the diapharam. I had the same problem, chock pulloff not working right made it had to start but once the spring warmed up no problem. Once I got mine fixed it started right up just had to adjust the fast idle ajustment.

02-13-2005, 03:03 AM	#16
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,342	chevytruckfan I am not following you. Is the choke pulloff the white piece on the left in the pic? thanks __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

02-13-2005, 03:09 AM	#17
72 CustomCamper huh ??? Join Date: Nov 2002 Location: Fredericksburg,Va. Posts: 3,369	This is the choke pulloff... Chuck Attached Images __________________ 90 Blazer Silverado 350w/ 700R4 and 32" Kelly's "I am a bomb technician. If you see me running try to keep up!"

02-13-2005, 03:25 AM	#18
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,342	If you mean this one circled in blue then ys ot does go back into the diapharam after I push the pedal. Attached Images __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234



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02-13-2005, 08:30 PM	#21
rage'nrat638 Account Suspended Join Date: Mar 2003 Location: THE FALL GUY CHICAGO IL Posts: 5,883	your on the right track my brother.....the devorced choke coil should pull the choke closed all the way...... the pull off will open it ....to the correct amount....if adjusted correctly.... mine has a little stumble....filling the power brake booster that bleeds off after sitting a long time...... bend the rod....with it cold to pull choke plate closed all the way.....

02-13-2005, 08:36 PM	#22
rage'nrat638 Account Suspended Join Date: Mar 2003 Location: THE FALL GUY CHICAGO IL Posts: 5,883	in fact after looking at your picture i see your using a very thin mounting gasket..... i like the stock gasket you get at the auto parts store about 1/4 thick... put one of those in and that will adjust the rod for you...might even give you a better seal.... check out the one in my picture.....this gasket has plastic barrels where the bolts go thru....to keep from over tighting Last edited by rage'nrat638; 07-12-2007 at 07:05 AM.

02-13-2005, 02:01 PM	#23
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,342	Thanks Mike. Guess its back to adjusting the choke rod. Should I make it longer or shorter? Thanks __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

02-13-2005, 10:38 PM	#24
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,342	I will shorten the rod and see what happens. __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

02-14-2005, 10:52 PM	#25
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,342	I am going to adjust the rod and post back. I will try making it shorter and see if that does it. __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

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