Help! Q Jet problem, again - The 1947 - Present Chevrolet & GMC Truck Message Board Network

dion · 12-07-2002, 04:52 PM

Here's what it's doing, it won't stay running at all, I have to keep the pedal down all the time, if I even let up even fpr a second it dies, it will die just going around a corner unless I keep the pedal down. It's very very rich and the engine gallops instead of loops. I have to put the pedal almost all the way down for it to really get going, even on the Highway.
So the two little screws at the bottom are the air and the bigger one above it the fast idle?

bigvinnie · 12-07-2002, 05:02 PM

had the same problem off an on til I got it rebuilt.... in my case it was the needle valve sticking open, probably for a number of reasons... gunk in the float bowl, gummed up from varnish, etc... I could fix it temporarily by pulling the carb, holding it upside down and shaking the he!! out of it...

put it back on and it would be fine for a couple weeks, then it would flood and I'd have to do it again... sounds ridiculous but it worked til I had the cash to get it rebuilt.

dion · 12-07-2002, 05:04 PM

This carb is about a week old, the other one I had on there was screwed up so they replaced it but this one has even more problems. Can't wait for that Holley 750 to get here.

jhow66 · 12-07-2002, 05:31 PM

Do you have a fliter on gas line? Is the one still in carb inlet? There is a piece of dirt etc. under needle. Take the fuel line loose from the side of fuel pump that comes from tank and plug off with a 3/8 bolt etc. Start engine and run until it stops. Reconnect gas line and start engine. This should wash and dirt under needle out and let it seal off. (Be sure you have some kind of filter.)
Was this a new carb?

chevy2racr · 12-07-2002, 06:48 PM

mine did somethign like that once, only, it'd fire fora second and die, fre and die, just fillin it full of fuel, I got me a holley Q-jey replacemment, its spead bore holley..
no problems since

supercheyenne · 12-08-2002, 03:19 AM

http://www.73-87.com/garage/myqjet.htm

See if he has any info (or links) that would help.

supercheyenne · 12-08-2002, 03:28 AM

Setting idle

http://www.73-87.com/garage/qjetidle.htm

dion · 12-08-2002, 03:00 PM

It seems that the mix and idle just aren't set right, when looking at the front of the carb the two screws at the base on either sides are the mix and the larger one above them on the right is the idle, right? i know you havr to keep the two at the bottom even, and I know they are not so can I just lightly tighten them both all the way and then bring them out evenly until it's running correctly? On the idle screw which was is fast and slow? Clock wise or counter clock wise? Thanks for the help guys. I'm just trying to get this thing to run decently for a week or so, I bought a Holley 750 that I'm going to switch it out with.

supercheyenne · 12-08-2002, 06:26 PM

http://www.geocities.com/novaessess/R4ex.htm

Exploded view of a 4 barrel Q-Jet.
Idle screws are #41.

Try this link first. There's also a link on that page for setting idle.
http://www.carbs.net/troubleshoot.htm

12-07-2002, 04:52 PM	#1
dion 72 Cheyenne Join Date: Oct 2001 Location: San Diego Posts: 2,086	Help! Q Jet problem, again Here's what it's doing, it won't stay running at all, I have to keep the pedal down all the time, if I even let up even fpr a second it dies, it will die just going around a corner unless I keep the pedal down. It's very very rich and the engine gallops instead of loops. I have to put the pedal almost all the way down for it to really get going, even on the Highway. So the two little screws at the bottom are the air and the bigger one above it the fast idle? __________________ Burnout Idle 1972Cheyenne 1966/67Stouts Last edited by dion; 12-07-2002 at 04:58 PM.

12-07-2002, 05:02 PM	#2
bigvinnie Registered User Join Date: Aug 2001 Location: escondido, ca 92026 Posts: 1,222	had the same problem off an on til I got it rebuilt.... in my case it was the needle valve sticking open, probably for a number of reasons... gunk in the float bowl, gummed up from varnish, etc... I could fix it temporarily by pulling the carb, holding it upside down and shaking the he!! out of it... put it back on and it would be fine for a couple weeks, then it would flood and I'd have to do it again... sounds ridiculous but it worked til I had the cash to get it rebuilt. __________________ '72 short step, 350, 700R4, tilt, ps, pdb, a/c, lowered coils, etc., other work in progress... San Diego, CA 72 Stepside Project

12-07-2002, 05:04 PM	#3
dion 72 Cheyenne Join Date: Oct 2001 Location: San Diego Posts: 2,086	This carb is about a week old, the other one I had on there was screwed up so they replaced it but this one has even more problems. Can't wait for that Holley 750 to get here. __________________ Burnout Idle 1972Cheyenne 1966/67Stouts

12-07-2002, 06:48 PM	#5
chevy2racr So Many Ideas, So Little Money Join Date: Sep 2001 Location: Marshalltown, IA Posts: 1,610	mine did somethign like that once, only, it'd fire fora second and die, fre and die, just fillin it full of fuel, I got me a holley Q-jey replacemment, its spead bore holley.. no problems since __________________ 72 Blazer 3/4 ton running gear 4.10s NP205/TH350 350 4in lift half doors 71 C10 with 454 99 S-10 5.1L SBC 700R4 09 Malibu Marshalltown, Iowa

12-08-2002, 03:19 AM	#6
supercheyenne Registered User Join Date: Dec 1999 Location: Newton, KS, U.S.A. Posts: 1,142	Try this for tuning info http://www.73-87.com/garage/myqjet.htm See if he has any info (or links) that would help.

12-07-2002, 05:31 PM	#4
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	Carb flooding Do you have a fliter on gas line? Is the one still in carb inlet? There is a piece of dirt etc. under needle. Take the fuel line loose from the side of fuel pump that comes from tank and plug off with a 3/8 bolt etc. Start engine and run until it stops. Reconnect gas line and start engine. This should wash and dirt under needle out and let it seal off. (Be sure you have some kind of filter.) Was this a new carb? __________________ 56 Chevy Bel-Air 2dr. HT (purchased new) 71 Chevy Cheyenne SWB PU (502HO) 65 GMC short bed step--work in progress and my gofer

12-08-2002, 03:28 AM	#7
supercheyenne Registered User Join Date: Dec 1999 Location: Newton, KS, U.S.A. Posts: 1,142	more links same site Setting idle http://www.73-87.com/garage/qjetidle.htm

12-08-2002, 03:00 PM	#8
dion 72 Cheyenne Join Date: Oct 2001 Location: San Diego Posts: 2,086	It seems that the mix and idle just aren't set right, when looking at the front of the carb the two screws at the base on either sides are the mix and the larger one above them on the right is the idle, right? i know you havr to keep the two at the bottom even, and I know they are not so can I just lightly tighten them both all the way and then bring them out evenly until it's running correctly? On the idle screw which was is fast and slow? Clock wise or counter clock wise? Thanks for the help guys. I'm just trying to get this thing to run decently for a week or so, I bought a Holley 750 that I'm going to switch it out with. __________________ Burnout Idle 1972Cheyenne 1966/67Stouts

12-08-2002, 06:26 PM	#9
supercheyenne Registered User Join Date: Dec 1999 Location: Newton, KS, U.S.A. Posts: 1,142	http://www.geocities.com/novaessess/R4ex.htm Exploded view of a 4 barrel Q-Jet. Idle screws are #41. Try this link first. There's also a link on that page for setting idle. http://www.carbs.net/troubleshoot.htm



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