Q-jet Carb Trouble - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Blue85 · 03-11-2007, 11:28 PM

So heres the problem, when the truck sits for a couple days, it is a complete pain in the a** to start, cranks and cranks for a long time, and then slowly starts to fire, once its running once during the day it will start perfectly barley even turn over and she's running. Any ideas on whats happening, ever since the carb was rebuilt it has been doing this, and to top it off the guy that did the rebuild has skipped town.

regal8r · 03-11-2007, 11:40 PM

IIRC thats just how a carburated engine is...do u pump the pedal before starting it after it has been sitting a while? if so, your accelerator pump might be shot. could also be a fuel pump problem.

**LockDoc** · 03-11-2007, 11:51 PM

-
Don't know if this is your problem or not but it sounds like it.

http://ramchargercentral.com/index.p...howtoshow;id=6

LockDoc

Blue85 · 03-11-2007, 11:57 PM

regal8r, my other trucks fire right up, even after sitting for a month, and yes i giver a pump or 2 to prime it and set the choke.

pimperout · 03-12-2007, 12:02 AM

i have the exact same problem i have found that when i pump the gas exactly 5 times it will fire up like nothing

regal8r · 03-12-2007, 12:07 AM

Quote:

Originally Posted by Blue85

regal8r, my other trucks fire right up, even after sitting for a month, and yes i giver a pump or 2 to prime it and set the choke.

sounds like its a fuel pump problem then

Blue85 · 03-12-2007, 12:12 AM

thought about the pump, but if i pull the fuel filter from the carb, there is lots of gas in the housing, think i'm gonna swap carbs with another truck and see if it starts better if no difference then i'll try a different pump

jhow66 · 03-12-2007, 12:22 AM

Sounds like your main well plugs are leaking. Carb is empty when you go to start it. Next time it sets for a few days before you go to start it pour a little gas in carb. If it starts right up and then dies this may be your problem.

jhow66 · 03-12-2007, 12:29 AM

This will show you what I am talking about. (scroll down to #12 photo)
http://www.carcraft.com/howto/57178/

**oldiron** · 03-12-2007, 12:34 AM

I agree with jhow66 about the leaking plugs. Q-jets were famous for that.

Blue85 · 03-12-2007, 12:38 AM

thanks for all of the input guys, i got another question for you, my buddy has a 81 that floods itself out when the motor is warm, and he shuts it off. Starts great when cold though, any ideas?

cooters · 03-12-2007, 08:44 AM

your buddy may have a choke that does not open completely. On yours, before starting , remove air cleaner and manually hit the throttle and watch for fuel to spray from the accelerator pump nozzle. My guess is there will be no fuel. Keep pumping till you see fuel, how many pumps does it take?

sneakysnake · 03-12-2007, 09:34 AM

I lightly scanned the above, Have you checked your "Acceleration pump" the one that squirts a stream of gas into the barrels when the pedal is pushed?
Sounds like you may not be getting the fuel you need for startup.

**WorkinLonghorn** · 03-12-2007, 11:08 AM

Jhow66 nailed it. That exact same problem (leaking Q-Jet) saved my last '69 from being stolen,they couldn't get it started. But I've heard that gas trickling down into your engine can wash away the oil in the cylinders and cause extra wear there so you really should pull it off and seal it up.

Blue85 · 03-12-2007, 03:02 PM

Man do i ever love this site, tore down the carb today, and sure enough, I could see where the old expoxy was detereoraited and the plugs were leaking from, so i ground the old junk out and resealed with jb weld, find out tomorrow if it worked. Any other tips on things i could do with the carb while its apart?

jacobs · 03-12-2007, 04:57 PM

The nozzles where the fuel is discharged into the venturies from the accelerator pump will sometimes plug. I've had this problem several times. Right now, one of mine is plugged and I need to fix it. If both plug, it's the same symptoms as a bad accelerator pump.

gmc1969custom · 03-12-2007, 05:28 PM

It sounds like you have your problem solved but you might also want to make sure your choke is working properly, I was having the same problem a few weeks ago. My problem was my choke linkage, it was not allowing the front butterfly to close completely on a cool morning. Now after a little bit of tinkering and freeing up the linkage, I just get in my truck, pump it once and within 2-4 seconds she fires right up everytime. Pumping it a few times doesnt hurt anything, but IMO a properly tuned Q-Jet should only have to be pumped 1 time to set the choke and it should fire up within seconds.

Blue85 · 03-13-2007, 07:21 PM

Well, i sealed up the holes, put a new accelerator pump in it, put it back together, installed it, and it fired up right away, now the real test is when i leave it overnight and see how it starts tomorrow. Thanks alot to everyone who helped me solve the problem.

03-11-2007, 11:40 PM	#2
regal8r Registered User Join Date: Oct 2006 Location: Lincoln, Nebraska Posts: 112	Re: Q-jet Carb Trouble IIRC thats just how a carburated engine is...do u pump the pedal before starting it after it has been sitting a while? if so, your accelerator pump might be shot. could also be a fuel pump problem.

03-11-2007, 11:51 PM	#3
LockDoc The Older Generation Join Date: Aug 2006 Location: Montezuma, Iowa Posts: 25,772	Re: Q-jet Carb Trouble - Don't know if this is your problem or not but it sounds like it. http://ramchargercentral.com/index.p...howtoshow;id=6 LockDoc __________________ Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 -

03-11-2007, 11:57 PM	#4
Blue85 Oilfield Trash Join Date: Sep 2003 Location: Raymore, Sk, Canada, Earth Posts: 3,170	Re: Q-jet Carb Trouble regal8r, my other trucks fire right up, even after sitting for a month, and yes i giver a pump or 2 to prime it and set the choke. __________________ 14 Dodge 3500 Mega Cab 08 Dodge 3500 Mega Cab 87 Chev 3+3 4x4 80 GMC K10 High Sierra bone stock 70 Chevelle 350SS long term project 68 GMC 3ton Grain Truck/Garbage wagon 50 Pontiac 2 Door Coupe Project "I've got a shotgun rifle and a 4 wheel drive and a country boy can survive" Hank Jr.

03-12-2007, 12:02 AM	#5
pimperout Registered User Join Date: Sep 2006 Location: Bow Island, AB, Canada Posts: 166	Re: Q-jet Carb Trouble i have the exact same problem i have found that when i pump the gas exactly 5 times it will fire up like nothing

03-12-2007, 12:12 AM	#7
Blue85 Oilfield Trash Join Date: Sep 2003 Location: Raymore, Sk, Canada, Earth Posts: 3,170	Re: Q-jet Carb Trouble thought about the pump, but if i pull the fuel filter from the carb, there is lots of gas in the housing, think i'm gonna swap carbs with another truck and see if it starts better if no difference then i'll try a different pump __________________ 14 Dodge 3500 Mega Cab 08 Dodge 3500 Mega Cab 87 Chev 3+3 4x4 80 GMC K10 High Sierra bone stock 70 Chevelle 350SS long term project 68 GMC 3ton Grain Truck/Garbage wagon 50 Pontiac 2 Door Coupe Project "I've got a shotgun rifle and a 4 wheel drive and a country boy can survive" Hank Jr.

03-11-2007, 11:28 PM	#1
Blue85 Oilfield Trash Join Date: Sep 2003 Location: Raymore, Sk, Canada, Earth Posts: 3,170	Q-jet Carb Trouble So heres the problem, when the truck sits for a couple days, it is a complete pain in the a** to start, cranks and cranks for a long time, and then slowly starts to fire, once its running once during the day it will start perfectly barley even turn over and she's running. Any ideas on whats happening, ever since the carb was rebuilt it has been doing this, and to top it off the guy that did the rebuild has skipped town. __________________ 14 Dodge 3500 Mega Cab 08 Dodge 3500 Mega Cab 87 Chev 3+3 4x4 80 GMC K10 High Sierra bone stock 70 Chevelle 350SS long term project 68 GMC 3ton Grain Truck/Garbage wagon 50 Pontiac 2 Door Coupe Project "I've got a shotgun rifle and a 4 wheel drive and a country boy can survive" Hank Jr.

03-12-2007, 12:22 AM	#8
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	Re: Q-jet Carb Trouble Sounds like your main well plugs are leaking. Carb is empty when you go to start it. Next time it sets for a few days before you go to start it pour a little gas in carb. If it starts right up and then dies this may be your problem. __________________ 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

03-12-2007, 12:29 AM	#9
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	Re: Q-jet Carb Trouble This will show you what I am talking about. (scroll down to #12 photo) http://www.carcraft.com/howto/57178/ __________________ 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 Last edited by jhow66; 03-12-2007 at 12:30 AM.

03-12-2007, 12:34 AM	#10
oldiron Designated Grumpy Old Man Join Date: Oct 2001 Location: arlington, washington usa Posts: 3,094	Re: Q-jet Carb Trouble I agree with jhow66 about the leaking plugs. Q-jets were famous for that. __________________ Never let the truth get in the way of a good story 71 Chev 1/2 ton 4X4 LWB Fleetside SOLD http://67-72chevytrucks.com/vboard/s...d.php?t=361222 http://www.youtube.com/watch?v=1LgREwtDfaA 68 Chev 1 ton flat bed http://www.youtube.com/watch?v=0bO8szzlD4A 56 Chev Handyman Wagon http://www.youtube.com/watch?v=9y-6ddpBTkM http://www.youtube.com/watch?v=lbLzZ7zY8wA 56 Chev Belair http://67-72chevytrucks.com/vboard/s...d.php?t=410667 http://www.youtube.com/watch?v=xoW0Ei7ZNIg

03-12-2007, 12:38 AM	#11
Blue85 Oilfield Trash Join Date: Sep 2003 Location: Raymore, Sk, Canada, Earth Posts: 3,170	Re: Q-jet Carb Trouble thanks for all of the input guys, i got another question for you, my buddy has a 81 that floods itself out when the motor is warm, and he shuts it off. Starts great when cold though, any ideas? __________________ 14 Dodge 3500 Mega Cab 08 Dodge 3500 Mega Cab 87 Chev 3+3 4x4 80 GMC K10 High Sierra bone stock 70 Chevelle 350SS long term project 68 GMC 3ton Grain Truck/Garbage wagon 50 Pontiac 2 Door Coupe Project "I've got a shotgun rifle and a 4 wheel drive and a country boy can survive" Hank Jr.

03-12-2007, 08:44 AM	#12
cooters Senior Member Join Date: Oct 2006 Location: Edmonton Alberta Posts: 458	Re: Q-jet Carb Trouble your buddy may have a choke that does not open completely. On yours, before starting , remove air cleaner and manually hit the throttle and watch for fuel to spray from the accelerator pump nozzle. My guess is there will be no fuel. Keep pumping till you see fuel, how many pumps does it take?

03-12-2007, 09:34 AM	#13
sneakysnake It's a catastrophic success. Join Date: Jan 2003 Location: Oklahoma Posts: 2,077	Re: Q-jet Carb Trouble I lightly scanned the above, Have you checked your "Acceleration pump" the one that squirts a stream of gas into the barrels when the pedal is pushed? Sounds like you may not be getting the fuel you need for startup.

03-12-2007, 11:08 AM	#14
WorkinLonghorn Senior Member Join Date: Dec 2006 Location: Studio City, Calif. Posts: 2,883	Re: Q-jet Carb Trouble Jhow66 nailed it. That exact same problem (leaking Q-Jet) saved my last '69 from being stolen,they couldn't get it started. But I've heard that gas trickling down into your engine can wash away the oil in the cylinders and cause extra wear there so you really should pull it off and seal it up. __________________ '69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme.

03-12-2007, 03:02 PM	#15
Blue85 Oilfield Trash Join Date: Sep 2003 Location: Raymore, Sk, Canada, Earth Posts: 3,170	Re: Q-jet Carb Trouble Man do i ever love this site, tore down the carb today, and sure enough, I could see where the old expoxy was detereoraited and the plugs were leaking from, so i ground the old junk out and resealed with jb weld, find out tomorrow if it worked. Any other tips on things i could do with the carb while its apart? __________________ 14 Dodge 3500 Mega Cab 08 Dodge 3500 Mega Cab 87 Chev 3+3 4x4 80 GMC K10 High Sierra bone stock 70 Chevelle 350SS long term project 68 GMC 3ton Grain Truck/Garbage wagon 50 Pontiac 2 Door Coupe Project "I've got a shotgun rifle and a 4 wheel drive and a country boy can survive" Hank Jr.

03-12-2007, 04:57 PM	#16
jacobs Registered User Join Date: Sep 2005 Location: 9000' Mountain Man Posts: 326	Re: Q-jet Carb Trouble The nozzles where the fuel is discharged into the venturies from the accelerator pump will sometimes plug. I've had this problem several times. Right now, one of mine is plugged and I need to fix it. If both plug, it's the same symptoms as a bad accelerator pump.



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03-12-2007, 05:28 PM	#17
gmc1969custom Registered User Join Date: Jan 2007 Location: Canton, TX Posts: 211	Re: Q-jet Carb Trouble It sounds like you have your problem solved but you might also want to make sure your choke is working properly, I was having the same problem a few weeks ago. My problem was my choke linkage, it was not allowing the front butterfly to close completely on a cool morning. Now after a little bit of tinkering and freeing up the linkage, I just get in my truck, pump it once and within 2-4 seconds she fires right up everytime. Pumping it a few times doesnt hurt anything, but IMO a properly tuned Q-Jet should only have to be pumped 1 time to set the choke and it should fire up within seconds. __________________ 1969 Custom w/Turquoise Interior. 75k miles, 350 V8, THM400 (Almost) All Original Last edited by gmc1969custom; 03-13-2007 at 10:02 AM.

03-13-2007, 07:21 PM	#18
Blue85 Oilfield Trash Join Date: Sep 2003 Location: Raymore, Sk, Canada, Earth Posts: 3,170	Re: Q-jet Carb Trouble Well, i sealed up the holes, put a new accelerator pump in it, put it back together, installed it, and it fired up right away, now the real test is when i leave it overnight and see how it starts tomorrow. Thanks alot to everyone who helped me solve the problem. __________________ 14 Dodge 3500 Mega Cab 08 Dodge 3500 Mega Cab 87 Chev 3+3 4x4 80 GMC K10 High Sierra bone stock 70 Chevelle 350SS long term project 68 GMC 3ton Grain Truck/Garbage wagon 50 Pontiac 2 Door Coupe Project "I've got a shotgun rifle and a 4 wheel drive and a country boy can survive" Hank Jr.

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