Q-Jet Rebuild - Problems Starting
Thread Starter
Racer
Joined: May 2013
Posts: 421
Likes: 6
From: Chicago IL
Q-Jet Rebuild - Problems Starting
I recently rebuilt my Q-jet per the paper from Lars and after installing it, the car would start and then die. I made sure the mixture screws were turned out 6 turns per the recommendation and it still does it. If I keep the rpm's up, it will eventually warm up and run ok. If I cover the air horn, the idle goes up and evens out. Does this mean it is running too lean? The only other thing I can think of is there is an air leak in the new gasket, but the bolts are torqued to spec. I have noticed the fan clutch getting much louder once the car is warmed up and accelerating as well - could that be from running too lean and the engine getting hotter?
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
It's absolutely impossible to troubleshoot carb problems via e-mail or Forum posts. You're going to get 35 suggestions on the problem, and not one of them is going to be correct. Here are a few issues, but not all of the issues, that can cause your problem, but it may not be any of these issues. Only a physical inspection of the carb after disassembly can reveal the actual problem. These are only the most common issues that will cause your problem - there are a dozen other factors that can also cause the issue:
- Incorrect choke linkage adjustment
- Incorrect pulloff setting
- Incorrect float level
- Incorrect APT setting
- Plugged IFRs
- Ruptured pulloff
- Incorrect rod/jet combo
- Incorrect throttle plate gasket
- Incorrect base gasket
- Vacuum leak (internal or external)
- Faulty PCV system
- Missing low speed bleeds
- Warped float bowl
- Warped airhorn
Thread Starter
Racer
Joined: May 2013
Posts: 421
Likes: 6
From: Chicago IL
@Redman76 - I am not sure on the choke, but I did not change it from where it was at before when it worked ok. I am thinking I have to adjust it because when I prime the carb, the plate stays almost straight up and down and doesn't snap to almost closed. How do I do that?
@Lars - Thanks again for all of your help and patience. I cant confirm the ones below, but everything else I can confirm is correct and functioning. Since the car levels out after it warms up and/or if I block the air horn, I am thinking the problem has to be in the choke.
Incorrect choke linkage adjustment
Faulty PCV system
Missing low speed bleeds
@Lars - Thanks again for all of your help and patience. I cant confirm the ones below, but everything else I can confirm is correct and functioning. Since the car levels out after it warms up and/or if I block the air horn, I am thinking the problem has to be in the choke.
Incorrect choke linkage adjustment
Faulty PCV system
Missing low speed bleeds
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
On cold start, the choke should snap fully closed when the throttle is cracked open prior to engine start - if it's staying vertical, you have a choke setup issue.
Lars
Lars
Melting Slicks
Joined: May 2006
Posts: 2,590
Likes: 403
From: Nashville TN
St. Jude Donor '09
@Redman76 - I am not sure on the choke, but I did not change it from where it was at before when it worked ok. I am thinking I have to adjust it because when I prime the carb, the plate stays almost straight up and down and doesn't snap to almost closed. How do I do that?
Thread Starter
Racer
Joined: May 2013
Posts: 421
Likes: 6
From: Chicago IL
Lars has some great papers on adjusting choke and rebuilding carb, you can email him and he'll send them to you.
I am going to try and mess with it tonight and see if I can get the choke adjusted properly. Thanks for the help guys!
Racer
Joined: Nov 2004
Posts: 485
Likes: 1
From: Oakville ON
choke rod?
My guess is that the rod that moves vertically to pull the choke closed ("intermediate choke rod"?) is not engaged in the lever (flat arm) that connects to the choke shaft. The rod passes through the air horn and into the main body (external to any air flow) inside the triangular passage. It has to engage the lever. I have found the only way to get the 90* bend at the bottom of the rod to go throught the hole in the lever (I am no expert) is to rotate the lever fully upwards and pop the rod end in, then return the lever to its (normally cold) lower position. If I remember correctly, you manipulate the lever by rotating the choke, or maybe you can pull it up with a piece of coat hanger with a small 90* bend at its end. I believe the early carbs had the rod external, but at least for the '75 and later carbs it goes inside inside the triangular passage. It has been a loooong time. 
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Thread Starter
Racer
Joined: May 2013
Posts: 421
Likes: 6
From: Chicago IL
Update - Ok, I fixed the choke last night. For some reason, it was stuck open and I had to re-adjust the tension and duration of the choke for it to correct itself. Took it out for a spin and everything was ok until the last stretch at WOT - I started to bog down as the rpm's increased. Thinking it could be the secondary spring needs adjustment now. Today I start it up, warms up just fine and comes down to about 1000 rpm. I put it in drive and it falls below 650 rpm and stalls out! I had to raise my idle to 1200 rpm just to get it back into the garage. Why does it seem like you fix one problem and another one pops up with these things!
Last edited by Jartanyon; Jul 24, 2013 at 10:23 AM.