Q -Jet carb help please?
06-11-2008, 07:36 AM
#1
Drifting
Thread Starter
Member Since: Aug 2004
Location: 2010 C6 Grand Sport Convertible
Posts: 1,321
Likes: 0
Received 4 Likes
on
4 Posts
Q -Jet carb help please?
My '78 has a replacement Edelbrock Q-Jet. The other day, I backed out of the garage, put her in drive and stepped on the gas, only to experience a backfire and hesitation on acceleration. The engine struggles as if the choke were partially closed, which it's not. No more backfiring has occured, only a bog on acceleration until I push the pedal down harder and get past that point. Nothing looks bent down the throttle openings. Carb cleaner down the carb while it's running hasn't helped either. I phoned Edlebrock yesterday. Edelbrock no longer sells nor supports the Q-Jet line of carbs, and would love to know where to begin to trouble shoot.
Thanks in advance.....
Mike
Thanks in advance.....
Mike
06-11-2008, 09:11 AM
#2
Melting Slicks
Make sure the accelerator pump is giving you a good shot of fuel into the primaries when you step on it. With the motor & air cleaner off rotate the linkage to WOT and observe. Other than that, go over the ignition timing, check advance. But like you said bro, it's just a place to start.
06-11-2008, 09:19 AM
#3
Racer
Member Since: Apr 2006
Location: Warrensburg MO
Posts: 340
Likes: 0
Received 0 Likes
on
0 Posts
Not sure if the car was warmed up yet, but if not, maybe the choke should be closed; at least partially. Make sure your choke is working along with the normal adjustments. Cheers
Tommy
Tommy
06-11-2008, 05:10 PM
#4
Melting Slicks
Sounds like you air valve is out of adjustment. Read Lars' sticky on the Quadrajet carburetor for the best in tech troubleshooting. 
06-12-2008, 06:44 AM
#5
Drifting
Thread Starter
Member Since: Aug 2004
Location: 2010 C6 Grand Sport Convertible
Posts: 1,321
Likes: 0
Received 4 Likes
on
4 Posts
I was reading Lar's tech notes last night. It has NO bog at all when I'm revving the motor in park. Once I drop it in drive and torque brake the car, the motor hesitates, bogs then finally pulls. So this condition is noticable when under load. I had replaced the fuel pump 6 months earlier. I'm wondering, since its a condition under load, if the $42 Advance Auto fuel pump hasn't taken a crap? Is there a somewhat reliable way to test the pump without a pressure gauge?
Mike
Mike
Last edited by 78pacer; 06-12-2008 at 06:47 AM.
06-12-2008, 06:51 AM
#6
Melting Slicks
No.
06-12-2008, 11:41 PM
#8
Melting Slicks
5-6 psi. If you have 7 or 8, it will dribble out the main boosters - very rich!
06-12-2008, 11:43 PM
#9
Melting Slicks
It still appears that you air valve adjustment is too loose. Set it to 3/4 to 7/8 of a turn and I'll bet your troubles go away.
06-13-2008, 12:08 AM
#10
Team Owner
Re-check your timing and make sure it hasn't shifted. If it is different from where you set it, you may have distributor problems or a timing chain problem.
