Accelerator Pump Off-Idle Stumble Adjustment
Thread Starter
Team Owner
Joined: Aug 1999
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From: Ontario
Accelerator Pump Off-Idle Stumble Adjustment
You find this diagram in many sites on the internet but it never states what is being measured, with what gauge, and to what tolerance. Can someone clue me in?
Here is the text.
ACCELERATOR PUMP ADJUSTMENT
1.) Close the primary throttle valves by backing out the 510w idle screw and making sure that the fast idle cam follower is off the steps of the fast idle cam.
2.) Bend the secondary throttle closing tang away from the primary throttle lever.
3.) With the pump in the appropriate hole in the pump lever, measure from the top of the choke valve wall to the top of the pump stem.
4.) To adjust, bend the pump lever while supporting it with a screwdriver.
5.) After adjusting, readjust the secondary throttle tang and the slow idle screw.
Measure what?
Here is the text.
ACCELERATOR PUMP ADJUSTMENT
1.) Close the primary throttle valves by backing out the 510w idle screw and making sure that the fast idle cam follower is off the steps of the fast idle cam.
2.) Bend the secondary throttle closing tang away from the primary throttle lever.
3.) With the pump in the appropriate hole in the pump lever, measure from the top of the choke valve wall to the top of the pump stem.
4.) To adjust, bend the pump lever while supporting it with a screwdriver.
5.) After adjusting, readjust the secondary throttle tang and the slow idle screw.
Measure what?
Last edited by Paul L; Nov 12, 2008 at 08:07 PM.
Race Director
Joined: May 2006
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From: Dayton, Ohio
Paul I tried my hand at coloring the area to measure.It was supposed to be red but its gray.Put your scale or ruler on top of accelerator plunger and measure up to the choke horn wall.The measurement depends on your # of carb. Aprox. 1/4 to 11/32
Thread Starter
Team Owner
Joined: Aug 1999
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From: Ontario
So you are not measuring a gap between the lever and the accelerator rod? That was my instinct.
Race Director
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From: Dayton, Ohio
Thread Starter
Team Owner
Joined: Aug 1999
Posts: 30,995
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From: Ontario
As a winter project I am trying to find an aluminum intake to replace the cast iron. But I can't find one with that type of EGR and the integral choke. Plan B is to find and use an electric choke (if available for that 7044206 carb) and a newer style EGR.
Last edited by Paul L; Nov 13, 2008 at 07:12 AM.
Thread Starter
Team Owner
Joined: Aug 1999
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From: Ontario
Melting Slicks
Joined: Nov 2005
Posts: 3,323
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From: Green Valley Arizona
That manifold should be easy to find....Edlebrock Performer I am sure has both of these....at least I am remembering seeing this when I was looking for a possible replacement for mine. I was looking for one without a EGR valve and electric choke and found one.
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Thread Starter
Team Owner
Joined: Aug 1999
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From: Ontario
From a full stop (stop sign, red light) it sputters a bit (1-2 seconds) at normal take-off. If I do a rolling take-off at 3-5mph it does not occur. Aside from this minor hiccup that drives me crazy the car just humms at speed! There is no hesitation if I hit WOT at any speed above idle.
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
I've never had to adjust a Q-Jet accel pump measurement to fix a stumble in the 1,000 Q-Jets I've rebuilt. If you have a stumble, it's not because of the pump adjustment.
More likely, the ethanol in your fuel has made the pump swell up and seize in the bore, thus not giving you a pump shot. If the pump locks up in the bore, the upper pump rod and lever arm will still move, but there will be no pump shot. Just look down the venturi and see if you are getting an instant shot of fuel on both sides - if not, you need to pull the airhorn off and replace the pump. If you are getting a pump shot on both sides and you still have a stumble, you have other fuel delivery or timing issues. But I'll bet you don't have an adjustment issue.
Lars
More likely, the ethanol in your fuel has made the pump swell up and seize in the bore, thus not giving you a pump shot. If the pump locks up in the bore, the upper pump rod and lever arm will still move, but there will be no pump shot. Just look down the venturi and see if you are getting an instant shot of fuel on both sides - if not, you need to pull the airhorn off and replace the pump. If you are getting a pump shot on both sides and you still have a stumble, you have other fuel delivery or timing issues. But I'll bet you don't have an adjustment issue.
Lars
Thread Starter
Team Owner
Joined: Aug 1999
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From: Ontario
I've never had to adjust a Q-Jet accel pump measurement to fix a stumble in the 1,000 Q-Jets I've rebuilt. If you have a stumble, it's not because of the pump adjustment.
More likely, the ethanol in your fuel has made the pump swell up and seize in the bore, thus not giving you a pump shot. If the pump locks up in the bore, the upper pump rod and lever arm will still move, but there will be no pump shot. Just look down the venturi and see if you are getting an instant shot of fuel on both sides - if not, you need to pull the airhorn off and replace the pump. If you are getting a pump shot on both sides and you still have a stumble, you have other fuel delivery or timing issues. But I'll bet you don't have an adjustment issue.
Lars
More likely, the ethanol in your fuel has made the pump swell up and seize in the bore, thus not giving you a pump shot. If the pump locks up in the bore, the upper pump rod and lever arm will still move, but there will be no pump shot. Just look down the venturi and see if you are getting an instant shot of fuel on both sides - if not, you need to pull the airhorn off and replace the pump. If you are getting a pump shot on both sides and you still have a stumble, you have other fuel delivery or timing issues. But I'll bet you don't have an adjustment issue.
Lars
Race Director
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From: Dayton, Ohio
Paul have you tried blocking the vacuum line going to the EGR valve and then testing to see if you still have the stumble?Back in the day some EGRs opened so quick they caused a stumble.
Thread Starter
Team Owner
Joined: Aug 1999
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From: Ontario
No, I haven't tried that. I'm making a list of things to check in the spring. That will be one.
Safety Car
Joined: Mar 2007
Posts: 3,652
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From: Bridgewater nj
If your acc. pump checks out OK like Lars said then check that dam EGR. They get crudded up, hang up, stick, ect....
Thread Starter
Team Owner
Joined: Aug 1999
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From: Ontario
I'm back-tracking mentally as that carb worked fine last May. In fact it was a re-build from NAPA. Worked fine initially after the car came to me with a bit of a messed-up Q-Jet that gave me some misery.
It was a "new" car to me at that time so I did a tune-up. The usual points, condensor, spark plugs, etc. I did replace the GM rather stiff distributor springs with "softer" versions. Those springs are from my former 1967. I'm beginning to wonder if that was a wise move.
It was a "new" car to me at that time so I did a tune-up. The usual points, condensor, spark plugs, etc. I did replace the GM rather stiff distributor springs with "softer" versions. Those springs are from my former 1967. I'm beginning to wonder if that was a wise move.
