Choke kicks in to late

[Peer81]

Hello everybody,

Small problem with my quadrajet. The problem is the same from the first day I have the vette, not a really big problem but now that the vette is almost finished also the smallest problems need to be fixed.

Last week I reset the choke by Lars doc's, corrected the choke valve to get the ideal cold mixture with the screw on the front vacuum pot. The electrical choke is set a little les then stock to let go of the choke a little sooner. I set the choke RPM to 1000 to 1200 and the normal RPM to 650 - 700. Now the problem, when I start the engine cold the choke doesn't kickin from the beginning, she starts "idling" at 550 and after a few minutes the choke kicks in.

Why isn't the choke kicking in from the start?
How does the choke get on the second or highest choke ramp, I think it's the spring load from the choke that "forces" the throttle linkage to get on the second or highest choke ramp but I doen't understand why this happens after a few minutes.
I already checked the choke element putting 12v on it for a while, and the choke spring moved about 2 inches if I remember correctly.

The q-jet has been rebuild by myself, also the vacuum system and all other things are fine.

Greetings Peter

 

[HammerDown]

Same here Pete...first start of the day it idles low and a tad rough then...wham... she kicks up to a smooth high RPM for a few minutes and after driving it kicks back down to a smooth 650 RPM (in gear).
I was in the electric choke unit and all seems good and the linkage is all free too.
Let me know what you come up with for a fix

 

[Vettehead Mikey]

Prior to the first turn of the key, do you pump the gas pedal once to 'set' the choke? This is mandatory. If so, is the choke plate closing completely and the high idle cam rotating to the proper position?

If so, the engine should stay at the high idle speed once started and the idle dashpot will open the choke to approx. 1/8". The RPM will slowly decrease as the choke opens and the cam returns to the 'hot' position.

 

[LLC5]

Hello everybody,

Small problem with my quadrajet. The problem is the same from the first day I have the vette, not a really big problem but now that the vette is almost finished also the smallest problems need to be fixed.

Last week I reset the choke by Lars doc's, corrected the choke valve to get the ideal cold mixture with the screw on the front vacuum pot. The electrical choke is set a little les then stock to let go of the choke a little sooner. I set the choke RPM to 1000 to 1200 and the normal RPM to 650 - 700. Now the problem, when I start the engine cold the choke doesn't kickin from the beginning, she starts "idling" at 550 and after a few minutes the choke kicks in.

Why isn't the choke kicking in from the start?
How does the choke get on the second or highest choke ramp, I think it's the spring load from the choke that "forces" the throttle linkage to get on the second or highest choke ramp but I doen't understand why this happens after a few minutes.
I already checked the choke element putting 12v on it for a while, and the choke spring moved about 2 inches if I remember correctly.

The q-jet has been rebuild by myself, also the vacuum system and all other things are fine.

Greetings Peter

If everything is sound with the carb, then it sounds like your choke pull off may not be set correctly for summer weather.

 

[HammerDown]

Prior to the first turn of the key, do you pump the gas pedal once to 'set' the choke? This is mandatory. If so, is the choke plate closing completely and the high idle cam rotating to the proper position?

If so, the engine should stay at the high idle speed once started and the idle dashpot will open the choke to approx. 1/8". The RPM will slowly decrease as the choke opens and the cam returns to the 'hot' position.

Absolutely and the choke slams shut...but the noted problem persist :eyerole

 

[HammerDown]

If everything is sound with the carb, then it sounds like your choke pull off may not be set correctly for summer weather.

Details man...details!

 

[lars]

With the engine cold and "off," push the accel pedal once to the floor and let it up. By doing that, the choke plate should snap fully closed, and the choke coil should lift the fast idle cam to the fully upright position and place the fast idle screw on the highest step of the fast idle cam. If the fast idle screw is on the high step of the cam, the engine idle speed will be as set on the high step. If the cam is not raising to allow the fast idle screw to hit the high step, re-adjust the linkage as outlined in my paper. If you're only idling at 550 on cold start, it sounds like the fast idle cam is not raising to the correct position, or the linkage is misadjusted to allow the pulloff to drop the cam down excessively.

Lars

 

[Peer81]

I'll look into it and let you know here. Thanks everybody

Greetings Peter

 

[Peer81]

Had some time to test the choke last week.

With the aircleaner off had a good view. With a fully cold engine I pushed the pedal ones yes the choke plate snaps to a fully close position, the fast idle screw is then also located on the highest cam position. But when I rev the engine again slightly the fast idle screw drops to the second highest position. At this point the mixture is very nice, when I move the choke plate more open or closest the idle only gets worse, idle is around 600 to 650 at this point. After around 1 minute idle rpm is raising to the set 900 to 1000. Mixture still fine.

As said. I followed Lars this paper, as I use a slightly thicker gashorn gasket I couldn't get a 5mm? drill inside the hole in the choke housing but as it closes earlier then normal and I can not extend the arm I think its fine. On the highest step also adjusted the arm behind the choke housing just a little to get it right. The last idle adjustment on the second highest step was to lean. I think that is because 81 carbs have very big idle bypass channels so corrrect that one to get the highest rpm on the mixture and that is also the best mixture looking at the wideband meter. But the question still is the same, why would the rpm take a few minutes to raise? I'll do the test ones more because I think with the fast idle screw on the highest cam it isn't possible to have a low rpm with a perfect air fuel mixture.

But if Lars could explain in short what I'm doing when I'm following and adjusting the choke to his paper then I have a bigger change to finding the problem.

Greetings Peter