Need Advice on Choke Adjustment
Thread Starter
Instructor
Joined: Jun 2008
Posts: 233
Likes: 9
From: Marietta Ga
Need Advice on Choke Adjustment
Just rebuilt the Quadrajet and it's a huge improvement. Bought the kit from Cliff and it was great with quality parts. 1973, 350 MT, divorced choke.
One problem remains that has to do with the choke. Seems like it stays on too long when cold and not enough choke after it sits. Let me know your ideas.
1) Car starts right up cold idles 1500 RPM
2) After a few minutes idle speed goes up to 2200 RPM.
3) Once hot, kicks down and stays at 900 RPM.
4) Re- starts fine hot.
5) After sitting for a couple hours starts at 900 RPM but doesn't want to idle without nursing throttle.
6) After a few minutes back to normal.
Where to start? Linkage adjustment, therm coil?
One problem remains that has to do with the choke. Seems like it stays on too long when cold and not enough choke after it sits. Let me know your ideas.
1) Car starts right up cold idles 1500 RPM
2) After a few minutes idle speed goes up to 2200 RPM.
3) Once hot, kicks down and stays at 900 RPM.
4) Re- starts fine hot.
5) After sitting for a couple hours starts at 900 RPM but doesn't want to idle without nursing throttle.
6) After a few minutes back to normal.
Where to start? Linkage adjustment, therm coil?
Drifting
Joined: Oct 2005
Posts: 1,615
Likes: 150
From: Forth Worth TX
With the engine cold, when you set the choke (by pushing the accelerator to the floor), the choke should close all of the way.
Once the engine starts, the choke should open about 1/4". As the choke thermo/coil heats, the choke should progressively open more and more.
Once the engine is at full operating temperature, the choke should be open all of the way (or near vertical).
If all of the above is happening, the choke should be set correctly.
What is your choke doing?
Once the engine starts, the choke should open about 1/4". As the choke thermo/coil heats, the choke should progressively open more and more.
Once the engine is at full operating temperature, the choke should be open all of the way (or near vertical).
If all of the above is happening, the choke should be set correctly.
What is your choke doing?
Thread Starter
Instructor
Joined: Jun 2008
Posts: 233
Likes: 9
From: Marietta Ga
Mine appears to be moving as the photos show, but follows the events I described. I need more choke when "just warm starting" and less as it warms up from cold. The extremes are fine....it's the mid ranges that seem screwed up.
Thread Starter
Instructor
Joined: Jun 2008
Posts: 233
Likes: 9
From: Marietta Ga
Yes, I set the choke to start and it fires right up. It stumbles around at this point unless I give it a little gas. Let off the gas and it drops down in RPM. It eventually gets hot enough and maintains idle.
Melting Slicks
Joined: Mar 2007
Posts: 2,520
Likes: 11
From: Hinckley OH
Have you looked at the choke once you have done this to see how far opened or closed it is? What I am trying to determine is whether it is stumbling because the choke isn't closed far enough or if the choke is closed too much and you are almost flooding it and the reason it still runs when you give it "gas" is that the throttle plates open to allow more air in.
So I would suggest trying to "warm" start it and before you give it gas go and look at where the choke is set. Let the car stumble or even stall so you can see where the choke is for a warm start.
Advanced
Joined: Oct 2010
Posts: 80
Likes: 2
From: near Nuremberg Bavaria
Attack one problem at a time.
If the choke stays on too long (which was the case with my '70 Q-Jet), you have to adjust (= bend) the rod that connects the choke coil to the first lever. Adjust as follows:
Having made this adjustment, on a sufficiently cold engine, setting the choke by slightly depressing the accelerator pedal should consistently close the choke plate fully. (If it doesn't, the choke coil itself might be bad.)
Then go from there, if other issues persist.
- Remove the rod from the lever. (It stays connected to the coil.)
- Close the choke plate fully by hand and hold in that position.
- Push down on the rod until it hits bottom.
- In this configuration, the TOP of the part of the rod that goes into the hole of the lever should be flush with the BOTTOM of said hole. Bend rod at the kink in order to achieve correct length.
Having made this adjustment, on a sufficiently cold engine, setting the choke by slightly depressing the accelerator pedal should consistently close the choke plate fully. (If it doesn't, the choke coil itself might be bad.)
Then go from there, if other issues persist.
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Thread Starter
Instructor
Joined: Jun 2008
Posts: 233
Likes: 9
From: Marietta Ga
Attack one problem at a time.
If the choke stays on too long (which was the case with my '70 Q-Jet), you have to adjust (= bend) the rod that connects the choke coil to the first lever. Adjust as follows:
Having made this adjustment, on a sufficiently cold engine, setting the choke by slightly depressing the accelerator pedal should consistently close the choke plate fully. (If it doesn't, the choke coil itself might be bad.)
Then go from there, if other issues persist.
If the choke stays on too long (which was the case with my '70 Q-Jet), you have to adjust (= bend) the rod that connects the choke coil to the first lever. Adjust as follows:
- Remove the rod from the lever. (It stays connected to the coil.)
- Close the choke plate fully by hand and hold in that position.
- Push down on the rod until it hits bottom.
- In this configuration, the TOP of the part of the rod that goes into the hole of the lever should be flush with the BOTTOM of said hole. Bend rod at the kink in order to achieve correct length.
Having made this adjustment, on a sufficiently cold engine, setting the choke by slightly depressing the accelerator pedal should consistently close the choke plate fully. (If it doesn't, the choke coil itself might be bad.)
Then go from there, if other issues persist.