The Ford Barn

MickyD · 03-08-2021, 06:31 PM

My choke control knob on my 28 roadster does not turn very far at the carburator or at the dash, Can it be taken apart at the carburator, and what is keeping it from turning very far.

Patrick L. · 03-08-2021, 06:54 PM

Separate it and then remove the whole GAV from the carburetor. It can then be taken apart to see if/what is wrong.

MickyD · 03-08-2021, 07:24 PM

Thank you Patrick. We were afraid to turn it at the carburator and maybe strip or break something. It was real tight but turned a couple of days ago. I bought some throttle lubricant and lubed it and then it pulled up real easy but does not turn as far as it did before. Also before I lubed it you could pull it up and push it down but not easily. Now it pulls up but will not stay up. I guess I put too much lubricant on it. Go figure.

JayJay · 03-08-2021, 07:39 PM

Quote:

Originally Posted by MickyD

Thank you Patrick. We were afraid to turn it at the carburator and maybe strip or break something. It was real tight but turned a couple of days ago. I bought some throttle lubricant and lubed it and then it pulled up real easy but does not turn as far as it did before. Also before I lubed it you could pull it up and push it down but not easily. Now it pulls up but will not stay up. I guess I put too much lubricant on it. Go figure.

Micky - in the words of countless mechanics, "it's supposed to do that". There should be a spring on the choke shaft between the firewall and the carburetor. That spring pushes the choke rod back down. So if it's now moving down on its own you've improved things!

On the choke rod between the spring and the carburetor is a steel sleeve about 4 inches long. That sleeve slides up the choke rod, compressing the spring. Once you have it up a bit then you expose the connection between the choke rod and the carburetor, that's how you separate the two.

Once you get the choke rod out, you can remove the whole GAV assembly. It unscrews from the carburetor. If you choose to "chase" the threads (not too good an idea unless you are going to be able to blow the chamber out from inside the carburetor) then be aware that's not a straight thread in the carburetor body, it's an 1/8" tapered pipe thread.

JayJay

MickyD · 03-08-2021, 08:11 PM

I am now thinking that maybe I did not wait long enough for the car to warm up. I thought the choke twisted more before now , but maybe not. I will start it up tomorrow and wait and see how it performs.

Ruth · 03-08-2021, 08:33 PM

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MickyD, the "choke" has two functions. You pull it the close the choke butterfly and you turn in the adjust the amount of gas (GAV = Gas Adjusting Valve). Turn CW to close, CCW to open.

Bob Bidonde · 03-09-2021, 08:19 AM

There are 2 types of GAV needle seats in Zenith carburetors. Carburetors of 1928 through January 1930 have a removable seat that is threaded into the carburetor's casting. It may be in your case that the GAV needle stuck in the seat and unscrewed the seat. A loose seat will impede the motion of the GAV. Take the GAV apart to find out.
The 2nd version of the GAV seat is cast into the carburetor's body making it impossible to unscrew. Refer to the Service Bulletin of January 1930, Page 415.

redmodelt · 03-09-2021, 10:56 AM

What the part you are working with is the gas valve adjustment (GVA).

The choke used in the Model A (or T) does not stay closed, it is used for priming the engine. Generally, if it has to be held closed (by holding the knob pulled out) there are other issues that would need to be addressed.

After setting your fuel mixture with key off hand throttle down a few notches and spark all the way up, pull choke out, crank over a few revolutions, release choke, key on, start.

After it starts, pull the spark lever about 1/2 way down.

After it warms up a bit, push the hand throttle back up and adjust the fuel mixture till engine runs best.

The other function of the knob, without pulling it out, is to set your fuel mixture. Turn clockwise gentle till it stops, the counter clockwise 1-1/2 turns approx to get your base setting for starting.

Kinda basic, but in the ball park, no two cars are the same, close. So you will have to do a little experimenting where yours runs best.

MickyD · 03-09-2021, 07:39 PM

Thanks redmodelt. Since I lubed it, it pulls up fine but will not stay in the up position. When I try to turn the knob it turns maybe 1/3 and no more. With it pulled up the car starts right away but will not idle correctly when it pops back down in the down position. I will try and take it apart at the carburator and hopefully find out why it won't turn hardly at all at the carburator. Hopefully my mechanics hand book will tell me something.

redmodelt · 03-09-2021, 07:54 PM

As was said above, it was not made to stay up. The only way it will stay up is if you hold it. yes if all else fails, read the manual!

MickyD · 03-11-2021, 06:04 PM

I pulled the choke needle out of the carburator and cleaned everything with a choke spray. It now works like it is suppose to. Thank you all for helping me on this one. I could not find anything specific about this problem in my mechanics manual.

03-08-2021, 06:31 PM	#1
MickyD Senior Member Join Date: Sep 2015 Location: Welcome NC Posts: 207	Choke control knob My choke control knob on my 28 roadster does not turn very far at the carburator or at the dash, Can it be taken apart at the carburator, and what is keeping it from turning very far.

03-08-2021, 06:54 PM	#2
Patrick L. Senior Member Join Date: May 2010 Location: Largo Florida Posts: 7,225	Re: Choke control knob Separate it and then remove the whole GAV from the carburetor. It can then be taken apart to see if/what is wrong.

03-08-2021, 07:24 PM	#3
MickyD Senior Member Join Date: Sep 2015 Location: Welcome NC Posts: 207	Re: Choke control knob Thank you Patrick. We were afraid to turn it at the carburator and maybe strip or break something. It was real tight but turned a couple of days ago. I bought some throttle lubricant and lubed it and then it pulled up real easy but does not turn as far as it did before. Also before I lubed it you could pull it up and push it down but not easily. Now it pulls up but will not stay up. I guess I put too much lubricant on it. Go figure.

03-08-2021, 08:11 PM	#5
MickyD Senior Member Join Date: Sep 2015 Location: Welcome NC Posts: 207	Re: Choke control knob I am now thinking that maybe I did not wait long enough for the car to warm up. I thought the choke twisted more before now , but maybe not. I will start it up tomorrow and wait and see how it performs.

03-08-2021, 08:33 PM	#6
Ruth Senior Member Join Date: May 2016 Location: Glide, Oregon Posts: 1,339	Re: Choke control knob Sponsored Links (Register now to hide all advertisements) MickyD, the "choke" has two functions. You pull it the close the choke butterfly and you turn in the adjust the amount of gas (GAV = Gas Adjusting Valve). Turn CW to close, CCW to open. __________________ Ruth "Sometimes you really DO need to read the whole thread"

03-09-2021, 08:19 AM	#7
Bob Bidonde Senior Member Join Date: May 2010 Location: Long Island, NY Posts: 3,463	Re: Choke control knob There are 2 types of GAV needle seats in Zenith carburetors. Carburetors of 1928 through January 1930 have a removable seat that is threaded into the carburetor's casting. It may be in your case that the GAV needle stuck in the seat and unscrewed the seat. A loose seat will impede the motion of the GAV. Take the GAV apart to find out. The 2nd version of the GAV seat is cast into the carburetor's body making it impossible to unscrew. Refer to the Service Bulletin of January 1930, Page 415. __________________ Bob Bidonde

03-09-2021, 10:56 AM	#8
redmodelt Senior Member Join Date: May 2010 Location: Portland OR Posts: 6,340	Re: Choke control knob What the part you are working with is the gas valve adjustment (GVA). The choke used in the Model A (or T) does not stay closed, it is used for priming the engine. Generally, if it has to be held closed (by holding the knob pulled out) there are other issues that would need to be addressed. After setting your fuel mixture with key off hand throttle down a few notches and spark all the way up, pull choke out, crank over a few revolutions, release choke, key on, start. After it starts, pull the spark lever about 1/2 way down. After it warms up a bit, push the hand throttle back up and adjust the fuel mixture till engine runs best. The other function of the knob, without pulling it out, is to set your fuel mixture. Turn clockwise gentle till it stops, the counter clockwise 1-1/2 turns approx to get your base setting for starting. Kinda basic, but in the ball park, no two cars are the same, close. So you will have to do a little experimenting where yours runs best. __________________ I know the voices aren't real but damn they have some good ideas!

03-09-2021, 07:39 PM	#9
MickyD Senior Member Join Date: Sep 2015 Location: Welcome NC Posts: 207	Re: Choke control knob Thanks redmodelt. Since I lubed it, it pulls up fine but will not stay in the up position. When I try to turn the knob it turns maybe 1/3 and no more. With it pulled up the car starts right away but will not idle correctly when it pops back down in the down position. I will try and take it apart at the carburator and hopefully find out why it won't turn hardly at all at the carburator. Hopefully my mechanics hand book will tell me something.

03-09-2021, 07:54 PM	#10
redmodelt Senior Member Join Date: May 2010 Location: Portland OR Posts: 6,340	Re: Choke control knob As was said above, it was not made to stay up. The only way it will stay up is if you hold it. yes if all else fails, read the manual! __________________ I know the voices aren't real but damn they have some good ideas!

03-11-2021, 06:04 PM	#11
MickyD Senior Member Join Date: Sep 2015 Location: Welcome NC Posts: 207	Re: Choke control knob I pulled the choke needle out of the carburator and cleaned everything with a choke spray. It now works like it is suppose to. Thank you all for helping me on this one. I could not find anything specific about this problem in my mechanics manual.