Why do I have to keep pulling the choke out ?
 

Hi new member here, Model A owner since 1979.
I have run out of ideas to get the motor in my '29 to run right.
Motor starts right up and runs ok for about 10 seconds, then begins to slow and starts sputtering. Pull and release choke and this cycle repeats for 3 to 5 minutes - which requires me to sit leaning over with my hand on the choke. After this long warm up phase it continues to run at idle without choking but always a little rough.
I assumed this to be either an intermittent fuel blockage or vacuum leak issue, so have done the following:
Added filter screen to fuel shutoff valve.
cleaned out fuel line.
Adjusted carb float level to 5/8".
Cleaned carb passages.
cleaned jets.
New throttle shaft - old shaft had wear.
New manifold gasket.
New intake gasket.

What else could this be ?
I have tried swapping the Zenith carb out for a Tillotson, but it still runs poorly.
Any ideas ?

Kevin

Re: Why do I have to keep pulling the choke out ?
 

Clogged gas cap vent. Loosen the cap and start the engine and see if that helps. Often times blowing compressed air around the inside of the cap will blow the crud out.

Re: Why do I have to keep pulling the choke out ?
 

Could be that your fuel cap is not venting (blocked vent) or that you may have a radiator cap being used as a fuel cap. They look similar but the radiator cap is not vented.
Try loosening you fuel cap a few threads or remove it all together and see if that overcomes your problem.
Welcome to The Barn, You will get lots of help here.

Re: Why do I have to keep pulling the choke out ?
 

Re: Why do I have to keep pulling the choke out ?
 

How far open do you have the GAV on warm up.

Re: Why do I have to keep pulling the choke out ?
 

See attached article.

Tom Endy

Re: Why do I have to keep pulling the choke out ?
 

Carb mounting bolts tight?

Re: Why do I have to keep pulling the choke out ?
 

Make sure the two mating flanges at the carb and manifold connection are flat. Put a file on them to make sure. You will see the warp. Clean it up.

Re: Why do I have to keep pulling the choke out ?
 

The last thing I can think of is a cracked intake manifold. Very hard to find, but they do crack and leak air.

Re: Why do I have to keep pulling the choke out ?
 

Other info.


https://www.fordbarn.com/forum/showt...r+running+lean


Do a search, example "poor running lean" which the above was the 1st result, will give you tons of ideas.

Re: Why do I have to keep pulling the choke out ?
 

Low fuel flow would be my guess, fuel valve on, gas cap not venting, you could remove the carb drain and test for flow, more than a baby food jar use a quart jar.
Let us know what you find!

Re: Why do I have to keep pulling the choke out ?
 

I have seen a video where the GAV is 3/4 turn open. Then when warmed about 1/4 turn open. This will vary from A to A of course. I would open the GAV a little more from where you have it set now.....maybe a quick fix.

Re: Why do I have to keep pulling the choke out ?
 

Methinks that even w/a blocked vent that it would run longer than 10 seconds.

Re: Why do I have to keep pulling the choke out ?
 

I had the same problem on my 29 Roadster. I had cleaned the carb a number of times myself to no avail. Finally set it to Jim Bullock in Texas and it came back looking like brand new. Put in on and it runs like a top - NO problems at all. Might want to consider this if all else fails.

Re: Why do I have to keep pulling the choke out ?
 

I had the same problem I had to constantly pull out the choke to keep the Motor running till it warmed up I found the tappet clearance to great from worn lifters.I ground the valves and replaced the tappets which solved the problem.Welcome to the Barn.

Re: Why do I have to keep pulling the choke out ?
 

When you get the car to run, spray carb cleaner around where the manifold meets the block and carb to manifold. Try not to get any directly into the carb intake. If there is a vacuum leak in those areas the engine will stumble then recover. Where are you setting the GVA? How many turns out is the air needle adjustment? I set mine 1-1/2 turns out to start with. The idle circuit is fed from the well, are all the holes in the well clear? They are on the small side. Did you take the well out when you cleaned the carb? It could be plugged up.

Re: Why do I have to keep pulling the choke out ?
 

Thanks for all the tips.
I started it up today with the gas cap off and no improvements, so we can rule out plugged gas cap.
I adjusted GAV from closed to open 1 turn trying to find a spot where it ran good but no big improvements.

I always drain the gas by removing the carb drain plug, and it dribbles out a good rate.

Exhaust stinks like it is running too rich.
Gas is dripping out the back of the carb so the float valve is leaky.

I aimed propane into the carb intake and it sped up. I was trying to use propane to search for manifold leaks but fan wash is probably diluting the propane too much to be useful.

I looked over the intake manifold when replacing the gaskets a few days ago and did not see any cracks. Manifold flanges looked good.

It runs just as poorly when I put a Tillotson carb on.

Is it time to open up the motor and check tappet clearances ?

Re: Why do I have to keep pulling the choke out ?
 

RE "I always drain the gas by removing the carb drain plug, and it dribbles out a good rate."
It should run out not dribble even when just draining the carb. You may have the ferrule too far back on the inline at the carb. The line should stick out from the ferrule just about 1/16" of an inch. Also did you replace the screen at the inlet? It could be plugged too. Gas can run out the back of the carb when you over choke it, that is normal. Does not mean the float is bad or miss set. Now if it runs out by itself while the car is just sitting, that is different. With the fuel line disconnected from the carb, how is the flow then? It should be a strong steady flow, if not you have blockage up stream.

Re: Why do I have to keep pulling the choke out ?
 

==============================================



Here is the Correct name of the small brass compression fitting that
fits on a fuel line to seal the line from leaking at the fitting.

It's name is "ferrule"




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Re: Why do I have to keep pulling the choke out ?
 

Changed the spelling, thank you :)