I have a 1973 F 250 390 with a 4 speed manual and am wondering what I can do to make my automatic choke stay open when it warms up. My Problem is when its Much colder here in the Great white north, My choke will open fully when warmed up but when I head out on the highway enough cold air must blow across the choke and make it close slightly. Because even after 5 miles on the highway and I pull up to a stop the engine is idleing at 1000 RPM again but will slow down if I let it warm up for a bit as choke fully opens again. The Carb I have on my Truck is a Edelbrock 1406 with an electric choke. I have it hooked to a keyed 12 volt power source. Always have seemed to take a while for the choke to open fully. and I have leaned it up considerably. Is the choke coil faulty? I always thought about three min for it to open fully in warm weather.Takes a good 5 min for mine to open fully.

 

The choke should be a contained unit and the coil should only be exposed to exhaust heat fed directly into the housing, so cold air blowing across the engine area really shouldn't affect that. Often though, the heater tube from the exhaust manifold rusts out in these and there are various ways guys suggest to rig them, but I don't think you can actually buy a correct replacement part for it. Now if its fully electric, then cold air shouldn't matter at all I wouldn't think. I'm wondering if your carb needs a little adjusting.


My solution to my choke woes a couple years ago? Manual choke from any big box auto parts store - $15ish.

 

Concur. Electric chokes are bad about getting out of adjustment. Most times gradually, and you don't notice it until its running rough, you've fouled plugs, or worse. A manual choke gives you full control and a happy face.

 

You may need to readjust the choke springs initial setting seasonally if you experience extreme temperature variations. Just mark where it is now and back pressure off the choke spring a little for winter. Building a small sheetmetal shield to box around the choke area and hood heat could help also.

From Edelbrocks instructions, at the bottom of the page.

Carburetor Frequently Asked Questions - Edelbrock, LLC.

"The length of time during which the choke will stay closed is determined by the position of the choke cap. As the choke cap is turned clockwise the choke will stay closed longer. To properly
set the choke loosen the chock housing retaining screws then turn the choke cap to the leanest notch on the choke housing and run the engine until normal operating temperature is reached.
With the engine running, slowly turn the choke cap clockwise until the choke valve begins to close. Now turn the choke housing one notch counterclockwise (lean) and tighten the choke
housing retaining screws. Periodic readjustment of the choke will be required as the temperature changes throughout the year. It is recommended that you use the notches in the choke
housing as a reference, one notch clockwise for rich or one notch counterclockwise for lean. After each adjustment verify that the choke valve opens fully after the engine is warm."

 

Fought this on a Weber in a Mazda pickup (still do some, still have the pickup). Same deal, fully electric choke, which, IMO, isn't that great of a design, but it's easy as far as retrofit/install. Like speedfreak78 said, you just need to tweak 'em a little more, seems like twice a year, a "cold weather" setting and a "warm weather" setting. I personally think this little Weber is double-whammy'd by still having that little fink air cleaner that they come with, ultimately I need to get a different top for the carb that'll accept a normal air cleaner, whether it gets adapted to a Toyota or a Chevy or a whatever, and then add the warm air manifold back on - that hose that connects down to the baffle plate off the exhaust manifold so you pull some warmer air into the actual carb body. But, not that high on the priority list.........

Which begs the question - do you still have your factory air cleaner, and does it still have that hot air hose hooked up? I'm not 100% sure how it actuates on a Ford, but I would think that that could be part of a problem like yours.

A quickie fix that sure seems to help this little pickup is a winterfront - you might try blocking off part of your grille just to keep the airflow a little more stagnant under the hood, see if it helps.

Before the ***** get me, there is a danger in putting cardboard directly on your radiator, it could possibly suck your fan into the radiator - but I guess I've never personally seen it happen.

Which sorta begs another question - is it staying at operating temp? If the motor is actually getting colder while you're driving, it might be cold enough under the hood it's legitimately making the choke come back on, then heat-soaks some when you're standing still idling.....

 

When i had an edelbrock on my truck i converted it to a manual choke as well.

 

My "final solution" was a manual choke conversion. Used properly, it's the best way.

 

Ford used to run one of the heater hoses close to the choke coil. There was a bracket that attached to the mounting points of the carb. After the advent of electric assisted chokes you didn't see it as much. Oher thing you could try is a shield to keep the underhood airflow away from the choke. This was done in later years when you saw fully electric chokes show up.
A properly operating heated air cleaner will help also, although it does more for drivability.

 

Does the Edelbrock electric choke have provisions for the thin hot air tube which presses into the manifold? If so, utilize it, and it will pull warm air into the choke housing. That's how the Motorcraft electric assisted chokes are which I've seen.

And X2 on building a reverse heat shield around the choke mechanism to keep heat in and cold drafts out. My '82 Mustang GT had a little plate bolted to the front of the choke housing on the 2150, presumably to keep cold air off of the choke.

 

Keep in mind fellas is that I have an aftermarket 1406 edelbrock carburetor and there is no way to utilize stock parts for this app. It may be possible to fabricate a shield to block cold airflo to choke coil tho.

 

Understand that, however a heat shield is easy to fabricate. Also running the heater hose near the choke is not hard to do. I am in Manitoba and can appreciate your issue. A winterfront will also help. Anything to reduce the windchill effect on the choke housing. If you adjust the choke to stay open you might not get enough choke to start and stay running under cold conditions. Can be quite a balancing act.

 

Oh I was kinda wondering if maybe I got a choke coil that was not sensitive enough. I set it leaner it will start and run and come off sooner but when it does warm up outside a cold start is harder because the choke won't close because of the leaner setting, But will close when it gets really cold. Yes a Balancing act!

 

Electric choke. STUPID simple and you dont have to babysit the truck till its warm

 

Install an electric start so you can stay cozy inside while baby heats up. Just make sure you have your e-brake on and your shifter in N or P(and well adjusted if an auto). or block heater( gets only in the 20s here but its a nicer 5 minute drive to work

 

First, are you running a dedicated 12v circuit to the choke? Or are you running the old Ford wire (White w/black stripe) to it?
If using the old stator wire it might not be putting enough voltage to the choke coil in the first place.
If you're running a keyed circuit that's best. But even if so, check it for full system voltage when it's been on for awhile. You never know with this old wiring. It might just be getting less voltage to the coil.

Running the heater hoses next to the choke cover is one possibility, but it's not as easy if your truck has A/C as the hoses would have to go through some pretty sharp curves to get where they're supposed to go.
But it's one more layer of help in keeping things warmer up there.

But the best first step is still likely to be what has already been mentioned. Turn the choke cover to a more lean setting.

Oh, and while you're at all of this, clean the carburetor's entire choke-side linkage with some carb/choke cleaner. Then a nice dowsing with some thin lube like WD-40 to free things up. Gunk and dirt and just life in general can get the linkage stuck a little on occasion. This could easily give you the false impression that your choke is closing.
It's more likely doing just what you say though, as that's very possible on a carburetor like that. And all it takes is for it to close a little bit to get that 1000rpm idle speed.

Good luck.

Paul