cold start/choke issues? What to look at?

[LARIAT 85]

Here's photos - I took 21 in all, but won't post them all - only as needed. Let's take a look to get started on figuring out what is here and what isn't.

What is the capped red thing in this photo? It rotates down to this position when throttle is fully opened.

Any insight you guys can provise will be helpful.

You are missing both choke tubes and that is not the original carburetor. The one you have on your truck is made for a vehicle with an AOD (Automatic Overdrive) transmission. You can tell by that linkage attached to the throttle lever.

This is how the thermostatic "hot air" choke originally worked on your truck:

Clean, filtered air from the air cleaner is pulled through the "fresh air" tube (a rubber hose that is connected to the carburetor air horn and attaches to an aluminum tube) and into the bottom of the choke stove chamber on the exhaust manifold, where the air is heated up when the engine is running. From there, the heated air goes back up through the insulated "hot air" tube (attached on the top of the choke stove chamber on the exhaust manifold) that connects to the choke cap. As the air gets hot, it closes the spring in the choke cap, which allows the choke plate to open up as the engine warms up to run on a leaner mixture.

Anyway, this is how the thermostatic hot air choke originally connected to the exhaust manifold:

I think it would be easy to fix your choke issue and get your truck running much better. First, you need to purchase one of these:

https://www.amazon.com/Dorman-HELP-03840-Choke-Stove/dp/B000COB3W8

This simple, cheap kit (about $10) is designed to bypass the choke stove chamber on the exhaust manifold and replace the stock choke tubes completely. The kit comes with a length of coiled up aluminum tubing that you can easily bend by hand, the tubing insulation, the hardware to mount the tube to the choke cap, and a little "dome" with a hole in one end for the tubing to push into. This dome clamps to the exhaust manifold or header pipe to trap the hot air when the engine is running and routes the hot air up to the choke cap.

Here is a picture of the universal Choke Stove Kit on my own truck. It's a Ford 302 with an Autolite 4100. The Autolite 2100/Motorcraft 2150 will hook up the same way:

The factory setup had a "fresh air" tube that routed from the carburetor air horn down to the bottom of the choke stove chamber on the exhaust manifold. This location provided filtered air because this area is located on the "filtered air" side of the air filter once the air cleaner is in place. I drilled a second hole on the other end of the dome that came in the Choke Stove Kit so that the hot air going into the choke cap would be filtered, more like how it originally was set up in the first picture. You can see where mine attaches to the carburetor air horn by the rubber hose right behind the choke cap.

The universal Choke Stove Kit doesn't use the "fresh air" portion of the hot air choke at all. It's actually a great way to control the choke - much better than any aftermarket electric choke would. Unlike electric chokes, the thermostatic choke works in lockstep with your actual engine temperature.

 

[rcarlisle]

You are missing both choke tubes and that is not the original carburetor. The one you have on your truck is made for a vehicle with an AOD (Automatic Overdrive) transmission. You can tell by that linkage attached to the throttle lever.

This is how the thermostatic "hot air" choke originally worked on your truck:

Clean, filtered air from the air cleaner is pulled through the "fresh air" tube (a rubber hose that is connected to the carburetor air horn and attaches to an aluminum tube) and into the bottom of the choke stove chamber on the exhaust manifold, where the air is heated up when the engine is running. From there, the heated air goes back up through the insulated "hot air" tube (attached on the top of the choke stove chamber on the exhaust manifold) that connects to the choke cap. As the air gets hot, it closes the spring in the choke cap, which allows the choke plate to open up as the engine warms up to run on a leaner mixture.

Anyway, this is how the thermostatic hot air choke originally connected to the exhaust manifold:

http://forum.garysgaragemahal.com/file/n97911/Choke_Stove.jpg

I think it would be easy to fix your choke issue and get your truck running much better. First, you need to purchase one of these:

https://www.amazon.com/Dorman-HELP-03840-Choke-Stove/dp/B000COB3W8

This simple, cheap kit (about $10) is designed to bypass the choke stove chamber on the exhaust manifold and replace the stock choke tubes completely. The kit comes with a length of coiled up aluminum tubing that you can easily bend by hand, the tubing insulation, the hardware to mount the tube to the choke cap, and a little "dome" with a hole in one end for the tubing to push into. This dome clamps to the exhaust manifold or header pipe to trap the hot air when the engine is running and routes the hot air up to the choke cap.

Here is a picture of the universal Choke Stove Kit on my own truck. It's a Ford 302 with an Autolite 4100. The Autolite 2100/Motorcraft 2150 will hook up the same way:

http://forum.garysgaragemahal.com/file/n97911/100_0271.jpg

The factory setup had a "fresh air" tube that routed from the carburetor air horn down to the bottom of the choke stove chamber on the exhaust manifold. This location provided filtered air because this area is located on the "filtered air" side of the air filter once the air cleaner is in place. I drilled a second hole on the other end of the dome that came in the Choke Stove Kit so that the hot air going into the choke cap would be filtered, more like how it originally was set up in the first picture. You can see where mine attaches to the carburetor air horn by the rubber hose right behind the choke cap.

The universal Choke Stove Kit doesn't use the "fresh air" portion of the hot air choke at all. It's actually a great way to control the choke - much better than any aftermarket electric choke would. Unlike electric chokes, the thermostatic choke works in lockstep with your actual engine temperature.

THAT IS EXCELLENT EXPLANATION! Let me pose a few questions. THe Dorman kit as it comes - it straps onto a hot pipe with one metal hose coming out. Since it doesn't hook into the actual exhaust, isn't it clean hot air? Why do you need the filtered air? With that said I really like how yours seemingly works with the original setup. I think your explanation is the best I've seen so far for me.

I don't really understand the two hoses in the original setup. Is the original setup tapped into the exhaust flow? Does the filtered air push that much?

 

[rcarlisle]

You are missing both choke tubes and that is not the original carburetor. The one you have on your truck is made for a vehicle with an AOD (Automatic Overdrive) transmission. You can tell by that linkage attached to the throttle lever.

This is how the thermostatic "hot air" choke originally worked on your truck:

Clean, filtered air from the air cleaner is pulled through the "fresh air" tube (a rubber hose that is connected to the carburetor air horn and attaches to an aluminum tube) and into the bottom of the choke stove chamber on the exhaust manifold, where the air is heated up when the engine is running. From there, the heated air goes back up through the insulated "hot air" tube (attached on the top of the choke stove chamber on the exhaust manifold) that connects to the choke cap. As the air gets hot, it closes the spring in the choke cap, which allows the choke plate to open up as the engine warms up to run on a leaner mixture.

Anyway, this is how the thermostatic hot air choke originally connected to the exhaust manifold:

I think it would be easy to fix your choke issue and get your truck running much better. First, you need to purchase one of these:

https://www.amazon.com/Dorman-HELP-03840-Choke-Stove/dp/B000COB3W8

This simple, cheap kit (about $10) is designed to bypass the choke stove chamber on the exhaust manifold and replace the stock choke tubes completely. The kit comes with a length of coiled up aluminum tubing that you can easily bend by hand, the tubing insulation, the hardware to mount the tube to the choke cap, and a little "dome" with a hole in one end for the tubing to push into. This dome clamps to the exhaust manifold or header pipe to trap the hot air when the engine is running and routes the hot air up to the choke cap.

Here is a picture of the universal Choke Stove Kit on my own truck. It's a Ford 302 with an Autolite 4100. The Autolite 2100/Motorcraft 2150 will hook up the same way:

The factory setup had a "fresh air" tube that routed from the carburetor air horn down to the bottom of the choke stove chamber on the exhaust manifold. This location provided filtered air because this area is located on the "filtered air" side of the air filter once the air cleaner is in place. I drilled a second hole on the other end of the dome that came in the Choke Stove Kit so that the hot air going into the choke cap would be filtered, more like how it originally was set up in the first picture. You can see where mine attaches to the carburetor air horn by the rubber hose right behind the choke cap.

The universal Choke Stove Kit doesn't use the "fresh air" portion of the hot air choke at all. It's actually a great way to control the choke - much better than any aftermarket electric choke would. Unlike electric chokes, the thermostatic choke works in lockstep with your actual engine temperature.

Check this photo. Am I understanding how this works?

Dorman would be similar without the air from air cleaner? Unless modified as you did yours? Looks as if the Dorman would fit loose enough to draw cold air in around that housing.

Yours looks great, but my question is "is the juice is worth the squeeze" running the extra tube? I'm not discounting it, just wondering. I see an extra heater tube kit from Dorman on Amazon as well. I may order all that and see what I can cobble up.

I'm actually getting stoked to choke. LOL

[rcarlisle]

Houston, we have a problem. Your choke doesn't have a connection on it for a wire, so doesn't have a provision for heating electrically. Given that, w/o the hot air tube it will never work correctly. If you give it enough choke to make it start well it'll take forever to come off and the engine will run very rich, if at all.

I can see several options:

• Fix the hot air tube and the cold air supply. This would be best.

• Get an electric choke cap. I think the Holley ones fit the Motorcraft. This isn't as good as hot air, but it'll work. I have an electric choke on Big Blue.

• Convert to a manual choke. There are kits for that which replace the choke cap and have a cable, like a throttle cable for a lawnmower, that runs into the cab where you can control it.

Ok, I have ordered the Dorman kit to try to make this work. When I do the heat tube, what else am I going to have to address? I'm worried something isn't right in the linkages triggering the throttle. With the truck not running (ambient temp), when I open the throttle to WOT, the choke plate is not moving. Linkage moves on choke side, but doesn't really seem to move the choke plate. Just wondering what's going on with that?

I'm not sure I see how adding the tube will correct that condition. I WISH I had the carb in my hands to be able to see up close how everything relates. But not ready to go down that road just yet.

 

[LARIAT 85]

Check this photo. Am I understanding how this works?

Dorman would be similar without the air from air cleaner? Unless modified as you did yours? Looks as if the Dorman would fit loose enough to draw cold air in around that housing.

Yours looks great, but my question is "is the juice is worth the squeeze" running the extra tube? I'm not discounting it, just wondering. I see an extra heater tube kit from Dorman on Amazon as well. I may order all that and see what I can cobble up.

I'm actually getting stoked to choke. LOL

The hot air does *not* hook into actual exhaust. There is a hollow tube-like compartment built on the side of the passenger stock exhaust manifold. It serves as a *chamber* to collect hot air generated off of the exhaust manifold. The choke tubes pressed into the top and bottom of the chamber (hot air rises) to circulate the air from the filtered side of the carburetor (when the air cleaner is in place) to the choke cap. Inside of this chamber would have been a mesh filter that would also serve to hold the heat in the chamber. It would look like this:

https://www.npdlink.com/product/fitting-and-screen-choke-stove-pipe/143995

The reason for the fresh air tube is so the choke cap will only see clean, filtered air. The air you pull into the choke assembly will ultimately make it's way into the engine. So ideally you would want to use filtered air. Some of the older carburetors like my Autolite 4100 used a piston in the choke cap to operate the choke. If it pulls dirty air, it can possibly jam up the piston and render the choke useless.

(If you do not run the fresh air tube, make sure to cap off the connection under the carburetor air horn so that it does not pull unfiltered air into the carburetor.)

That is why I tapped the second hole in the other end of the [chamber] dome and ran another tube up to the carburetor air horn connection. I purchased the filter above and pushed it into a slighter larger copper tube, and placed that assembly under the [chamber] dome. Then I pushed the choke tubes into either side of the [chamber] dome so it mimicked the factory setup as close as possible. It has been like that for about ten years now, and I haven't had any problems.

[rcarlisle]

The hot air does *not* hook into actual exhaust. There is a hollow tube-like compartment built on the side of the passenger stock exhaust manifold. It serves as a *chamber* to collect hot air generated off of the exhaust manifold. The choke tubes pressed into the top and bottom of the chamber (hot air rises) to circulate the air from the filtered side of the carburetor (when the air cleaner is in place) to the choke cap. Inside of this chamber would have been a mesh filter that would also serve to hold the heat in the chamber. It would look like this:

https://www.npdlink.com/product/fitting-and-screen-choke-stove-pipe/143995

The reason for the fresh air tube is so the choke cap will only see clean, filtered air. The air you pull into the choke assembly will ultimately make it's way into the engine. So ideally you would want to use filtered air. Some of the older carburetors like my Autolite 4100 used a piston in the choke cap to operate the choke. If it pulls dirty air, it can possibly jam up the piston and render the choke useless.

(If you do not run the fresh air tube, make sure to cap off the connection under the carburetor air horn so that it does not pull unfiltered air into the carburetor.)

That is why I tapped the second hole in the other end of the [chamber] dome and ran another tube up to the carburetor air horn connection. I purchased the filter above and pushed it into a slighter larger copper tube, and placed that assembly under the [chamber] dome. Then I pushed the choke tubes into either side of the [chamber] dome so it mimicked the factory setup as close as possible. It has been like that for about ten years now, and I haven't had any problems.

Ok, again thanks for the EXCELLENT EXPLANATION. Somewhere I was reading yesterday it made out like the exhaust manifold was providing DIRTY air and the routing of cold air hose was fixing that.

I ordered the Dorman and an extra heat tube kit to be able to try to replicate your setup with my iron manifolds and Y pipe down pipe. Have to figure out where to best mount it up. Drill a new hole in blank end, install hose. Figure out how the mesh filtering between the two.

Now to just hope the linkage actually works correctly when all that is done.

[LARIAT 85]

Ok, again thanks for the EXCELLENT EXPLANATION. Somewhere I was reading yesterday it made out like the exhaust manifold was providing DIRTY air and the routing of cold air hose was fixing that.

I ordered the Dorman and an extra heat tube kit to be able to try to replicate your setup with my iron manifolds and Y pipe down pipe. Have to figure out where to best mount it up. Drill a new hole in blank end, install hose. Figure out how the mesh filtering between the two.

Now to just hope the linkage actually works correctly when all that is done.

Glad I could help you.

The Motorcraft carburetor you have is the best, simplest 2-barrel carburetor ever made. And the thermostatic choke works better than any other choke style. You will find that when you get it tuned right and the choke set up correctly, it will run almost as good as any fuel-injected vehicle.

[rcarlisle]

Glad I could help you.

The Motorcraft carburetor you have is the best, simplest 2-barrel carburetor ever made. And the thermostatic choke works better than any other choke style. You will find that when you get it tuned right and the choke set up correctly, it will run almost as good as any fuel-injected vehicle.

Here's a good video on basic choke operation - mine has a vacuum thing on back of all this choke stuff, but this shows me how it all is supposed to work together.

 

[LARIAT 85]

Here's a good video on basic choke operation - mine has a vacuum thing on back of all this choke stuff, but this shows me how it all is supposed to work together.

The beauty of keeping the stock Ford carburetor on a stock engine is that the Ford engineers already did the work and made all the adjustments for your specific vehicle. Unlike an aftermarket carburetor that is designed to work on any engine, the stock Ford Autolite and Motorcraft carburetors are engineered to run on a specific engine size and engine family, automatic or manual transmission, vehicle size and weight, and even specific emissions equipment.

When you purchase a rebuild kit, you will get a rebuild sheet telling you exactly how to make all of these adjustments to get it back exactly where it should be for an easy installation. Only minimum adjustments to the choke and the air/fuel mixture screws will be needed.

 

[Rusty_S85]

Yeah, I know what "proper" is supposed to be. But this one ain't proper for sure.

Thanks for all the information you included. But I can tell you in all honesty, I'm not that inspired to fix this thing. It does start and run. It will start on one pump, just usually sputters out. Probably better than 90% of the trucks on FB?. You guys here are that last 10%. The upper echelon.

If the choke would close up some, it would probably stay running. If I can get the choke plate working somewhat, I'm sure I'll be happier. If not, it's like an old car or motorcycle - just have to let it warm a bit more. Usually I just keep my foot on pedal to give it a fast idle while I get me adjusted and seat belt on, etc.

As for your off idle stumble, when I worked for the state motorcycle program (stay with me), the majority of our Honda 250 cc Nighthawks and Rebels had a stumble off idle. On some investigation, turned out the ones that didn't stumble had a bigger idle jet. My solution for the ones that stumbled was to put a #4 brass washer under the top of the needle to shim the plunger needle up a bit. Made 300 bikes run better in NC. There is probably a similar solution for the truck carb - figure out how to richen it up between idle and that acc pump squirt. The Hondas had an honest-to-God accelerator pump on them.

If I could get to the carb to study it better, this choke thing would be a lot easier. When I get photos tonight, I will be able to study it all a llittle closer. But there are still a lot of moving parts behind the choke pot thing. Thought about buying a new carb, but till I figure out if all the stuff is there, it might not fix it.

Thats a possibility for mine. But the 2V 2150 carb on my '82 is the same one on my '78 351W, they are both 351cfm 2150s. No stumble on my 351W but stumble on my 302. Cant be too much fuel from the accelerator pump as when I increased the squirt it made a positive difference in reducing some of the stumble.

But I am getting away from all that, aftermarket fuel injection is where I am going myself. Everything works on my carb but the stumble is what got me and the more I think about it I rather have aftermarket fuel injection with way more adjustability that will actually change with elevation and ambient air temperature.