Trying to fix tough starts...no chokin

[pharmin06]

I've got a 77', 302 with the bone stock everything. I've researched and seems to be a 2150? Anyway truck runs decent enough but has never started easy cold. So I thought I'd learn to adjust the choke...Omg. So the choke plate never closes all the way....can't even push it down. Loosened the choke thermostat screws and very little movement when rotating forward or back. I've watched a few videos by "mikes carburetor" but I just can't seem to figure out what to adjust. Also the "choke pull down"??? It has a arm attached to it and the fast idle? But there is never any tension...hot or cold, it just seems to flop around if you touch it, I'll post a pic.
Any help is appreciated!

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[JAFO]

Could be that the choke thermostat internally has an issue or someone has one time adjusted it way wrong. The thermostat is a bi-metal coil that expands and contracts with changes in temperature. Works just like the old round Honeywell furnace thermostat you found in homes years ago. Also, if your carb expects 12 volts fed to the carb, that is just so a resistor strip inside that generates heat and makes the bi-metal heat up. Are you feeding the thermostat 12 volts as it should? or maybe by your picture it is getting some exhaust heat from that tube and doesn't take voltage? I have a holley on mine and it gets 12 volts to the carb thermostat. Your picture doesn't show the thermostat fully.

If the choke does not close all the way, then something is out of whack with the linkage or internal of the thermostat if that is what is keeping it from closing. And the choke should not just flop around. But also, when you try to close it, you would also need to move the throttle linkage open so that it is not hindering the choke.

 

[pharmin06]

Could be that the choke thermostat internally has an issue or someone has one time adjusted it way wrong. The thermostat is a bi-metal coil that expands and contracts with changes in temperature. Works just like the old round Honeywell furnace thermostat you found in homes years ago. Also, if your carb expects 12 volts fed to the carb, that is just so a resistor strip inside that generates heat and makes the bi-metal heat up. Are you feeding the thermostat 12 volts as it should? or maybe by your picture it is getting some exhaust heat from that tube and doesn't take voltage? I have a holley on mine and it gets 12 volts to the carb thermostat. Your picture doesn't show the thermostat fully.

If the choke does not close all the way, then something is out of whack with the linkage or internal of the thermostat if that is what is keeping it from closing. And the choke should not just flop around. But also, when you try to close it, you would also need to move the throttle linkage open so that it is not hindering the choke.

Thanks for the reply! In the picture I was showing the arm that comes out of the back of the choke pull-down. It's the arm with the slot in the pic with the "hooks top and bottom? In the pic I tried to show the wire linkage that is about1/4" from the end of the arm. I'm assuming it should work the diaphragm but there is no tension on hot or cold....just can't figure out if maybe something is missing


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[blubuckaroo]

Pull the thermostat cap off and make sure the bimetallic spring is engaging the slot in the linkage.

That diaphragm is the choke pull-off. It should have slack in it until there is engine vacuum. It should allow the choke to close completely when you press the accelerator pedal, then crack the choke open slightly once the engine starts and creates vacuum.

 

[pharmin06]

Pull the thermostat cap off and make sure the bimetallic spring is engaging the slot in the linkage.

That diaphragm is the choke pull-off. It should have slack in it until there is engine vacuum. It should allow the choke to close completely, then crack the choke open slightly once the engine starts and creates vacuum.

Thanks for the reply, I took it off last night and double checked it and made sure it was in the slot but it just doesn't move anything when clocked forward or backwards. Any idea on the linkage on the plunger in the pic?


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[blubuckaroo]

Any idea on the linkage on the plunger in the pic?


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The plunger in your photo is the choke pull-off diaphragm I referred to. It should allow the choke to close freely with the engine off, then pull back on the attached linkage when the engine starts. It opens the choke slightly to allow the engine to run. The little barbs on the shaft have no purpose that I know of.
Make sure the choke pull-off isn't keeping the choke plate from closing. I've had to replace the pull-off several times in my car's lifetime. The diaphragm gets hard, cracked, and sometimes stuck.

 

[JAFO]

If the bi-metal coil is doing its job it should be trying to force the choke closed when cold. When you twist the thermostat body you are apply more or less pressure on the choke depending on which way you spin it. Then as the coil heats it releases pressure on the choke. And the diaphragm as mentioned is pulling opposite from the bi-metal, trying to open the choke. They work together to keep the choke where it needs to be depending on engine temp.

 

[Rustytruck]

Are you using proper starting procedure as stated in the owners manual? turn the key to run position. Push gas peddle to floor, release peddle and turn key to start to engage starter. Or something close to that. When I was using the stock carb it was closer to pump the peddle twice instead of once. Blended fuels and hot running Broncos have not made this any easier.

 

[JAFO]

Another reason to push the pedal is it will release the choke. Typically the choke linkage is being obstructed by the throttle linkage until you move the throttle open some. Then the choke will snap closed if the bi-metal spring is working correctly.

 

[B RON CO]

Hi, as mentioned, the choke thermostat should snap the choke closed when cold. I believe you say the choke plate just flops around, and the thermostat does not loosen or tighten the choke plate. So do the parts in the housing move when the thermostat is removed? Maybe the metal parts are stuck in there. If you twist the little lever counterclockwise the choke should close. Your hot air choke is a complicated piece of engineering and there is a lot to check out. Good luck

 

[jckkys]

All the adjustments to the choke are included in the rebuilding kit for your 2150. I think the instructions that come in a rebuilding kit, are most valuable part of the kit. The shop manual doesn't give you these specs unfortunately. The pull down diaphragm needs to hold a vacuum. If it's cracked or perforated it won't do it's job. These don't normally come in the rebuilding kits. They cost 25-30 or about as much as the kit.