Vintage Mustang Forums banner

Rebuild or replace?

  • Rebuild the 2100

    Votes: 14 93.3%
  • Replace with an aftermarket

    Votes: 1 6.7%
1 - 20 of 43 Posts

·
Registered
1966 289 3-speed
Joined
·
771 Posts
Discussion Starter · #1 ·
I'm at a cross roads with my 2100. Since day one of owning the car the automatic choke has never worked. I discovered early on the the piston was frozen. However even after I freed it up I've still never been able to get the choke to work. The fast idle wont engage for anything. I tried several times to make adjustments following the procedure and no luck. I even got a new thermostatic spring housing and nothing. So a few weeks ago I took it to a local recommended shop that does reso-mod work. They played with it and said it fast idle was working, but after sitting for a few days it was the same thing. The fast idle wont engage and the the car takes at least 5 minutes of continuous gas peddle at start up or it will die. Even then I have to turn up the warm idle to about 800 to get it to stop sputtering. The weird thing is once finally warm its runs great on the road if not for a slightly high idle. But let it sit over night or a day or two and its the same thing all over again.

So at this point I figure the carb probably needs a full rebuild and perhaps an electric choke conversion by a shop that does vintage carbs. But that got me thinking... if I'm going to rebuild and add the electric choke, maybe a new more reliable aftermarket carb is the way to go? The car is mostly stock minus the smog equipment and pertronix. It has the original rebuilt 289 and intake and I'd like to keep it that way. Its a weekend driver that I want as reliable and stockish as possible. I'm not interested in a 4 barrel swap and the EFI snipers are too spendy. So I'm asking for opinions...are there any other 2 barrel carbs I should consider upgrading to or is keeping and rebuilding the one I have the best way to go?
 

·
Registered
Joined
·
7,476 Posts
I'm still running an antique 2100 on my truck. Every several years or so it needs a rebuild so I get a kit and go through it. The fast idle on mine seems to be either too much or not enough for reasons I have never taken the time to figure out. I got an electric choke for mine. I have also had 2 barrel Holleys and they work good too. They seem to be fairly expensive these days though but so is a reman'd 2100.
 
  • Like
Reactions: Blues Power

·
Registered
Joined
·
5,401 Posts
Just rebuilding the carb will not solve the problem if it is the symptom and not the cause. What is your hot air source for the choke or do you run an electric choke? Any little bit of crud can get in there and mess up the piston motion. Electric choke is the easiest way out unless you are a stickler for original.
 

·
Registered
Joined
·
5,786 Posts
the ford hot air choke is worry free
im thinking your either missing parts or not sure how to set it up the choke

the thermo spring needs to catch the tang lever notch. without that it will do nothing.

also pop the hot air choke manifold fitting and make sure the tube is in tact. it should just coil up and return to the other side

ive seen one or two rot and get pin holes
 
  • Like
Reactions: stanglocal

·
Registered
Joined
·
3,658 Posts
AZ, the 2100 Autolite carbs are VERY reliable. My guess is that you need a rebuild with some good gaskets. And how about considering a manual choke ? It will always do EXACTLY what you tell it to. LSG
 

·
Registered
1966 289 3-speed
Joined
·
771 Posts
Discussion Starter · #7 ·
Just rebuilding the carb will not solve the problem if it is the symptom and not the cause. What is your hot air source for the choke or do you run an electric choke? Any little bit of crud can get in there and mess up the piston motion. Electric choke is the easiest way out unless you are a stickler for original.
The carb looks to need a rebuild anyway. As mentioned in my original post it is an automatic (hot air) choke and I did remove and clean the piston.
the ford hot air choke is worry free
im thinking your either missing parts or not sure how to set it up the choke

the thermo spring needs to catch the tang lever notch. without that it will do nothing.

also pop the hot air choke manifold fitting and make sure the tube is in tact. it should just coil up and return to the other side

ive seen one or two rot and get pin holes
The only part missing is the fresh air tube going from the carb to the manifold. But I cant see how that would effect the fast idle function. That's the biggest mystery. I'm aware how the spring housing attaches and it is correct. I have not taken the manifold fitting off, again not sure how that would cause the fast idle not to engage.
 

·
Registered
1965 C-code Coupe, Silver Metallic Blue, 3-speed toploader, 3.00 rear
Joined
·
172 Posts
The carb looks to need a rebuild anyway. As mentioned in my original post it is an automatic (hot air) choke and I did remove and clean the piston.

The only part missing is the fresh air tube going from the carb to the manifold. But I cant see how that would effect the fast idle function. That's the biggest mystery. I'm aware how the spring housing attaches and it is correct. I have not taken the manifold fitting off, again not sure how that would cause the fast idle not to engage.
I'm a little unclear; could you post pictures of your setup so we can be sure as to what we're dealing with?

The tube going from the carb to the exhaust manifold is not a fresh air tube; it is what heats the thermostatic coil/piston combination in the choke. Without the tube, no heat transfer happens to the choke coil and the choke will not operate properly. Additionally, the fast idle cam will not reset to the dominant position after cooling and flipping the throttle after sitting overnight.

So if this is missing as you say, my guess is this is your problem.
 
  • Like
Reactions: Blues Power

·
Registered
1966 289 3-speed
Joined
·
771 Posts
Discussion Starter · #9 · (Edited)
I'm a little unclear; could you post pictures of your setup so we can be sure as to what we're dealing with?

The tube going from the carb to the exhaust manifold is not a fresh air tube; it is what heats the thermostatic coil/piston combination in the choke. Without the tube, no heat transfer happens to the choke coil and the choke will not operate properly. Additionally, the fast idle cam will not reset to the dominant position after cooling and flipping the throttle after sitting overnight.

So if this is missing as you say, my guess is this is your problem.
I'm a little unclear; could you post pictures of your setup so we can be sure as to what we're dealing with?

The tube going from the carb to the exhaust manifold is not a fresh air tube; it is what heats the thermostatic coil/piston combination in the choke. Without the tube, no heat transfer happens to the choke coil and the choke will not operate properly. Additionally, the fast idle cam will not reset to the dominant position after cooling and flipping the throttle after sitting overnight.

So if this is missing as you say, my guess is this is your problem.
I have the tube connected that you are referring to. However my understanding is that there are two tubes - the one you described going from the manifold to the piston, and the other is a fresh air tube going from the carb to the manifold.

As for the fast idle cam - if the car is cooled and the choke plate is closed it should engage by pressing the peddle down and then releasing it no?
 

Attachments

·
Registered
1965 C-code Coupe, Silver Metallic Blue, 3-speed toploader, 3.00 rear
Joined
·
172 Posts
I have the tube connected that you are referring to. However my understanding is that there are two tubes - the one you described going from the manifold to the piston, and the other is a fresh air tube going from the carb to the manifold.

As for the fast idle cam - if the car is cooled and the choke plate is closed it should engage by pressing the peddle down and then releasing it.
Ok good; it seemed you were referring to the manifold tube as the fresh air tube. So you should be good to go there.

If the choke is adjusted properly, it should spring back after blipping the throttle cold. But the fresh air tube is needed to pull the hot exhaust manifold air through the choke passage; without it, it will take longer to heat up.
 

·
Registered
1966 289 3-speed
Joined
·
771 Posts
Discussion Starter · #11 ·
Ok good; it seemed you were referring to the manifold tube as the fresh air tube. So you should be good to go there.

If the choke is adjusted properly, it should spring back after blipping the throttle cold. But the fresh air tube is needed to pull the hot exhaust manifold air through the choke passage; without it, it will take longer to heat up.
Thanks. My main issue it that the fast idle doesn't engage at all on cold startup. I'm having to manually press the peddle down to get the rpms up or it dies. I have to do this for several minutes. I'm told fast idle cam should engage by pressing the peddle down once and releasing BEFORE turning the key on a cold engine.

On a side note - should the choke plate always be closed on a cold engine regardless of ambient temp?
 

·
Registered
Joined
·
754 Posts
I'm not sure if we covered it in your other thread on the carb, but you need to adjust the bolt/screw in the plastic lever to make the fast idle screw rest on the fast-idle cam's highest notch in order to be on fast idle. If your choke is closing when cold, then you have to make sure that in this spot, the screw is on that high step. Then you'll need to adjust the fast-idle-speed screw (on the back of the carb--kind of hard to reach) in order to increase RPM to where you want it. It's basically a prop to keep your throttle slightly open, and that's how it works. It may be that the screw isn't turned in enough to make it run fast when choked and you're suffocating the engine on startup.

--and yes, the choke should always close when the engine is cold, regardless of ambient temps. That's where you have to adjust the position of the spring housing. The ideal setting is to turn it until it just closes completely, then it will begin dechoking as soon as you begin to warm the engine, and your fast idle will always engage to help you start the car.
 

·
Registered
1965 C-code Coupe, Silver Metallic Blue, 3-speed toploader, 3.00 rear
Joined
·
172 Posts
^This. :)
 

·
Registered
1966 289 3-speed
Joined
·
771 Posts
Discussion Starter · #14 ·
I'm not sure if we covered it in your other thread on the carb, but you need to adjust the bolt/screw in the plastic lever to make the fast idle screw rest on the fast-idle cam's highest notch in order to be on fast idle. If your choke is closing when cold, then you have to make sure that in this spot, the screw is on that high step. Then you'll need to adjust the fast-idle-speed screw (on the back of the carb--kind of hard to reach) in order to increase RPM to where you want it. It's basically a prop to keep your throttle slightly open, and that's how it works. It may be that the screw isn't turned in enough to make it run fast when choked and you're suffocating the engine on startup.
Got it. I know I have adjusted that already but I will take another look.
--and yes, the choke should always close when the engine is cold, regardless of ambient temps. That's where you have to adjust the position of the spring housing. The ideal setting is to turn it until it just closes completely, then it will begin dechoking as soon as you begin to warm the engine, and your fast idle will always engage to help you start the car.
I can tell you the plate isn't closing all the way when cold so that's one thing to fix right off the bat.
 

·
Registered
Joined
·
5,401 Posts
The choke should not close all the way, or at least it should not be set that way. There is a spec for your particular setup for how open it should be. It is a small amount but necessary. The FSM says to use a drill bit the correct spec to set the choke closure. First set the carb up to factory spec and then tune. Then see if your problem still exists. The FSM also shows how to make the piston setting tool from a paper clip. Handy thing to have in the kit.
The heater pipe: Where it goes into the manifold, did you blow out the rust dust that is the remnants of the old metal filter material in the manifold? I hit these with the air nozzle, outside, face turned away because usually a large cloud of orange rust blows out of there. These particles can get pulled into the piston and the vacuum passage way and can clog, cause friction and eventually freeze it up. Seen it tons of times. That's the Achilles heel of this system.
Your carb shafts; everything really freely moving? Any resistance when unloaded will cause the idle step to not return correctly. Carbs need to be clean to work properly. Some shellac starts building up on the shafts and the whole thing stops acting right.
 
  • Like
Reactions: Blues Power

·
Registered
Joined
·
5,786 Posts
Dont touch the key. Leave engine off.


When ice cold and you push pedal to the floor once does the choke plate snap closed with about 1/16 gap.

If not your linkage is out of wack or missing parts.

800 hot idle isn't too bad.
Should be about 750 but if 800 works leave it there for now
 

·
Registered
Joined
·
38,218 Posts
Just remember.... there is a big difference between a true carb "rebuild" and "hosing it off and installing a kit". If you didn't have to replace any Welch plugs you didn't do a rebuild.
 

·
Registered
Joined
·
754 Posts
Yes, it must close fully or you’ll have erratic function at best. It’s the only repeatable position to set it to. The spec in the shop manual that you use the drill bit to set is the “pull down clearance”. This will be where vacuum applied to the choke piston pulls the plate down to after startup. The way the shop manual describes it is very confusing. When you start the car, the choke should be fully closed, and the fast idle speed screw on the highest step of the cam. You should start at around 1500 RPMs...now, you don’t exactly want to put in gear at this speed and take off, so you give the throttle one tap, and the pull-down effect happens opening the choke a crack (approx. 1/8”...this is the drill-bit gauge setting). At this point, the fast idle speed screw should be on the second step marked with the sideways “V” indicator, and your idle speed will drop a step, say to 1,000 RPM. The shop manual makes this confusing, because they mention setting all this up in this position implying that this should be where your choke is set to when cold. That’s not the case, however, it is the position where both of those measurements correspond to each other. The problem is that if you don’t set to the fully closed position, you will never be on the high side of the cam and take full advantage of the fast idle function.
 

·
Registered
1966 289 3-speed
Joined
·
771 Posts
Discussion Starter · #19 ·
The choke should not close all the way, or at least it should not be set that way. There is a spec for your particular setup for how open it should be. It is a small amount but necessary. The FSM says to use a drill bit the correct spec to set the choke closure. First set the carb up to factory spec and then tune. Then see if your problem still exists. The FSM also shows how to make the piston setting tool from a paper clip. Handy thing to have in the kit.
The heater pipe: Where it goes into the manifold, did you blow out the rust dust that is the remnants of the old metal filter material in the manifold? I hit these with the air nozzle, outside, face turned away because usually a large cloud of orange rust blows out of there. These particles can get pulled into the piston and the vacuum passage way and can clog, cause friction and eventually freeze it up. Seen it tons of times. That's the Achilles heel of this system.
Your carb shafts; everything really freely moving? Any resistance when unloaded will cause the idle step to not return correctly. Carbs need to be clean to work properly. Some shellac starts building up on the shafts and the whole thing stops acting right.
Yeah I set the gap with a drill bit and did the paper clip thing last time. It should be pretty close to spec.

So get this - Car had been sitting over night and all day today. I came home and took the air cleaner off to check, and sure enough the choke was wide open. I loosened the spring housing screws and turned the housing just a bit counter clockwise. The choke closed (with a gap) and didn't take much of a turn. When I did this I could see the fast idle cam was engaged down below. Gave the throttle a little pull, went in the car, turned the key, and I'll be dammed it started right up with no pedal! The fast idle was slow so I turned it up. After about a minute I watched as the choke slowly opened. I pulled the throttle linkage and the fast idle kicked off. All seems good for now...

But here's the weird thing...I've done this exact exercise before and it didn't work. So I suspect maybe the piston or linkage is still maybe sticking intermittently. I'm going to try and drive it to work tomorrow so fingers crossed.

As for the heat shroud - I took it off and confirmed the heat tube is connected but the bottom clean air tube is totally gone. So I ordered a new on and will blow out that hole as you suggested.

Anyway I'll report back tomorrow. Thanks to everyone who chimed in!
 

Attachments

·
Registered
Joined
·
5,786 Posts
Choke should be open until you mash the pedal once

It won't close by itself or on its own.
You have to release it by mashing the pedal

Heat shroud is not your problem
I been driving without one for 35 years.
 
1 - 20 of 43 Posts
Top