2100 carb choke question
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2100 carb choke question
I just put a re-manufactured carb on my 79 F-100 and I'm having trouble getting it to start when its cold. I am not afraid to try to do anything but I'm not knowledgeable on this. I adjust the choke to start then the idle is too high when it warms up. So I set the warm idle down to the desired speed then it won't start again when it is cold, without nursing the throttle. I installed a heat riser so the thermostat reads the temperature of the engine. My dad said if you press the throttle to the floor and start it, it should set the choke then when it warms up you quickly press the throttle again and it kicks the choke open and slows down the idle. How does this work and why doesn’t mine do this?
Posting Guru
Joined: Sep 2003
Posts: 2,313
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From: Northeast LA
It may just be a bad carb. I know a lot of people on here have had bad experiences with re-manned ones and had to return a few of them before they ever got a good one. I wasn't willing to go through all that so I just broke down and paid the extra cash for a brand new Holley 4412 for my truck and I'm so glad I did.
Cargo Master
Joined: Mar 2008
Posts: 2,409
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From: Goliad, Texas
yeah, sometimes reman can be good; sometimes not.
if your press the pedal to the floor and start it, it should set the choke. and yes when you press it again it should kick off. maybe did you buy a manual choke carb?
if your press the pedal to the floor and start it, it should set the choke. and yes when you press it again it should kick off. maybe did you buy a manual choke carb?
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Your dad is correct. The trouble with reman carbs is that you really have no control over how all the settings will come. It's not necessarily a bad carb, but out of whack. Setting the choke, fast idle, and fast idle index is a pretty complicated procedure on a 2100, actually. Moreso than other carbs. Here is a write-up I made on how to get everything set up correctly. Ignore the first couple paragraphs about the float.
https://www.ford-trucks.com/forums/7...ml#post6422219
There is what's called a fast idle cam that holds the throttle open while the choke is on. As you're driving and the throttle opens and closes, the fast idle cam slowly drops down. Once the choke is all the way open, the fast idle cam drops out of the way and the throttle plates rest on curb idle. When you shut the truck off and it sits overnight, the choke cools and tries to close, but the throttle shaft pins the fast idle linkage, and the choke can't shut. This is why you must pump the gas once in the morning - it pulls back the throttle, frees the fast idle linkage and lets the choke snap shut.
https://www.ford-trucks.com/forums/7...ml#post6422219
There is what's called a fast idle cam that holds the throttle open while the choke is on. As you're driving and the throttle opens and closes, the fast idle cam slowly drops down. Once the choke is all the way open, the fast idle cam drops out of the way and the throttle plates rest on curb idle. When you shut the truck off and it sits overnight, the choke cools and tries to close, but the throttle shaft pins the fast idle linkage, and the choke can't shut. This is why you must pump the gas once in the morning - it pulls back the throttle, frees the fast idle linkage and lets the choke snap shut.
Cargo Master
Joined: Dec 2006
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From: hinckley ohio
the black round thing will set time choke stays on it my take some time to get it set up.and you said you adjusted the screw for the high idle.adjust it alittle more to high side this has a cam set up so you put pedel to floor to set it then as engine warms up it turns it self down on r.p.m.s till its warm enough or you press gas pedel and cancel it.that is round black thing has a spring like thing and the heat riser heats the spring it turns the choke plate open.I would turn black thing till your choke plate is about closed to start with. it is hold by three flat head screws loosen them and turn it.I would not close choke plate all the way.Hope this helps it will take some time to get it right but its worth it.
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Thanks for all the info. it does have an automatic choke on it and tomorrow I'll look to see and compare to that article. It runs great once its warm so hopefully its just a few kinks to work out.
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https://www.ford-trucks.com/forums/7...ml#post6422219
There is what's called a fast idle cam that holds the throttle open while the choke is on. As you're driving and the throttle opens and closes, the fast idle cam slowly drops down. Once the choke is all the way open, the fast idle cam drops out of the way and the throttle plates rest on curb idle. When you shut the truck off and it sits overnight, the choke cools and tries to close, but the throttle shaft pins the fast idle linkage, and the choke can't shut. This is why you must pump the gas once in the morning - it pulls back the throttle, frees the fast idle linkage and lets the choke snap shut.
Though I do have a few questions:1. My spec sheet with my carb kit lists two different carbs, one with .180 and .140 on the other for the pulloff clearance.The carb doesn't have a tag,so is there any way to tell which one I need?
2. Is the fast idle cam suppose to rest on the fast Idle screw? Mine wasn't even close to the cam.
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MSEE
Joined: Apr 2004
Posts: 10,386
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From: Austin, TX
1. Honestlly, it won't make too much of a difference. If you have a 5/32" drill bit, use that as a gauge. That is about 0.16 which is right in the middle.
2. There were two types of carburetors, 2100 and 2150. The 2100 has a small lever that rests on the cam, instead of the fast idle screw. For this model, the screw does not touch the cam. The 2150 has a fast idle screw that touches the cam directly. You can tell a 2100 apart from a 2150 by the choke pulloff. If the pulloff is mounted vertically on the back of the air horn, it's a 2100. If the pulloff is mounted horizontally on the passenger side of the carburetor, it's a 2150.
2. There were two types of carburetors, 2100 and 2150. The 2100 has a small lever that rests on the cam, instead of the fast idle screw. For this model, the screw does not touch the cam. The 2150 has a fast idle screw that touches the cam directly. You can tell a 2100 apart from a 2150 by the choke pulloff. If the pulloff is mounted vertically on the back of the air horn, it's a 2100. If the pulloff is mounted horizontally on the passenger side of the carburetor, it's a 2150.
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