Autolite 4100

Ozsum2 · Sep 15, 2004

302 coupe said:
I was with you before you even knew it....

Sounded like you got lost there for a while. Let me know if I can be of further assistance.

notny41 · Sep 15, 2004

I'm not at the car right now, but I had been monkeying with the choke also, so I probably have that all F'd up by now too. It is a an automatic choke (driven by a thermo-spring) and I had it apart because it never seemed to fully close off when your first start the car - maybe it isn't supposed to. But in my efforts to try to get it to fully close I turned screws and cranked the cover almost all of the way to the rich side.

So, do I start with trying to get the choke dialed in correctly, or do I start with timing, or do I start with idle mixture screws? It is never going to get driven in really cold weather so if I can get by without the choke, that is just one less thing for me to feel like I screwed up.

Let me also say that this was a two barrel carb at one time and the previous owner threw on the 4100 and the 4 v intake and spacer. Don't know if that is important info here or not.

Ozsum2 · Sep 15, 2004

notny41 said:
I'm not at the car right now, but I had been monkeying with the choke also, so I probably have that all F'd up by now too. It is a an automatic choke (driven by a thermo-spring) and I had it apart because it never seemed to fully close off when your first start the car - maybe it isn't supposed to. But in my efforts to try to get it to fully close I turned screws and cranked the cover almost all of the way to the rich side.

So, do I start with trying to get the choke dialed in correctly, or do I start with timing, or do I start with idle mixture screws? It is never going to get driven in really cold weather so if I can get by without the choke, that is just one less thing for me to feel like I screwed up.

Let me also say that this was a two barrel carb at one time and the previous owner threw on the 4100 and the 4 v intake and spacer. Don't know if that is important info here or not.

To start with, get it to operating temp. Then, loosen the choke housing and turn it so that the choke plate is fully opened. Then you can adjust the idle richness and the timing, but always bring it up to temp first before making any adjustment.

Once you have made these adjustments, let it cool completely back down. Then, get in and press the gas pedal all the way down just once. This will set the choke plate with the fast idle cam. Check to see if the choke plate closed. If it did, start the car and see what the idle rpm is. If it didn't, the choke is hanging up. The little cylinder in the auto choke sometimes get grit in it and that is all it takes to keep it from working. On 2100's, there is a hose that draws air to the choke spring from filtered air. If it closes and when the engine startes, the rpm isn't say around 1000 to 1200 rpm, the fast idle cam needs adjusted. Before I go into this detail, let's see if it needs it first.

notny41 · Sep 15, 2004

When I had the cover off the autochoke I did see that little piston/cylinder in there and wondered what that does. Seemed like it was trying to open the choke. I gave it some spray lube to make sure it could slide up and down (kind of at an angle) and it seemed to move freely.

I have the hood open and the air filter off so I can see what is going on when I start the car and even if the choke is fully closed when I start the car, the choke butterfly will open up about the width of 3/8". Is that supposed to happen. It seems like the draft of the carb sucking in air is making it do that. Then while it is idling (or trying to) I will go and push the butterfly all the way closed and the engine will rev very rapidly (like I was stepping on the gas) and then die out if I continue to hold the butterfly closed.

Any of that sound normal?

Max Power · Sep 15, 2004

Yes.

The choke has to be at least a little bit open to let air in. That's why it dies when you hold it closed. It's never supposed to be completely closed, there is always a little gap for air flow.

Ozsum2 · Sep 15, 2004

Max is correct. Now, does it open all the way up when fully warm? What is the idle rpm when you first start it up? Guess.

notny41 · Sep 15, 2004

It does open all the way up once it is warm.

I've been tinkering with the idle alot but when I first start it up and it needs to be fed (by pumping the pedal) I would say it probably runs between 500 - 800 rpm. I don't have a tach though. But again ... I've played around alot with the screw that holds the idle and also with the idle mixture screws.

I was home for a little bit and tried starting it again without pumping the gas and it just turns over without firing. Then when I pumped it once it started but then immediately went back into the needing-to-be-pumped mode again.

My goal here is to be able to pump it once and turn the key and the engine runs without having to touch the pedal again.

JB66 · Sep 15, 2004

A little bit of further info... When you "set" the choke to start it, the butterfly should FULLY close with some tension on it to keep it there.(by setting the housing to the "richer" side) When you start the engine, there is a "choke pull off" (that little piston, you saw) which is pulled by vacuum to open the butterfly. If you notice, immediately after the engine fires, the butterfly is pulled partially open and the car stalls. The pull off is adjusted by bending the butterfly rod at the kink. It needs to be adjusted to about 1/8" of butterfly opening (or less)(measured from the front lip of the butterfly to the lip of the air horn) to keep the engine running. There are specs for each carb. You will have to play with it until you get it to keep running. Also check the setting on the accelerator pump. Raising it to the top hole should give you plenty of fuel to start it. Hope this helps.

notny41 · Sep 15, 2004

OK guys...don't laugh at me but I only get to spend time with my baby (Mustang) after the kids and my wife go to bed. And my wife told me I can't start the thing late at night because "it's too loud".

So, I didn't get a chance to check timing or idle mixtures or any of that. But that didn't stop me from going out there and looking at it and brainstorming. So as I was sitting in the garage looking at it, I thought the carb looked a little funny. It looked like it was not level. So I got out my level and laid it across the two top front screws and the two top back screws and sure enough the thing is not even close to being level. It is quite a bit lower on the passenger side of the car.

Now, I've been wondering if I have a bad motor mount because, one time (not at band camp) I did a burnout and in the middle of it the clutch pedal went to the floor and I heard a big clunk. I ended up breaking the equalizer bar pivot (engine side). I replaced that and was up and running again, but when I accelerate hard from a start now, it gives me a funny feel on the clutch pedal sometimes.

So:

1. Could a bad motor mount be giving me carb problems if the engine (and thus the carb) is not level in the engine bay?

2. How can I check to see if the motor mounts are good or bad?

It's a good thing I love this car so much or I'd have probably sold it by now...

notny41 · Sep 15, 2004

Well, I did a search in this forum on motor mounts and I spotted one called Wheelhop and I have experienced this on almost all the times I spin the tires. I am thinking among other problems I probably have a motor mount issue...

Is there a way to test if the MM's are good or bad?

notny41 · Sep 15, 2004

Well, I confirmed it. I crawled under the front end with a flashlight and the passenger side motor mount rubber has a big diagonal crack in it and even I can tell it is in need of replacing.

Didn't mean to hyjack a carb thread with motor mount stuff, but could this possibly be giving me idle and symptoms of running rough while going down the road?

Ozsum2 · Sep 16, 2004

notny41 said:
Well, I confirmed it. I crawled under the front end with a flashlight and the passenger side motor mount rubber has a big diagonal crack in it and even I can tell it is in need of replacing.

Didn't mean to hyjack a carb thread with motor mount stuff, but could this possibly be giving me idle and symptoms of running rough while going down the road?

NO. You have other issues. Try adjusting the butterfly. Like someone said, it may be open too wide when it startes. You shouldn't have to "bend" something though. There should be a linkage or nylon nut.

JB66 · Sep 16, 2004

Ozsum67 is very correct. There is an adjusting nut for the butterfly. My apologies for the misinformation. From what I see in my shop manual, the floats on the 4100 pivot on the drivers side, so if the engine is leaning to the pass. side the float levels would be too high. You can go to my web page http://home.stny.rr.com/bomansinusa and 4100 info for further info and pictures of the 4100.

JB66 · Sep 16, 2004

I looked up the de-choke specs. for you. Clearance for the butterfly on engine start is .100 to .120. #10 or 12 drill or about 3/32 to 1/8. Try that to start.

notny41 · Sep 23, 2004

Ozsum2, you were right. I replaced the motor mount and got the carb level and it still runs rough. I'm wondering if maybe I need a new coil for how it runs when I'm out on the road.

But the thing still requires constant monitoring and pedal pumping to keep it running once it starts so I am going to continue to work on that choke butterfly gap.

65Mustang2+2 · Sep 23, 2004

Paul,
Your car is having the same problem that my car is having! It sounds like the hot idle is not set right! When I drive my car and it gets warm the idle revs and you have to tap on the gas to get it to kick back down! It sounds just like my car, same carb same problem! Just try adjusting the "Hot idle" screw when the car gets warm. Hope it helps. Old cars are a pain in my ass, but thats why we love them. Let me know if it helps you!

JB66 · Sep 23, 2004

The choke setup procedure from the service manual is included in the information on my website.

Ozsum2 · Sep 24, 2004

..........................also in ther Ford Shop Manual. I will take up where Super Dave left off and advocate that everyone should have one.

notny41 · Sep 24, 2004

Well, I attempted the choke adjustment with the help of your docs JB66. Thanks! I also set the idle mixture screws to 1 3/4 turns out from fully seated as someone had mentioned in a previous post was the starting point.

I won't know how the adjustments worked until later today. We had company last night and I was out in the garage tinkering pretty late and didn't want to wake the beast for fear that it might wake our company (and my wife).

I didn't have the 10-8 tool that the instructions made mention of but I think someone had said that the opening for the choke should be about 1/8" so I used that size drill bit in making my adjustments.

Also pulled all of the plugs last night and they all looked good (no fouling). Checked the dwell and condition of the point contacts and that all looked good too.

JB66 · Sep 24, 2004

As added info, If it starts right up and stalls almost immediately, decrease the butterfly opening. If it starts right up and starts running rough and putting out black smoke, increase the opening. Do it in small increments though. The choke pulloff adjustment is very tempramental and seasonal, too.

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