Carter carb question

[cbolt]

I'm looking for some ideas here. I have a Carter AFB that all of a sudden doesn't come up to fast idle when cold. The choke seems to be adjusted and working but the fast idle cam only moves slightly, just to the first indent on the adjustment and stops there. I have tried adjusting the choke with no luck. I can manually put the fast idle cam in the correct spot and the carb operates correctly however with a normal start (sitting behind the wheel and not lifting the hood) the fast idle is virtually inoperative. I have power to the electric choke and like I said the butterfly operates correctly, just not the fast idle cam. Without bending a rod as per the instructions is there any other things I can look at or check? Has anyone else encountered a similiar issue? I have a hard time believing that an adjustment rod has bent itself while installed in the car, in my garage, with the hood closed. Any help or suggestions would be appreciated.

[wallaby]

I'm not a Carter guy, but most factory carbs use the choke thermostat to close the choke plate and move the linkages...and gravity causes the fast idle cam to rotate to a position to hold the throttle open a bit. The catch is that you need to pump the throttle before starting the engine to allow the gravity arm to drop into place. When you let the throttle return, it should be resting on the fast idle part of the cam.

As the choke thermostat warms up it pulls the choke plate open and linkage rotates the cam to a lower idle speed position.

So the choke coil will force the cam to go to slower steps as it forces the choke open...but the choke coil will not force the cam to go faster as the choke plate closes. That's where gravity and a free-moving idle cam come in.

[cbolt]

Right. The Carter isn't much different, using the choke spring tension to move the linkages to the fast setting and possibly gravity as the engine warms and the spring tension lessens. Suspecting a broken/won/dislodged spring I took the housing apart and everything seemed normal with the exeption of not having what I felt was proper spring tension on the cover. (You know, how it would move when loosened) Since it all looked normal I put it all back together and it seems like it will work now. I am going to test it by letting it sit for a few hours to cool and then checking it again. Could have been it just needed to be disassembled and reassembled but I won't be sure until I let it cool and test it again. Weird since it appears everything is clean in there.

[Winston Wolf]

With the electric choke coil cold, you need to press the pedal to the floor. The fast idle cam will not work without first moving the throttle enough to release pressure on it. The fast idle cam works on gravity/weight to rotate and then reset against the fast idle screw. The choke pulls the cam off the screw as it warms up and tightens. You can adjust the speed at which that happens by loosening the screws at the choke and rotating it. The cam has notches in the new ones, or curved angle in the old ones to give you the different idle speeds. Lightly tapping the pedal will pull it off high idle. The fast idle screw can wear into a angle over time which can affect how it works. If that is the case, simply re-file it flat and reset the speed. I would make sure the linkage is working freely and not binding.

 

Just look at how if works and you should be able to tell what's not happening.

 

If you cant get it, let me know and i can take some pitures to show you how to adjust it.

[cbolt]

Wolf,

 

I have made the adjustments to both the choke by loosening the screws and turning the housing cover and to the cam detent area via the screw on the accelerator linkage and what appears to be happening is that when I press the accelerator (or grab the linkage and do it by hand) the fast idle rod and cam rotates slightly but not enough to pull it all the way to the fast idle setting. I can then move the fast idle cam to the proper setting manually and it doesn't seem to bind but it won't move fully to fast idle simply by pressing the gas to the floor, which it used to do. I can't see any obstructions or binding in the linkage and I know Carter says that the linkage is designed to operate dry so lubrication is out of the question. Still scratching my head. I am wondering if the choke adjustment housing has somehow tured 360 degrees, taking most of the tension off the spring and I need to adjust it one full turn back to its original setting.

 

Having said all that I would love some pictures of how to make adjustments. I may see something I hadn't thought of or you may know a few tricks I don't. I'm almost to the point of just getting a rebuild kit and starting from scratch. (after the mini-meet in old town, that is) I hate doing that because this is mostly just a minor inconvenience at this point, the car runs great after I get it started and warm.

[Winston Wolf]

Here is how is should sit in the morning, not having been run, choke cooled off.

 

Choke will fall back closed as it cools and fast idle cam linkage will rotate until it hits the fast idle screw.

 

 

 

Press down on the pedal, takes pressure of the fast idle cam and it will fall down to the position shown due to gravity.

 

 

When you release the pedal, the screw will now rest on the high idle cam. Basically holds the throttle open slightly. This is the old style cam, the newer ones have several steps instead of a taper.

 

 

When the choke warms up and pulls the flapper open, it also lifts up the high idle cam and it can't contact the screw.

 

 

You can see how this screw is worn. That may be why they went to the stepped design, idk. But if you aren't getting a high enough idle and the linkage seems to be working as it should, just adjust the screw in further to turn up the speed. That's probably what happened anyways, the screw just worked loose.

 

Make sure the linkage moves freely, maybe squirt some wd40 on the pivot points in the carb body.

 

All the electric choke does is pull on the linkage to take off the choke. Turning it one way or the other just controls how fast it happens. It should be set so that as soon as the car is up to opperating temp, it's pulled the choke all the way off.

 

I don't think anything in the rebuild kit will address the problem you are having.

[stangeba]

Winston, great pictures and description!

Bruce

[cbolt]

those are great pictures! What is not happening with mine is in the third picture from the top. When I press my throttle the cam doesn't fal down into the position shown due to gravity, only down about as far as the position in the picture above it. According to Carter the linkages are designed to operate dry which to me says no WD-40 so that leaves me with the question how do I get the fast idle cam to move to the correct position when the engine is cold and the gas has been pressed?

[Winston Wolf]

Start taking linkage rods off and check each pivot point until you find out where it is binding. Just because the Carter book says it is designed to run dry doesn't mean that if you use some lube to fix your problem it will melt or something. May be some dirt or oxidation that is making it move harder. It's a simple mechanism so just trace the fault piece by piece.

[cbolt]

Yea, I think there is something binding the linkage but only slightly and oxidation or small dirt build up could very well be the culprit. Carter says not to use lube in order to avoid any material sticking to the lubricant and causing this very issue (I suspect this issue anyway) The problem could be at the screw holding the cam because the rods themselves look clean even at the joints. I'm gonna pull it out into the sunshine and play with it this morning. I took pictures of my own to compare with the ones in this thread and it is clear that the cam isn't moving as far as it should. It really is a simple mechanism and I have never seen an issue with a fast idle cam before so you can imagine how frustrating it is. This is my second Carter afb (different vehicles) and it has run flawlessly for 9 years since I did the initial tuning. Guess I'm rusty at carb troubleshooting nowadays.

[Winston Wolf]

I don't think it would be a rod itself that is binding, I think it would be the pivot points into the carb body or the pivot point that is a large screw.....

[cbolt]

that's what I am heading out to look at now.

[cbolt]

Well, I took the linkage apart at the pivot point, cleaned it really good and reassembled it. Now I am just waiting for it to get cold again so I can see if it is working or not. It better be #$%&&*@#$ working!!! Hopefully this has got it but I have said that before.