I am about to rebuild the 2150 on my F250 400. The PO had put on a manual choke, which I am planning on keeping. Do I need to keep the choke pull off on the carb? Is it doing anything with a manual choke?

Also, there is a broken piece on the choke linkage - will this cause me problems? Thanks!

 

Here's the pic: http://i1133.photobucket.com/albums/...Lips/choke.jpg

 

Keep the manual choke. It works best

 

I will stick with the manual choke. My question is what about all of the automatic choke related linkages - the pull off, the fast idle cam - are they still needed?

I ask because the fast idle cam on my carb is frozen (even after a day soaking in carb cleaner). Also, the yellow plastic fast idle cam linkage is broken (no doubt from trying to move against a frozen cam).

What do folks with a manual choke do? Leave all of the linkages in place and just bolt on the choke kit? Can I ditch the fast idle cam and linkages between the choke and throttle and go totally manual? Thanks!

 

All of the fast idle linkage is still necessary. The fast idle linkage is responsible for maintaining the idle speed while the choke is engaged, independent of the mechanism behind opening the choke.

The plastic fast idle arm you've shown in your picture is very susceptible to breaking as you've shown, and must be replaced. It couples the choke shaft with the fast idle cam; without it the fast idle will never come on. This will be a problem for cold starts.

Your question about the pulloff is interesting. The pulloff is responsible for fighting the choke thermostat tension and keeping the choke plate open just enough for the engine to run when it first starts. Without it, the automatic choke will cut off the throat of the carburetor. I'm not sure if it would work with a manual choke setup because it would have to be able to push the choke cable backwards. With a manual setup you could at least mimic the pulloff's behavior yourself. At the very least, if you do remove the pulloff, you need to plug off its vacuum source.

 

Thanks for the reply FMC! All of your posts on choke operation have been extremely helpful to this newb.

Last night I dry fit the linkages back together and came to the same conclusion. I found a source for the plastic idle arm and will replace that.

One other issue I noticed is the fast idle screw (in the bottom picture that rides on the fast idle cam) does not reach the warm idle portion of the cam. It could be screwed in a little more, but I don't think it will be enough (plus, the spring is already pretty compressed). It appears the only way to correct this is to loosen the nut on the throttle rod and rotate the bracket so the screw touches the cam. Is there some documented procedure for setting this (i.e. how far should the throttle plates be open when the cam is at warm idle)?

All of the carb rebuild instructions I have seen recommend leaving the choke linkages connected and warn about messing with the throttle rod - it may be too late for that.

 

This might help you.

http://www.therangerstation.com/tech..._2150_carb.pdf

 

Yep - that's the rebuild guide I have been using. Unfortunately, it doesn't say anything about adjusting the bracket on the end of the throttle rod - if indeed that is what I need to do.

 

The fast idle screw isn't supposed to touch the "warm idle" step of the cam. There are three steps to the cam. When you press the pedal down once before a cold start to set the choke (with an automatic choke, it snaps shut; with a manual choke, you do it yourself) the fast idle screw touches the highest point of the cam. Once the engine is running and the choke plate is in the pulloff position, the end of the fast idle speed screw drops to the second step and touches the "V" notched in the cam. The end of the screw rests on this step of the cam as the choke opens. Note that the throttle has to open for the cam to be able to move, otherwise the fast idle linkage is pinned in place. So the process only happens as you drive the vehicle (and accelerate). In your picture, you can see the end of the screw is about halfway through the second step. This would correspond with the choke plate being about halfway open. Once the choke plate opens all the way, the fast idle linkage is pushed even farther until the end of the screw is pushed off the middle step. The fast idle screw never actually touches the third step. At this point, the throttle plates are at their normal position and idle is adjusted by the curb idle screw on the driver side of the carburetor.

The advantage to the 2100/2150 carburetors is that the relationship between the choke plate position (degrees of rotation) and the position of the end of the screw relative to the fast idle cam is completely adjustable. This adjustment is called the fast idle index. It's done with the hex screw in the plastic fast idle arm. This arm is central to the mechanism, so until you replace it you won't be able to make the adjustment.

I did a write-up on making the adjustment, here's the link: https://www.ford-trucks.com/forums/7...ml#post6422219

 

Ahh, excellent - glad I don't have to worry about it then. I am looking forward to getting the plastic fast idle arm and seeing how it works (properly) assembled.

I already have your instructions printed out as part of my rebuild notes. Thanks a ton for help!