Packard Forum Index » Post-War (1946-54)

Can someone explain the Carter WGD fast idle circuit theory?
Perhaps with a good pic?

I feel like I'm missing something.
I have no fast idle on my '51 and have spent the last 2 hours trying to figure out how the fast idle circuit is supposed to open the throttle. Or am I totally missing the point on how it works?

Can't help on the theory but Service Counselor 23 #11https://www.packardinfo.com/xoops/html/downloads/SC/SC-VOL23NO11.pdf has some pretty decent pictures and the procedure to adjust.

The clearance spec was changed in 51 (SC 25 #3) from the original .026 mentioned in the procedure to .023 to slow the idle slightly. It sounds like you bend the rod to get the specified clearance so as to keep the throttle plates open a small amount under certain conditions.

Yes, but what actually makes the difference between fast and curb idle? I get the feeling something is either WAY out of whack or I'm missing a part.

Let's say I bend the choke connector rod to make the fast idle link "Top out" and give me the correct spacing on the throttle valve. What causes it to close to curb idle? Heat expansion of the fast idle link? Something is very wrong here.

There is a terminology problemm here that is making it difficult to understand the problem and discuss it.

There is an "idle circuit" for the fuel which delivers fuel for both fast and slow idling, not for driving. There are mechanical linkages, a thermostatic spring inside the choke cover, stop screws and cams which regulate the fast and slow idle.

The service manual describes it in detail and gives adjustment procedure which ususally must be done in order.

In your carb there is a little cam attached to the choke shaft in the housing behind the thermostatic coil. When your choke is closed this cam rotates with it and presents its highest point to that flat vertical bar that slides up into the housing. On a cold start, when you open the throttle the choke snaps shut. The car starts and you let off the gas. Because the choke is mostly shut, the vertical bar is held down by the cam. By means of the link you mention, the throttle is held slightly open. Once the car has warmed up, the choke swings open and that bar is no longer held down.

Now that little cam is actually spring loaded so that the choke can move as the car warms without disturbing the high idle til you blip the throttle and let it loose. I am wondering if that little spring (behind the cam) is missing or broken on yours.

Sorry about the nomenclature mix-up...

The cam does not seem to ever touch the vertical bar.
I don't see any mechanism where the cam ever touches the vertical bar. The unloader touches the bar, but when choke is applied it releases if anything. at what point is the cam supposed to make contact with the vertical bar? I get the feeling something is missing.

Here is a video of what I am talking about:
WGD Fast Idle Video 1

Without looking I forgot about the unloader link. I'll try to take a picture today. Now I'm wondering if one of the little arms has broken off your unloader.

I have a spare WGD 10 feet from me in the garage. I'll take it apart and take a pic in 10 seconds. BRB.

I'm back! Took longer than 10 seconds, sorry. Keep in mind that my carb base isn't hooked up, so the little "input sliding lever" on the right is held up by my finger in one of the pics and left to dangle in the other. I BELIEVE it is mostly up when the engine is cold. This choke for sure worked for me as a test carb a couple weeks ago.

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I watched your video on line and it seems to me that the arms and tabs are working fine. The two tabs or arms if I am looking at it correctly do not connect

I believe your problem is with the choke adjustment. With the carb cold connect the outside plastic cover with the spring back onto the carb body and adjust the cover so that the tab just closes the throttle. That should adjust your cold idle speed correctly.