In Part I, we examined the elements of the Choke Processes.
In this article, we want to adjust the Heating Element so that the Choke Plate will respond properly as the engine is working to arrive at operational temperature.
The time to adjust the Heating Element is when the engine is cold and the Key is NOT in the Ignition.
Remove the Air Breather for ease of access to the Carburetor and so that you can see the Choke Plate inside the throat of the Carburetor.
We need the Idle Cam to be free during the adjustment process. You can remove the Accelerator Lever (or Arm) Return Spring, for the moment, to disable the Accelerator Lever.
Slightly loosen the Three Heating Element Screws at the Retaining Bezel. This will allow us to move the Heating Element clockwise or counter-clockwise.
If we turn the Heating Element counter-clockwise, the Bi-Metal Spring Hook (inside the Choke Heater Housing) will catch the Upper Arm of the Choke Plate Shaft, forcing the Plate to close.
If we turn the Heating Element clock-wise, we release pressure upon the Upper Arm of the Choke Plate Shaft, allowing the Choke Plate to open.
Perform this exercise while watching the Choke Plate. You soon will have a feel for this adjustment. Not every Carburetor will adjust the same due to the nuances of mass-produced Heating Elements and Carburetors and old Carburetors, etc.
Our objective is to put enough pressure upon the Choke Plate so that it comes almost to a fully closed position. But not quite. If we force the Choke Plate fully closed, it will take the Heating Element too long to heat in order to relax the Bi-metal Spring. When the Choke Plate is closed hard, the Fuel Mixture remains charged with gasoline, but with insufficient air, so that the engine begins to struggle for a less enriched mixture as it begins to attain operating temperature. (Even more so if this occurs during warm or hot weather when it should not take as long for the Heating Element to heat the Bi-metal Spring.)
David Brown tells us: “I feel that in most cases the Choke is set too “rich”, that is, closed too far to begin with. When setting the Choke in real cold weather, I set it to lightly closed. When setting it in warmer weather, I set it to close only to about 3/8″ or so from fully closed. VWs don’t really need much choke.”
David continues—“ The Choke setting affects not only the cold starting but the length of time the Choke is active. If it’s off too soon….before the engine is ready to idle without the choke’s help….it’ll stall at the first stop sign. If it’s on too long, it will waste gasoline, carbon up the spark plugs and may even run poorly.”
Once you believe that you have the Heating Element turned so that the Choke Plate is properly tensioned, hold the Heating Element so that it does not slip. Gently tighten the Three Screws at the Bezel. Do not over-tighten and strip the threads! Once the Screws are tightened, test the Choke Plate.
To do this, flip the Idle Cam. The Choke Plate will respond and return to rest as you have set it—at a loose closure. If you see that the Plate is too loose or too tight, repeat the process. Once you have become familiar with the process, you will find it easier the next time.
Another general method for setting the Choke is to use the three “Pips” (see the photo).
Align the groove on the Choke Heater with the Center Pip. This is not exacting and is to be used only as a reference point, I feel.
David Brown says, again: “The “pips” on the Choke Housing and the line on the Choke Element make for a pretty close setting. If your choke is needing a setting way off of those pips, there is something wrong.” (could be the wrong Choke Heater Element?)
(Update)–David Brown writes:
The Factory Service Manual, Section K , Fuel Systems, SPECIFIES that the choke be assembled on the center pip. There are NO OTHER mentions of adjusting the choke in any other way!! So, there you have it right from the Factory. I still would adjust them to suit the weather, but only slightly. (No mention of the purpose of the other Pips.)”
Reengage the Accelerator Lever Return Spring. Replace the Air Breather.
Now go and drive your Beetle and enjoy the feel of the road!
1. Thank you, David Brown, as always, for your great contributions.
2. Thanks, also, to Barry Blythe, a Texas VW Engine Builder of many years—for his advice concerning the Choke Plate Settings.
3. Thanks to our daughter, Janeva Sulman for her videography abilities!