Adjusting a Thermostatic Spring Choke


Many cars have a thermostatic spring choke. Some are riv­eted in place and can only be overhauled by a mechanic, but if you have an older car and have trouble starting it in the morning, you may be able to adjust yours.

thermostatic spring choke

Before you fiddle with the choke, check the specifications for your automatic choke and see whether it’s properly set (if the proper notch on the carburetor housing is opposite the indicator on the plastic cap shown). If the choke is properly set and the valve doesn’t close, try adjusting the thermostatic spring choke to a richer setting. If the choke is not properly set, adjust it to the proper setting. To accomplish either of these tasks, follow these steps:

1. Loosen the three screws that keep the plastic cap, in place.

2. Turn the cap until the notch on it lines up with the proper mark on the carburetor housing. On the back of the cap are the words Lean and Rich with arrows to indi­cate direction. Your specifications may read "one notch Lean," in which case you turn the cap until the indicator lines up with the first mark on the Lean side of the carburetor housing.

thermostatic spring choke

If your cap was already set at the specified mark, just turn the cap one notch to the richer side and see how that works the next morning.

3. If you car still doesn’t start properly, try setting the cap one more notch richer. These chokes are generally set on the lean side, so they often run better cold when set a notch richer. Never adjust more than one notch at a time.

4. When you’re done, tighten down the three screws.

Adjusting a Thermostatic Spring Choke was last modified: December 31st, 2015 by George Sitompul