Jeeper  Adventures Under the Hood  Jeeper

Electric Choke

The electric choke sticks out on the right side of the carburetor, and has red-with-white-tracer wires plugged into it. It's operation is straight ahead. When the engine is started, the electric heating element is energized through a relay tied to the oil pressure switch, gradually opening the choke.

Also shown in this photo is the Wide Open Throttle switch (blue and black wires).

Electric Choke

Your Jeep gives you trouble when you start it up cold. As soon as you give it a little gas pedal, it sputters and stalls, or maybe it continues to run but misses badly and possibly blows some smoke out the tailpipe. Once it warms up, it's fine.
These are both classic symptoms of a carburetor choke that is malfunctioning and/or out of adjustment.

Adjusting the choke

  • With the engine completely cold, the choke door (after depressing the accelerator pedal once) should be completely closed. The colder the outside temperature, the tighter the choke door should be closed, but it shouldn't be ridiculously tight. In summer it should be lightly closed, in winter more firmly.

    • To adjust the choke, block the throttle partially open so the fast idle cam steps don't interfere.
    • Loosen the three screws that hold down the plastic part of the choke mechanism just enough that it can be turned. You'll have to move the air cleaner out of the way to gain access.
    • As you turn the plastic part of the choke, you'll see the choke door moving. Set the choke door closed as described above, and then tighten the three screws.

  • When the engine starts, the choke pull-off should open the door partially, and the choke heating element should begin to heat the bi-metal spring in the choke. If the door doesn't open far enough, the engine will quickly begin to shudder and blow smoke. If it opens too far, the engine will probably spit and die if you try to drive away. I use two pairs of long-nose pliers to quickly bend the pull-off tang to get the best, smooth fast-idle. This may require a few tries to get it right, always starting with a cold engine.
  • As the engine warms up the choke should gradually open all the way. It should be wide open long before the engine reaches normal operating temperature. Once the engine is shut off, the choke door should remain open for quite a while as the engine cools down—if it's even partially closing right away, something isn't right.

Things that can go wrong

  • The choke sticks or hangs.
  • The choke is way out of adjustment.
  • The bimetal spring is tired and no longer has enough travel between hot and cold.
  • The heating element doesn't work.
  • The heating element is not getting the required 12 volts.

First, check the heating element with an ohmmeter. Find the plug at the choke and unplug it. Check between the choke contact and ground. It should read in the neighborhood of 3.8 ohms. If it's far higher, or open, it's defective.

With the choke plugged in and the engine running, check for 12—14 volts at that contact. If there is no voltage then you'll have to trace the wires backward to find out why.

Also, those bimetal springs can wear out as I mentioned above, and they no longer will move the choke door far enough — if it's set with the proper tension when cold, it won't open all the way — if it's set to open all the way, it won't close completely. There is nothing to do here except buy a new choke mechanism.

With a properly adjusted choke, a cold engine should start easily in any weather, run nicely, and you should be able to drive away immediately. As it warms up, nothing should change regarding engine smoothness, except the fast idle should quickly drop down.
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