If your Autolite 1100 carburetor doesn't start with the choke closed, there are several potential reasons for this issue:
Overly Rich Mixture: When the choke is fully closed, it enriches the fuel mixture. If the mixture becomes too rich (too much fuel and not enough air), the engine may flood and fail to start. You might notice a strong fuel smell or wet spark plugs if this happens.
Incorrect Choke Adjustment: The choke plate might be set too tightly, completely blocking the airflow. The choke should be adjusted so that it partially closes when cold, allowing just enough air in to start the engine.
Choke Sticking or Binding: If the choke is not opening slightly as the engine cranks, it can restrict airflow too much. This might be due to a sticking choke mechanism or a faulty choke cable/linkage.
Fuel Delivery Issues: If the carburetor is not getting fuel, the engine won't start regardless of the choke position. Check the fuel pump, lines, and filter for blockages or failures.
Ignition Issues: Even with the choke closed, the engine needs a good spark to ignite the rich mixture. Faulty spark plugs, ignition coil, or distributor issues could prevent starting.
Incorrect Idle Speed Setting: If the idle speed is set too low, it may not allow the engine to run with the choke closed. Ensure that the idle speed and mixture settings are correctly adjusted.
Vacuum Leaks: Vacuum leaks can disrupt the air/fuel mixture balance, making starting difficult, especially when the choke is closed. Check for any disconnected or cracked hoses.
To troubleshoot, try opening the choke slightly when cranking the engine to see if it starts more easily. If it does, then the choke is likely set too tightly or needs adjustment. Checking spark plugs for signs of flooding and ensuring proper fuel delivery can also help identify the root cause.
