1940 Hard Starting

Hard starting in a vehicle with a Holley 1940 carburetor can be caused by several issues. Here are some common causes and solutions:

1. Choke Problems:

   • Choke not closing properly: The choke plate should close fully when the engine is cold. If it’s not closing correctly, it can cause hard starting. Check for proper adjustment and ensure the choke linkage moves freely.
   • Choke stuck open: If the choke remains open, the engine may not get the rich fuel mixture needed for cold starting. Ensure the choke moves to the closed position when the engine is cold.
   • Starting Hot: The choke valve should be open. If not, then the air/fuel will be too rich on a hot start.
     

2. Fuel Delivery Issues:

   • Empty fuel bowl: If the carburetor’s fuel bowl is empty or low, it can cause hard starting. Check for leaks or fuel evaporation. Make sure the fuel pump is functioning properly.
   • After turning off your engine look down the carburetor to see if gas is dribbling out of the main discharge. If so, then it is being siphoned by a blocked vent, check ball not seating, or maybe you have a non vented gas cap. The siphoning will cause fuel to drain into the intake.
   • Clogged fuel filter: A clogged fuel filter can restrict fuel flow to the carburetor. Replace the fuel filter if necessary.

3. Carburetor Adjustment:

   • Incorrect idle mixture: The idle mixture might be too lean or too rich. Adjust the idle mixture screws to achieve the correct air-fuel ratio.
   • Float level: The float level in the carburetor might be set too low or too high. Adjust the float level according to the manufacturer’s specifications.

4. Ignition Issues:

   • Weak spark: A weak spark can make starting difficult. Check the ignition system, including spark plugs, wires, distributor cap, rotor, and ignition coil.
   • Timing: Incorrect ignition timing can cause hard starting. Check and adjust the timing as needed.

5. Vacuum Leaks:

   • Leaking gaskets or hoses: Vacuum leaks can lean out the air-fuel mixture, making it hard to start. Inspect all vacuum hoses and carburetor gaskets for leaks and replace any damaged components.

6. Engine Temperature:

   • Cold weather: In cold weather, the engine requires a richer fuel mixture to start. Ensure the choke is functioning correctly and consider using a block heater if necessary.
   • How to Start Cold: Press down on the accelerator once. This allows the fast idle to fall into place and also provides a squirt of gas from the main discharge into the carb. A cold engine needs a little extra fuel to get going.
   • How to Start Hot: If you suspect too much gas, hold the throttle all the way to the floor while cranking. Crank 5 or so seconds then allow to sit 5 or so seconds and try again.

7. Fuel Quality:

   • Bad fuel: Stale or contaminated fuel can cause starting issues. If the fuel is old or contaminated, drain the fuel tank and refill it with fresh fuel. Gas that has turned to varnish, and you will be able to smell it, will coat the inside of the carburetor, fuel lines and gas tank. Rebuild the carburetor, remove and clean the gas tank and flush out the gas lines.

8. Carburetor Cleanliness:

   • Dirty carburetor: A dirty or gummed-up carburetor can restrict fuel flow and affect starting. Clean the carburetor thoroughly and ensure all passages are clear.

By systematically checking and addressing these potential issues, you can improve the starting performance of your vehicle with a Holley 1940 carburetor.