Are you using full choke when you try to start the cold engine? Ideally, if the fast idle cam is working properly, you should pull the choke knob all the way out, and crank the engine with your foot off the gas until the engine fires, then quickly push the choke knob in partway to keep the engine from stalling from too much choke. Most people pump the gas pedal, or hold the throttle partway open and don't use enough choke on a cold engine.
If the one-way check valves in the fuel pump get a little leaky, the pump will have to fill the fuel line and the float bowl in the carburetor before the engine fires.
Jerry
