Help! My truck starts, then dies

[pjmoreland]

I'm struggling with a problem with my truck. When the engine is cold and I start it, it starts right up, but then after about 5 seconds, the engine stumbles and dies. If I time it just right, I can keep it from dying if I pump the gas pedal lightly and quickly. But then about every 5 seconds or so, the engine starts to die again. I have to repeat the pedal pumping about 10 times. Then finally after about two minutes the engine will idle consistently. It usually ends up dying when I shift it into gear. It's quite an ordeal to get the truck going in the morning.

The carburetor is a Quadrajet with a heat-activated coil choke. The choke closes completely when the engine is cold and the gas pedal is tapped. Once the engine starts, the vacuum diaphragm pulls the choke open and the engine runs at around 1300 RPM before it dies. I have the idle mixture screws adjusted to give the highest RPM. They are screwed out about 1/2 turn.

My timing is adjusted at 10 degrees. I'm at high altitude, and I've been told that the extra 2 degrees help with the thin air. All spark plugs are firing consistently.

Once the engine is warm, it runs great. Any ideas? Thanks for the help.