how are you starting the truck - you should push the pedal to the floor once to close the choke, then when it starts, hit the pedal again to drop down 1 notch on the cam. If it doesn't work that way, your linkage is hanging up for the choke. The choke adjustment ragrag timetime mentioned is important also, as the choke is a spring that unwinds when it heats up to open the choke, if it is wound too tight it will open slowly, if at all; too loose and it won't set