What would cause long crank time on a 2000 chevrolet silverado?

Bad fuel pressure regulator? Or weak fuel pump? Try tuning the key on (but not start) for about 5 seconds then off then on for 5 then off then on and then try to start. This should run the fuel pump to build up pressure. Sometimes as the pump gets weak it needs more power to run and with the colder temps and an older battery there just may not be enough power for the pump when the engine is cranking. Running the pump before cranking may build up enough pressure that the engine can start which then brings the alternator online and gives the weak pump enough power to keep running. If its the fuel pressure regulator your MPG wont be as good as it used to be. You can also try the key cycle thing for that and holding the gas pedal to the floor. If the regulator is bad the pressure in the fuel system floods the engine. Holding the pedal to the floor (with engine not running) tells the computer to turn off the fuel so if its flooded this should help to clear it. Same thing if it was a leaking injector.