Since it's gotten cold out (below 40) my blazer won't start on the first try after turning the ignition for 2 seconds (as long as it would take to normally start), but trying the 2nd time it starts okay. If I hold the key for much longer than 2 seconds it starts chugging but won't start and if I try a second time it chugs faster and will eventually start. It's got about 160k miles, I got a tune up 2 years, 10k miles ago, and that fixed the problem once before. Coolant temperature sensor (new) has recently been put in and a mass airflow sensor (from junkyard) has also been put in.

 

Try a new fuel filter, It seems like its not getting enough fuel the first time the pump cycles.

 

if a new fuel filter wont work check the Fuel PSI you may need a new fuel pump

if thats the case, make sure to get Delphi or AC Delco