I have a 2000 blazer 4.3 If the temp is below 60 it will turn over but will not start. I if it's 60 or above it will fire right up and run like a champ. We have changed the fuel pump and filter, temperature control sensor, and a full tune up. Any ideas???

 

Regulated fuel pressure and leak down test. It may still be leaking under the plenum. I'd perform the test when it's cold and going to act up.

 

thank you. I will try that.

 

What does "full tune up" mean exactly? Was this Delco cap, rotor, plugs, wires?

The problem is likely due to fuel delivery; follow advice from Rusty.