'00 S10 2.2 hard 2 start when warm

I recently put a new (remanned) 2.2 in the S10 and it starts great on the first start of the day as a fuel injected motor should. Hit the key and BAM!, it fires in the first revolution of the engine. Anytime after the first start of the day, Whether 10 minutes or after finishing work 9 hours later, it takes from 5 to 8 seconds of cranking and when it does catch, it takes some pedal to clear it up and then all is good. I haven't taken pump pressures yet and I guess the pump could be the issue if it don't provide optimum pressure when warm at all, even after 9 hours though? I'm only getting 21 MPG and was hoping for better out of a 2.2. Do I check fuel pressure at the capped fitting in the engine compartment on the line feeding the fuel rail? Any other thoughts out there?

I recently put a new (remanned) 2.2 in the S10 and it starts great on the first start of the day as a fuel injected motor should. Hit the key and BAM!, it fires in the first revolution of the engine. Anytime after the first start of the day, Whether 10 minutes or after finishing work 9 hours later, it takes from 5 to 8 seconds of cranking and when it does catch, it takes some pedal to clear it up and then all is good. I haven't taken pump pressures yet and I guess the pump could be the issue if it don't provide optimum pressure when warm at all, even after 9 hours though? I'm only getting 21 MPG and was hoping for better out of a 2.2. Do I check fuel pressure at the capped fitting in the engine compartment on the line feeding the fuel rail? Any other thoughts out there?

Yes check fuel pressure at scrader valve.
Any codes or check engine liights?
When was last good AC delco tune up?
Does engine crank over good when hard to start?

Thanks MT-2500, I do have a CEL, my fuel gauge flips out at times so I have a code for that and the after CAT O2 sensor. Can the O2 sensor be telling the computer something cuz it's still warm? I replaced the plugs and wires when I installed the new motor as well as the fuel filter. New battery cranks well anytime.

Thanks MT-2500, I do have a CEL, my fuel gauge flips out at times so I have a code for that and the after CAT O2 sensor. Can the O2 sensor be telling the computer something cuz it's still warm? I replaced the plugs and wires when I installed the new motor as well as the fuel filter. New battery cranks well anytime.

Bad or shorted 02 Snensor can cause all kinds of problems.
What are the code no?
Also check fuel pressure?