Will not start on cold days?

Hello,

You probably want to make sure you are getting proper fuel pressure when its cold.
You could have a faulty fuel pressure regulator that acts up when cold but works just fine as it warms up.
Check the fuel pressure on the cold morning to see what its producing.
You will need a pressure gauge for fuel pressure check. You can typically get those testers from your local auto parts store to use.
You should have 41-47 PSI of fuel pressure.

Here is a helpful video of how to check fuel pressure:

https://youtu.be/aITQclp7zIE

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

I have attached diagram for your reference.

Please let me know of any questions.

Thank you.