I have noticed when it is colder outside around 40-50 degrees, the sender directly on the FASS lift pump block, the pressure at start up will spike around 18-20 PSI and will lower towards 10-12 PSI normally truck runs at a steady 15 PSI, but during the day it seems to hold steady, any ideas?

 

Possible faulty sender

 

So the cold won't affect the pump? I wonder how I could run a test on the pump and sender?