Why is fuel pressure low/

Hello, assuming gasoline engine not Diesel. Key on engine off should be 35-45 PSI. So, stop there. If you're not getting that kind of fuel pressure at the fuel rail, you have a likely pump issue. I know you said the pump is "new". How are you measuring the fuel pressure? Did you replace the full pump and sending unit assembly, or did you just replace the pump part itself and leave the rest? If you did not replace the entire assembly with a Ford unit, I would do that before anything else. Replacing the pump piece can sometimes yield an ineffective result or could even be faulty. If you need some guidance and assistance, reach out to a shop near you. https://repairpal.com/auto-repair-near-me Click the link or call us at 877-913-1554. We'll gladly find you a certified RepairPal shop in your area.