When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Fuel pressure if I am not mistaken is like 60-120 psi from the lift pump, the pump itself increases the pressure when it delievers fuel to the injectors at 1400 psi(new injectors typically open at 1700). to check the pressure on 6.9 engines check it at the 3/16" hose barb on the fuel filter outlet elbow, and on 7.3 at the fuel filter orifice/return line fitting or restricted filter sensor port. If checking either at the filter return line fitting, plug the return hose. Fuel pressure here should be 1 psi minimum at idle. Lift pump pressure is taken at the fuel filter bleed schrader port and should be 2 psi minimum at idle. Its not much but thats what i believe it is.
The lift pump produces only 5-7 lbs. at the filter head. There is a schrader valve on the fuel filter head (looks like a tire valve) to check the pressure. Air leaks on the return side usually makes for a longe cranking time when trying to start after setting for a while. If you think you have an air leak, remove the fuel filter after the truck has been setting over night to check to see if it is full.