jo c; What make and model of truck are you working on? What you can do for now is to verify that fuel pressure, and then if fhe pressure is high and to what degree you may be able to tweek it to within spec of 4.6 to 4.8 psig at engine's coolant temp of 80 C. For this procedure take the following steps: 1. Apply the park brake and block up the drive wheels to prevent truck movement. 2. Close off the fuel tank's supply valve and disconnect fuel hose from supply take. 3. In a well ventilated area with the key sw off crack open the 1/8 inch BSP
on the top side of the regulator. 4. Replace the 1/8 plug with barb fitting, hose & 10 psi guage. 5. Reconnect the fuel line at the tank and turn on the fuel. 6. Turn on key sw and read the pressure guage at the fuel regulator. What is the pressure you are seeing with a cold engine?