finished up preventive maint. & got 69psi at idle 64 pushing hard,what's the max allowed,has gold spring with new FRX.

 

I don't know, but...bump...

 

It’s not the pressure as much as at what point do you exceed what volume "requirements". Stock, around 55/45 is more than sufficient at the Fuel Bowl and 35/40 at the Head. Immediately following the injection the barrel fills and is ready for the next cycle. Only so much fuel can enter the barrel regardless of pressure (higher). Lower pressure begins to affect the amount at 42 psig causing a lean condition. When is too much, too much? When the pressure causes laminar flow to become tabulate, This cause a lean condition as well. All things considered, more fuel is returned than used during any injection event.

 

According to my ISSPRO fuel pressure gauge, the PSI in my truck is right where you are during normal operation. From what I have read, this is a little high, but no problems caused by it at this pressure. When you get into the low 40's and below is where you should be concerned.

 

I did forget to state that higher pressure = shorter fuel pump life. The Fuel Pump is cooled by the Diesel moving through it carrying away heat from the electric motor. But, again, "who knows where "Too High a Pressure" is".

 

IIRC The basic Ford specification for fuel pressure is 45-65 psi. You could go with a lighter spring if you wanted to. As long as your not dropping below 45 on a WOT run you should be good.

 

Ok Thanks for the info,might try the silver spring instead of the gold