What's inside a fuel pump? I wonder if it has a diaphram similar to an accelerator valve on a carburator. If the pump has a diaphram in it, it could very easily have developed a pin hole leak. This would still get you your 42psi when fired up but also provide a loss of pressure over time allowing fuel to get back to the tank.
Don't replace the fuel rails unless you are certain they're bad. That gunna cost $$$.
I personally would look into the fuel pump having a leak.
Don't replace the fuel rails unless you are certain they're bad. That gunna cost $$$.
I personally would look into the fuel pump having a leak.