I am having fuel pressure problems rail pressure is varrying. I have had the truck die but start right back up. I have a monitor on the truck for fuel rail pressure and for pressure going to the pump. I have noticed that the rail pressure sometimes drops to about 2000 psi but I have also seen the pressure running more than 25000 psi. The gauge readings are accurate and I can tell that the truck has less power as rail pressure decreases. I originally thought it was the rail relief valve but I do not suspect it anymore due to the varying rail pressures. Also it seems the truck only does this in cold weather.

I am considering changing the injector pump but hate spending that much money guessing at problems.

 

Lift pump

 

I have a gauge and alarm for low supply pressure

 

I am not 100% sure, gas engines have a pressure regulator on the fuel pump. If diesel's do too could be that. Although the rail pressure relied can cause this as well, of it is opening intermittently.