I got a question for someone that works on these more than me. I got a D5K LGP YYY01549 that has the 4.4 Acert in it. It started cutting out when you throttle it up and continues to cut out and puff black smoke as it catches itself. Rail pressure is all over the place so I replaced the return valve and rail pressure sensor. This was after I checked for air bubbles in the fuel and replaced the fuel filters. I’ve also changed out the fuel primer. I put injectors in it about two years ago. Has no issue starting. My question is can you get the fuel regulator separate or do I have to change the whole pump? Cat says I have to do the whole pump.
Questions: Has the fuel tank drain been opened to check for water/sediment in the tank.? Have you had the head off the fuel filter/water separator, removed the plugs/elbows, and blown air or run a wire through all the ports.? Have you pulled the Diagnostic Codes.? The only separate part listed on the HP fuel pump is the secondary speed/timing sensor.
I checked the tank right out the gate and even put my own source of fuel to the filter housing to eliminate the tank and the fuel lines. The filter housing has also been replaced with a new one. No codes just rail pressure is all over the place by thousand of psi compared to desired pressure.