I have a 1999 K1500 Suburban with a 5.7l. It exhibits an instant 10psi drop in fuel pressure when the fuel pump stops while doing a key on engine off test. It goes from 61-62psi (in spec) while the pump is running to 51-52psi (out of spec) when it is off. It holds there.
I have followed the service manual's fuel system diagnosis flow chart and isolated the fuel system at the fuel filter with a J 42873-1 shut off valve. I get an acceptable 2-4 psi drop when the valve is shut isolating the front 3/4 of the fuel loop. So it seems like something in the supply line before the fuel filter is causing the majority of the 10psi drop. Before replacing the the fuel line from the sender to the fuel filter, what could cause such a large instantaneous drop and then hold? Any help before plunking down $150 bucks would be greatly appreciated.
FWIW: I have a new fuel pump and a new MPFI spider injector that came with a new regulator.
Here is video of the drop. [If the video does not play click on the YouTube icon in the player]
I have followed the service manual's fuel system diagnosis flow chart and isolated the fuel system at the fuel filter with a J 42873-1 shut off valve. I get an acceptable 2-4 psi drop when the valve is shut isolating the front 3/4 of the fuel loop. So it seems like something in the supply line before the fuel filter is causing the majority of the 10psi drop. Before replacing the the fuel line from the sender to the fuel filter, what could cause such a large instantaneous drop and then hold? Any help before plunking down $150 bucks would be greatly appreciated.
FWIW: I have a new fuel pump and a new MPFI spider injector that came with a new regulator.
Here is video of the drop. [If the video does not play click on the YouTube icon in the player]
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