I think my lift pump is bad again, but what is going on? At idle or when you let off throttle pressure is at 5-7 psi, if you step on it the pressure jumps to 11-12 psi. WOT is about 10. Pressure will jump up and down at idle. The truck has 162k on it and this is the third lift pump. Is there any sort of a relief on the return side of vp that could be acting up?

 

Check out this thread. https://www.dieseltruckresource.com/...ad.php?t=91935

 

The lift pump can be moved to the frame below the tank using the bracket off the engine. This puts gravity feed to the LP at all times and with any amount of fuel in the tank.