Hi everyone,

I have a 2003 Ford Excursion 6.0 PSD that's been rebuilt and modified pretty heavily over the years. About a year ago I noticed that the pump in the FASS Fuel System would make these clicky, whiney noises when the gas tank was 1/3 full or less. Gradually I began to have issues with fuel pressure bouncing all over the place, from 0 to pinned at 110. About 3 months ago the truck actually staled a few times and wouldn't restart due to no fuel pressure.

A little trial and error later, the FASS system was replaced as well as the fuel sending unit.

Everything is fine when the tank is full. Once the fuel gauge starts to drop below full the fuel pressure gauge starts to bounce. This seems to settle down after 15 or 20 minutes of driving but will come back again if the engine is turned off.

As the fuel level gets lower and lower the fuel pressure gets more and more erratic, bouncing from 0 to being pinned at 110. And I still get the whiney noise from the fuel pump when the tank gets below 1/2 full. Is my replacement fuel sender faulty? Ghosts in the machine? Any clue is greatly appreciated

I've attached an audio clip that captures the sound of the fuel pump when the tank gets low.

 

sounds like air is in the system

 

Thanks for your response.

I found this page that discusses bleeding the fuel line after servicing the fuel filters and their instructions are:

To prime the fuel system and bleed out any air, turn the ignition to the Run position three separate times—for 30 seconds each time.

Is there another process I should consider?

 

I suspect you have a leaky suction pipe inside the fuel tank.
The easiest thing to Check, is to remove the tank and check the fuel supply to the HFCM.