I have used this place many times to get info but have not seen anyone with this problem.

I have a 04.5 5.9 Diesel that runs for a bit then the engine dies. It’s not consistent and sometimes runs for a few miles to just a short distance. Doing a little trouble shooting on the fuel system I discovered after the engine died that if I tried to bleed off the fuel water separator it sounds like air sucking in through the drain tube. I have a FASS fuel pump installed that is just over three years old. I did remove the fuel line on the FASS and tested it to see if it was pumping fuel and it seems to run just fine. What I am wondering is the air in the Fuel Water Separator and the engine being starved of fuel, caused by the FASS pump failing and the CP3 pulling out all the fuel until it starves the engine and causes the vacuum. I am at a loss, anyone have any ideas what may be causing this? Thanks for the help....

 

any codes?

 

Yes, P0628 for fuel lift pump.

 

can you put a fuel pressure gauge just after the fass to see if fuel pressure is dropping off also check the wiring and relay for the fass ,relay might be getting hot and kicking off

 

Thanks, I will give that a try. I need to go get a pressure gage. The more I trouble shoot it, the more it keeps pointing back to the FASS. The code is just the lift pump and should not effect the fuel since the FASS is taking its place? I will let you know what I find.