What to do with fuel filter
- Thread starter pavetim
- Start date
Leave it on when you first put on the lift pump so any trash that gets into your fuel lines from the install gets trapped in the filter. There is another option. I did a FASS filter bowl delete. This replaces the filter with a machined bowl and still has the water detector on the bottom. I did this for a couple of reasons. First it is nice to have the bleeder when needed. Second the bowl has a 1/8th pipe plug in it. This allowed me to install an adjustable fuel pressure switch. I set mine for about 5 psi. Below 5 psi the switch makes a ground. Power comes from the relay that powers the lift pump when the ignition key is ON. This powers a small LED post light that I mounted on the dash. When the key is first turned on it takes a second to build pressure so I get a momentary flicker of the led letting me know it is working. Remember your lift pump (FASS or AD) should be putting out 8 to 10 psi. Any higher can damage the low side of teh CP3 or CP4. This is a great indicator when the fuel system is under a load during acceleration. Lets me know if a filter is getting clogged, fuel is starting to gel in the winter time, or if there is an issue with my lift pump.
This really helped when my FASS 95 started to fluxuate pressure at idle. My LED would flicker on at idle and troubleshot to the pressure relief port on my lift pump. The ball would stick momentarily at very low loads. Got it replaced by FASS with thier flow thru restrictor kit and took care of that. Dean
This really helped when my FASS 95 started to fluxuate pressure at idle. My LED would flicker on at idle and troubleshot to the pressure relief port on my lift pump. The ball would stick momentarily at very low loads. Got it replaced by FASS with thier flow thru restrictor kit and took care of that. Dean
The above that is bolded is incorrect. While the ideal pressure for a duramax is 8-10psi it's purely because some regulators don't like to work properly above that and can cause pressure to be uncontrollable. My race truck and many other trucks run rising rate fuel pressure. I know I see 55-60psi on my old single turbo setup of fuel pressure as I have it feeding 50psi max of boost to the top of the regulator to increase pressure as load rises to help keep my old 14mm pump filled with fuel.
You can raise the fuel pressure. I have mine set at 14psi, anything more it lopes really bad. You can use the port they give you but I ran another gauge from under the hood. I also have redone all my fuel lines under the hood with AN fitting so I added a guage port.
Well, finally having some time to do a bit of research it appears I owe everyone an apology. I picked up some information about this on a previous Duramax forum where they discussed the damage. They even had pics of separate low side gear rotor style pump that showed damage due to the high supply pressure. Shame on me for not researching it further back then. That thread and pics are gone, everything else I looked at did not show any basic difference in design between the Duramax, Dodge, or Ford CP3s. I did contact FASS to see why they put the limit on supply pressure and this was their response. Dean
"Hello Dean-
It really wouldn’t do a whole lot of damage over 10 psi. We keep it low because the factory system is a vacuum system so going much higher would usually cause the truck to lope at idle and could throw a high fuel rail pressure code.
Thank you,
Gene Brown
Diesel Performance Products Inc.
FASS Fuel Systems
16234 State Hwy. O
Marthasville, MO 63357
Ph: 636-433-2962
Thanks for contacting FASS. We would appreciate your opinion about the service we provided, and we are trying to learn from your experience."
no hard feelings. we are all making mistakes and learning. to add what FASS said, you can make changes to the tunes to accommodate higher pressure and operate without throwing codes but if you lost the lift pump it would end up with low fuel pressure and additional codes and run like crap. by leaving it around 10-14 psi you can run it with or without the LP. kinda a failsafe
