What to do with fuel filter

pavetim

Member
Jan 10, 2011
299
5
18
I am gonna put in a air dog 4g 2 soon and wonder what is the best way to deal with oem filter. Put racor back on, cat 2 micron or do a delete?
 

Dean E

Active member
Mar 30, 2022
104
41
28
Blair, NE
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
 

Bdsankey

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Feb 1, 2018
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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
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.
 

2004LB7

Well-known member
Dec 15, 2010
6,275
1,683
113
Norcal
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.
and to back that up, stock VW TDIs feed their CP4s with 75 psi fuel pressure.
 

pavetim

Member
Jan 10, 2011
299
5
18
Just got an airdog 4g 2 for my 2015 3500. Should I adjust the pressure and if so to what? Anybody know fitting size for the pressure gauge port?
 

2004LB7

Well-known member
Dec 15, 2010
6,275
1,683
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Norcal
I don't have an airdog so I'm not sure if they preset the pressure but I always turn it up until it lopes then back it down till it smooths out
 

pavetim

Member
Jan 10, 2011
299
5
18
Ok I called airdog fitting is 1/8" not and fuel pressure is preset 8-10psi for duramax, lp5 is different tho
 

ZeroGravity58

Well-known member
Mar 23, 2008
1,375
46
48
38
Maryland
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.
 

Dean E

Active member
Mar 30, 2022
104
41
28
Blair, NE
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.
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."
 

2004LB7

Well-known member
Dec 15, 2010
6,275
1,683
113
Norcal
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
 
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