I am planning on modifying my fuel filters in the coming weeks, totally a personal preference move not required the OEM set up is pretty good. However it has some quirks I don't love and honestly I just like to tinker a bit.

I have been looking at the kits available on the market and I have cobbled together a plan. My pre-pump/lower filter is an HSM kit I picked up.



For a post pump filter I am going to tap into the fuel lines along the frame here:


And run a 1R0750 (or cross reference) as the secondary filter. At some point prior to the winter I am going to throw a fuel heater on the prepump and possibly the post pump filter, we will see what I determine at the time.

As far as deleting the factory upper filter I am planning on running a 1/2 line up from the quick connects under the cab to the input of the distribution block of my SPE DPK, which will look something like this:

Which leaves me the injector/fuel rail return line and where I am conflicted. In the OEM application, the return fuel is recycled back through the secondary filter and pumped back into the high pressure system or at least so it seems.


Most koozie spin on upper filters seem to follow the same idea, as does the FASS drop in kit that actually runs the fuel all the way back to the fuel filters in front of the tank to push it back through the secondary filter and back to the high pressure system.




https://fassride.com/wp-content/uplo...-1001_Rev2.pdf

Kits like the SPE and G&R diesel, include a fuel log that returns the injector return fuel to mix with the incoming fuel from the secondary filter but the injector return fuel seems to bypass going back to the secondary filter.




I get why Ford ran the return fuel through the filter since it is extra filtration and convenient for plumbing, that said the fuel has already passed through the fuel filtration system so is it really necessary?

So the TLDR version, I am debating do I run a tee fitting on the distribution block of my SPE DPK and have the injector return fuel go there or do I run the injector return fuel all the way back to the secondary filter in front of the tank and have it run through the secondary filter again?

If you made it this far, thanks for reading and let me know what you think please.

 

I'm going to dive further into this at one point as I don't have an Alumina Duty so I don't have that set up... But kudos for wanting to do what you want and thinking outside the box. I like it...

 

The return line on the secondary filter is not a receptacle for rail return fuel to be filtered.


the secondary fuel filter return meets the rail return then travels to the fuel cooler.. then to the tank.


if your trying to make a wiz bang super fuel flow system. Run individual lines from any added accessories like lift pumps, etc, to the back of the cab and use a fill neck adapter to setup a new return point .


these converging return lines near the engine bay build up pressure and obstruct lift pump pressure.

 

Thanks I appreciate it.

JUST the mad scientist I was looking for....

See picture below.... specifically I am inquiring about item 3, the injector/pressurized fuel rail return line (or at least that is what I believe it to be) that flows into the OEM secondary fuel filter.



Am I following you in saying that fuel isn't filtered by the secondary filter and just resent to the HPFP? How does it return to the fuel cooler? I can see how the HPFP return fuel, item number 5, goes back to the cooler and the tank but where would the injector line jump back in? Or am I totally off base on my labeling?

Great point on the fuel pressure convergence.... ok in that case maybe I return the injector return line fuel all the way back to the secondary filter. Instead of having the secondary filter near the tank maybe I need to mount it under the cab and tap into the pressure line next to the transmission like HSM does for their new under body upper fuel filter relocation. Full disclosure I will be running a low pressure fuel pressure gauge to monitor this set up.

https://hs-motorsports.com/collectio...relocation-kit

I am planning on using this filter head, just plugging the coolant ports but 4 ORB ports will make it easier to plumb.

https://www.wvodesigns.com/heated-fi...1-14.html.html

It is a few extra bucks over the Wix 24770 head but I would rather ORB fittings than NPT.

Thanks for the input guys!

 

no…that is not a fuel injector return line

if you disconnect it, with the engine off, and prime the fuel system, fuel comes out of the filter and not the line you disconnected.

the fuel filter return line is to return excess pressure from unused fuel the lift pump sends it.

the fuel filter return meets with the fuel rail return and then flows back to the tank.

there is no filtration going on at the fuel filter return …it is a prefilter element pressure relief.

 

Gotcha, I was going off FASS instructions for their upper filter delete kit.



Do you happen to know what triggers the pressure relief, is there a pressure valve on the OEM fuel filter (not the cold weather bypass) causing it or is it just fuel coming in too fast to all pass through the filter so therefore it flows out the port?

What would be the best way to re-plumb that line? A fuel log set up like what SPE and G&R use? Or could I use with the Tee fitting idea. See below:


I would mount that tee fitting on the distribution block of my DPK

Glad I posted this thread, thanks guys.

 

The return fuel from the fuel filter return always flows

When the metering valve on the cp4 closes..pressure builds up as the valve closes and increases exit fuel at the fuel filter return…when the valve opens…pressure decrease's at the smaller fitting on the fuel filter and less fuel exits the fuel filter thru the return.

 

The fuel filter return line and the fuel rail return line are parallel paths…not serial paths

 

Gotcha, so the HPFP actually throttles the flow based on flow downstream.

I am confused, doesn't the return line converge with the rail return to flow back to the tank?

Looks like fass hooks it into the supply line to the supply upstream of the secondary fuel filter



Think copying that is probably my best bet or should I tap into the other outlet the fuel filter head has since I am planning on using a 4 port (2 in and 2 out) secondary fuel filter head?

 

Agreed... but need to make sure there's no unintended consequences when wrestling this bear.

 

Trying to stick to the "first do no harm .." Worst case I can grab the black market performance upper filter put a 1-14 thread insert on it and run that.

 

im not understanding the difference between what you said vs what I said.

main point is that the returns are parallel..not serial…rail return fuel does not pass thru secondary filter return….

i think this is another case of

see spot run
see, spot run
see spot, run

 

Haha I hear ya Troy but I'm not the one doing this... Sounds like Rufus is doing his homework on this first..
But I do have plans to feed my DFCM with the Air Dog I bought... I have notes, diagrams and have talked to Air Dog about what I want to do, what their original units for our gen trucks did and that's feed the DFCM so they sent me the 10 PSI spring for the regulator. I'm probably going to wait until I go with a 50 gallon Titan fuel tank...

 

did airdog say

put 10psi airdog between tank and fuel conditioning module? (2 micron filter before a 10 micron filter)

or

put 10 psi airdog between fuel conditioning module and oem secondary filter? (10 micron filter before a 2 micron filter).

For 2017 thru 2019 trucks afe wants their 10 psi pump ( which has a 4 micron filter stock) between stock tank and stock engine bay filter.

by defualt afe wants the filter in passive mode (no pump) and they want you to buy a switch kit which turns on their pump at 5 psi of boost. Boost switch is adjustable.


there are other filters that fit afe threads that go down to 2 microns.

 

Here are some good pictures on where and how afe connects their 10 psi lift pump on 2017 thru 2019’s.


they connect the suction and feed about midway in the fuel stream using existing oem disconnect points.

then they run their return off a quick disconnect near the fuel cooler.


in a prior version they connected using disconnects in front of the fuel tank near the transfer case. Me personally broke the oem fuel disconnect with the yellow tab and had to use a repair kit on it. The new location is easier to disconnect.

Just posting for more pics of different places to connect.

If you want the prior version…let me know.


https://www.dieselpowerproducts.com/mm5/graphics/00000001/42-13051_ins_2.pdf