My CUCV spin on fuel filter mod

Matt S · Mar 27, 2021

Whitfield said:
Duramax Fuel Filter installed and up running. Line size @ filter is closer to 1/2 inch but fresh 3/8" line will stretch into place over the Duramax inlet & outlet. I do have the fuel heater wired up using new DIY weather pack connectors. I have not wired up the water separator yet as I wish to modify the Duramax design to retain the CUCV 3rd wire / bulb check function.

Did you figure out the wiring for the WIF sensor?

Matt S · Jun 29, 2021

Whitfield said:
Duramax Fuel Filter installed and up running. Line size @ filter is closer to 1/2 inch but fresh 3/8" line will stretch into place over the Duramax inlet & outlet. I do have the fuel heater wired up using new DIY weather pack connectors. I have not wired up the water separator yet as I wish to modify the Duramax design to retain the CUCV 3rd wire / bulb check function.

Keep me away from the matches!!!!

I've had 2 different filter heads like this in the truck over the past few months. I can't get them to not leak...and I'm being nice with the term leak. They are pounding out diesel. Way worse than the stock one I removed. I even tried a rebuild kit on one but it only progressively got worse.

I'm need to find another alternative. I was hoping to keep a fuel heater but I might get something that wraps around the filter itself and is separate.

Whitfield · Jul 1, 2021

Matt S said:
Keep me away from the matches!!!!

I've had 2 different filter heads like this in the truck over the past few months. I can't get them to not leak...and I'm being nice with the term leak. They are pounding out diesel. Way worse than the stock one I removed. I even tried a rebuild kit on one but it only progressively got worse.

I'm need to find another alternative. I was hoping to keep a fuel heater but I might get something that wraps around the filter itself and is separate.

Where did you source these from? If they are defective from the manufacturer is there no resolution? Mine is still going strong but I have heard of a few duramax guys finding a bad batch of filter heads. I tried to source a GM part to avoid this issue - but with most everything made in the far east now sometimes even OE can be a roll if the dice.

Matt S · Jul 2, 2021

Whitfield said:
Where did you source these from? If they are defective from the manufacturer is there no resolution? Mine is still going strong but I have heard of a few duramax guys finding a bad batch of filter heads. I tried to source a GM part to avoid this issue - but with most everything made in the far east now sometimes even OE can be a roll if the dice.

A mix of sources. I bought one from ebay and another off Amazon. I bought the rebuild kit off Amazon. It was ok after the rebuild but now it is so bad I won't start it. I'm surprised it has enough fuel pressure to run.

I might try the Napa style next. I'd like a Racor but I'm not having good luck finding those. I would like a fuel heater but I don't need a water in fuel sensor.

GunnyM1009 · Jul 14, 2021

Doing this conversion with the Napa 4770 base this weekend. Thanks to the OP and everyone else who has contributed to this thread. I'm fitting out my M1009 for trail riding and the spin ons are a much easier filter to find locally if something goes wrong in the woods.

Matt S · Sep 19, 2021

Matt S said:
A mix of sources. I bought one from ebay and another off Amazon. I bought the rebuild kit off Amazon. It was ok after the rebuild but now it is so bad I won't start it. I'm surprised it has enough fuel pressure to run.

I might try the Napa style next. I'd like a Racor but I'm not having good luck finding those. I would like a fuel heater but I don't need a water in fuel sensor.

UPDATE - I went with a Racor 445R with fuel heater. It cost more than the Duramax filter set up (but not by much when I ordered 2 sets of filters and bases) but it has been in the truck for a few months.

I think the Duramax filters might have worked for me if I re-routed fuel filter before the lift pump but I didn't want to mess with that. I didn't order the WIF light but I have a clear bowl to see the fuel. Also I've never had a WIF light come on in over 25 yrs of owning and driving diesel trucks.

firefox · Oct 4, 2021

I suspect that the WIF stuff was put in there because the military has this tendency to cross rivers without using a bridge....

Tyler benkowski · Nov 18, 2021

Whitfield said:
Duramax Fuel Filter installed and up running. Line size @ filter is closer to 1/2 inch but fresh 3/8" line will stretch into place over the Duramax inlet & outlet. I do have the fuel heater wired up using new DIY weather pack connectors. I have not wired up the water separator yet as I wish to modify the Duramax design to retain the CUCV 3rd wire / bulb check function.

great writup with pics and information. I too am going to be doing the Duramax spin on conversation. I ordered some diy weather pack connectors.for the fuel heaters, Would you be able to tell me what color wires on the filter coincide with the original wires from the box style filter setup? Thankyou!

Rennat_2006 · Feb 18, 2022

Just did the dmax filter conversion myself and was hoping someone had updated this thread with the electrical hookups. Whitfield and others have you guys got these hooked up? Im gonna go look in the manuals for wiring diagrams

Matt S · Feb 20, 2022

I just clipped the and spliced the wires from the original filter to the new one. That way the truck side was the same.

vanaisa · Feb 21, 2022

Rennat_2006 said:
Just did the dmax filter conversion myself and was hoping someone had updated this thread with the electrical hookups. Whitfield and others have you guys got these hooked up? Im gonna go look in the manuals for wiring diagrams

Look here - post nr.5

6.2 fuel filter assembly how does it work?

I have a thirst to know how everything works but dont want to take mine apart until I have to. Cant find much info on it in the manuals, I know the top 2 wires are fuel heater. The schematics show a vaccum switch and water in fuel solenoid but doesnt show how it all works together. What makes...

www.steelsoldiers.com

BenderIsGreat · Mar 20, 2022

It's good to see people still working on this mod!

The truck has 3 wires to the original water in fuel sensor. The duramax filter bottom has 2 wires. I haven't found the actual harness wiring for the WIF in the TM's yet... Trying to keep the WIF light working if I can.

Or at least know which of the two wires I need to connect to. Maybe the factory wiring has +V, GND, sensor return?

combatmonkeywrench · Jun 9, 2024

BenderIsGreat said:
It's good to see people still working on this mod!

The truck has 3 wires to the original water in fuel sensor. The duramax filter bottom has 2 wires. I haven't found the actual harness wiring for the WIF in the TM's yet... Trying to keep the WIF light working if I can.

Or at least know which of the two wires I need to connect to. Maybe the factory wiring has +V, GND, sensor return?

im doing this mod, looks like its been a few years since anyone rogered up regarding wiring. Any updates on wIrving?

plugugly86 · Jun 26, 2024

Im really torn with which setup to go with. In california, so the fuel heater isnt super important to me.

the duramax one is like 100 dollars for a dorman part
the gf647, if you can find one, is also about 100 bucks
this RACOR knock off is pretty cheap but questionable https://www.amazon.com/dp/B07GQPRJRB?psc=1&ref=ppx_pop_dt_b_product_details
and then the wix 4913 can be about 70 bucks, but I can not figure out where to get the hand primer.

is it just buyers preference on which to go with? Which offers better filtration and ease of filter locating?

TechnoWeenie · Jun 26, 2024

plugugly86 said:
Im really torn with which setup to go with. In california, so the fuel heater isnt super important to me.

the duramax one is like 100 dollars for a dorman part
the gf647, if you can find one, is also about 100 bucks
this RACOR knock off is pretty cheap but questionable https://www.amazon.com/dp/B07GQPRJRB?psc=1&ref=ppx_pop_dt_b_product_details
and then the wix 4913 can be about 70 bucks, but I can not figure out where to get the hand primer.

is it just buyers preference on which to go with? Which offers better filtration and ease of filter locating?

Don't overthink it.

Diesel is good to about -40F with anti-gel additives.

As far as priming, they make pass-through electric pumps. I wired one into mine. Push a button under the hood and it primes the lines. Literally takes 10 seconds tops. I also put a one way bleed valve with a shutoff so it essentially self primes and won't let air back in.

I made a parts list..