Re: Cat fuel filter for Duramax

Thanks for your insight.


i believe many folks who install the 2 micron Cat filter are using it as their only filter, risking early particulate loading. At the same time however, as a regular participant on the Duramax Forum, i dont read of folks encountering difficulties related to use of the Cat and suspect it may only be troublecome if the filter has been in use for an extended period of time, and then perhaps only when the engine is encountering a heavy, sustained load requiring fuel delivery beyond what a well-used Cat may be able to supply. My stock LB7 has never exhibited fuel starvation (OEM Racor/AC Delco filter) so i don't have any experience in knowing how that situation presents. i would seem a 2micron Cat would load up faster, negating any cost saving while indeed providing addirtional protection for the CP3 and injectors.


The matter of no longer having the benefits of the OEM, coalescing filter should be of concern too.


Oh well. I nealry bought a Cat adapter, but thought better of it.



Regular Contributor

Re: Cat fuel filter for Duramax

"And somewhere I read Cat filters are designed to operate with pressurized fuel at their inlet (?). Does it matter?"


That is a great question.  CAT secondary fuel filters do function in a pressurized environment, as they perform theat function after the transfer fuel pump, whereas the primary fuel filters are on the "vacuum" side of that fuel transfer pump. 


The 1R CAT secondary fuel filters are manufactured in a manner which allows them to be located in the low pressure side of the fuel system; HOWEVER; the filter requires an approbriate larger micron primary filter to remove almost all water contamination in addition to removing the larger micron contaminants, thus saving the engine from premature filter plugging.


Re: Cat fuel filter for Duramax

Hi gang,


Looks like no one is rising to the bait and would appreciate it if someone could provide a referral to a Cat associate who may provide insight.




Cat fuel filter for Duramax



Reliable information is getting harder to come by on the interwebs and everyone with a keyboard seems eager to voice an opinion. I've decided to come here, where a quick perusal of the Forum indicates many intelligent, well-informed members.


As many may know, Duramax engines are factory equipped with a dual-media A/C Delco (Racor) filter which includes a water separator and sensor (driver notification only/no comm to ECU). The dual media filter was introduced by A/C Delco not too many years after the LB7 injector fiasco (I own one and R&R'ed injectors last summer, 3rd set in 150k) cost GM millions to replace the Bosch units which were suffering from cracked bodies, eroded ball seats and coked tips (the latter likely due to the VCO design which was replaced with SAC's in later Dmax engines.).


Current owners, who have by and large resigned themselves to 75k injector replacement ($5,000 at a dealer, $3000 DIY) have been looking for better filtration and one of the options has been using an adapter to mount a Cat 1R series, 2 micron filter (without water separation) in place of the Racor unit.


Here comes my question.


It is my understanding ACDelco (Racor) designed the dual media filter, which has a 15 (or thereabouts) micron outer element with a 6 micron inner element for Duramax, the reasoning being that the outer element acts as a pre-filter which allows the finer, secondary filter to do its job without loading up. I believe this change happened at some point late in the LB7 model run (01-04 1/2). I should also add the Bosch CP3 fuel pump in the Duramax operates with suction, pulling fuel from the tank. And somewhere I read Cat filters are designed to operate with pressurized fuel at their inlet (?). Does it matter?


Obviously CAT and A/C Delco are two highly respected organizations, and I don't want to get into an argument over who is right here, but it certainly seems to me (and at the risk of answering my own question) Duramax owners would be better advised to stick with the dual media/water separating filter recommended by GM and that using a 2 micron CAT filter (with no pre-filter) would not be a good idea.


As I mentioned much earlier, the interwebs are full of advocates for the CAT ($20 vs $45), offering anecdotal evidence (to me, the worst kind) with most changing the CAT @ 10k and having (anecdotally) good luck.


Well, if you read this far, thanks!


I'd appreciate comments from Forum members collective wisdom and experience.