Ivylog: Are you saying your forgot to change your secondary filter once; and then you had a slight performance concern... Changed the primary. Not the problem. Then changed the 2x old secondary and that was the problem?
You have 2 filters right?
I now have 3 filters: 20, 10 and 2 micron respectively. I have not yet need to change them. But when I do I would like to first have a reference (like PSI) or in your case engine performance degrade. And then I want to experiment with changing out one of my filters at a time, until I arrive at the bad filter. I'm just wondering if that would be my 20u or my 10u or my 2u filter?
With my FASS setup I am seeing a slight drop in my electric cockpit PSI gauge; and I think this is because I have ~8,500 miles on my 3 filters. ...But I bet only one is getting restricted more than the other two, but which one?
TR4: Again your sound reasoning helps me out. Thank you! And yes, I do have a 10mm thread port on top of my #3 filter housing/mount. (This would have been the primary filter when the Coach was shipped, but now it's my #3 fiter after I installed the FASS TS Pump. (Which comes as you know with 2 filters... the first is under suction... the 2nd FASS filter is under pressure.)
Here's the 10mm to 1/8"NPT adapter off amazon you can order. I choose the 1/8" NPT because it has a smaller glass gauge diameter vs. the 1/4"NPT type.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
And for those who just want to mount a pressure gauge on top of your filter set up... If you have a FASS pump delivering positive fuel pressure to your CAPS Injection Pump then you should order this oil-filled gauge:
https://www.amazon.com/gp/product/B0...2L81RV9O&psc=1
If you have a stock filter setup where your CAPS gear pump is sucking fuel through your filters, then you will want a vacuum gauge, but make sure it's oil-filled to deal with the engine vibrations. This one will cover both negative and positive fuel pressures... so when the day come you upgrade to a FASS TS Pump you will have a pressure gauge ready to go!
https://www.amazon.com/dp/B00GMU2C62...v_ov_lig_dp_it
CLARIFICATION: I only use a biocide in my fuel when I store my rv for 1 month or more.
Also, years ago, I called Cummins filtration and discovered all this micron rating stuff on the retail end has more to do with marketing. There is a science to it, but one filter manufacture's tests and rating do not necessarily correspond to another filter manufacture's tests and ratings. I.e., a Napa gold will give me a (5u) filter when I tell them I have a Fleetguard 1022 (10u) filter. So which is more accurate if they test and rate their filters differently?
I guess somewhere along the line most people, including myself at one time, think a better filter has smaller micron rating. NOT SO! ESPECIALLY WHEN IT COMES TO A CUMMINS ENGINE AS TR4 points out. (Which to me is just another indicator the CAPS gear driven suction pump is not the right application for a diesel pusher!!!)
==> I am so mad at Cummins for not owning up to the poor design they gave us when it comes to fuel delivery! ...So thank god for FASS!!!
To clarify, when I list micron ratings for each of my filters I am referring to Fleetguard (Cummins Filtration) brand filters for my #1 & #2. And as for that 2-micron #3 FASS filter... I have no idea if that would be considered a 5-micron accorting to Fleetguard test & ratings system? ...But I know it's small... very small.
So back to the subject at hand: Do you think a 2-micron FASS filter will clog up sooner then my 10 or 20 micron Fleetguard... just because its 2u and smaller filters always clogg up before larger micron filters? ... I really do not know? ...What's the norm here?
My guess is that there is no norm; and Milford_47 has probably stated it best:
You should change your filters based on whatever makes you feel "comfortable." ...Or until your engine starts to loose performance, like Ivylog says happened to him.
I am willing to accept Ivylog's example -- now that I have a FASS TS Pump! But that's only because I have upgraded to a FASS lift pump.
Back to fuel filters: I think it's possible fuel filters don't actually clog-up. Rather, they create fuel restriction (even when new); and that restriction builds up over time and with use. (Paper deteriorates too so let's not forget this. And Algae does grow!) And then we change them because someone told us to. But is this really necessary if you store your RV with bicide and you have a FASS fuel pump?
Story time: I experienced "restriction" in my fuel delivery system first hand -- when my 3-lift pump bolts got loose; and I found myself changing filters first at 9,000 miles; and then at 5,000 miles.
The problem was that my filter restriction was increasing with time and use, and one day that restriction reduced the vacuum pressure (suction) in my fuel line to the point where my engine would start and then it would quit 1 minute or 2 minutes later.
And over time I came to realize those partially clogged/restricted filters where not the real problem at all. The problem was those 3 loose lift pump bolts that let air to be sucked into the fuel line, between the lift pump, which was working properly, and the lift pump manifold. That's what happens when a gasket breaks its seal. So when you hear people say their Lift Pump Failed, I'll bet your mechanic told you that and 8x out of 10 all you really had to do was to tighten those 3 lift pump bolts by accessing the top of your engine... in the bedroom.
Anyway, this resulted in fuel starvation to my CAPS pump several times. And that's why I upgraded to a FASS TS Lift Pump... because I wanted to protect my CAPS injection pump from fuel starvation!!!
Moral of the story: The sooner you upgrade to a FASS fuel pump the longer can probably go between fuel filter changes -- and the likelihood you will ever starve your CAPS injection pump is no longer a problem!