I strongly agree with the Racor 500 recommendation but I use a 2 micron filter in the primary and secondary filters. This way I don't need to think about which filter is plugged - I change the Racor and leave the secondary filter alone.
On a Perkins 4.108
changing the secondary filter when it plugs at the worst possible time, is a major hassle that more often than not requires bleeding the entire system. I fill the Racor 500 with a small electric fuel pump
plumbed into the fuel line so changing the filter usually takes less than one minute. No bleeding necessary.
I also filter everything going into the tank with a water separating filter. During the 15 years of using this system, I have had two problems. Some sludge from the bottom of a jerry can went into the filter but I wasn't worried about it until the filter cylinder that sits in the middle of the filter came loose and let the sludge go into the tank.
Next, we had our fuel polished and tank cleaned and it is very likely that the guy who did the work
, left a paper towel in the tank. Here is what we found inside the Racor where there is a little ball with appropriate density to prevent water from getting through it. Water wasn't the issue in this case:
I have followed the debate on 30 vs 20 vs 10 vs 2 as a primary filter for a long time and I am quite happy with this set up. I am sure that many others will definitely have a different view.