I believe you are right, but this is confusing to me as the Primary is the (first) filter between the lift pump and the tank, and the secondary is under pressure after the lift pump.
Got me interested, I found this, https://books.google.com/books?id=vHI__6p_uxQC <https://books.google.com/books?id=vHI__6p_uxQC&pg=PA146&lpg=PA146&dq=secondary+filter+gauge&source=bl&ots=2XrLgc30QZ&sig=ACfU3U0rAWI6VQoGFsYnBTciGpMUnhCLJg&hl=en&sa=X&ved=2ahUKEwiIqJKf9erlAhVFVd8KHfIrA1IQ6AEwEHoECAgQAQ#v=onepage&q=secondary%20filter%20gauge&f=false> &pg=PA146&lpg=PA146&dq=secondary+filter+gauge&source=bl&ots=2XrLgc30QZ&sig=ACfU3U0rAWI6VQoGFsYnBTciGpMUnhCLJg&hl=en&sa=X&ved=2ahUKEwiIqJKf9erlAhVFVd8KHfIrA1IQ6AEwEHoECAgQAQ#v=onepage&q=secondary%20filter%20gauge&f=false and it seems you would need a pressure gauge, but not sure of the range. You could certainly T something in. However in some 30 years, I have never had a secondary filter clog. I think I may have preventively replaced a couple, but mostly the primaries, where all the crap ends up. This article makes an interesting point, that putting too fine a micron on your primary can destroy your lift pump. I think Andy alluded to only using 20 or 30 microns as the primary a bit ago. Bill Coleman From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Bruce Whitmore via CnC-List Sent: Thursday, November 14, 2019 6:48 PM To: C&C List Cc: Bruce Whitmore Subject: Stus-List Fuel filter vacuum gauge(s) Hello all, I mentioned a while back that adding a vacuum gauge to my fuel filter was on my list. Not an emergency, but just something that will give me a bit more piece of mind. I understand that I should tee in between the Racor and the lift pump, and any significant vacuum would mean the Racor is getting clogged. However, is there a way to also plumb in a gauge to know the condition of the the primary filter on the engine as well? It occurred to me that since the line leading into the primary filter on the engine would be under pressure from the lift pump, a vacuum gauge wouldn't work. Thoughts? Bruce Whitmore C&C 37/40+ "Astralis" Madeira Beach, FL (847) 404-5092 (mobile) bwhitm...@sbcglobal.net
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