How to use fuel filter pressure guages.

[Triskele]

Installed pressure guages on my fuel filters. How do I use the guages to know when to change out the filters? The guages are located in front of the fuel pump (btwn the fuel supply and pump). Therefore, as the filters become clogged (dirty), the guage should indicate a vacuum (neg. pressure reading). When the engines are off, the guages read 0 psi. At this time, when running, the guage reads -2.5 psi. At what guage reading should the filters be changed out. Is a small vacuum pressure reading acceptable due to resistance caused by the filters themselves or is any vacuum unacceptable and time for a change? Again, I guess the bottomline for me is when and how do I know when to change the fuel filters using guage readings from the filters as an indicator?

 

[davidwigler]

I was told to check the vacuum with a new filter and change them when it goes up by 5. If you are starting at 2.5 psi change them out at 7.5.

 

[Hat52MY]

Just replaced my fuel filters this weekend. They were reading about 5Hg while underway, now back at 2.5Hg. They probably still had some life in them...but filters are cheap compared to bad fuel. If you have a fuel polishing system, the readings may read at materially higher levels depending on the fuel pumps you have installed for polishing. According to Parker Racor...

"The actual reading at which you should change the filter will depend on many factors as fuel systems vary so greatly. As a rule, many pumps have trouble delivering fuel to the engine when restriction reaches 7"-10" of mercury (inHg). Some falter much earlier, some later. Carry an extra Racor filter (or two) and at the first indication of power loss -usually at high RPMs - note the gauge reading. This should provide an idea when future service is needed. Replace dirty filter with a new Racor filter at the earliest opportunity."

 

[Triskele]

Just replaced my fuel filters this weekend. They were reading about 5Hg while underway, now back at 2.5Hg. They probably still had some life in them...but filters are cheap compared to bad fuel. If you have a fuel polishing system, the readings may read at materially higher levels depending on the fuel pumps you have installed for polishing. According to Parker Racor...

"The actual reading at which you should change the filter will depend on many factors as fuel systems vary so greatly. As a rule, many pumps have trouble delivering fuel to the engine when restriction reaches 7"-10" of mercury (inHg). Some falter much earlier, some later. Carry an extra Racor filter (or two) and at the first indication of power loss -usually at high RPMs - note the gauge reading. This should provide an idea when future service is needed. Replace dirty filter with a new Racor filter at the earliest opportunity."

Thanks David. Good advice. Makes sense.