Fuel Pressure Increase to RED

[Newkentboy]

Just had my annual done.  Had minor  fuel leaks in both wings.  These were repaired,   Fuel filter was replaced at 180 hours, now at about 320 hours, so not due until about 380.  Flight home of about 30 minutes was uneventful.  I had fuel down to about 10 gallons and today was going to fly to a place about 15 minutes away where fuel is about 50 cents less than home field.  I use only 100LL as Mogas not readily available near me and I don’t trust it.  On way, I noticed fuel pressure steadily increasing from normal of 45/46 to about 49.  Decided to return home.  Fuel pressure steadily increased and on short final pressure was in the red at 55.  Called A&P and he and I agreed we should replace fuel filter before next flight.  Any other thoughts on this?  Does pressure increase when below 10 gallons?  Normally I fill it up below 20, but had it low so A&P could more easily pull the wings. 

Posting this on Rotax forum suggested that a clogged in-line fine filter would indicate a low pressure situation, not high pressure.  Suggested I look at down line issues such as fuel pressure regulator or simply the fuel pressure sensor.

This is a 2019 Super Sport i, with the 912iS at about 320 hours.

Looking for some guidance.

[Roger Lee]

Yes it can be the fuel filter. I have seen this several times and changing the filter has always corrected it. That said when I have cut the filters open I never seem to find anything. It must be very fine debris. I'm surprised it does this since it's a large filter for the amount of fuel we use. It's a Bosch car filter and cars use far more fuel than we do.

[Tom Baker]

I'm not sure about the Super Sport, but the CTLSi I have seen the fuel pressure sensor is down stream of the fuel filter. To me a clogged filter in this situation should decrease pressure. I had one customer who was getting consistent high pressure warnings, and replacement of the fuel pressure regulator fixed his issues.