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Fuel low pressure warning came up in flight

mxhossai

Active Member
An incident happened last night flying back a two hour flight from North Carolina back to Northern VA: close to destination airport, saw fuel pressure drop to 2.5 psi or so, Dynon lady coming on (as much as soothing her voice, don't think it helped). I had the electric pump on all the time (I have switch to turn it off), so that was surprising, since both electric and default mechanical fuel pumps were on. Then just to try something different, thought I turn it off(electric pump) and saw the pressure come up to the green 3.5psi or so and was good until I landed.

Any thought?
 
You mention two-hour return flight so I assume you re-fueled with 100LL? Was fuel a blend of 100LL and Mogas? Perhaps the electric fuel pump had debris in check valve. Having fuel pump switch “on” does not necessarily mean it is pumping fuel.
 
Sounds like a red cube issue as opposed to the pump. Have you tried running just the electric pump with the engine shutdown to see what fuel flow is indicated with just return flow?
 
Had the exact same issue,so I replaced the Facet cube elect fuel pump to the newer version which has slightly more fuel pressure than the orig ones,and that fixed it.Worked perfect since i did that.
 
You mention two-hour return flight so I assume you re-fueled with 100LL? Was fuel a blend of 100LL and Mogas? Perhaps the electric fuel pump had debris in check valve. Having fuel pump switch “on” does not necessarily mean it is pumping fuel.

Piper J3: Yes, I run Mogas at home and refueled with 100LL. I didn't add any additives (though had it, but forgot), you think this could cause an issue?

Monir
 
Sounds like a red cube issue as opposed to the pump. Have you tried running just the electric pump with the engine shutdown to see what fuel flow is indicated with just return flow?


RFSchaller: good talking to you again. Red cube issue?
 
Had the exact same issue,so I replaced the Facet cube elect fuel pump to the newer version which has slightly more fuel pressure than the orig ones,and that fixed it.Worked perfect since i did that.

hiline: Interesting. A part and/or link you can share?
 
The fuel flow sensor is the red cube that a lot of people refer to.

The reason I zeroed in on that is that it doesn’t make sense that the fuel pressure increases when you turn the electric pump off.
 
I use to have low fuel pressure warnings pop up from time to time, usually when descending from altitude (or near water of course). Replaced pressure sensor, no difference. Engine ran fine. Use a lot of Mogas so was thinking it was a quality issue. Never was able to sort it out.

At my 5 year, replaced both engine and facet pumps. Never had the problem pop up again. My fuel pressure now is usually pushing into the high yellow range. One or both of those pumps was evidently not working as intended. Suspect you have a failing pump issue.
 
An aside, why are you running the facet pump all the time. If your engine driven pump fails you will not get a warning. It is generally considered safer to use the facet for engine start, then turn it off and only restart it for take off and landing. That way you get a warning.
I would assume that the facet could fail in your situation and pressure loss by reverse flow through it.
 
An aside, why are you running the facet pump all the time?

The RV-12 fuel system was designed to have the electric pump in operation at all times. In the U.S., you must follow the plans exactly if the aircraft is to be registered as an E-LSA. Some RV-12 owners have added a switch after the initial airworthiness inspection; others have left the fuel system as designed. There are lots of threads in the RV-12 forum discussing this.
 
Thank you all! I have a condition inspection this month. So will definitely look into upgrading the pressure sensor and anything else that may related to this issue. Your comments and debugging is invaluable.
 
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