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Old 10-24-2020, 08:55 AM
bill.hutchison bill.hutchison is offline
Join Date: May 2020
Location: Northern VA
Posts: 180
Default FP-5 Fuel Computer - Pressure Fluctuations?

Please forgive the basic nature of many of my questions - I am new to this (Ownership and troubleshooting) and will probably make 101-level stuff look like graduate school. On with the schooling...

While flying my new-to-me RV6A to VA from TX I got an annunciator for low fuel pressure. The previous(er) owner had the limits set to alarm when the pressure would go below 2.4psi, it seems.

I turned on the boost pump, and the pressure came back up to around 5.8 PSI. I turned the boost pump off and it crept back down to around 2.4 or so. This became repeatable so I took a video of it.

I got some videos of this behavior. Trying to figure out how to share.

If I turned the boost pump on, it would come back up.

After a while, at cruise, leaned out properly, the fluctuations would stop and the pressure would be pretty consistent. For the rest of the flight, there weren't any issues.

Next day, similar behavior - around 10-15 minutes of flight time, climbing to altitude and leveling off, this would go on for a little while, and eventually stop.

No roughness from engine, EGTs/CHTs all in normal ranges, airplane flew just fine.

I called the previous owner and mentioned it - he says he has had that happen before, but that it stabilizes on level off and leaning operations for cruise.

Okay - so we have some consistent behavior. What I'm wondering is:

1) Why
2) Is this something I need to worry about
3) If the answer to 2 is yes, how I go about the analysis and troubleshooting.

Any thoughts, guidance and ruler-slapping-my-wrist for stupidity would be appreciated.
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Old 10-24-2020, 08:35 PM
RV-4 RV-4 is offline
Join Date: Oct 2007
Location: St-Jerome,Quebec,Canada
Posts: 1,170

Hi Bill

I have the exact same problem with my FP-5L and talking with the manufacturer support ( EI International ) , they said that it is most likely the fuel pressure little Black Box ( Sorry can't remember the exact name ) that is faulty and that it needs to be send back to be check which cost $65 or $100 for a new one..

I haven't decided what to do yet ( I just live with it for now) but I will be curious to know if you go that way if it will fix your problem..

Plse, let us know if you do get it fix.


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