Indication of fuel pump issue?

[cirrusjetpilot]

I am getting a big fluctuation on my fuel pressure indication on my last flight. For the experts out here, could this be an indication the fuel pump is about to go bad or this could be a probe sensor not working right.

Engine seems to be running pretty smooth.

Here's a link to a video where shows the fuel PSI fluctuation.

https://www.dropbox.com/s/r9k7qjku9k2lbm3/oil%20pressure.mp4?dl=0

Any ideas?
Thanks
ALex

[jiott]

Do you have a damping orifice in your fuel pressure sense line? It was recommended on my fuel pressure sensor installation. I can't remember the size, but it was rather small-say about 0.015" diameter.

The quick movement in your video seems rather jittery, but the total range of 4.0 to 4.8 doesn't seem bad at all to me.

[Dave S]

Hi Alex,

Unfortunately, I didn't have any luck opening the video; however, mechanical fuel pump (diaphragm type) failure modes are normally expressed with a reduction in fuel pressure with increased power (increased fuel demand) as a leaking or worn pump may not keep up with the the demand.....high power = low fuel pressure and low power = normal or somewhat higher fuel pressure.

Did this occur only when flying; or, did it happen all the time including idling and on the ground?

A gauge or sensor issue, involving an electrical device can express itself in all kinds of manners.....erratic indications, wide fluctuations, inconsistent readings, unexplained zero or full gauge readings etc. It is frustrating; but, It seems to happen that a gauge can fail as easily as what it is trying to measure:mad:

In diagnosing things like this, if at all possible, I like to install a test gauge and compare what the electrical gauge shows compared to my testing gauge.

[cirrusjetpilot]

Do you have a damping orifice in your fuel pressure sense line? .

To be honest, I don't know. I can barely takeoff and land!! :D

[cirrusjetpilot]

Hi Alex,

Unfortunately, I didn't have any luck opening the video; however, mechanical fuel pump (diaphragm type) failure modes are normally expressed with a reduction in fuel pressure with increased power (increased fuel demand) as a leaking or worn pump may not keep up with the the demand.....high power = low fuel pressure and low power = normal or somewhat higher fuel pressure.

Did this occur only when flying; or, did it happen all the time including idling and on the ground?

A gauge or sensor issue, involving an electrical device can express itself in all kinds of manners.....erratic indications, wide fluctuations, inconsistent readings, unexplained zero or full gauge readings etc. It is frustrating; but, It seems to happen that a gauge can fail as easily as what it is trying to measure:mad:

In diagnosing things like this, if at all possible, I like to install a test gauge and compare what the electrical gauge shows compared to my testing gauge.

It happened during cruise flight. I did not notice when idling. The video should play and might take few additional seconds if your internet connection is slow.

It does seems like erratic indication as the indication seems rather quickly up and down the line.

The suggestion to get a test gauge and compare seems a really good option. Thanks.

[Dave S]

Alex,

Got the video to work:o......I'd agree with Jim that the reading remains within a normal range for a rotax mechanical pump.

After seeing the video (now) I'd be inclined to believe that the fluctuation you are seeing would not likely be due to a pump defect or impending pump failure.

A person could consider that the fuel pressure is a global indicator of the fuel systems performance...not necessarily specific to the fuel pump - could be something else in the system too.

Might be worth it to try the cheap stuff first....tracing the wiring and see if there is a connection on the gauge end or sensor end which is not 100% secure, or a wire connecting the two that might be damaged along it's run.

I normally do both a fuel pressure test with a test gauge and a flow test of the fuel system during the annual condition inspection to validate the fuel system performance - that way I have some idea what is normal and if something has changed.

[Wheels]

I am currently installing a Dynon DS10. the manual discusses the fuel sensors Dynon is using, and establishes some software update criteria. I'm not ready to join this discussion but ... did you install and update all the new stuff?
I also watched the video and have to say that sometimes, we have too many gauges. "a minor fluctuation can steal your bliss over nothing" or it can indicate that your about to test ALL of your skill. I didn't see anything that scared me, but I don't really count as I sit here on this computer and you fly that little ship into the sea of air that we call ... sky.

[68niou1]

Alex- do you have a fuel regulator? When my fuel pressure started fluctuating like that it was my regulator, and the mechanical gauge didn't pick it up but my digital did- FWIW

Scott

[cirrusjetpilot]

Thank you for all suggestions. I did absolutely nothing and today's flight I didn't notice any variation.

I am guessing here I had a little air on the fuel line or perhaps a bit vapor that could cause this. It was hot that day and vapor could possibly be the reason.

Will see if happens again. Hopefully not.