Electric fuel pump failure mode

[Ausflyer]

Hi all,
My -12 has now 76 hours on it and the last time I shut it down, after a 1.5 hour flight, the noise made by the electric fuel pump had obviously changed. Instead of a steady hammering at now has a regular two-tone hammering. I will replace it before I fly again but I am interested to know if this is a typical failure mode, or does it usually just stop working and go quiet?
Rod

 

[artrose]

Was it hot? Was it a cavitation sound due to a partial vapor lock?

 

[Ausflyer]

Art, thanks for your questions.
The flight was on a day with mild temperature (max 27 C) and the max RPM was about 5200. Altitude mostly above 3500 ft. Landed with 25 litres in the tank So I don’t think the op envt was the cause.
I have pulled my tank out a few times, emptying it through the gascolator drain (Mueller sender, leaking rivets, mounting mod) so I am too familiar with the noise the pump makes as the fuel pump cavitates, then runs dry. Also with the sound it makes with the fuel stop valve on and off. This noise was new.
I will run the pump again before I change it , to check if the noise is back to normal.

 

[RetiredRacer]

Rod, I'm interested in this as we have two pumps (one in each wing root). One pump has the regular hammering as you explain it and the other has a different sound, like you explain it as a two tone hammering, and slightly a little louder than the other pump.

Both pumps have about 100 hrs (200 hrs shared) now and they are still going strong with the same pressures as the day they were fired up.

I would have to check with the wife, but we might be able to duck down on Sunday (about 1.5 hrs from Watts Bridge). Besides any excuse to go for a fly and catch up with a fellow RV'r .

Bob & Robyn Dennis
RAA registered RV9a

 

[Ausflyer]

Hi Bob,
It would be good to see you on Sunday. My 12 is hangared at Ballina. I will PM you my ph nos
Rod