Fuel Pump Failures

<<< Aircraft is a Super Petrel LS.  >>>

Where are the fuel pumps in relation to the fuel tank?
If they are ABOVE the fuel tank, the fuel will slowly backflow to the tank leaving the Fuel Pumps sucking air for the first few seconds of every start cycle.
The pumps are lubricated and cooled by the fuel.

Listen closely to the pumps at the first activation of the day.
They run fast until the fuel rail pressurizes.
It sound a lot like "EeeOwwwww" with the Eee part lasting about a second.
If the Eee lasts longer than that, you have lost the pump prime and are sucking air .  "EeeeeeeeeeeeeeeeeeeeeeeOww"

680 hr on Mogas here no problems...

Pumps are level with the feed tank.  Your noise descriptioin is correct after changing pump assemblies and waiting for pumps to prime. Thanks.

I have replaced the fuel pump assembly 4 times, in less than 7 hours, since new. On a VANS RV-12iS

Using MOGAS, lucky the pumps have failed during runup and most of the times only one of the 2 have failed at the same time.

My local Rotax dealer has been unresponsive to my multiple requests for a root cause analysis of the failures, they have only confirmed that the pumps I have returned for exchange did indeed fail. Nothing else from them, very disapointing.

This is getting worrisom as the RV-12iS needs the electric pumps working all the time...

Suggestions?

A

I have a 50 hour total time 912is in a Super Petrel. After a very strong 100LL smell I found I had a HOLE in one of the gas pumps. After landing  I found I had very dangerouslly  lost some 3 gallons of fuel that had accumulated in the hull and was partially expelled by the water pump. It looked like a "gasfall" of 100ll coming  out of the pump.

Anyone had this problem of a hole in the pump?

Comments appreciated