Fuel pumps high pitch whining?

Hi Paul,

For some reason my updated pumps are louder also.  I would not say really loud, but maybe 25% louder than before. It may be fine, however a loud high pitch whine can indicate the pump is cavitating if vapor is forming on the inlet side.  Make sure that no hoses got kinked on the suction side of the pump during the swap.  Also, if you are running Mogas you could try a tank of Avgas to see if they quiet down. If they do quite down, that could indicate a cavitation when using Mogas. A while back I did a test with Mogas in one tank and Avgas in the other.  It was a very warm winter day, and the mogas was a high RVP winter blend. What I found is that when using the Avgas tank the pumps were quiet, switching to the Winter Mogas fuel produced a whine. However, this was an unusually hot winter day, and the plane had been sitting in the sun for several hours.  It was clear that the winter fuel was forming vapor on the suction side. It was not enough to affect the fuel pressure, but enough to change the sound of the pump. 

Jeff. That is a very interesting guess/theory. Yes winter MoGas has a much higher volatility and I run MoGas 100%. Generally it is cold now when we start up, less than 40F but it is something to think about. The change in volume with one verses the other and both on.......

Any way gives me something to ponder/experiment/troubleshoot. I have separate wing tanks so 100LL is an easy check. None of my other 3 fuel injected engines get it running the same MoGas......

Paul, 

It's very possible the pumps are just noisy. For unknown reasons some seem louder than others. I only mentioned the Mogas/Avgas as a possibility, but in cold conditions it not at all likely.  However, I would verify good flow to the pump inlets.