[RV7AV8R]

I noticed while on a long cross while in stable cruise if I turn on the boost pump the fuel flow went up about 0.5 gph. There was an initial surge in flow and then a stable higher rate. The fuel pressure goes up with the pump ON but I would think the float valve would keep the flow constant. Any one else notice this? Is it normal or do I have my float misadjusted?

 

[Ironflight]

Not unusual.

I always see a higher fuel flow INDICATION when my boost pump is on - the flows are not higher (confirmed by hundreds of hours of fuel receipts), it just adds a little "Safety Bias" to the fuel remaining numbers. I think it is due to the 'ducer being closer to the boost pump than ideal - but design is the art of compromise....

Paul

 

[jrvssgl]

I see that as well. Also on the ground with pump on and engine not running. It shows me burning 5 litres and hour.

 

[DennisRhodes]

Fuel Flow

Anytime the RV9 boost pump is on , the flue flow indicated is considerably higher than actual. I believe it's because of the boost pump location and the rather abrupt piping route from boost pump into the flow sensor. There is just not enough room there to get "it all in the bag"

 

[Brantel]

Most people that have their sensor between the boost pump and the engine driven pump state that they get false readings when the boost is on.

Most that put the sensor after the mechanical pump say that all is well.

I will let you know in a month or so how mine works out!

 

[Mike S]

I will let you know in a month or so how mine works out!

GREAT.

Good Luck, hope all goes well.

 

[Mel]

Most people that have their sensor between the boost pump and the engine driven pump state that they get false readings when the boost is on.
Most that put the sensor after the mechanical pump say that all is well.
I will let you know in a month or so how mine works out!

Mine is BEFORE the boost pump and I still see an increased flow rate with the pump on.

 

[RV7AV8R]

Interesting, my sensor IS between the boost pump and the gascolator. Next in line is the engine driven pump. Perhaps the pressure pulses from the boost pump cause the little paddle wheel in the senor to move forward. Any air in the system, for example in the gascolator, will allow some flow with each pulse of pressure from the boost pump. The flow will likely be faster in the forward direction and slower in the reverse. You guys are convincing me this is a sensor issue and nothing to worry about.