You didn't mention if you meant the engine pump or an electric boost pump, but in any case, the fuel flow sender manufacturer doesn't give positioning recommendations for aviation use. We've heard it works pretty well pretty much no matter where it is located. Our latest installation manual gives the following general guidelines:
GENERAL PLACEMENT RECOMMENDATIONS
When placing the sensor, ensure that the three wire leads are pointed straight up. A filter should
be placed upstream from the sensor to screen out debris. Ensure that the transducer has 6” of
straight fuel line before and after it. Placement of the fuel flow sender relative to other items in
the fuel system like fuel pumps is left to the builder. The manufacturer of the fuel flow sender
does not make strong recommendations on this point. It is not uncommon, though, to place the
sender downstream of any auxiliary electric boost pumps but upstream of the engine driven fuel
pump. For best measuring performance, the fuel should travel uphill by one to two inches after
leaving the fuel flow sender.
