Mailing List flyrotary@lancaironline.net Message #51294
From: Lynn Hanover <lehanover@gmail.com>
Subject: Float bowl
Date: Mon, 24 May 2010 08:26:59 -0400
To: <flyrotary@lancaironline.net>
here is a picture of the fuel system, tried the scanner and the file was to large.  Fuel must be seeping back thru the L.P. regulator and fuel pumps.  JohnD      To soon old, to late smart, which comes a bit at a time.
 
Fuel can flow through a sliding vane pump. It takes a while, but the vanes can slip out of contact with the housing, and the pump can loose its prime, or a disconnected fuel line hanging below the fuel level in the tank can empty the tank.

 

When the pump has recently made pressure, the pump will not leak through, and this can lead to a misunderstanding. Like two sliding vane pumps in series would have redundancy. No, not the case, one pump cannot push through a second pump, if the second has failed. The second pump cannot pull fuel through the first if the first has failed. Same with high pressure roller pumps like used in fuel injected cars. Treat them like lengths of very small diameter fuel line when they are not energized.
 
On the other hand it is not likely that a stopped vane style pump can flow enough to support much more than a fast idle.
 
The rotary can empty the float bowl at fast idle (2,200 RPM) in less than one minute. Even if some fuel is getting to the float bowl, I doubt that it would be enough to show up on a Fuel/Air meter.
 
Lynn E. Hanover
 
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