<VV> Mechanical Fuel Pump reverse flow?

[Dave Morris "BigD"]

Yeah, I'm a student of William Wynne's conversion 
(www.FlyCorvair.com).  Until recently, he was recommending the mechanical 
pump, but then starting talking about a leakage problem that prompted him 
to install a catchment bowl under the pump to collect dripping fuel and 
drain it away from the engine 
(http://www.flycorvair.com/601sep046.jpg).  He said you'd have to 
re-tighten the screws on the housing several times to keep it from 
leaking.  Now he is recommending eliminating the mechanical pump altogether 
and using dual electric pumps (http://www.flycorvair.com/601Sep2004.html)

I just thought if the leakage problem was solved, it would be better to 
save 1.5 amps of constant current requirement and use a mechanical pump 
that the engine was designed with.

Dave Morris


At 06:55 PM 12/29/2004, you wrote:
>     The mechanical pump has two check valves to allow fuel moving in one 
> direction only while the diaphragm pulsates so, if you connect both 
> outlets, the fuel from the electric pump will not pass (reverse flow) 
> thru the mechanical pump, assuming the check valves are in good 
> condition. Pulsating electric pumps have check valves, too but don't know 
> if rotary ones allow reverse flow or not.
>     I remember having seen something about fuel pumps in airplanes at 
> <http://flycorvair.com/>http://flycorvair.com/ , think you could get good 
> ideas in this website.
>
>     Daniel Monasterio
>
><<On my airplane's Corvair engine, I am planning to use the mechanical fuel
>pump but also have an electric fuel pump in parallel that I can switch in,
>in case of vapor lock or failure of the mechanical pump.  Does anybody know
>whether the mechanical pump has a mechanism that would act as a check
>valve, preventing the reverse flow of fuel backward through the pump when I
>switch the electric one on?>>