Hi Mike,
It does sound as if the pump is sucking air. My electric pump test was
a
marginal pass but fine on mechanical pump. I tried a new pump and it
was no
better.
The pump should self prime if it is fitted in the standard location and
there is enough fuel in the tank.
A few tips I learned along the way:
Make sure the tank is full. A good head of fuel makes a big difference.
Try it with the aircraft in flying attitude.
Check to see if it is same on main and reserve to see if there is
blockage
in the system.
Check the flow straight out of the pump to see how much flow you are
losing
through the selector/ filters and pipework.
Check the flow before and after the mechanical pump to see if there is a
restriction.
Check that you have fitted the flow restrictor in the return line.
The flow rate test is very sensitive to the set fuel pressure. Check
that
you are using an accurate fuel pressure guage. If you are using the
Factory
test rig I dont think the guage has been calibrated for a very long
time.
Sorry, I never checked the free stream flow rate.
Hope that helps.
Regards
Brian Davies
_____
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of mike gamble
Sent: 08 July 2010 20:39
Subject: Europa-List: Fuel Pump Problem?
Today I carried out the fuel flow check of the electric fuel pump on my
912S
mono. I adjusted the fuel pressure to 2.2psi (as well as able) and timed
the
flow of fuel into a measured container. I managed to draw 1.5-1.6 litres
in
4 mins against the requirement for 2.25 litres in 4 mins. The flow
without
any pressure increasing restriction was about 1litre/min. The throughput
was
the same from main and reserve sides of the tank.
The pump was quite noisy in operation ( more like a miniature pile
driver as
a colleague described it on his a/c) though It did become somewhat
quieter
when fuel started passing through it. It is the listed model 'facet
40106.
The flow through the filters seems to be very turbulent with the glass
about
=BD to 2/3 full and the pump seems to vary in speed and noise
occasionally.
Does the pump require special priming?
Can anyone confirm the flow rate expected with no pressure applied?
Am I missing something here?
Have I got myself a duff pump?
I=92m ready to get the engine fired up when this is sorted so any help
would
be appreciated.
Mike
G-CFMP
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