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mp.gamble(at)talktalk.net
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 Posted: Thu Jul 08, 2010 11:41 am Post subject: Fuel Pump Problem? |
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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 ˝ 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’m ready to get the engine fired up when this is sorted so any help would be appreciated.
Mike
G-CFMP
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brian.davies(at)clara.co.
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| Posted: Fri Jul 09, 2010 10:56 am Post subject: Fuel Pump Problem? |
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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(at)matronics.com [mailto:owner-europa-list-server(at)matronics.com] On Behalf Of mike gamble
Sent: 08 July 2010 20:39
To: europa-list(at)matronics.com
Subject: 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 ˝ 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’m ready to get the engine fired up when this is sorted so any help would be appreciated.
Mike
G-CFMP
[quote]
href="http://www.matronics.com/Navigator?Europa-List">http://www.matronhref="http://forums.matronics.com">http://forums.matronics.com
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frans(at)privatepilots.nl
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| Posted: Fri Jul 09, 2010 1:55 pm Post subject: Fuel Pump Problem? |
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On 07/09/2010 08:54 PM, Brian Davies wrote:
| Quote: | It does sound as if the pump is sucking air.
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Not necessarily.
I had the same problem when I tried the pump for the first time. I spent
hours to search for an air leak, but couldn't find one.
That day was a very warm day.
I finally realized that a drop in pressure, like you have on the suction
side of a pump, lowers the boiling point of the fluid... Combined with
the high temperature, the fuel was partly vaporizing.
Indeed, the "air" I was seeing was just fuel vapor.
Nothing to worry about, as on the pressure side of the pump the fuel
returns to a fluid state. But I could hear the pump gurgling and I saw
lots of bubbles in the fuel filter.
Frans
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