Today's Message Index:
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1. 12:57 AM - air entering fuel system on suction side - or is my Pierburg electrical pump broken? (Sacha)
2. 05:27 AM - Re: air entering fuel system on suction side - or is my Pierburg electrical pump broken? (william sullivan)
3. 10:52 AM - Re: air entering fuel system on suction side - or is my Pierburg electrical pump broken? (Bob Harrison)
Message 1
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| Subject: | air entering fuel system on suction side - or is my |
Pierburg electrical pump broken?
Hi Folks,
Yesterday was supposed to be my final fuel flow test before taking to the
air again. I have recently installed a fuel return line in my 912 system
and also a fuel pressure gauge. The a/c is a Kitfox tri-gear, so high-wing
with tanks in each wing and a header tank located behind the seats. The
fuel flow test was performed on the ground with the aircraft in "take-off"
attitude with tail on the ground (approx 17 degrees).
Previous tests showed 100 l/hr (26 gal/hr) at the exit of the electrical
fuel pump and before the mechanical pump. This time, to be more realistic,
I measured the fuel flow after the mechanical fuel pump, at the entry of the
4-way junction that goes the carbs and to the fuel return line. In 18
minutes, the pump put out 18 litres, so 60 l/hr (16 gal/hr), which is still
acceptable, though 40% lower than the first measurement. But then,
something strange happened: the fuel flow went down dramatically, to approx.
20 l/hr (just over 5 gal/hr). I checked the gascolator and found it to be
clean.
A further investigation revealed that the fuel that was being pushed out
contained some air bubbles, which to me means that air must be entering the
fuel circuit on the suction side of the electrical pump. Or else the
electrical fuel pump is somehow broken and is letting air in. A further
data point is that if I hook up all the hoses and run the electrical fuel
pump the fuel pressure gauge indicates lower than usual pressure (0.25 bar
instead of 0.45 bar).
So before I go and investigate the suction side of the fuel system I'd like
to ask any experts out there:
1) Is it possible that I damaged the electrical fuel pump by letting it run
continuously for 20 minutes?
2) Is anyone aware of such failure modes for the Pierburg electrical fuel
pump?
3) How would you go about investigating the suction side of the fuel
system? My idea was to disconnect the hose at the exit of the fuel pump
and clamp it closed and then pressurize the circuit between the header tank
and the exit of the electrical fuel pump with an airline and search for
bubbles using soap water.
Thanks in advance for any help... the weather is beautiful flying weather
but I'm grounded until I can sort this out :(:(:(
Sacha
Message 2
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| Subject: | Re: air entering fuel system on suction side - or is |
my Pierburg electrical pump broken?
Sacha- I can think of a couple of things to check before blaming the pump. First,
are the tanks vented? Are the vents functioning? Second, make sure that
there isn't something blocking the fuel intake. I had this problem once on
a new piece of equipment with a diesel engine. It would sit and run at full throttle
for hours, but if it went down the street it would suck air, and shut
the engine down. It drove us nuts for a while, until we pulled the fuel tank
and found a 1" square piece of masking tape drifting around in the fuel. When
it sloshed over to the sucker tube, it blocked it and shut down the engine.
Air in the fuel always makes me think of that. We found it by pulling the plug
at the bottom and trying to drain it. The fuel would stop running. Poke a
wire in there, and it would run again. It was invisible when soaked with fuel.
We had to pull the tank to get it out. The tape had been used to cover all
openings when shipped from one
factory to another, and a piece dropped in when the manufacturer pulled it off.
Bill Sullivan
--------------------------------------------
On Sun, 6/22/14, Sacha <uuccio@gmail.com> wrote:
Subject: RotaxEngines-List: air entering fuel system on suction side - or is my
Pierburg electrical pump broken?
To: rotaxengines-list@matronics.com
Date: Sunday, June 22, 2014, 3:56 AM
--> RotaxEngines-List message
posted by: "Sacha" <uuccio@gmail.com>
Hi Folks,
Yesterday was supposed to be my final fuel flow test before
taking to the
air again. I have recently installed a fuel return
line in my 912 system
and also a fuel pressure gauge. The a/c is a Kitfox
tri-gear, so high-wing
with tanks in each wing and a header tank located behind the
seats.----
A further investigation revealed that the fuel that was
being pushed out
contained some air bubbles, which to me means that air must
be entering the
fuel circuit on the suction side of the electrical
pump.
RotaxEngines-List Email Forum -
- MATRONICS WEB FORUMS -
List Contribution Web Site -
-Matt
Dralle, List Admin.
Message 3
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| Subject: | air entering fuel system on suction side - or is |
my Pierburg electrical pump broken?
Hi! Sacha,
Have you checked the thimble filter in the Pierburg electrical pump? It
needs a very sharp needle or pointed hooked instrument but only apply it to
the plastic collar and be careful replacing it with a wooden very blunt
pencil pushed home in to place very carefully, do not damage the gauze
filter element because they will NOT supply a replacement .....it would need
an entirely new pump.
Regards
Bob Harrison Europa G-PTAG c/w 914 Rotax and two electric fuel pumps.
-----Original Message-----
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Sacha
Sent: 22 June 2014 08:57
Subject: RotaxEngines-List: air entering fuel system on suction side - or is
my Pierburg electrical pump broken?
Hi Folks,
Yesterday was supposed to be my final fuel flow test before taking to the
air again. I have recently installed a fuel return line in my 912 system
and also a fuel pressure gauge. The a/c is a Kitfox tri-gear, so high-wing
with tanks in each wing and a header tank located behind the seats. The
fuel flow test was performed on the ground with the aircraft in "take-off"
attitude with tail on the ground (approx 17 degrees).
Previous tests showed 100 l/hr (26 gal/hr) at the exit of the electrical
fuel pump and before the mechanical pump. This time, to be more realistic,
I measured the fuel flow after the mechanical fuel pump, at the entry of the
4-way junction that goes the carbs and to the fuel return line. In 18
minutes, the pump put out 18 litres, so 60 l/hr (16 gal/hr), which is still
acceptable, though 40% lower than the first measurement. But then,
something strange happened: the fuel flow went down dramatically, to approx.
20 l/hr (just over 5 gal/hr). I checked the gascolator and found it to be
clean.
A further investigation revealed that the fuel that was being pushed out
contained some air bubbles, which to me means that air must be entering the
fuel circuit on the suction side of the electrical pump. Or else the
electrical fuel pump is somehow broken and is letting air in. A further
data point is that if I hook up all the hoses and run the electrical fuel
pump the fuel pressure gauge indicates lower than usual pressure (0.25 bar
instead of 0.45 bar).
So before I go and investigate the suction side of the fuel system I'd like
to ask any experts out there:
1) Is it possible that I damaged the electrical fuel pump by letting it run
continuously for 20 minutes?
2) Is anyone aware of such failure modes for the Pierburg electrical fuel
pump?
3) How would you go about investigating the suction side of the fuel
system? My idea was to disconnect the hose at the exit of the fuel pump
and clamp it closed and then pressurize the circuit between the header tank
and the exit of the electrical fuel pump with an airline and search for
bubbles using soap water.
Thanks in advance for any help... the weather is beautiful flying weather
but I'm grounded until I can sort this out :(:(:(
Sacha
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