rparigor(at)suffolk.lib.n
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 Posted: Tue Jan 09, 2007 1:08 pm Post subject: 914 fuel pumps info share |
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I will share with group my boring findings about 914 fuel pumps.
I am using Europas recommended schematic, only difference is I am using
Andair 375 Gasculators instead of supplied filters.
For testing I added supplied clear filters between gasculator and pump
input, and a clear automotive filter at the output of fuel system. I used
my aux fuel tank with 7.5 gallons of filtered 100LL.
Info below not in any specific order:
****I ran pumps 1 at a time for 2 hours each (no suction head), the output
filter was black as the fuel hoses! The gasculators and filters between
gasculator and input of pumps were clean of the black. The output filter
was a automotive filter that was clear with a pleated orangish paper
looking element. I called Kerry at Lockwood and he thought it may be
Molykote used in pump assembly?? Note there is a finger filter in the
intake of each 914 fuel pump, Lockwood suggests cleaning annual or every
100 hours. Probably a good deal not running P2 along with P1 at first so
as not not put any black into P2 sock filter.
****P1 is primary pump, G1 is primary gasculator.
Fuel pumps are semi transparent to flow in proper direction. On the
recommended series with bypass schematic, if P2 is on, it flows ~80% from
G2 and about 20% from G1! If I stall P1, and turn off, then turn on P2, G2
flows ~98% and G1 bout 2%, I guess there is a 1 way inside pump and almost
stalling seats it a bit harder? This finding makes me want to keep P1 as
primary pump, as it will only draw from G1, thus keep G2 clean for a
second chance with max duration before it too clogs.
****I had concern about ability of pumps to meet my dry suction head needs
in worst case which is 10 or so inches. Pulling a 40" dry suction head is
not a problem on 1 pump, as long as you don't restrict the output and
develop too much pressure. If the fuel pressure regulator allows passage
of air without much restriction, I am a happy guy. My fuel lines only
easily allowed 40" test.
****I am going to install a aux fuel tank vent via a 1 way valve. I have a
diaphragm style 1 way PVDF body / Viton seal Mcmaster PN6079T59 that
requires less than 1 pound crack. I also have a ball checkvalve nylon with
SS ball that requires 1 pound of crack pressure. McMaster PN47245K37,
mouth blow is easy with diaphragm, hard with ball.
It is not a true test of letting in air, but a much more severe test to
put one of these check valves in series with pick up line. You see the 1
way will see full flow where the true tank vent will only see flow of fuel
used, and it will be flowing air not fuel. Anyway results:
Ball checkvalve 1 pump will dry suction head ~ 20" max
Ball checkvalve 2 pumps will dry suction head 40" in about 9 seconds
Diaphragm checkvalve 1 pump will dry suction head 40"
Diaphragm checkvalve 2 pumps will dry suction head 40" in about 3 seconds
Again this is with little backpressure on output of pump, any pressure
will lower dry suction head.
With 1 pump and ball checkvalve motor was laboring a bit at both 20" and
once a suction was developed 40" labor even more, 2 pumps helped labor,
but with Daiphragm checkvalve, little labor.
This was a test of ability to pull vent from possible lower cabin air. I
will use a Diaphragm 1 way, with a Wicks Aircraft 1 way in series which is
screened and has a free ball in it (attitude dependent). Very little
restriction with both.
****As mentioned above 2 pumps pull a higher dry suction head than 1.
Seemed in a non scientific test of slowing pumps by restricting output, 2
pumps perhaps increase pressure by ~10%. Again not too scientific, but
there is not much of a change. Flow by observing stream with no output
restriction seems same P1, or P2 or P1+P2. Perhaps with output demanding
pressure, 2 pumps may be slight better, but I don't think much. Dry
difference with 2 pumps is pretty dramatic, and with a restriction on
output when testing dry suction head 2 pumps are again dramatic better
(Finger over output restricting, perhaps 25% of max pressure
restriction?).
****I was a bit surprised to see plenty of bubbling going in 2 filters
between the Gasculators and input to system and the one on the output of
system. I was not able to get air out of filters, it just bubbles happily
along, does not seem to cause a problem, very steady stream at output
going back to tank with or without making system develop pressure. There
was no leaks causing air injestion in my system. If I opened a sump, even
just a tiny bit on gasculator and allow air injestion, the filters go
foamy right now.
****In the Europa schematic, if you sump either gasculator, it will
introduce air to either of the pumps or both if pump/s are running.
****It seems that P1 is just a bit happier pulling a dry suction head
compared to P2, P2 does have a 1 way and a slight longer plumbing run with
2 90 degree fittings.
****If voltage is up because of charging system compared to below, all
should work even better.
****I had pumps run at least 2 hours before I did testing so they should
have been broken in, Manual states 20% increase (I forget if it was flow
or pressure) after break in
Conclusion
Will use P1 as primary
Will use aux vent as described
I highly recommend running pumps with filters to clean and break in. I for
1 don't want Black Europa Snot in my FlowScan transducers, fuel pressure
regulator, carbs, or back into tank to go back through gasculator fine
filters.
Will clean fuel pump socks 100 hrs or annual. Note that these filters just
pull out, but can't get a replacement, so be careful.
Ron Parigoris
Testing 01-07-2007
Used a 12 volt 12 amp Gel Cell Battery, ~ 12.6V static, 1 pump loaded to
almost stall ~12.2V and 2 pumps loaded to almost stall ~11.8V
Filled aux 10 gallon tank with 7.5 gallons of 100LL
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