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mtherr(at)yahoo.com
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 Posted: Sun Jul 02, 2006 4:54 am Post subject: Fuel pump puzzle |
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Good morning!
I recently discovered that my fuel pumps are less
efficient in flight. Fuel pressure (which is measured
at the gascolator) gets down to ONE psi.
I have one pump at each wing tank (Fred, I'm not
sucking fuel  I also have a third pump at the
firewall.
Performance is the same with both the left and right
pumps. I feel the pressure is a tad higher when using
the firewall pump.
I did a test on the ground. Fuel flow is exactly the
same from the 3 pumps and is same as new pumps (25
gal/hr). Fuel pressure on the ground is normal (5 psi
per pump approx).
Anybody would know why I don't get the usual 3-5 psi
in flight? (now it is more like 1 to 3)
Yesterday, as a workaround, I used the firewall pump
in conjunction with the wing pumps (firewall pump is
in series) and I got 4-6 psi.
Michel
PS: the pumps I use are the Facet 40108 pumps. The
wing pumps have approx 200 hours of use each.
Firewall pump is much less solicitated.
----------------------------
Michel Therrien CH601-HD, C-GZGQ
http://mthobby.pcperfect.com/ch601
http://www.zenithair.com/bldrlist/profiles/mthobby
http://pages.infinit.net/mthobby
__________________________________________________
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bryanmmartin
Joined: 10 Jan 2006
Posts: 1018
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| Posted: Mon Jul 03, 2006 11:07 am Post subject: Fuel pump puzzle |
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I am but I haven't seen any similar problem with my plane. It sounds
like a fuel tank venting issue. That's the only thing I can think of
offhand that would show these symptoms.
On Jul 3, 2006, at 12:53 PM, Michel Therrien wrote:
| Quote: |
Test test test... no response yet...
Anybody here using Facet pumps?
>
> Good morning!
>
> I recently discovered that my fuel pumps are less
> efficient in flight. Fuel pressure (which is
> measured
> at the gascolator) gets down to ONE psi.
>
|
--
Bryan Martin
N61BM, CH 601 XL,
RAM Subaru, Stratus redrive.
do not archive.
| | - The Matronics Zenith-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive. |
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mtherr(at)yahoo.com
Guest
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| Posted: Mon Jul 03, 2006 1:41 pm Post subject: Fuel pump puzzle |
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I noticed when I fueled up at an airport recently
(with 91 octane mogas). The performance of the pump
(the fueling pump) was very poor for the first 20
seconds (fuel was flowing very slowly). The man
mentioned something about fueling be slow when
gasoline temperature is high (due to vapor, or
whatever). As a matter of fact, as soon as cool
gasoline entered the pump, it became faster.
Could this be the same type of problem? I suppose the
gas is fairly hot in those alum wing fuel tanks.
Any way to improve this?
Michel
--- Bryan Martin <bryanmmartin(at)comcast.net> wrote:
| Quote: |
<bryanmmartin(at)comcast.net>
I am but I haven't seen any similar problem with my
plane. It sounds
like a fuel tank venting issue. That's the only
thing I can think of
offhand that would show these symptoms.
On Jul 3, 2006, at 12:53 PM, Michel Therrien wrote:
>
<mtherr(at)yahoo.com>
>
> Test test test... no response yet...
>
> Anybody here using Facet pumps?
>
>
>>
>> Good morning!
>>
>> I recently discovered that my fuel pumps are less
>> efficient in flight. Fuel pressure (which is
>> measured
>> at the gascolator) gets down to ONE psi.
>>
--
Bryan Martin
N61BM, CH 601 XL,
RAM Subaru, Stratus redrive.
do not archive.
browse
Subscriptions page,
FAQ,
http://www.matronics.com/Navigator?Zenith-List
Admin.
|
----------------------------
Michel Therrien CH601-HD, C-GZGQ
http://mthobby.pcperfect.com/ch601
http://www.zenithair.com/bldrlist/profiles/mthobby
http://pages.infinit.net/mthobby
__________________________________________________
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bryanmmartin
Joined: 10 Jan 2006
Posts: 1018
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| Posted: Mon Jul 03, 2006 9:03 pm Post subject: Fuel pump puzzle |
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If the fueling station has underground tanks and above ground pumps
that are sitting out in the sun, the fuel in the pumps may partially
vaporize and cause slow pumping at first. The pumps are sucking the
gas up out of the tanks, which makes the problem worse. High octane
auto gas is easier to vaporize than low octane and all auto gas is
easier to vaporize than avgas. Also, auto gas made for winter use has
a higher vapor pressure than summer auto gas.
With the fuel system you described in your earlier post, I wouldn't
think vapor at your pump inlets would be a problem since any vapor
that forms in the tank should rise to the top of the tank and away
from the tank outlets and the pumps.
If your tank screens are starting to clog up, you may see a drop in
pump pressure as you demand higher fuel flows with high throttle
settings. If this is the problem, it should also show up on the
ground during a high power run-up. If your tank vents are restricted,
it may take a while for a drop in pump pressure to show up because it
takes a while to form a partial vacuum in the tank. I don't know how
your tanks are vented but you should check for blockage (mud wasps
are notorious for clogging up small tubing for instance). Any
restriction in your fuel lines upstream of your pumps can cause
pressure drops at higher fuel flows.
On Jul 3, 2006, at 5:39 PM, Michel Therrien wrote:
| Quote: |
I noticed when I fueled up at an airport recently
(with 91 octane mogas). The performance of the pump
(the fueling pump) was very poor for the first 20
seconds (fuel was flowing very slowly). The man
mentioned something about fueling be slow when
gasoline temperature is high (due to vapor, or
whatever). As a matter of fact, as soon as cool
gasoline entered the pump, it became faster.
Could this be the same type of problem? I suppose the
gas is fairly hot in those alum wing fuel tanks.
Any way to improve this?
Michel
>>>
>>> Good morning!
>>>
>>> I recently discovered that my fuel pumps are less
>>> efficient in flight. Fuel pressure (which is
>>> measured
>>> at the gascolator) gets down to ONE psi.
>
|
--
Bryan Martin
N61BM, CH 601 XL,
RAM Subaru, Stratus redrive.
do not archive.
| | - The Matronics Zenith-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive. |
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frank.hinde(at)hp.com
Guest
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| Posted: Wed Jul 05, 2006 6:28 am Post subject: Fuel pump puzzle |
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I assume there is a bypass around the firewall pump? Or are you pumping
through it?
If your pumping through it you might try removing this pump altogether
(really is not necessary anyway) at least temporarily. It maybe that the
little checkvalve on the third pump may be acting up.
Either that or it sounds like a venting issue.
In the HDS I had a 40106 pump in each wing root and that always gave me
5psi or so at the carb inlet.
What do you use for filtration?...Filters plugging?
Frank
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mtherr(at)yahoo.com
Guest
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| Posted: Wed Jul 05, 2006 7:00 pm Post subject: Fuel pump puzzle |
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I'm actually pumping through the firewall pump.
My plan was to remove it as I became convinced it was
useless... not so sure anymore since it brings back my
fuel pressure to an acceptable level (when used in
conjunction with wing pumps).
I'll check for venting, but I'd be surprised (I saw
fuel dropping out of vents when I moved the plane with
fuel gas tanks last weekend. Of course, visually,
vents look clean.
Filtration?
. finger screen in tanks, gascolator at the bottom of
the firewall, fuel filter at the carburetor.
The fuel pressure sender is on the gascolator. I just
checked and cleaned the gascolator screen upon doing
my annual inspection, about a month or so ago.
I'll inspect my finger screens.
Michel
--- "Hinde, Frank George (Corvallis)"
<frank.hinde(at)hp.com> wrote:
| Quote: |
George (Corvallis)" <frank.hinde(at)hp.com>
I assume there is a bypass around the firewall pump?
Or are you pumping
through it?
If your pumping through it you might try removing
this pump altogether
(really is not necessary anyway) at least
temporarily. It maybe that the
little checkvalve on the third pump may be acting
up.
Either that or it sounds like a venting issue.
In the HDS I had a 40106 pump in each wing root and
that always gave me
5psi or so at the carb inlet.
What do you use for filtration?...Filters plugging?
|
----------------------------
Michel Therrien CH601-HD, C-GZGQ
http://mthobby.pcperfect.com/ch601
http://www.zenithair.com/bldrlist/profiles/mthobby
http://pages.infinit.net/mthobby
__________________________________________________
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frank.hinde(at)hp.com
Guest
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| Posted: Thu Jul 06, 2006 7:22 am Post subject: Fuel pump puzzle |
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I would bypass that firewall pump, I'm pretty suspicious of that iand it
it is pretty useless as you say...
Farnk
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dredmoody(at)cox.net
Guest
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| Posted: Thu Jul 06, 2006 7:39 am Post subject: Fuel pump puzzle |
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Let me put my two cents in here.... as long as the pump is istalled and wired, I would keep it but plumb in a valved bypass just incase. One "T" and a valve won't cost or weigh much and might be very handy one day. The valve would allow you to direct fuel flow either through the bypass line or through the fuel pump. Under normal operations, I would definitely bypass the firewall area pump because the last thing we want is lower pressure in the line from the tanks to the pump. That's the area in which we are most likely to vaporize a bubble from sun-warmed ethanol blend fuel. However, if one of the other pumps fails, it would be nice to at least pressurize the line from the firewall to the carb.
Ed Moody II
Rayne, LA
601XL / wings
---- "Hinde wrote:
| Quote: |
I would bypass that firewall pump, I'm pretty suspicious of that iand it
it is pretty useless as you say...
Farnk
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