Today's Message Index:
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1. 11:47 AM - Drop of fuel pressure (georg.stiller@arcor.de)
2. 12:44 PM - Re: Drop of fuel pressure (PHILLIPS I)
3. 06:07 PM - Re: Drop of fuel pressure (Bob Comperini)
4. 07:39 PM - Re: Drop of fuel pressure (Roger Lee)
Message 1
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| Subject: | Drop of fuel pressure |
Hi all,
I have a problem with dropping fuel pressure. It happened twice so far. Conditions
were similar.
Conditions yesterday were: Rotax 912, 80 hp, 250 hrs, outside temp. minus 10 centigrade,
carb. intake temp. with carb. heat minus 1,5 centigrade.
Fuel pressure after engine start, warm up and for about 30 min. flight at 4600
rpm was constant around 0,3 bar. Than fuel pressure started to drop and after
about half a minute reached the red line of 0,14 bar. That's when I engaged the
electric fuel pump. Pressure than increased back to just below 0,3 bar.
I returned to the field, landed, had a break, checked the fuel pump visually and
it just looked fine.
After half an hour or so I took off again, flew for 20 minutes and fuel pressure
was in the specified range at about 0,3 bar without engaging the electric pump.
Fuel pressure gauge (type 'Skydrive') is of manometer type. A fuel line goes to
the gauge, no external sensor involved.
Any help would be highly welcome.
Regards, Georg
Message 2
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| Subject: | Re: Drop of fuel pressure |
At the air temperture you were flying at i whould suspect some water
freezing in the feed pipe reducing fuel flow,
On 10 February 2012 19:46, <georg.stiller@arcor.de> wrote:
>
> Hi all,
>
> I have a problem with dropping fuel pressure. It happened twice so far.
> Conditions were similar.
>
> Conditions yesterday were: Rotax 912, 80 hp, 250 hrs, outside temp. minus
> 10 centigrade, carb. intake temp. with carb. heat minus 1,5 centigrade.
>
> Fuel pressure after engine start, warm up and for about 30 min. flight at
> 4600 rpm was constant around 0,3 bar. Than fuel pressure started to drop
> and after about half a minute reached the red line of 0,14 bar. That's when
> I engaged the electric fuel pump. Pressure than increased back to just
> below 0,3 bar.
>
> I returned to the field, landed, had a break, checked the fuel pump
> visually and it just looked fine.
>
> After half an hour or so I took off again, flew for 20 minutes and fuel
> pressure was in the specified range at about 0,3 bar without engaging the
> electric pump.
>
> Fuel pressure gauge (type 'Skydrive') is of manometer type. A fuel line
> goes to the gauge, no external sensor involved.
>
> Any help would be highly welcome.
>
> Regards, Georg
>
>
Message 3
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| Subject: | Re: Drop of fuel pressure |
>
>I have a problem with dropping fuel pressure. It happened twice so far. Conditions
were similar.
For what ever its worth.. welcome to the world of crappy Rotax 912 fuel pumps.
I, and several other people I know experience similar things. Doesn't happen all
the time, and often doesn't even happen twice in the same day. In my case,
freezing is never an issue. My episodes appear to happen after a long time at
cruise altitude, during a descent, and it appears to happen when I descend about
2000 feet below my starting altitude.
As you probably know, Rotax came out with "Version 3" of their fuel pumps just
this past summer.
Now, do you have the "fuel return line" and all that stuff in your system?
This is not to say your fuel pump is the cause.. obviously, there are still plenty
of other things that could be going on. But in many circles, it is known that
these pumps are not fool proof.
--
Bob Comperini
e-mail: bob@fly-ul.com
WWW: http://www.fly-ul.com
Message 4
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| Subject: | Re: Drop of fuel pressure |
You need to find out first if the reading is real or a false reading. You need
to place a mechanical gauge in line and see if it match's what you see in the
cockpit. This is the only real way to diagnos your problem whithout playing hit
and miss and throwing money at the problem and hoping you get a hit. You can
make a $20 setup for this with a 0-10 psi gauge and some copper tubbing from
the hardware store. Until you do this everything else is stricly a guess. Once
you put a gauge on it it will tell you where the problem is.
--------
Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Repair Center - Heavy Maint. Rated
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056
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