Today's Message Index:
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1. 12:45 AM - Re: Fuel pressure fluctuations anyone? (John Vormbaum)
2. 07:24 AM - Re: Fuel pressure fluctuations anyone? (Ricardo Otaola)
3. 08:04 AM - Re: Fuel pressure fluctuations anyone? (CloudCraft@aol.com)
Message 1
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| Subject: | Re: Fuel pressure fluctuations anyone? |
--> Commander-List message posted by: "John Vormbaum" <john@vormbaum.com>
Wow, Alan....a long and expensive journey. I don't have dams in my sump
(damns? Damn that "S" word!) and I've never had that problem. But I'm
Lycoming powered so maybe it's something specific to Contis. Either way,
I'll take a look at my fittings to see if they're straight through or angled
(just out of curiosity).
/J
PS: Next time you fly a 2-hr. leg, make sure it ends in the Bay Area and
I'll buy you lunch ;-).
----- Original Message -----
From: "Alan Kucheck" <akucheck@hotmail.com>
Subject: Commander-List: Fuel pressure fluctuations anyone?
> --> Commander-List message posted by: "Alan Kucheck"
<akucheck@hotmail.com>
>
> This is a long one, but I hope it will be useful to any others that have
> similar issues out there. I know at least one other 500A owner out there
> has...
>
> Since acquiring N811D, a 500A Colemill, in July of 2003 I have had some
fuel
> pressure fluctuations, primarily on the right engine, but once or twice on
> the left as well. By that I mean that the fuel "flow" needle wags up and
> down kind of like a reverse pendulum - ever larger displacments above and
> below normal pressure until the engine coughs and sputters. Application
of
> boost pump immediately rectifies the problem.
>
> When I took possession of the 11D the engines were just past TBO. About 6
> months later we replaced the engines with zero-time overhauls. I have not
> had a problem with the left engine since. However, the right engine
> behavior continued unchanged. Well, replacing an engine is an expensive,
> but effective way of eliminating some variables - now the problem was
> isolated to the airframe. The problem only happened at altitude, 8000' or
> above. Sometimes was clearly associated with turbulence - get a jolt,
lose
> the engine. Sometimes a turn was enough - briskly crank in 30 degrees,
> cough, cough, boost pump. But neither was necessary - while calmly
cruising
> along, needle starts to wag, amplitude increases and there she goes. This
> might happen several times in the course of a 2 hour flight. After one
> flight my right shoulder was sore the next day; I realized my right hand
had
> been hovering next to boost pump switch most of the flight the day before.
> Bad.
>
> So we have been progressively looking for some way for air to get into the
> system, or for some blockage. We removed the fuel filter bodies [corroded
> and resined] and cleaned the screens. Same thing. We switched the
screens
> left/right. The problem remained on the right side.
>
> We overhauled the fuel shutoff valve and replaced the hoses [it was time]
> from there forward, thinking that perhaps the shutoff had a bad seal was
> sucking air into the line somewhere. Same problem.
>
> In great frustration, I took a step back and saw something I had not
noticed
> earlier: the fitting just forward of the firewall that attaches to the
fuel
> filter bodies was different. On the left engine, the fitting was
> straight-through. The right engine had a right angle fitting. I noticed
in
> some photos from Dayton that other birds have all manner of fitting here -
> straight, 30/60/90 degrees. We replaced it with a straight-through
fitting.
> No cough. The needle still wagged, but it appeared that just changing
that
> fitting was enough to keep the engine running, a convenient feature. This
> was confirmed in multiple flights, wag but no cough. Finally, a clear,
> repeatable, positive change in behavior.
>
> However, the problem that was causing the needle wag was still there. The
> last item was the sump. That is now replaced [same corrosion]; see my
post
> on 4/17/2005. When my mechanic put everything back together we had one
leak
> around the right boost pump. He replaced the O-ring and we were done.
>
> The good news: I am declaring the problem gone. I just flew 2 two-hour
> legs and the needle was [like the left one] like a rock. It used to
bounce
> quite a bit almost all the time. Now, rock steady.
>
> So...I don't know whether it was the leaky O-ring around the right boost
> pump, or the dams that are in the new sump but were not in the old one.
But
> replacing the sump fixed my problem. Long, expensive, frustrating
journey.
> But I am very pleased with what I now have.
>
> ak
>
>
> --
>
>
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Message 2
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| Subject: | Fuel pressure fluctuations anyone? |
--> Commander-List message posted by: "Ricardo Otaola" <otayca@telcel.net.ve>
Hi friend:
I have a 680F and have had that problem for a lonng looooong time. The best
way to resolve are as follows:
1- Fuel Unit (Not the fuel punp). Have it overhauled!!
2- Fuel lines, make sure they all have smooth curves from the sump into
the motor.
3- Fuel valves. Check for leaks.
4- Fuel air line (the ones on the wings) make sure they are not clugged
up.
Point one is the most important one.
-----Original Message-----
From: owner-commander-list-server@matronics.com
[mailto:owner-commander-list-server@matronics.com] On Behalf Of Alan Kucheck
Subject: Commander-List: Fuel pressure fluctuations anyone?
--> Commander-List message posted by: "Alan Kucheck" <akucheck@hotmail.com>
This is a long one, but I hope it will be useful to any others that have
similar issues out there. I know at least one other 500A owner out there
has...
Since acquiring N811D, a 500A Colemill, in July of 2003 I have had some fuel
pressure fluctuations, primarily on the right engine, but once or twice on
the left as well. By that I mean that the fuel "flow" needle wags up and
down kind of like a reverse pendulum - ever larger displacments above and
below normal pressure until the engine coughs and sputters. Application of
boost pump immediately rectifies the problem.
When I took possession of the 11D the engines were just past TBO. About 6
months later we replaced the engines with zero-time overhauls. I have not
had a problem with the left engine since. However, the right engine
behavior continued unchanged. Well, replacing an engine is an expensive,
but effective way of eliminating some variables - now the problem was
isolated to the airframe. The problem only happened at altitude, 8000' or
above. Sometimes was clearly associated with turbulence - get a jolt, lose
the engine. Sometimes a turn was enough - briskly crank in 30 degrees,
cough, cough, boost pump. But neither was necessary - while calmly cruising
along, needle starts to wag, amplitude increases and there she goes. This
might happen several times in the course of a 2 hour flight. After one
flight my right shoulder was sore the next day; I realized my right hand had
been hovering next to boost pump switch most of the flight the day before.
Bad.
So we have been progressively looking for some way for air to get into the
system, or for some blockage. We removed the fuel filter bodies [corroded
and resined] and cleaned the screens. Same thing. We switched the screens
left/right. The problem remained on the right side.
We overhauled the fuel shutoff valve and replaced the hoses [it was time]
from there forward, thinking that perhaps the shutoff had a bad seal was
sucking air into the line somewhere. Same problem.
In great frustration, I took a step back and saw something I had not noticed
earlier: the fitting just forward of the firewall that attaches to the fuel
filter bodies was different. On the left engine, the fitting was
straight-through. The right engine had a right angle fitting. I noticed in
some photos from Dayton that other birds have all manner of fitting here -
straight, 30/60/90 degrees. We replaced it with a straight-through fitting.
No cough. The needle still wagged, but it appeared that just changing that
fitting was enough to keep the engine running, a convenient feature. This
was confirmed in multiple flights, wag but no cough. Finally, a clear,
repeatable, positive change in behavior.
However, the problem that was causing the needle wag was still there. The
last item was the sump. That is now replaced [same corrosion]; see my post
on 4/17/2005. When my mechanic put everything back together we had one leak
around the right boost pump. He replaced the O-ring and we were done.
The good news: I am declaring the problem gone. I just flew 2 two-hour
legs and the needle was [like the left one] like a rock. It used to bounce
quite a bit almost all the time. Now, rock steady.
So...I don't know whether it was the leaky O-ring around the right boost
pump, or the dams that are in the new sump but were not in the old one. But
replacing the sump fixed my problem. Long, expensive, frustrating journey.
But I am very pleased with what I now have.
ak
--
Message 3
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| Subject: | Re: Fuel pressure fluctuations anyone? |
--> Commander-List message posted by: CloudCraft@aol.com
In a message dated 03-May-05 07:25:33 Pacific Daylight Time,
otayca@telcel.net.ve writes:
1- Fuel Unit (Not the fuel punp). Have it overhauled!!
The IGSO-540 has a Simmonds fuel control unit (as you -F and -FL owners know)
and there is a very fine mesh screen that rides behind the fuel pump impeller
vanes that needs to be ultrasonically cleaned often!
This screen is so fine, it's almost like cloth. I've had several loads of
junk fuel and/or the gick that forms in the fuel bladders over time clog up the
Simmonds.
Capitan Otaola is correct about overhauling the Simmonds periodically, but
the fuel screen can be pulled and cleaned while keeping the unit on the engine,
and can be done when needed.
Wing Commander Gordon
Life is not simple anywhere. Probably less so elsewhere.
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