Today's Message Index:
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0. 12:22 AM - Please Make A Contribution To Support Your Lists (Matt Dralle)
1. 04:28 AM - Re: Air in fuel lines? (jakent@unison.ie)
2. 06:48 AM - Re: Air in fuel lines. (Dennis Holbrook)
3. 11:11 AM - Re: Air in fuel lines. (teamgrumman@aol.com)
4. 04:19 PM - Re: Air in fuel lines. (Jim Aitken)
5. 06:10 PM - Re: Re: Air in fuel lines? (Charlie England)
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Subject: | Please Make A Contribution To Support Your Lists |
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Message 1
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Subject: | RE: Air in fuel lines? |
Subject: Engines-List: Air in fuel lines.
Hi all:
Been having a lot of trouble with a rough idle problem on my Fuel Injected
0-360 parallel valve engine. I've been going through several tests trying
to locate the source of the problem but so far no joy. One suggestion that
I have received concerns air getting into the fuel lines. It seems a little
far fetched that air could get in through a fitting that is not leaking fuel
but I'm running out of ideas so I'll go through and tighten all my fittings
to see if that helps.
But, that leaves one other possibility and that's air getting in through the
fuel selector valve. I'm using the Van's fuel selector that came with my
RV-6 kit. It sat in its little brown bag on the shelf in my shop for several
years before it got used but seems to working fine. It's not hard to move
the selector and its not leaking, at least externally.
Anyone experience leaking of this valve or any issue with that might let air
into the fuel lines through it? Any ideas on how I might test the valve to
see if it's leaking air into the system?
I'm using the Van's high pressure pump setup that puts the pump ahead of the
selector valve so there will be some suction at the valve. I'm running out
of ideas and thinking about switching to a carb. Hate to do that but can't
find anything wrong after working on it for the last year, maddening.
Thanks.
Dean Psiropoulos
RV-6A N197DM
Hi Dean,
Have you checked the air induction system thoroughly for air leaking in at
low power settings. A slight tightening of all the hose clips improved
things for me. Also you could re-check the idle mixture setting when you
are sure the induction leak is not happening?
John Kent (EI-DIY RV-4)
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Subject: | Re: Air in fuel lines. |
Dean:
Rough idle covers a fairly broad range. My variety of roughness was usually
associated with heat and probably best described as a series of 'pauses' in
an otherwise smooth idle. I worked with Don Rivera at Airflow Performance
who set me up with smaller injectors and a stiffer flow divider spring to
increase fuel pressure downstream of the fuel control. Don's theory was
simple: heat causes partial vaporization of the fuel... increased pressure
decreases vaporization. Worked for me.
Dennis
RV6/IO360/N54X
Message 3
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Subject: | Re: Air in fuel lines. |
Interesting thing about that air in the fuel line.
In the early 90s there were a few Slingsby T-3 Firefly crashes. These pla
nes were used by the U.S. Air Force Academy for flight training. The beli
ef, at that time, was air in the fuel lines.
The Division in which I worked at that time was tasked with determining if
there was air in the fuel lines. We built a mock-up of the fuel system
and, sure enough, there was air in the fuel lines. Problem solved . . .
or so we thought. As it turned out, the air we followed from the pump
to the divider disappeared as the air/fuel mixture was sprayed through th
e injector nozzle. No big gaps of air sprayed out.
Any time a fuel pump pumps, air is separated from the fuel. The only way
to keep the air out, is to raise the fuel line pressure above the pressur
e at which air separates out. This happens, partly, in the fuel divider.
If your engine is carbureted, the float does that; it lets the air vent
into the top of the carb.
Just for grins, hook up 20 feet or so of clear hose to the outlet of the
fuel pump and pump fuel from one wing to the other. LOTs of air.
As for the crashes, we speculated the crashes were due to instructors tell
ing the new pilots NOT to lean. Why? Jets don't have to be leaned so why
teach leaning? Even at the academy's 7200 foot elevation one observer to
ld us the planes would cough black smoke while taxiing.
-----Original Message-----
From: Dennis Holbrook <dholbrook7@cox.net>
Sent: Sat, Nov 7, 2009 6:48 am
Subject: Re: Engines-List: Air in fuel lines.
Dean:
Rough idle covers a fairly broad range. My variety of roughness was usual
ly
associated with heat and probably best described as a series of 'pauses'
in
an otherwise smooth idle. I worked with Don Rivera at Airflow Performance
who set me up with smaller injectors and a stiffer flow divider spring to
increase fuel pressure downstream of the fuel control. Don's theory was
simple: heat causes partial vaporization of the fuel... increased pressur
e
decreases vaporization. Worked for me.
Dennis
RV6/IO360/N54X
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Message 4
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Subject: | Air in fuel lines. |
Then reason that you get air in a fuel line is that the shaft of the fuel
selector valve is usually sealed with a single O ring. If the selector shaft
is on the suction side of the pump air will be drawn in past the O ring. An
O ring is designed to seal with pressure pushing it into a small crevass in
a U shaped groove, and it works quite well. The shaft seal will not leak
under pressure, which is the normal way to test for leaks, but the O ring
will be sucked out of position in a U groove under suction and allow air
draw in. The groove for an O ring for negative pressure service is
trapezoidal in shape. The Parker O ring catalogue shows this style. The
trapezoidal groove is difficult to machine in a narrow hole and probably not
considered. An old fashioned packing shaft seal with a compression nut is
better for negative pressure.
Jim Aitken, P.Eng.
-----Original Message-----
From: owner-engines-list-server@matronics.com
[mailto:owner-engines-list-server@matronics.com] On Behalf Of DEAN
PSIROPOULOS
Sent: November 6, 2009 9:46 PM
Subject: Engines-List: Air in fuel lines.
<dean.psiropoulos@verizon.net>
Hi all:
Been having a lot of trouble with a rough idle problem on my Fuel Injected
0-360 parallel valve engine. I've been going through several tests trying
to locate the source of the problem but so far no joy. One suggestion that
I have received concerns air getting into the fuel lines. It seems a little
far fetched that air could get in through a fitting that is not leaking fuel
but I'm running out of ideas so I'll go through and tighten all my fittings
to see if that helps.
But, that leaves one other possibility and that's air getting in through the
fuel selector valve. I'm using the Van's fuel selector that came with my
RV-6 kit. It sat in its little brown bag on the shelf in my shop for several
years before it got used but seems to working fine. It's not hard to move
the selector and its not leaking, at least externally.
Anyone experience leaking of this valve or any issue with that might let air
into the fuel lines through it? Any ideas on how I might test the valve to
see if it's leaking air into the system?
I'm using the Van's high pressure pump setup that puts the pump ahead of the
selector valve so there will be some suction at the valve. I'm running out
of ideas and thinking about switching to a carb. Hate to do that but can't
find anything wrong after working on it for the last year, maddening.
Thanks.
Dean Psiropoulos
RV-6A N197DM
Message 5
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Subject: | Re: RE: Air in fuel lines? |
jakent@unison.ie wrote:
>
>
> Subject: Engines-List: Air in fuel lines.
>
>
> Hi all:
>
> Been having a lot of trouble with a rough idle problem on my Fuel Injected
> 0-360 parallel valve engine. I've been going through several tests trying
> to locate the source of the problem but so far no joy. One suggestion that
> I have received concerns air getting into the fuel lines. It seems a little
> far fetched that air could get in through a fitting that is not leaking fuel
> but I'm running out of ideas so I'll go through and tighten all my fittings
> to see if that helps.
>
> But, that leaves one other possibility and that's air getting in through the
> fuel selector valve. I'm using the Van's fuel selector that came with my
> RV-6 kit. It sat in its little brown bag on the shelf in my shop for several
> years before it got used but seems to working fine. It's not hard to move
> the selector and its not leaking, at least externally.
>
> Anyone experience leaking of this valve or any issue with that might let air
> into the fuel lines through it? Any ideas on how I might test the valve to
> see if it's leaking air into the system?
>
> I'm using the Van's high pressure pump setup that puts the pump ahead of the
> selector valve so there will be some suction at the valve. I'm running out
> of ideas and thinking about switching to a carb. Hate to do that but can't
> find anything wrong after working on it for the last year, maddening.
> Thanks.
>
> Dean Psiropoulos
> RV-6A N197DM
>
> Hi Dean,
> Have you checked the air induction system thoroughly for air leaking in at
> low power settings. A slight tightening of all the hose clips improved
> things for me. Also you could re-check the idle mixture setting when you
> are sure the induction leak is not happening?
> John Kent (EI-DIY RV-4)
I'd 2nd that thought. I've had the pressed-in intake stubs in the sump
get loose, causing bad idle (carb engine, but would cause the same thing
with injection).
Here's another, somewhat remote possibility. One of my neighbors flies a
Cont IO360 Swift. It has a lot of AN hose between the tanks & the fuel
pump. It developed the problem of quitting when he would bank at certain
angles. 2 or 3 deadstick landings while trying various things to find
the problem. He tried a lot of different things & ultimately discovered
that if he air-pressurized the suction side AN hose, it would 'blow
bubbles' all over the fabric coating if it was wet down with water. (No
noticeable gas leaks) He replaced the hoses, & hasn't had it quit since.
The best guess is that it was sucking air through the hose sidewalls.
(Hose was quite a few years old.)
Charlie
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