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sam(at)fr8dog.net
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 Posted: Mon Mar 17, 2008 7:13 am Post subject: Fuel pressure problems |
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The first fifty hours were trouble free, as far as fuel pressure goes, but now for the past 40 hours or so, I'm getting fuel pressure fluctuation's. Normally the F/P runs in the mid to low 20's, but now constantly fluctuates from 8 to 27 psi. The engine runs ok, but it's disconcerting. Has anybody experienced this on an IO540D4A5 before, would the engine actually keep running if the F/P was really down to 8psi?
Sam Marlow
#40157
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bhughes(at)qnsi.net
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| Posted: Mon Mar 17, 2008 7:51 am Post subject: Fuel pressure problems |
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Could this be related to the Fuel Injection AD was published last week?
Bobby Hughes
From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Sam
Sent: Monday, March 17, 2008 9:11 AM
To: rv10-list(at)matronics.com
Subject: Fuel pressure problems
The first fifty hours were trouble free, as far as fuel pressure goes, but now for the past 40 hours or so, I'm getting fuel pressure fluctuation's. Normally the F/P runs in the mid to low 20's, but now constantly fluctuates from 8 to 27 psi. The engine runs ok, but it's disconcerting. Has anybody experienced this on an IO540D4A5 before, would the engine actually keep running if the F/P was really down to 8psi?
Sam Marlow
#40157
[quote]
href="http://www.matronics.com/Navigator?RV10-List">http://www.matronics.com/Navigator?RV10-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
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sam(at)fr8dog.net
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| Posted: Mon Mar 17, 2008 9:02 am Post subject: Fuel pressure problems |
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Possibly, I haven't checked that yet, but it's inconsistent. The fluctuation's can subside for minuets at a time in cruise.
Bobby J. Hughes wrote: [quote]
Could this be related to the Fuel Injection AD was published last week?
Bobby Hughes
From: owner-rv10-list-server(at)matronics.com (owner-rv10-list-server(at)matronics.com) [mailto:owner-rv10-list-server(at)matronics.com (owner-rv10-list-server(at)matronics.com)] On Behalf Of Sam
Sent: Monday, March 17, 2008 9:11 AM
To: rv10-list(at)matronics.com (rv10-list(at)matronics.com)
Subject: Fuel pressure problems
The first fifty hours were trouble free, as far as fuel pressure goes, but now for the past 40 hours or so, I'm getting fuel pressure fluctuation's. Normally the F/P runs in the mid to low 20's, but now constantly fluctuates from 8 to 27 psi. The engine runs ok, but it's disconcerting. Has anybody experienced this on an IO540D4A5 before, would the engine actually keep running if the F/P was really down to 8psi?
Sam Marlow
#40157
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jesse(at)saintaviation.co
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| Posted: Mon Mar 17, 2008 12:29 pm Post subject: Fuel pressure problems |
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That sounds like a sensor issue, maybe either a bad crimp or a bad ground.
Don't ask me how I might know.
do not archive.
Jesse Saint
Saint Aviation, Inc.
jesse(at)saintaviation.com
www.saintaviation.com
352-427-0285
Sam wrote:
| Quote: | The first fifty hours were trouble free, as far as fuel pressure goes,
but now for the past 40 hours or so, I'm getting fuel pressure
fluctuation's. Normally the F/P runs in the mid to low 20's, but now
constantly fluctuates from 8 to 27 psi. The engine runs ok, but it's
disconcerting. Has anybody experienced this on an IO540D4A5 before,
would the engine actually keep running if the F/P was really down to 8psi?
Sam Marlow
#40157
|
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sam(at)fr8dog.net
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| Posted: Mon Mar 17, 2008 2:06 pm Post subject: Fuel pressure problems |
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That's what I thought to, but when I turn on the boost pump, it immediately returns to normal pressure.
Jesse Saint wrote: [quote] | Quote: | --> RV10-List message posted by: "Jesse Saint" <jesse(at)saintaviation.com> (jesse(at)saintaviation.com)
That sounds like a sensor issue, maybe either a bad crimp or a bad ground.
Don't ask me how I might know.
do not archive.
Jesse Saint
Saint Aviation, Inc.
jesse(at)saintaviation.com (jesse(at)saintaviation.com)
www.saintaviation.com
352-427-0285
Sam wrote:
| Quote: | The first fifty hours were trouble free, as far as fuel pressure goes,
but now for the past 40 hours or so, I'm getting fuel pressure
fluctuation's. Normally the F/P runs in the mid to low 20's, but now
constantly fluctuates from 8 to 27 psi. The engine runs ok, but it's
disconcerting. Has anybody experienced this on an IO540D4A5 before,
would the engine actually keep running if the F/P was really down to 8psi?
Sam Marlow
#40157
|
|
[b]
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Tim Olson
Joined: 25 Jan 2007
Posts: 2881
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| Posted: Tue Mar 18, 2008 6:19 am Post subject: Fuel pressure problems |
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The closest thing I can relate to this is a very very intermittent
thing....something I only see on a handful of flights, and usually
just in warmer temps.
If you climb at low airspeeds, like try to do a 90-100kt climb
on a hot day, I start to see a drop in fuel pressure. It starts
to fluctuate a bit, and then will start to drop. My audio warnings
fire up under about 12psi, so I don't run it too low to see how
it goes....I usually hit the boost, and drop the nose for better
cooling. Once you drop the nose and get more cooling airflow,
it goes away. Also, note that this happens in climb, when you
have lots of fuel flow. As soon as I level off, lean out, and
the fuel flows drop, it doesn't do it anymore. So, my guess is
that with high flow requirements in climb, and high heat, they
combine and produce low and fluctuating pressure. Since dropping
the nose has shown to eliminate the problem (like climbing at
120kts if I see this happening) and since pulling back the mixture
takes care of it once level, that is my best guess. But, as I
said, it isn't something I see very often...just on the hot
days or where I've done extended climbs...maybe see it 10-15
times a season...or something like that, but that's over 100-200
hours a season.
At one point I had tried to order a fuel pump cooling shroud
but the place didn't get them in stock. One of these days
I still would like to try that, along with perhaps some
heat shielding foam over the fuel lines forward of the
firewall. But, my thought is, if you get your cowl set up
with great cooling, it's probably something you wouldn't
see too often.
I'm not 100% sure of any of this....but it is something to
consider.
Tim Olson - RV-10 N104CD - Flying
do not archive
Sam wrote:
| Quote: | That's what I thought to, but when I turn on the boost pump, it
immediately returns to normal pressure.
Jesse Saint wrote:
>
>
> That sounds like a sensor issue, maybe either a bad crimp or a bad ground.
> Don't ask me how I might know.
>
> do not archive.
>
> Jesse Saint
> Saint Aviation, Inc.
> jesse(at)saintaviation.com
> www.saintaviation.com
> 352-427-0285
>
> Sam wrote:
>
>> The first fifty hours were trouble free, as far as fuel pressure goes,
>> but now for the past 40 hours or so, I'm getting fuel pressure
>> fluctuation's. Normally the F/P runs in the mid to low 20's, but now
>> constantly fluctuates from 8 to 27 psi. The engine runs ok, but it's
>> disconcerting. Has anybody experienced this on an IO540D4A5 before,
>> would the engine actually keep running if the F/P was really down to 8psi?
>> Sam Marlow
>> #40157
>>
>>
>
>
>
>
>
>
>
>
>
*
*
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sam(at)fr8dog.net
Guest
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| Posted: Tue Mar 18, 2008 9:26 am Post subject: Fuel pressure problems |
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Thanks for the reply Tim, but my pressure problem occurs at any flight attitude, or temp. So maybe were talking about a different problem. Normally at cruise my fuel pressure is in the low to mid 20's. When it does drop,a flip of the pump switch puts it back to normal.
I also experience engine surging at idle power settings on the ground, when the temp is above 75 or so degrees. It's fine in the winter months.
Thanks,
Sam
Tim Olson wrote: [quote]--> RV10-List message posted by: Tim Olson <Tim(at)myrv10.com> (Tim(at)myrv10.com)
The closest thing I can relate to this is a very very intermittent
thing....something I only see on a handful of flights, and usually
just in warmer temps.
If you climb at low airspeeds, like try to do a 90-100kt climb
on a hot day, I start to see a drop in fuel pressure. It starts
to fluctuate a bit, and then will start to drop. My audio warnings
fire up under about 12psi, so I don't run it too low to see how
it goes....I usually hit the boost, and drop the nose for better
cooling. Once you drop the nose and get more cooling airflow,
it goes away. Also, note that this happens in climb, when you
have lots of fuel flow. As soon as I level off, lean out, and
the fuel flows drop, it doesn't do it anymore. So, my guess is
that with high flow requirements in climb, and high heat, they
combine and produce low and fluctuating pressure. Since dropping
the nose has shown to eliminate the problem (like climbing at
120kts if I see this happening) and since pulling back the mixture
takes care of it once level, that is my best guess. But, as I
said, it isn't something I see very often...just on the hot
days or where I've done extended climbs...maybe see it 10-15
times a season...or something like that, but that's over 100-200
hours a season.
At one point I had tried to order a fuel pump cooling shroud
but the place didn't get them in stock. One of these days
I still would like to try that, along with perhaps some
heat shielding foam over the fuel lines forward of the
firewall. But, my thought is, if you get your cowl set up
with great cooling, it's probably something you wouldn't
see too often.
I'm not 100% sure of any of this....but it is something to
consider.
Tim Olson - RV-10 N104CD - Flying
do not archive
Sam wrote:
| Quote: | That's what I thought to, but when I turn on the boost pump, it immediately returns to normal pressure.
Jesse Saint wrote:
| Quote: | --> RV10-List message posted by: "Jesse Saint" <jesse(at)saintaviation.com> (jesse(at)saintaviation.com)
That sounds like a sensor issue, maybe either a bad crimp or a bad ground.
Don't ask me how I might know.
do not archive.
Jesse Saint
Saint Aviation, Inc.
jesse(at)saintaviation.com (jesse(at)saintaviation.com)
www.saintaviation.com
352-427-0285
Sam wrote:
| Quote: | The first fifty hours were trouble free, as far as fuel pressure goes,
but now for the past 40 hours or so, I'm getting fuel pressure
fluctuation's. Normally the F/P runs in the mid to low 20's, but now
constantly fluctuates from 8 to 27 psi. The engine runs ok, but it's
disconcerting. Has anybody experienced this on an IO540D4A5 before,
would the engine actually keep running if the F/P was really down to 8psi?
Sam Marlow
#40157
|
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*
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ricksked(at)embarqmail.co
Guest
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| Posted: Tue Mar 18, 2008 10:46 am Post subject: Fuel pressure problems |
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Sam,
Can you observe your fuel flow or do you just have pressure drop? I wonder if your getting bubbles or foaming in the line somewhere. Might want to see if there is a long expanse of unsupported fuel line that could be vibrating. Just throwing out an idea.
Rick Sked
40185
---
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rv10(at)sinkrate.com
Guest
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| Posted: Tue Mar 18, 2008 11:21 am Post subject: Fuel pressure problems |
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To add to Rick’s comment…
Is your fuel line from the servo to the spider close to the exhaust stack? I ask cause I know of one RV-9A that spits and coughs on the ground and we think its caused by vapor lock like symptoms due to excessive heat from the exhaust pipes that run right in front of the fuel line. I wouldn’t think you would get this at cruise because airflow should be sufficient to keep temps down but…. just another thought.
-Ben
From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Rick Sked
Sent: Tuesday, March 18, 2008 11:43 AM
To: rv10-list(at)matronics.com
Subject: Re: Fuel pressure problems
Sam,
Can you observe your fuel flow or do you just have pressure drop? I wonder if your getting bubbles or foaming in the line somewhere. Might want to see if there is a long expanse of unsupported fuel line that could be vibrating. Just throwing out an idea.
Rick Sked
40185
---
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sam(at)fr8dog.net
Guest
|
| Posted: Tue Mar 18, 2008 12:54 pm Post subject: Fuel pressure problems |
|
|
I suppose that's possible, it's a plans built RV10, so nothing out of
the ordinary. But nothing obvious.
Rick Sked wrote:
[quote]
Sam,
Can you observe your fuel flow or do you just have pressure drop? I
wonder if your getting bubbles or foaming in the line somewhere. Might
want to see if there is a long expanse of unsupported fuel line that
could be vibrating. Just throwing out an idea.
Rick Sked
40185
---
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sam(at)fr8dog.net
Guest
|
| Posted: Tue Mar 18, 2008 12:56 pm Post subject: Fuel pressure problems |
|
|
It's a fire sleeved line, that's standard positioning, not near the
exhaust at all.
Ben Westfall wrote:
[quote]
To add to Rick’s comment…
Is your fuel line from the servo to the spider close to the exhaust
stack? I ask cause I know of one RV-9A that spits and coughs on the
ground and we think its caused by vapor lock like symptoms due to
excessive heat from the exhaust pipes that run right in front of the
fuel line. I wouldn’t think you would get this at cruise because
airflow should be sufficient to keep temps down but…. just another
thought.
-Ben
------------------------------------------------------------------------
*From:* owner-rv10-list-server(at)matronics.com
[mailto:owner-rv10-list-server(at)matronics.com] *On Behalf Of *Rick Sked
*Sent:* Tuesday, March 18, 2008 11:43 AM
*To:* rv10-list(at)matronics.com
*Subject:* Re: Fuel pressure problems
Sam,
Can you observe your fuel flow or do you just have pressure drop? I
wonder if your getting bubbles or foaming in the line somewhere. Might
want to see if there is a long expanse of unsupported fuel line that
could be vibrating. Just throwing out an idea.
Rick Sked
40185
---
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toaster73(at)embarqmail.c
Guest
|
| Posted: Tue Mar 18, 2008 1:13 pm Post subject: Fuel pressure problems |
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|
Depending on the style of fire sleeving (impregnated on the line or actually
just a sleeve)....the fire sleeving can hide a kinked line. A kinked line
could produce erratic flow dependent on fuel demand.
-Chris Lucas
#40072
---
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sam(at)fr8dog.net
Guest
|
| Posted: Tue Mar 18, 2008 1:39 pm Post subject: Fuel pressure problems |
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|
On a IO540 it's a straight shot from the servo to the spider, or almost. But it could be just a bad hose, that's one of the last things I intend to check, because of the $dollar factor.
Chris wrote: [quote]--> RV10-List message posted by: "Chris" <toaster73(at)embarqmail.com> (toaster73(at)embarqmail.com)
Depending on the style of fire sleeving (impregnated on the line or actually just a sleeve)....the fire sleeving can hide a kinked line. A kinked line could produce erratic flow dependent on fuel demand.
-Chris Lucas
#40072
---
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scottmschmidt(at)yahoo.co
Guest
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| Posted: Tue Mar 18, 2008 9:13 pm Post subject: Fuel pressure problems |
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|
OK, here is my theory on this one because I have the same issue.
It only occurs for me if I am climbing out for an extended period of time with full fuel tanks.
What I believe happens is that the breather tubes get filled with fuel and as you start to burn fuel it cannot bring air into the tank because of the "column" of fuel above the breather which causes low fuel pressure warnings. I have found that if I level off it is immediately gone or if I make sure there is 1-2" below the filler neck I don't get this problem.
By leveling off and turning on the fuel pump, I think it can clear the breather and everything starts to work fine.
This is just my theory but something you may want to look at. I'd be interested to see if it happens with tanks at 3/4 or at lower angles of attack.
You would think that the full tanks would have a good column of fuel to supply the pickup with plenty of pressure but possibly at high angle of attacks (which causes the fuel to have to flow "uphill") combined with fuel in the breather causing a low pressure in the tanks may just be enough to cause this issue.
I have also correlated it to climb outs that are greater than 4000 feet (could just be extended climbs again) but everytime I fill the tanks completely full and takeoff from a sea level airport and climb to 10k+ feet it seems to occur.
I've been wanted to sit down and work out the math, I know someone out there would love to do that.
Scott Schmidt
---
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dlm46007(at)cox.net
Guest
|
| Posted: Tue Mar 18, 2008 9:41 pm Post subject: Fuel pressure problems |
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By breather tubes , are you referring to the vent lines? If so do you have the tips of the vent lines cut diagonally and facing forward. This is intened to provide a positve "ram" pressure to the vent lines if they contain fuel.
From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Scott Schmidt
Sent: Tuesday, March 18, 2008 10:11 PM
To: rv10-list(at)matronics.com
Subject: Re: Fuel pressure problems
OK, here is my theory on this one because I have the same issue.
It only occurs for me if I am climbing out for an extended period of time with full fuel tanks.
What I believe happens is that the breather tubes get filled with fuel and as you start to burn fuel it cannot bring air into the tank because of the "column" of fuel above the breather which causes low fuel pressure warnings. I have found that if I level off it is immediately gone or if I make sure there is 1-2" below the filler neck I don't get this problem.
By leveling off and turning on the fuel pump, I think it can clear the breather and everything starts to work fine.
This is just my theory but something you may want to look at. I'd be interested to see if it happens with tanks at 3/4 or at lower angles of attack.
You would think that the full tanks would have a good column of fuel to supply the pickup with plenty of pressure but possibly at high angle of attacks (which causes the fuel to have to flow "uphill") combined with fuel in the breather causing a low pressure in the tanks may just be enough to cause this issue.
I have also correlated it to climb outs that are greater than 4000 feet (could just be extended climbs again) but everytime I fill the tanks completely full and takeoff from a sea level airport and climb to 10k+ feet it seems to occur.
I've been wanted to sit down and work out the math, I know someone out there would love to do that.
Scott Schmidt
----- Original Message ----
From: Tim Olson <Tim(at)myrv10.com>
To: rv10-list(at)matronics.com
Sent: Tuesday, March 18, 2008 8:15:59 AM
Subject: Re: Fuel pressure problems
--> RV10-List message posted by: Tim Olson <Tim(at)myrv10.com (Tim(at)myrv10.com)>
The closest thing I can relate to this is a very very intermittent
thing....something I only see on a handful of flights, and usually
just in warmer temps.
If you climb at low airspeeds, like try to do a 90-100kt climb
on a hot day, I start to see a drop in fuel pressure. It starts
to fluctuate a bit, and then will start to drop. My audio warnings
fire up under about 12psi, so I don't run it too low to see how
it goes....I usually hit the boost, and drop the nose for better
cooling. Once you drop the nose and get more cooling airflow,
it goes away. Also, note that this happens in climb, when you
have lots of fuel flow. As soon as I level off, lean out, and
the fuel flows drop, it doesn't do it anymore. So, my guess is
that with high flow requirements in climb, and high heat, they
combine and produce low and fluctuating pressure. Since dropping
the nose has shown to eliminate the problem (like climbing at
120kts if I see this happening) and since pulling back the mixture
takes care of it once level, that is my best guess. But, as I
said, it isn't something I see very often...just on the hot
days or where I've done extended climbs...maybe see it 10-15
times a season...or something like that, but that's over 100-200
hours a season.
At one point I had tried to order a fuel pump cooling shroud
but the place didn't get them in stock. One of these days
I still would like to try that, along with perhaps some
heat shielding foam over the fuel lines forward of the
firewall. But, my thought is, if you get your cowl set up
with great cooling, it's probably something you wouldn't
see too often.
I'm not 100% sure of any of this....but it is something to
consider.
Tim Olson - RV-10 N104CD - Flying
do not archive
Sam wrote:
| Quote: | That's what I thought to, but when I turn on the boost pump, it
immediately returns to normal pressure.
Jesse Saint wrote:
> --> RV10-List message posted by: "Jesse Saint" <jesse(at)saintaviation.com (jesse(at)saintaviation.com)>
>
> That sounds like a sensor issue, maybe either a bad crimp or a bad ground.
> Don't ask me how I might know.
>
> do not archive.
>
> Jesse Saint
> Saint Aviation, Inc.
> jesse(at)saintaviation.com (jesse(at)saintaviation.com)
> www.saintaviation.com
> 352-427-0285
>
> Sam wrote:
>
>> The first fifty hours were trouble free, as far as fuel pressure goes,
>> but now for the past 40 hours or so, I'm getting fuel pressure
>> fluctuation's. Normally the F/P runs in the mid to low 20's, but now
>> constantly fluctuates from 8 to 27 psi. The engine runs ok, but it's
>> disconcerting. Has anybody experienced this on an IO540D4A5 before,
>> would the engine actually keep running if the F/P was really down to 8psi?
>> Sam Marlow
>> #40157
>>
>>
>
>
&g t;>
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[quote]>
>
>
>< br>>>
>
>
>
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dlm46007(at)cox.net
Guest
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| Posted: Tue Mar 18, 2008 10:24 pm Post subject: Fuel pressure problems |
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Another thought. Anybody experienced engine failure in an extended slip or steep turn into the selected tank. Given that the fuel pickup is on the inboard end the selected tank could unport considering the fuel level.
From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of David McNeill
Sent: Tuesday, March 18, 2008 10:36 PM
To: rv10-list(at)matronics.com
Subject: RE: Fuel pressure problems
By breather tubes , are you referring to the vent lines? If so do you have the tips of the vent lines cut diagonally and facing forward. This is intened to provide a positve "ram" pressure to the vent lines if they contain fuel.
From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Scott Schmidt
Sent: Tuesday, March 18, 2008 10:11 PM
To: rv10-list(at)matronics.com
Subject: Re: Fuel pressure problems
OK, here is my theory on this one because I have the same issue.
It only occurs for me if I am climbing out for an extended period of time with full fuel tanks.
What I believe happens is that the breather tubes get filled with fuel and as you start to burn fuel it cannot bring air into the tank because of the "column" of fuel above the breather which causes low fuel pressure warnings. I have found that if I level off it is immediately gone or if I make sure there is 1-2" below the filler neck I don't get this problem.
By leveling off and turning on the fuel pump, I think it can clear the breather and everything starts to work fine.
This is just my theory but something you may want to look at. I'd be interested to see if it happens with tanks at 3/4 or at lower angles of attack.
You would think that the full tanks would have a good column of fuel to supply the pickup with plenty of pressure but possibly at high angle of attacks (which causes the fuel to have to flow "uphill") combined with fuel in the breather causing a low pressure in the tanks may just be enough to cause this issue.
I have also correlated it to climb outs that are greater than 4000 feet (could just be extended climbs again) but everytime I fill the tanks completely full and takeoff from a sea level airport and climb to 10k+ feet it seems to occur.
I've been wanted to sit down and work out the math, I know someone out there would love to do that.
Scott Schmidt
----- Original Message ----
From: Tim Olson <Tim(at)myrv10.com>
To: rv10-list(at)matronics.com
Sent: Tuesday, March 18, 2008 8:15:59 AM
Subject: Re: Fuel pressure problems
--> RV10-List message posted by: Tim Olson <Tim(at)myrv10.com (Tim(at)myrv10.com)>
The closest thing I can relate to this is a very very intermittent
thing....something I only see on a handful of flights, and usually
just in warmer temps.
If you climb at low airspeeds, like try to do a 90-100kt climb
on a hot day, I start to see a drop in fuel pressure. It starts
to fluctuate a bit, and then will start to drop. My audio warnings
fire up under about 12psi, so I don't run it too low to see how
it goes....I usually hit the boost, and drop the nose for better
cooling. Once you drop the nose and get more cooling airflow,
it goes away. Also, note that this happens in climb, when you
have lots of fuel flow. As soon as I level off, lean out, and
the fuel flows drop, it doesn't do it anymore. So, my guess is
that with high flow requirements in climb, and high heat, they
combine and produce low and fluctuating pressure. Since dropping
the nose has shown to eliminate the problem (like climbing at
120kts if I see this happening) and since pulling back the mixture
takes care of it once level, that is my best guess. But, as I
said, it isn't something I see very often...just on the hot
days or where I've done extended climbs...maybe see it 10-15
times a season...or something like that, but that's over 100-200
hours a season.
At one point I had tried to order a fuel pump cooling shroud
but the place didn't get them in stock. One of these days
I still would like to try that, along with perhaps some
heat shielding foam over the fuel lines forward of the
firewall. But, my thought is, if you get your cowl set up
with great cooling, it's probably something you wouldn't
see too often.
I'm not 100% sure of any of this....but it is something to
consider.
Tim Olson - RV-10 N104CD - Flying
do not archive
Sam wrote:
| Quote: | That's what I thought to, but when I turn on the boost pump, it
immediately returns to normal pressure.
Jesse Saint wrote:
> --> RV10-List message posted by: "Jesse Saint" <jesse(at)saintaviation.com (jesse(at)saintaviation.com)>
>
> That sounds like a sensor issue, maybe either a bad crimp or a bad ground.
> Don't ask me how I might know.
>
> do not archive.
>
> Jesse Saint
> Saint Aviation, Inc.
> jesse(at)saintaviation.com (jesse(at)saintaviation.com)
> www.saintaviation.com
> 352-427-0285
>
> Sam wrote:
>
>> The first fifty hours were trouble free, as far as fuel pressure goes,
>> but now for the past 40 hours or so, I'm getting fuel pressure
>> fluctuation's. Normally the F/P runs in the mid to low 20's, but now
>> constantly fluctuates from 8 to 27 psi. The engine runs ok, but it's
>> disconcerting. Has anybody experienced this on an IO540D4A5 before,
>> would the engine actually keep running if the F/P was really down to 8psi?
>> Sam Marlow
>> #40157
>>
>>
>
>
&g t;>
|
[quote]>
>
>
>< br>>>
>
>
>
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Tim Olson
Joined: 25 Jan 2007
Posts: 2881
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| Posted: Wed Mar 19, 2008 3:20 am Post subject: Fuel pressure problems |
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You may have something there, because while I can't say with 100%
certainty, most of the time I think it's also with full fuel,
and at high climb angles, and I know it's usually when climbing
like I do here....say 900AGL up to 8-10K'msl. So the symptoms
sound very much alike. It really seems benign as I get plenty
of audio warning and turn on the boost....but, even the couple
times I've let it ride it doesn't seem to go too low. I never
thought about the breather, but that's an idea.
Tim Olson - RV-10 N104CD - Flying
Scott Schmidt wrote:
[quote] OK, here is my theory on this one because I have the same issue.
It only occurs for me if I am climbing out for an extended period of
time with full fuel tanks.
What I believe happens is that the breather tubes get filled with fuel
and as you start to burn fuel it cannot bring air into the tank because
of the "column" of fuel above the breather which causes low fuel
pressure warnings. I have found that if I level off it is immediately
gone or if I make sure there is 1-2" below the filler neck I don't get
this problem.
By leveling off and turning on the fuel pump, I think it can clear the
breather and everything starts to work fine.
This is just my theory but something you may want to look at. I'd be
interested to see if it happens with tanks at 3/4 or at lower angles of
attack.
You would think that the full tanks would have a good column of fuel to
supply the pickup with plenty of pressure but possibly at high angle of
attacks (which causes the fuel to have to flow "uphill") combined with
fuel in the breather causing a low pressure in the tanks may just be
enough to cause this issue.
I have also correlated it to climb outs that are greater than 4000 feet
(could just be extended climbs again) but everytime I fill the tanks
completely full and takeoff from a sea level airport and climb to 10k+
feet it seems to occur.
I've been wanted to sit down and work out the math, I know someone out
there would love to do that.
Scott Schmidt
---
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Tim Olson
Joined: 25 Jan 2007
Posts: 2881
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| Posted: Wed Mar 19, 2008 3:20 am Post subject: Fuel pressure problems |
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|
I'm pretty sure mine are, per plans....but I don't know how
much real ram air pressure is generated there.
Tim Olson - RV-10 N104CD - Flying
David McNeill wrote:
| Quote: | By breather tubes , are you referring to the vent lines? If so do you
have the tips of the vent lines cut diagonally and facing forward. This
is intened to provide a positve "ram" pressure to the vent lines if they
contain fuel.
|
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Tim Olson
Joined: 25 Jan 2007
Posts: 2881
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| Posted: Wed Mar 19, 2008 3:23 am Post subject: Fuel pressure problems |
|
|
I have not, but I've rarely landed with less than 5 or 6 gallons in
a tank, and when the fuel is under 10 gal I treat it like my old
sundowner than was placarded against extended slips for the same
reason.....I just fly crabbed in for those approaches.
I've also done some slips with and without flaps and not seen
issues...while we're talking about slips.
Tim Olson - RV-10 N104CD - Flying
David McNeill wrote:
| Quote: | Another thought. Anybody experienced engine failure in an extended slip
or steep turn into the selected tank. Given that the fuel pickup is on
the inboard end the selected tank could unport considering the fuel level.
|
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sam(at)fr8dog.net
Guest
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| Posted: Wed Mar 19, 2008 4:35 am Post subject: Fuel pressure problems |
|
|
You might be on the something there Scott. I know that after the fuel is
lower in the tank, the fuel pressure stabilizes. Not sure how much lower
than full though.
I wonder if a NACA vent would help? It's non icing, and would pressurize
the tank slightly. Both are desirable features.
Sam
Scott Schmidt wrote:
[quote] OK, here is my theory on this one because I have the same issue.
It only occurs for me if I am climbing out for an extended period of
time with full fuel tanks.
What I believe happens is that the breather tubes get filled with fuel
and as you start to burn fuel it cannot bring air into the tank
because of the "column" of fuel above the breather which causes low
fuel pressure warnings. I have found that if I level off it is
immediately gone or if I make sure there is 1-2" below the filler neck
I don't get this problem.
By leveling off and turning on the fuel pump, I think it can clear the
breather and everything starts to work fine.
This is just my theory but something you may want to look at. I'd be
interested to see if it happens with tanks at 3/4 or at lower angles
of attack.
You would think that the full tanks would have a good column of fuel
to supply the pickup with plenty of pressure but possibly at high
angle of attacks (which causes the fuel to have to flow "uphill")
combined with fuel in the breather causing a low pressure in the tanks
may just be enough to cause this issue.
I have also correlated it to climb outs that are greater than 4000
feet (could just be extended climbs again) but everytime I fill the
tanks completely full and takeoff from a sea level airport and climb
to 10k+ feet it seems to occur.
I've been wanted to sit down and work out the math, I know someone out
there would love to do that.
Scott Schmidt
---
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