Today's Message Index:
----------------------
1. 05:29 AM - Re: Ongoing fuel pressure problems (bill.peyton)
2. 08:22 AM - Re: Ongoing fuel pressure problems (John Miller)
3. 12:01 PM - Re: Re: Ongoing fuel pressure problems (Dan Charrois)
4. 05:05 PM - Re: Ongoing fuel pressure problems (Lenny Iszak)
5. 05:08 PM - Re: Ongoing fuel pressure problems (John MacCallum)
6. 07:02 PM - Re: Ongoing fuel pressure problems (Kelly McMullen)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Ongoing fuel pressure problems |
I would look at the pressure sending unit. You did not mention what you were using
for engine data. Both Garmin and Dynon supply a Kavlico fuel pressure sending
unit that has the vent internal to the connector housing. I had an issue
with fuel pressure dropping in the climb and never returning to normal. It
turns out that the silicone gasket inside the connector, was preventing the pressure
from equalizing. Removing that gasket eliminated the problem. The final
solution was drilling a #50 hole to allow the pressure to equalize.
This does not sound like your issue since the pressure seems to be stable for some
period of time and then drop, but it's worth mentioning.
--------
Bill
WA0SYV
Aviation Partners, LLC
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=480908#480908
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Ongoing fuel pressure problems |
Dan,
I would not worry too much. Same setup as yours, and occasionally during full
power climbs and hot temps, I see the same thing. When that happens I just turn
on the boost pump for a minute or two.
grumpy
12 yrs flying mine
do not archive
> On Jun 14, 2018, at 6:45 PM, Dan Charrois <dan@syz.com> wrote:
>
>
> Hi everyone. I've had my RV-10 flying for about a year and a half now. Everything's
working fine except one issue - I periodically get low fuel pressure
warnings when just on the engine pump and haven't been able to isolate the problem.
>
> My setup is pretty stock - a factory new Lycoming IO-540 D4A5 through Van's with
their pre-installed engine fuel pump, electric fuel pump assembly in the tunnel
as per Van's instructions, fuel plumbing as per Van's instructions, etc.
The only "deviation" from plans was that I had to install wing root gascolators
as per Canada's requirements.
>
> My fuel totalizer is in the tunnel also as per instructions, though I realize
now that's a bad location in that it tends to over-read by 50% or more when the
electric boost pump is on. Not the end of the world since it's only an issue
when the electrical boost pump is on (which isn't really that much) and I'd
rather it read pessimistically instead of optimistically anyway. Maybe one day
I'll relocate it, but I mention it here in case someone thinks it's relevant
to my real problem.
>
> And the real problem is this - normally in cruise above 10000', I have fuel pressure
readings around 19-21 psi. But periodically (and unpredictably) sometimes
the fuel pressure will plummet - I've seen it get as low as 10 psi before
climbing back up again. Originally, as soon as it would start dropping I'd turn
on the electric boost pump but as it's happened more and more often and I've
become more brave, I've held off at least a few seconds and so far it's always
recovered before the engine started stumbling.
>
> I've never seen this happen with the boost pump on - just when the engine pump
is working on its own. Though as I said, I don't normally fly with the boost
pump on, so I obviously have less data with the boost pump on.
>
> What's particularly interesting is that it only seems to happen at higher altitudes.
Above 10000' or so, I can count on it happening at least once an hour
- at 13000', it sometimes happens every 10 or 15 minutes (though sometimes it
doesn't happen at all either for an hour). At 9500', I've seen it happen only
rarely, and I don't recall it ever occurring at 8500' or below.
>
> When it drops, it tends to fall over the course of about 5-10 seconds and then
climb back up over 5-10 seconds. The whole event is over with within 15-20
seconds, and doesn't seem to "linger" at low PSI. I'm not sure if this is "real"
or an artifact of sensor filtering of the EFIS.
>
> It isn't specific to when the engine is particularly hot - I always climb with
the boost pump on, so when the engine is running hotter I never see the issue.
This happens after I've been flying around at cruise power settings at altitude,
often with a below freezing outside temperature and CHTs in the 310-350
range, and usually lean of peak burning in the neighbourhood of 10 gph.
>
> I have a blast tube aimed towards the fuel pump (though not a full shroud).
I've even tried removing my gascolator screens in case they were potentially restricting
fuel flow.
>
> It's been suggested that perhaps my fuel pressure sensor is having issues. I
could certainly change it out, but since I haven't seen an issue with the electric
boost pump on, and since it only seems to happen at altitude, I would expect
if it was a sensor issue neither of these two factors would have an effect.
>
> Does anyone have any suggestions on what to try? I have tons of engine sensor
data logged from the EFIS that I could send if helpful.
>
> I'm a bit apprehensive of changing out the fuel pump (in that I haven't done
so before and would want to ensure that a new one is installed correctly so I
don't damage anything). Has anyone done that before and could offer any advice?
On the other hand, I've lived with this one issue for long enough and as it's
the one thing I'm not completely happy with, I would like to try and finally
resolve it so I can better trust things.
>
> Thanks for any advice!
>
> Dan
> ---
> Dan Charrois
> President, Syzygy Research & Technology
> Phone: 780-961-2213
>
>
>
>
>
Message 3
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Ongoing fuel pressure problems |
Hi Bill.
I have a Kavlico fuel pressure sending unit as well - I'll be sure to have a good
look at it. I'll probably try replacing the sensor first anyway - it's an
easier and likely less expensive thing to try before tackling the fuel pump itself.
Dan
> On 2018-Jun-15, at 6:27 AM, bill.peyton <peyton.b@sbcglobal.net> wrote:
>
>
> I would look at the pressure sending unit. You did not mention what you were
using for engine data. Both Garmin and Dynon supply a Kavlico fuel pressure
sending unit that has the vent internal to the connector housing. I had an issue
with fuel pressure dropping in the climb and never returning to normal. It
turns out that the silicone gasket inside the connector, was preventing the
pressure from equalizing. Removing that gasket eliminated the problem. The final
solution was drilling a #50 hole to allow the pressure to equalize.
> This does not sound like your issue since the pressure seems to be stable for
some period of time and then drop, but it's worth mentioning.
>
> --------
> Bill
> WA0SYV
> Aviation Partners, LLC
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=480908#480908
>
>
>
>
>
>
>
>
>
---
Dan Charrois
President, Syzygy Research & Technology
Phone: 780-961-2213
Message 4
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Ongoing fuel pressure problems |
Dan,
Does the pressure drop affect the EGTs, RPM or fuel flow readings at all? If it
does, it's definitely not a pressure sensor problem.
--------
Lenny Iszak
Palm City, FL
2014 RV-10, N311LZ - 400 hrs
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=480913#480913
Message 5
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Ongoing fuel pressure problems |
That=99s correct there does need to be a differential pressure from t
he inlet to outlet of the FI Servo. The point that Tim Henderson makes in th
e Amazing Ubiquitous Diaphragm Fuel Pump Video is that down to about 9 psi b
eing delivered to the Servo at High fuel flows the engine will still run fin
e. High fuel flows like take off power and around 94 ltrs an hour. At cruise
power lean of peak and around 46 ltrs per hour I would expect to see fuel p
ressure between 95 - 172 kpa (14-25 psi). As for take off power I always ru
n the boost pump so it=99s always up around 170 kpa.
Cheers John MacCallum
> On 15 Jun 2018, at 12:22, Kelly McMullen <apilot2@gmail.com> wrote:
>
> It is not that simple. What pressure you are talking about depends on wher
e in the system you are looking, what brand system you have, etc.
> In general, the Bendix/Precision style injection system needs about 14-15 p
si minimum at the input to the fuel servo. Pressures going to the fuel divid
er will be lower, and the flow divider shuts down flow at around 4-5 psi to p
revent run-on at idle cutoff. The amount of pressure at the inlet is importa
nt to have the system function correctly, and to get good atomization at the
nozzles. While the engine may run at 9 psi, I'd not be at all comfortable t
o see below 15.
> I don't know what pressures the AFS system needs. The Continental system w
orks quite differently and needs very steady and precise pressures at the in
let that have to be checked annually.
> Kelly
> Sent from my IBM-360 main frame
>
>> On Thu, Jun 14, 2018 at 6:06 PM, John MacCallum <john.maccallum@bigpond.c
om> wrote:
>> Hi Dan,
>> =46rom a Video I watched about Fuel Injected engines as long as there is p
ositive pressure above about 5 PSI at high fuel flows to the FI Servo the en
gine will run fine. The Video was from Tempest Aero parts and it talked abou
t Engine driven Fuel Pumps and Boost Pumps. The Video was Titled, =9C
The Amazing Ubiquitous Diaphragm Fuel Pump.=9D
>>
>> Anyway the Video said nothing to worry about down to about 9 psi. What ty
pe of boost pump do you have? My Andair Electric boost pump is in the tunnel
and so is the red cube. I have no issues with inaccurate flow readings but I
do occasionally get fuel pressure fluctuations in very hot weather. That is
ambient ground temps above 35 C. I solve this by running the boost pump unt
il at altitude and the OAT has dropped below 30 C.
>>
>> Cheers John MacCallum
>> VH-DUU
>>
>>
>>
>>
>
Message 6
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Ongoing fuel pressure problems |
IIRC the minimum fuel spec for the Bendix/Precision RSA 5 system is around
14 psi. I would be very uncomfortable with one showing 9-10, high fuel flow
or not. Assuming there isn't a sensor problem giving a false reading.
I see 24-25 psi on takeoff without boost, 26 with it, and have the
Dynon\Kavlico sensor.
Sent from my IBM-360 main frame
On Fri, Jun 15, 2018 at 5:06 PM, John MacCallum <john.maccallum@bigpond.com
>
wrote:
> That=99s correct there does need to be a differential pressure fro
m the
> inlet to outlet of the FI Servo. The point that Tim Henderson makes in th
e
> Amazing Ubiquitous Diaphragm Fuel Pump Video is that down to about 9 psi
> being delivered to the Servo at High fuel flows the engine will still run
> fine. High fuel flows like take off power and around 94 ltrs an hour. At
> cruise power lean of peak and around 46 ltrs per hour I would expect to s
ee
> fuel pressure between 95 - 172 kpa (14-25 psi). As for take off power I
> always run the boost pump so it=99s always up around 170 kpa.
>
> Cheers John MacCallum
>
> On 15 Jun 2018, at 12:22, Kelly McMullen <apilot2@gmail.com> wrote:
>
> It is not that simple. What pressure you are talking about depends on
> where in the system you are looking, what brand system you have, etc.
> In general, the Bendix/Precision style injection system needs about 14-15
> psi minimum at the input to the fuel servo. Pressures going to the fuel
> divider will be lower, and the flow divider shuts down flow at around 4-5
> psi to prevent run-on at idle cutoff. The amount of pressure at the inlet
> is important to have the system function correctly, and to get good
> atomization at the nozzles. While the engine may run at 9 psi, I'd not be
> at all comfortable to see below 15.
> I don't know what pressures the AFS system needs. The Continental system
> works quite differently and needs very steady and precise pressures at th
e
> inlet that have to be checked annually.
> Kelly
>
> Sent from my IBM-360 main frame
>
>
> On Thu, Jun 14, 2018 at 6:06 PM, John MacCallum <
> john.maccallum@bigpond.com> wrote:
>
>> Hi Dan,
>> From a Video I watched about Fuel Injected engines as long as there is
>> positive pressure above about 5 PSI at high fuel flows to the FI Servo t
he
>> engine will run fine. The Video was from Tempest Aero parts and it talke
d
>> about Engine driven Fuel Pumps and Boost Pumps. The Video was Titled,
=9CThe
>> Amazing Ubiquitous Diaphragm Fuel Pump.=9D
>>
>> Anyway the Video said nothing to worry about down to about 9 psi. What
>> type of boost pump do you have? My Andair Electric boost pump is in the
>> tunnel and so is the red cube. I have no issues with inaccurate flow
>> readings but I do occasionally get fuel pressure fluctuations in very ho
t
>> weather. That is ambient ground temps above 35 C. I solve this by runnin
g
>> the boost pump until at altitude and the OAT has dropped below 30 C.
>>
>> Cheers John MacCallum
>> VH-DUU
>>
>>
>>
>>
>>
>
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|