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heinz.staehli(at)gmx.ch
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 Posted: Mon Nov 15, 2021 4:51 am Post subject: Fuel Pressure high |
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Hi all !
I fly a Glastar with a TMX O-360. Fuel pressure comes from an engine driven pump and is routed to the Dynon fuel pressure sensor via a T-fiiting at the In-port of the carburetor. Min pressure acc the Lyc manual is 0.5, max is 8.0 PSI.
Now on my last flight I got a red Master Warning with FUEL PRESS HIGH alert from the EMS. Analysis of its data showed normal pressure (around 6.7) during the first part of the cruise, then a sharp rise within 15 sec to 8.2 and after approx one min a slow decrease again to 6.7, where it stayed for the rest of the flight. The engine ran normally during the event, and fuel flow looked normal too. Now I have no idea what could cause such a pressure jump, and what to look after before next flight.
Any help is greatly appreciated, thank You very much !
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heinz.staehli(at)gmx.ch
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| Posted: Mon Nov 15, 2021 5:11 am Post subject: Fuel Pressure high |
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Hi all !
I fly a Glastar with a TMX O-360. Fuel pressure comes from an engine driven pump and is routed to the Dynon fuel pressure sensor via a T-fiiting at the In-port of the carburetor. Min pressure acc the Lyc manual is 0.5, max is 8.0 PSI.
Now on my last flight I got a red Master Warning with FUEL PRESS HIGH alert from the EMS. Analysis of its data showed normal pressure (around 6.7) during the first part of the cruise, then a sharp rise within 15 sec to 8.2 and after approx one min a slow decrease again to 6.7, where it stayed for the rest of the flight. The engine ran normally during the event, and fuel flow looked normal too. Now I have no idea what could cause such a pressure jump, and what to look after before next flight.
Any help is greatly appreciated, thank You very much !
Scanned by McAfee and confirmed virus-free.
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arcticarrow(at)gmail.com
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| Posted: Mon Nov 15, 2021 9:47 am Post subject: Fuel Pressure high |
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I believe your fuel pump is a constant volume type. It may have a pressure adjustment screw, but does not change pressure without adjustment. So if the pressure indication changes then a likely cause is a change in the flow down stream of the pump. An open line would show a drop in pressure. While a pinched line would show an increase. A temporary partial obstruction would show what you saw. If the obstruction was before the pump the pressure would drop then increase as it passed. If vanes, gears or diaphragm, depending upon the style of pump are wearing out the pressure would drop and not return to normal.
B Winston
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| Quote: | On Nov 15, 2021, at 3:14 AM, Heinz Stähli <heinz.staehli(at)gmx.ch> wrote:
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Hi all !
I fly a Glastar with a TMX O-360. Fuel pressure comes from an engine driven pump and is routed to the Dynon fuel pressure sensor via a T-fiiting at the In-port of the carburetor. Min pressure acc the Lyc manual is 0.5, max is 8.0 PSI.
Now on my last flight I got a red Master Warning with FUEL PRESS HIGH alert from the EMS. Analysis of its data showed normal pressure (around 6.7) during the first part of the cruise, then a sharp rise within 15 sec to 8.2 and after approx one min a slow decrease again to 6.7, where it stayed for the rest of the flight. The engine ran normally during the event, and fuel flow looked normal too. Now I have no idea what could cause such a pressure jump, and what to look after before next flight.
Any help is greatly appreciated, thank You very much !
Scanned by McAfee and confirmed virus-free.
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Kellym
Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ
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| Posted: Mon Nov 15, 2021 11:55 am Post subject: Fuel Pressure high |
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Most carbureted Lycomings have a mechanical diaphragm pump, which is
non-adjustable. With an old mechanical fuel pressure gauge you would
never have noticed the blip in pressure, and it is not significant.
The carburetor float is what controls the flow, and if it sticks just a
little, the pressure may rise a bit before the needle valve opens.
If you were telling us that the pressure was say 12 or 15, then that
would be a concern, but less than a whole digit above the Lycoming spec
is not something to worry about as long as it isn't enough to force the
needle valve open and flood the carburetor bowl.
Kelly
A&P/IA
On 11/15/2021 10:46 AM, Bernie wrote:
| Quote: | I believe your fuel pump is a constant volume type. It may have a
pressure adjustment screw, but does not change pressure without
adjustment. So if the pressure indication changes then a likely cause is
a change in the flow down stream of the pump. An open line would show a
drop in pressure. While a pinched line would show an increase. A
temporary partial obstruction would show what you saw. If the
obstruction was before the pump the pressure would drop then increase as
it passed. If vanes, gears or diaphragm, depending upon the style of
pump are wearing out the pressure would drop and not return to normal.
B Winston
Sent from my iPhone
> On Nov 15, 2021, at 3:14 AM, Heinz Stähli <heinz.staehli(at)gmx.ch> wrote:
>
>
>
> Hi all !
>
> I fly a Glastar with a TMX O-360. Fuel pressure comes from an engine
> driven pump and is routed to the Dynon fuel pressure sensor via a
> T-fiiting at the In-port of the carburetor. Min pressure acc the Lyc
> manual is 0.5, max is 8.0 PSI.
>
> Now on my last flight I got a red Master Warning with FUEL PRESS HIGH
> alert from the EMS. Analysis of its data showed normal pressure
> (around 6.7) during the first part of the cruise, then a sharp rise
> within 15 sec to 8.2 and after approx one min a slow decrease again to
> 6.7, where it stayed for the rest of the flight. The engine ran
> normally during the event, and fuel flow looked normal too. Now I have
> no idea what could cause such a pressure jump, and what to look after
> before next flight.
>
> Any help is greatly appreciated, thank You very much !
>
> ------------------------------------------------------------------------
>
> <https://home.mcafee.com/utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
>
>
>
> Scanned by McAfee
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> and confirmed virus-free.
>
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Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
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