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  #11  
Old 09-02-2021, 10:55 AM
Fltnut Fltnut is offline
 
Join Date: Jan 2021
Location: Payson, AZ
Posts: 14
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I can't tell you that I haven't seen a fluctuation but it's very rare. Before moving the fuel line the pressure would jump around on every flight, once the coolant warmed up.
Any changes that do happen are very small and of no concern (to me anyway) now. There are no alarms now.

Last edited by Fltnut : 09-02-2021 at 10:58 AM.
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  #12  
Old 09-02-2021, 07:05 PM
TS Flightlines TS Flightlines is offline
 
Join Date: Apr 2010
Location: Ridgeland, SC
Posts: 2,862
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Scott--as we tell everyone that has an issue like you are describing, check the actual fuel pressure with a know good mechanical gauge tee'd into the FP hose. That way you can see if its a 'real' pressure fluxation, or instrumentation.

But from the sound ot things, with no other erratic engine operation, no surges, no rpm or map, cht, egt fluxuations, it points to a sender/wireing/ground/power, interface problem.

Tom
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Tom Swearengen, TS Flightlines LLC, AS Flightlines
Joint Venture with Aircraft Specialty
Teflon Hose Assemblies for Experimentals
Proud Vendor for RV1, Donator to VAF
RV7A Tail Kit Completed, Fuse started-Pay as I go Plan, on hold while we develop new products for RV builders
Ridgeland, SC
www.tsflightlines.com, www.asflightlines.com
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  #13  
Old 09-04-2021, 06:18 AM
RV12JT RV12JT is offline
 
Join Date: Jul 2017
Location: Keystone State
Posts: 134
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I have the same issue with my SLING 2, with 912 ULS. It started a year after I had it and frankly, it scared the **** pout of me the first time i noticed it. Other than the drop in pressure on the G3X screen, normally I see 3.8 and as high as 4.2 or so, it dropped as low as 1.7, 1.9, but usually around 2.0 for a few seconds, the 912 ran strong without issue.

I came to find this is a well know issue and there was an SB from The Airplane Factory (Sling Aircraft) and ROTAX that addresses the issue…but wait, there’s more…my SLING came with the additional IN-LINE filters, meant to regulate pressures better.

I know its not the answer or solution we all want, but I’ve been told again and again…they know about it and absent any rough running or stumbling there is no cause for alarm. Really?

Ive learned to live with it. The scary part for me, is it normally happens when I toggle off the fuel pump once I reach my desired altitude and sometimes on climb out. I’m running 91 no ethanol unleaded 95% of the time and 100LL when I need to flop off on a X-country. Test with both and no difference, so it ain’t the fuel.

Last edited by RV12JT : 09-04-2021 at 06:22 AM.
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  #14  
Old 09-04-2021, 06:54 AM
TS Flightlines TS Flightlines is offline
 
Join Date: Apr 2010
Location: Ridgeland, SC
Posts: 2,862
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John---again the big thing is to determine if its a 'real' pressure drop due to the pump, or minor fuel leak somewhere, or if its instrumentation. From what you say, this is a constant thing no matter if the boost pump is on or not.

Personally speaking, the instrumentation issue is one thing, but obviously real pressure drop is a bunch more serious. We always recommend that a known good mechanical gauge be installed along with the electrical sender, so you visually see the 2 different types of systems read the same pressure. Obviously the mechanical gauge is a pain, but its NOT dependent on any electrical system component to read the fuel pressure. This way, you can monitor the pressure and when the electrical version starts to fluxate, you can do a verification really quick. If the mechanical gauge agrees with the electrical version, then you have a realtime issue. IF the mechanical gauge reads fairly normal pressure and the electrical shows the fluxuation, then that validates your theory of instrumentation.

I would caution however, dont just blame the sender, the wiring or connections for the issue. You might have to dig deeper to find the culprit.

Tom
__________________
Tom Swearengen, TS Flightlines LLC, AS Flightlines
Joint Venture with Aircraft Specialty
Teflon Hose Assemblies for Experimentals
Proud Vendor for RV1, Donator to VAF
RV7A Tail Kit Completed, Fuse started-Pay as I go Plan, on hold while we develop new products for RV builders
Ridgeland, SC
www.tsflightlines.com, www.asflightlines.com
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  #15  
Old 09-04-2021, 08:45 AM
Bob Y Bob Y is offline
 
Join Date: Jul 2017
Location: Piedmont, SC
Posts: 275
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Iím a Dynon guy, but did stumble across this for the G3X. Donít know if it could be an issue for your case or not, but seems worth checking out if you havenít yet.

http://static.garmin.com/pumac/2069a.pdf
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N569TT first flight 2/9/2020
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