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11-16-2016, 12:15 PM
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Join Date: Jan 2005
Location: Martinsville, IN
Posts: 2,326
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Fuel Pressure Drop at Runup
I just started having this issue. Cold start-up is normal. The engine oil is warming as I slowly taxi out to the end our runway. Once oil temp is green, I do a mag check and the fuel pressure drops down into the yellow and I get a warning. Reduce throttle and the fuel pressure goes back up. On takeoff, I sometimes get an alarm. All other times, there's no indication of a problem.
The only difference is that I am still running 100LL in the tank, left over from my last trip. This only happens before the first flight and only when I advance the throttle to do the run up. Both pumps are running as I pulled the breaker to check and the pressure dropped, but not into the yellow at idle.
Any ideas?
__________________
Randy Pflanzer
Greenwood, IN
www.pflanzer-aviation.com
Paid through 2043!
Lund fishing Boat, 2017, GONE FISHING
RV-12 - Completed 2014, Sold
427 Shelby Cobra - Completed 2012, Sold
F1 EVO - partially completed, Sold
F1 Rocket - Completed 2005, Sold
RV-7A - Partially completed, Sold
RV-6 - Completed 2000, Sold
Long-EZ - Completed 1987, Sold
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11-16-2016, 12:30 PM
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Join Date: Apr 2008
Location: Riley TWP MI
Posts: 3,068
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Fuel pressure senders are notoriously inaccurate.
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Joe Gores
RV-12 Flying
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11-16-2016, 01:25 PM
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Join Date: Jan 2005
Location: Martinsville, IN
Posts: 2,326
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Yes, and I've replaced mine already but it seems to go up and down accurately with pulling the fuse of the electric fuel pump and with the engine RPM. I would expect it to do crazy jumping around at unexpected times, but it's not doing that.
I might try cleaning out the fuel pressure line and the sending unit and see if that makes a difference. It bugs me that it just started doing that. If it's a prelude to a failure, I'd love to find it now.
__________________
Randy Pflanzer
Greenwood, IN
www.pflanzer-aviation.com
Paid through 2043!
Lund fishing Boat, 2017, GONE FISHING
RV-12 - Completed 2014, Sold
427 Shelby Cobra - Completed 2012, Sold
F1 EVO - partially completed, Sold
F1 Rocket - Completed 2005, Sold
RV-7A - Partially completed, Sold
RV-6 - Completed 2000, Sold
Long-EZ - Completed 1987, Sold
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11-16-2016, 02:19 PM
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Join Date: Nov 2011
Location: Aurora, OR
Posts: 841
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The pressure always remains greater than zero?
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Greg Hughes - Van's Aircraft - Community, Media, Marketing
Van's web site | Instagram | Facebook
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.
Building RV-8A since Sept 2014 (N88VX reserved)
Dual AFS 5600, Avidyne IFD 440, Whirlwind 74RV, Superior XP IO-360
VAF build thread - Flickr photo album - Project Facebook page
Aurora, OR (EAA Chapter 105)
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11-16-2016, 02:44 PM
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Join Date: Mar 2011
Location: Bosschenhoofd, Netherlands
Posts: 151
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I am annoyed and worried about fuel pressure fluctuations for a long time and cannot find the cause.
I don't like fuel alarms and do all I can to find it, but no luck after 220 hours of flying. The drops come up very irratic and may stay away for hours and suddenly return for half an hour or do. I have the feeling it happens more frequent after a long flight and slow descent.
We have two identical RV12's and on the oldest one with 580 hours it has never been a problem. Rock stable and just a slight drop at full throttle which seems normal.
The new plane has exactly the same components and had problems all the time, but the old Rotax never missed for a second.
I cleaned the tank, filters and fuel lines with no effect.
Replaced the pressure sensor with the exact same result.
Now i even have two identical pressure sensors installed at different locations of the fuel system. The additional one has an analogue gauge connected.
The two sensirs read exactly the same all the time so I am convinced it is not related to the sensor.
It is also not related to the electrical fuel pump as the problem persists with the pump disconnected.
I can only conclude the actual pressure is unstable and I suspect the pump as a last option however both planes have the same type (vented) cast pump.
On the other hand how can a pump vary the pressure? It works or it does'nt.
A new pump is expensive so I want to make sure that is the probable cause before ordering it.
Anyway it worries me as well.
__________________
Jack Netherlands
PH-SEP and PH-SES
RV12 #120519 and #120790
Hobbs 700+ hours and 400+ hours
Dual SV1000 Skyview 15, Pocket FMS and Powerflarm 6.0 (ADSB)
RV10 PH-USN Hobbs 350 hours
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11-16-2016, 02:59 PM
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Join Date: Jan 2005
Location: Martinsville, IN
Posts: 2,326
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Quote:
Originally Posted by greghughespdx
The pressure always remains greater than zero?
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Yes. Starts around 4.0 if memory serves me correctly. Drops to 1.5 at run-up then back up to normal.
__________________
Randy Pflanzer
Greenwood, IN
www.pflanzer-aviation.com
Paid through 2043!
Lund fishing Boat, 2017, GONE FISHING
RV-12 - Completed 2014, Sold
427 Shelby Cobra - Completed 2012, Sold
F1 EVO - partially completed, Sold
F1 Rocket - Completed 2005, Sold
RV-7A - Partially completed, Sold
RV-6 - Completed 2000, Sold
Long-EZ - Completed 1987, Sold
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11-16-2016, 03:27 PM
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Join Date: Aug 2005
Location: Falmouth, MA
Posts: 355
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With about 60 hours on the plane, mine also started to randomly drop to 1.5-2.5 at high power. It was also leaking a small amount of oil from the drain tube. Most of my fuel has been mogas with alcohol.
At the recommendation of Lockwood, I replaced the pump and all is fine now. In my case, they are replacing it under warranty.
Mitch
Last edited by Mitch757 : 11-16-2016 at 03:28 PM.
Reason: added info..
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11-16-2016, 03:55 PM
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Join Date: Aug 2015
Location: Lopez Island, Wa.
Posts: 178
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Fuel press drop
The other day for first time I had fuel pressure drop from normal 4.5 to 2.2 and yellow warning...I turned back to airport just in case but after a short time the pressure returned to 4.5...kinda unnerving..suggestions..thanks
__________________
Retired Firefighter/Para-Medic
Sold 182 Skyelane
sold Super Cub
Building RV 12 E-LSA
Paid thru 2016, even though exempt
RV 12 completed, waiting DAR
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11-16-2016, 04:27 PM
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Join Date: Apr 2014
Location: Port Orange, Fl
Posts: 931
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That started happening to me. Eventually my fuel pressure went to zero and stayed there. Replacing the red cube fixed it.
__________________
Tom
Port Orange, Fl
EAA #51411
RV-12 N121TK ELSA #120845; first flight 06/10/2015; 700 hrs as of 02/2020
RV-12 N918EN ELSA #120995 Eagles Nest Project; first flight 05/18/2019
SPA Panther N26TK; First Flight 03/13/2020
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11-16-2016, 04:34 PM
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Join Date: Jan 2005
Location: Martinsville, IN
Posts: 2,326
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Quote:
Originally Posted by tomkk
That started happening to me. Eventually my fuel pressure went to zero and stayed there. Replacing the red cube fixed it.
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That's curious. I've replaced the red cube over 100 hours ago. Not sure how that would affect the fuel pressure unless it was completely blocked. In my case the fuel flow went to zero but the pressure was fine.
__________________
Randy Pflanzer
Greenwood, IN
www.pflanzer-aviation.com
Paid through 2043!
Lund fishing Boat, 2017, GONE FISHING
RV-12 - Completed 2014, Sold
427 Shelby Cobra - Completed 2012, Sold
F1 EVO - partially completed, Sold
F1 Rocket - Completed 2005, Sold
RV-7A - Partially completed, Sold
RV-6 - Completed 2000, Sold
Long-EZ - Completed 1987, Sold
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