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fuel Pressure

olderthandirt

Well Known Member
so today coming back from flight the fuel pressure went to 5.7 PSI and started blinking yellow, I pulled electric fuse and it settled to 5.6 and no yellow blinking light..anything to worry about?? Also climbing out today at 75 MPH I was getting 5140 RPM not 5200 again anything to worry about???l Thanks
 
Low Fuel Pressure Warning

Finally got some good flying weather in Upstate NY yesterday and was able to do the first flight. What a blast and what a great handling airplane.

I have a couple small issues, mainly with the Dynon, but the one that concerns most is with a fuel pressure warning on climb out. Pressure drops to 2.2psi and the "fuel pressure" starts chiming in the headset.

I have 18 gal. fuel onboard and engine is smooth as can be. Strainer was cleaned before flying. Fuel pressure in straight and level flight is 2.9psi and flow is 5.2gph.
Any ideas where to look?
Thanks,
Dan
 
You should see ~ 2psi from the electric pump when master is switched on. When engine starts the mechanical pump adds ~ 3psi. So, with engine running and both pumps operating ~ 5 psi is what you should be seeing as normal operating fuel pressure.
 
Finally got some good flying weather in Upstate NY yesterday and was able to do the first flight. What a blast and what a great handling airplane.

I have a couple small issues, mainly with the Dynon, but the one that concerns most is with a fuel pressure warning on climb out. Pressure drops to 2.2psi and the "fuel pressure" starts chiming in the headset.

I have 18 gal. fuel onboard and engine is smooth as can be. Strainer was cleaned before flying. Fuel pressure in straight and level flight is 2.9psi and flow is 5.2gph.
Any ideas where to look?
Thanks,
Dan

Dan, first of all you would probably get a better response on the forum if you had started a new thread with a more descriptive title. You have hooked on to an old thread that sounds like a different problem. Be that as it may, in order to make any kind of helpful suggestion more information is needed.

Fuel pressure with engine off and electric fuel pump on.

Ground run pressures at several RPM points ranging from idle to WOT. Do this twice, once with electric pump on, and agin with electric pump off.

Let us know results and we can go from there.
 
Will do as you suggested John next time I am able to get to the airport. What are most seeing for fuel pressure? Should I be in the 5psi range at all phases of engine run and flying?
Thanks
 
I just checked mine recently. 2.8 psi on electric pump only, 5.1 w/ electric & engine pumps. I run both pumps in the air but did check the engine pump only in cruise and saw 3.5 - 4.2 on engine pump only. I tried that on another flight and saw as low as 2.? - don't remember the precise pressure but it was just at the bottom of the green on the engine pump only.

This is all with 93 octane auto fuel with 10% ethanol.
 
Any ideas where to look?

With a brand new airplane the first thing to check should be the screen in the gascolator.
Once you start taxiing around and sloshing fuel in the tank it is not uncommon for some debris to get flushed out of the tank and hoses, and plug a portion of the gascolator screen.
 
Whatever the fuel pressure readout is displaying, it is meaningless until verified. Those fuel pressure senders are notoriously inaccurate.
 
Many of us have seen decreasing fuel pressure on climb out. Many have seen decreasing fuel pressure when descending from high altitudes.

Search this forum and you will find a number of threads related to the fuel pressure anomalies.

I do not believe anyone has found the root cause after ruling out the obvious, ie. sensor issues, gascolator issues, etc.
 
Marty,
I find this problem concerning and as I posted in another thread last week, my first flight "fuel pressure" warning in the headset had my attention on takeoff. The engine did not miss a beat however and I continued the flight, even completing 4 takeoffs and landings. The warning is coming occasionally as pressure drops into the 2.0psi range on run up and climb out.

As this is a brand new aircraft, before I fly again I will go through all options including flushing the fuel system again, cleaning the strainer screen and carb bowls and checking the vent system. Also as Big John suggested I will log pressures in all phases of engine run, including idle, WOT, and 4000 rpm run up. With and without the electric fuel pump. I am not sure however this will solve anything. I feel as if there maybe something else going on for so many to report this issue.
 
Whatever the fuel pressure readout is displaying, it is meaningless until verified. Those fuel pressure senders are notoriously inaccurate.

Dan --- Joe has given you some good advice here. Prior to taking the time spinning your wheels recording a bunch or readings, first tap into the fuel system and verify with a pressure gauge that the fuel pressure readings the fuel pressure sending unit is sending to the SkyView is correct.

A good point to begin would be using the pressure gauge to make a reading with the engine off and the electric fuel pump on and see how it compares to the reading the SkyView is displaying. Repeat with the engine running.

May also be a good idea while your at it to have another person monitor the cockpit displayed fuel pressure while you slowly and gently move and flex the wires to the fuel pressure sending unit at the connector or any splices you may have to verify the pressure drop is not caused by a faulty wiring/connector issue.
 
Dan,

May I ask where you have your fuel pressure alarm set at? Back in 2011, Van's solution to the fuel pressure issue, reported by many, was to set the "red-yellow" alarm point at 0.7 psig. (RV-12 Presets document). See my thread from years ago. I did not follow their advice and left it at 2.1/2.2 psig.


http://www.vansairforce.com/community/showthread.php?t=75825&highlight=2.1+psig


Maybe many now have the alarm set to 0.7 psig? The current POH states a 2.2 psig alarm point.
 
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Marty,
-----
As this is a brand new aircraft, before I fly again I will go through all options including flushing the fuel system again, cleaning the strainer screen and carb bowls and checking the vent system. Also as Big John suggested I will log pressures in all phases of engine run, including idle, WOT, and 4000 rpm run up. With and without the electric fuel pump. I am not sure however this will solve anything. I feel as if there maybe something else going on for so many to report this issue.

If you have SkyView or D-180 you don't have to manually log anything.
As you say you have a new airplane (with SkyView?) you may be not be aware, that you can very easily dump a data log to a USB stick and analyze the data on a free website: savvyanalysis.com. And you can get a graph of anything that the EFIS sees. This is a very useful tool for troubleshooting. You don't have to pay unless you want Savvy to analyze a problem for you.

You can plot your fuel pressure coincidental with other parameters, here is a plot of fuel pressure and rpm.
i-HM2b5Hz-L.png


You can do the same thing with the D-180 except it's not quite as easy there you have to hook up a laptop to the D-180 using the factory supplied dongle. With SV you just dump the data log to the USB stick and take it home with you. One of my RV12 pals looks at his data after every flight! He's plane crazy.
 
Marty,
the alarm sounds when the pressure drops below 2.2 psi. therefore I believe it is set as you described.

John and Tony,
Thanks for the advise. I will verify pressure with a gauge and check connections. Also will download the data as described.
 
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