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Old 05-29-2018, 07:17 PM
Join Date: Jan 2012
Posts: 44
Default Fuel pressure

Took the plane up tonight, on the first takeoff I heard an audible low fuel pressure warning. Everything felt fine, the pressure was fluctuating between 3.5-5.2 psi. On the next go round same warning but this time I felt a slight hiccup in the engine. The third time the same warning and the engine sputtered quick. Called it a day after that. When I was shutting down the engine I pulled the fuel pump fuse. The fuel pressure steadily dropped to almost 0 PSI. Can a failed electric pump starve fuel from the mechanical pump or is the mechanical pump my problem. Any thoughts, thanks, Joe
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Old 05-29-2018, 08:05 PM
RFSchaller RFSchaller is offline
Join Date: Oct 2010
Location: Phoenix, AZ
Posts: 2,460

What does it do on the ground when you run it and donít have the fuse in? No or low fuel pressure would suggest a failed engine driven pump. If the pressure comes back with the fuse back in it would seem the engine driven pump is definitely bad.

Iíd check the hoses for blockage too and the carb bowls for debris just to be sure. I have experienced low pressure from vapor lock with old gas, but I also got a high fuel flow alarm. I have a switched electric pump, and turning it on eliminated the low pressure. Iíve only had vapor lock in the summer months here in Phoenix.
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Old 05-29-2018, 08:50 PM
Mich48041 Mich48041 is offline
Join Date: Apr 2008
Location: Riley TWP MI
Posts: 2,839

Others with the same problem have attributed it to either vapor lock or bad engine driven fuel pump.
Joe Gores
RV-12 Flying
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Old 05-30-2018, 10:02 PM
Aircraft Specialty Aircraft Specialty is offline
Join Date: Jan 2012
Location: Oconomowoc, WI
Posts: 382

As has been mentioned, I would definitely check for debris.

I am not sure if you have the original rubber lines, or Teflon lines.

But this debris was documented and found inside a stock RV-12 Fuel system and was causing sporadic low pressures and engine issues.

Here is the original picture showing the debris clustered together.

So it is definitely something that warrants investigation to make sure that you aren't getting a blockage of some sort.

Steve Tschurwald- Aircraft Specialty LLC (Your source for Custom Parts for Experimental Aircraft), AS FLIGHTLINES (Joint Venture with TS Flightlines)
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