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Scrapman1959

Low fuel pressure warning during climb

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I have gotten low fuel pressure warnings during climbout a few times in last two weeks. Went into yellow zone, and then comes back and maybe does it one or two more times, before stabilizing at 3.6 to 3.9 or so for rest of the flight. I now do an extended high power run up to simulate this on the ground, and it works. So once it flashes in the yellow, of course this is after oil temps are 130 or above at high idle, then I just keep the power in until it goes into green arc and stays there. Then I take off and it stays in green the whole flight. Any ideas if this is a real fuel pressure issue, or maybe just a faulty sensor? My grounding issues have long ago been taken care of. 

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Anticept   

This is normal. In the rotax service bulletin regarding fuel pump replacement, there is the following text:

Quote

3.6.1) Check of fuel pressure
NOTE: The fuel pump part. 893110 has different characteristics as the fuel pumps part no. 892542 and part no. 892546.
Low fuel pressure indications are possible and allowed. But the pressure must stabilize to the operating limit within 5 seconds. If not, the cause should be determined and rectified. Due to the technical design and installation conditions (construction of the return line, etc.) pressure fluctuations, at the fuel pump part no. 893110 are possible. These pressure fluctuations within the specified operating limits are not considered to a problem.

If you have a dynon unit installed, remember that it uses software smoothing of indications. As a result, it can take as much as 10 seconds to stabilize.

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I have a similar issue on take offs with a hot engine in the summertime. After replacing fuel pressure senders without any improvement It seems the fuel in line which goes over the engine to the pressure sensor vaporises while setting on the ramp. If I take off with a just flown and hot engine I sometimes get the low pressure alarm. It goes off after about 10 seconds as I guess new fuel flows through the lines to the sensor. I think it's the my 2008 CTLS sensor line is routed. Engine has never sputtered. Just my theory.  

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Thx Guys. This is always with "cold" ( first flight of the day) engine under WOT throttle. I will continue to monitor it more closely. Wasn't sure if I should service the screen/filter? 

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