pkofman Posted June 3, 2017 Report Share Posted June 3, 2017 Continuing education Today i was flying the m20m and i noticed that my fuel pressure gauge was in the green as it should be ( actually at the bottom of the green ) but i also noticed that the needle was giving me tiny oscillations. ( power setting was 29/2400 at 5500 high boost pump off ) . The engine was running really well . I hit the high boost and the pressure went all the way up to the top of the arc as i believe it should. I then switched off the high boost and the gauge settle back to the same spot at the bottom of the arc with tiny movements ... It is probably no big deal or I may not have ever really paid enough attention but just wanted t0 know if it has to be dead solid ,( i.e. no movement) , or if that is normal behaviour. These are very small tiny little movements so maybe its always been like this. From past experience I'm hyper sensitive to any needle fluctuations. I am sensitive because in my m20j i has a bobble on the oil gauge, a simple flicker, and then within about 5 minutes i experience a complete oil blowout because i lost a vacuum seal... Please let me know if this is normal Thank you Peter Quote Link to comment Share on other sites More sharing options...
Guillaume Posted June 4, 2017 Report Share Posted June 4, 2017 (edited) Are the oscillations related to the engine RPM (ie : The higher the engine RPM, the higher the frequency of oscillation)? I had a similar issue with rather strong fuel pressure needle oscillation. The engine would run just fine and turning on the fuel pump would bring back the pressure steady in the green. The oscillations were related to the engine RPM. Turned out to be the mechanical fuel pump starting to fail. Edited June 4, 2017 by Guillaume Quote Link to comment Share on other sites More sharing options...
pkofman Posted June 4, 2017 Author Report Share Posted June 4, 2017 I don't think that the rpm or mp move at all. The fuel pressure gauge sits at the lower end of the green scale when the boost pump is off when the pump is on it is at the other extreme In both cases my engine seems to be solid. I guess I'll have them look at the mechanical fuel pump, maybe its nothing Pete Quote Link to comment Share on other sites More sharing options...
DVA Posted June 4, 2017 Report Share Posted June 4, 2017 Pete, that sounds like the normal variations you see. Mine is the same. It will really get jittery if its hot, indicating some vaporization. That's when you need to activate the electric boost pump to help clear it out. Quote Link to comment Share on other sites More sharing options...
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