Fuel pressure sensor

[cbretana]

Can you guys tell me anything about normal failure modes of the Fuel pressure sensor included with your 4 cylinder carbureted Lycoming EMS package? Recently, I had intermittent fuel pressure readings below 1 psi, (at times it got as low as 0.3 - 0.4 psi), although it recovered and went back up to 3.8 - 4.0 psi. These readings were all with my electric auxiliary fuel pump off.

So I am concerned about whether these readings are an indication of impending engine-driven fuel pump failure, failure of the sensor itself, or just a blockage in the line feeding the sensor. I have not observed any fuel flow irregularities, irregular RPM, or other aberrant engine behavior.

 

[kurtfly]

Have you thought about vapor lock. Sounds like you may have bubbles in the fuel. Is there any other indication like fuel or oil dripping out of the diaphragm port? This is the drain port between the two diaphragms on the mechanical fuel pump.

Kurt

 

[swatson999]

My system is injected, not carbureted, but on very rare occasions (like, once every 6 months or so), I see similar behavior. Fuel pressure will drop from the nominal upper 20s down to 14 PSI or less, then recover, all within about 4-6 seconds or so. Not a hint of stumble or roughness, no change in fuel flow, RPM, nothing.

I have yet to figure it out. It's *not* an instrumentation problem as far as I can see (it's a definite signal in the data...it's not noise). If it drops low enough to trip the alarm, it gets my attention for sure, but I recognize it now and don't jump out of my skin .

I also think that there must be some routing somewhere in the system that causes a bubble to form under the right conditions, momentarily (cavitation), and that might be it, but I've never figured out where that might be.

 

[cbretana]

Is the Dynon Fuel Pressure Sensor that comes with the Lycoming L-4C EMS package (part Number
103755-000 ) a solid state transducer or old diaphragm style ?


... I have it from other source that the one I have is a solid state transducer...

 

[GaryRay]

I have seen a fuel line problem that was at a high spot in the path from the tanks to the fuel pumps. It did not leak fuel due to being a local high
spot. The fuel line fitting began to allow air to mix into the fuel inside the line. This produced varying fuel pressure at the gauge, fuel pumps not priming correctly and engine roughness. I had to remove the fuel line and pressure test it to find the leak.