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Failed fuel pressure sensor?

tomkk

Well Known Member
I was out flying today and suddenly I got a fuel pressure warning and my fuel pressure gauge had a big red X through it. Engine continued running, fuel flow normal, etc.

Previously, the fuel pressure readout was normal and steady, not the fluctuating readouts others have reported.

I thought I might have a bad connection but I checked that out and everything seems OK.

The pressure sensor is stamped with: "E1858" (I think means manuf. date of May 18, 2015) and "P4055-5025-1".

I measured resistances on my sensor and got:
red-black: open
red-green: variable between approx. 0.5K and 1.5K briefly then open
green-black: open

I checked the airframe cable and the red has +5v.

This looks like a sensor failure to me but is there anything I should check before getting a new one?
 
Did you turn on the boost pump and see your usual increase in flow/pressure?

Could be the sensor, could be an impending failure of the engine driven pump, could be a blockage in a line (did you switch tanks during analysis).
 
Thanks for the reply. The -12 has only one tank and I was getting normal fuel flow, both in the air on the way back to the airport as well as on the ground on the electric pump only.

I'm also getting good fuel flow from the fuel line that goes to the sensor with the electric pump.

It seems like any problems like these, though, would result in strange pressure readings, not the Big Red X?
 
Thanks for the reply. The -12 has only one tank and I was getting normal fuel flow, both in the air on the way back to the airport as well as on the ground on the electric pump only.

I'm also getting good fuel flow from the fuel line that goes to the sensor with the electric pump.

It seems like any problems like these, though, would result in strange pressure readings, not the Big Red X?

Tom,
A big red X is usually an indicator that the EMS doesn't recognize that a sensor is connected (value that it is reading falls somewhere with the normal range that it expects). This is usually caused by a wiring problem. I don't recall seeing a bad sensor cause it but it might be possible.
 
Just to close this out, the problem was indeed the fuel pressure sensor.

I'd verified +5v across the red/black wires at the fuel pressure sensor and verified continuity of the green wire from the sensor all the way to the EMS connector. That just left the sensor itself and replacement corrected the problem.

I hadn't heard of this particular symptom with a fuel pressure sensor failure. Always one more new and innovative problem ...
 
I got exactly the same failure last Saturday. Replaced the sensor with the same part number from Dynon and fuel flow now is (almost) normal. It is now reading about 2 psi lower across the board than the old sensor.

Mitch Garner
RV12 12060 flying
 
I had a momentary low pressure experience a while back. Climbing out, the Dynon read 1-2 lbs pressure, but after a minute or two it was back at 5.5-5.8 lbs. Engine didn't skip a beat so I figured it was a sensor.

The electric pump only seems to add a small amount of extra pressure, like 5.2 with just the mechanical, and 5.5 to 5.8 with both pumps on.

I fly with both pumps on all the time. I've heard of some people using the electric only on takeoff and landings, but I've discussed this with others and it seems best to me to just run both pumps, and fly the plane.
 
Are these Kavlico sensors? I have a friend sorting an oil pressure one now. I thought they were very reliable, is this data that says not?
 
Mine is a Kavlico. This is my 2nd replacement in 185 hours. The first had fluctuating fuel pressure and the second had a failure that resulted in the big red "X" over the fuel pressure gauge on the EMS.
 
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