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Low Fuel Pressure

JCutrer

I'm New Here
I am getting low fuel pressure indications on D-180. The last time I flew, as I throttled back for landing, after a 45 min flight, the pressure dropped to .9. It came back up after landing. Today I ran the engine up to operating temp and fuel pressure was 4+ to 5+ no matter RPM. Pulled the electric pump fuse and no drop in pressure. When the engine is not running electric pump only, pressure is around 2.5 to 2.9. Flew today and pressure was good through run-up. Took off and pressure dropped to minimum 2.9.
What should fuel pressure be with just electric pump?
 
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Sounds like its on a carb d engine. Thats about what I see on my 0320, However, I have also had the low fuel pressure indications and have replaced the transducer at least twice in AFs 700 hrs. I believe there may be a better quality transducer out now for that. If its a single wire transducer be sure the transducer body is grounded well. You may want to check the single connection on that model transducer and or both connections on the two wire model. Ive found that bad,loose and or dirty wire connections have made for low readings in my case. Sometime influenced by the temperature inside the cowl. My transducer is mounted on the FW and isolated from the engine vibs via a flex hose , but still experiences the heat in normal service.
 
Sounds like your sensor is dying. It?s nice having so much instrumentation when it works, but there seem to be a lot of failures that send us down rabbit holes.
 
I am getting low fuel pressure indications on D-180. The last time I flew, as I throttled back for landing, after a 45 min flight, the pressure dropped to .9. It came back up after landing. Today I ran the engine up to operating temp and fuel pressure was 4+ to 5+ no matter RPM. Pulled the electric pump fuse and no drop in pressure. When the engine is not running electric pump only, pressure is around 2.5 to 2.9. Flew today and pressure was good through run-up. Took off and pressure dropped to minimum 2.9.
What should fuel pressure be with just electric pump?

Per lycoming .5 low 4 desired 8 max... carburetor O320. In theory the float in the carb restricts too much fuel, so no overflow. I would adjust low pressure warning on EIS to not alarm till .5
 
Have you performed the fuel volume test in the production acceptance procedure ? I have seen this fail due to a blockage and the plane displayed the symptoms you have.
 
On your fuel line assembly, do you have the older 5-point spider valve?
Or the newer fuel bolt valve ?stacked assembly??
 
Both of our ULS RV-12's do that from time to time, sometimes on climbout, sometimes on throttle back.

I think it has been discussed here before, do a search.

We are not concerned and carry on.
 
I talked to the builder and he had changed VDO sensor a few times and the pressure reading would come back up. I changed the sensor and pressure reading increased to normal. Thanks for everyone?s input.
 
I talked to the builder and he had changed VDO sensor a few times and the pressure reading would come back up. I changed the sensor and pressure reading increased to normal. Thanks for everyone?s input.

Awesome! Glad to hear that the fix was relatively easy for you.
 
I know this is a jinx saying this, but my original sensor has had no issues in 8 years and 950 hours (bound to break now that I said that). I did, however, have issues with my oil pressure sensor so I changed it twice only to find the second time it was a sensor lead issue. If you have any more issues you may want to replace the sensor wires.
 
Both of our ULS RV-12's do that from time to time, sometimes on climbout, sometimes on throttle back.

I think it has been discussed here before, do a search.

We are not concerned and carry on.

Like you said, I?ve had it happen a few time in my Sling. Have been told it?s a well known ROTAX problem, nothing to see here...move on. Head shaking...

As long as it?s not effecting engine operation, no stumble, hesitation, I was told not to be worried about it. My issue is on climb out where pressure drops below the minimum 2.2 psi. It?s been as low as 1.4, setting of the EFIS alarm for a second or so, however engine runs perfectly.

I was told it?s excess fuel bypassing the carbs or some such thing. We are going to take a good look on the next inspection.
 
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