Bill Boyd
Well Known Member
Carb'ed O-320 E2D with standard RV-6A fuel system (electric boost pump in series with engine-driven pump) and GRT EIS with newly-replaced (due to age) pressure senders (about 20 hours on them).
I normally see fuel pressures of about 5-6psi with the Facet alone and no change with the engine running. The last two flights I have had a high fuel pressure alarm (I think I set the limit at 8) and have seen pressure readings as high as 9.3 psi on the ground. In cruise it now settles around 7.3-7.5, but on landing rollout and taxi, back into the red at 9+ psi. Turning off the boost pump in cruise or on the ground has no effect on the readings I'm seeing.
Not sure if the limits are set too conservatively on the gauge, but it's the CHANGE in behavior rather than the absolute value that concerns me. The needle and float are obviously preforming their job; there is no sign of richness or rough running in any flight regime. I'm just not sure why the higher readings have appeared.
My first two thoughts are a partial obstruction in the outflow from the engine-driven pump to the carb inlet screen, or (more likely IMO) a pressure transducer starting to fail prematurely.
On the risk side, I don't want to see fuel flooding the carb float bowl, nor a perforation of the mechanical pump diaphragm. Neither would be a good day.
Thoughts?
I normally see fuel pressures of about 5-6psi with the Facet alone and no change with the engine running. The last two flights I have had a high fuel pressure alarm (I think I set the limit at 8) and have seen pressure readings as high as 9.3 psi on the ground. In cruise it now settles around 7.3-7.5, but on landing rollout and taxi, back into the red at 9+ psi. Turning off the boost pump in cruise or on the ground has no effect on the readings I'm seeing.
Not sure if the limits are set too conservatively on the gauge, but it's the CHANGE in behavior rather than the absolute value that concerns me. The needle and float are obviously preforming their job; there is no sign of richness or rough running in any flight regime. I'm just not sure why the higher readings have appeared.
My first two thoughts are a partial obstruction in the outflow from the engine-driven pump to the carb inlet screen, or (more likely IMO) a pressure transducer starting to fail prematurely.
On the risk side, I don't want to see fuel flooding the carb float bowl, nor a perforation of the mechanical pump diaphragm. Neither would be a good day.
Thoughts?