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High fuel pressure?

Paul Eastham

Paul Eastham

Well Known Member
Hi,
i am seeing occasional high fuel presure, usually when entering the pattern from altitude and pulling back the power. Boost pump on, the pressure can hit 11psi. Lycoming says 8 psi max,3 psi desired.

Fuel pressure also fluctuates and is on the high side (6+ psi) in cruise.

Any cause for concern? Brand-new Aerosport O-320, FP prop, standard Facet boost pump.

Thanks,
Paul
 
Fuel pressure

I had this problem before my 1st flight and it caused the carb to overflow. That can be a very serious problem, especially in flight. We ended up having to replace the fuel pump. Never found a reason for it, but it ran toward the high limit and sometimes would shoot up enough to cause the leak. I had three A&P's tell me it was impossible. It was always at relatively low fuel flow. Changed out the FP and no more problems. Not saying that is it but it CAN happen! Be very careful of high fuel pressure as an overflow at altitude could ruin your day!

Bob Kelly
 
The pressure is monitored by a Dynon EMS. The transducer is a small metal can hung off the sensor manifold, brand unknown.

For those saying you replaced your fuel pump -- which one? Electric or engine?

I suppose it is also worth mentioning that I have a fuel flow meter installed, which reads very high when the pump is on - double that of the pump-off reading. However, I believe this to be an incorrect reading since the fuel totalizer does not match the refueling amount. Pulses from the electric pump are confusing the gauge, I guess.

Thanks for the data points...
 
Oops!

Paul Eastham said:
The pressure is monitored by a Dynon EMS. The transducer is a small metal can hung off the sensor manifold, brand unknown.

For those saying you replaced your fuel pump -- which one? Electric or engine?
Click to expand...

Sorry to omit that detail! It was the engine driven pump. The way we finally determined it to be the cause was bypassing it--going directly from the electric FP to the carb. Not difficult with just a coupling in place of the FP in/out fittings. Of course we were on the ground and didn't have to worry about the electric pump being the only source of pressure. With that setup we never saw a major pressure fluctuation. YMMV

Bob Kelly
 
Paul Eastham said:
The pressure is monitored by a Dynon EMS. The transducer is a small metal can hung off the sensor manifold, brand unknown.

For those saying you replaced your fuel pump -- which one? Electric or engine?

I suppose it is also worth mentioning that I have a fuel flow meter installed, which reads very high when the pump is on - double that of the pump-off reading. However, I believe this to be an incorrect reading since the fuel totalizer does not match the refueling amount. Pulses from the electric pump are confusing the gauge, I guess.

Thanks for the data points...
Click to expand...
Make sure the conections on the transducer are tight and clean. I replaced the fuel pump and transducer before I found the problem.
 
Thanks for the ideas guys. I am thinking this might be a problem with the sender or the grounding of the sender. I just remembered that I have been seeing fuel pressure prior to starting the engine or pump (1-2 PSI) -- that didn't seem right to me.

I will check the ground, and try grounding and opening the signal line to the Dynon to see what happens.
 
Hmm, sensor calibrated correctly at 10 psi when I put 10psi of air on the sender. I guess I really do have high fuel pressure.
 
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