Weird High Fuel Pressure

On two separate, consecutive flights I had some strange fuel pressure readings. 0-320, carb and standard Vans fuel system. Flying along in the cruise and the fuel pressure suddenly climbs from the normal 4 psi to between 10 to 14 psi. The engine continues to run normally and FF remains unchanged. Turning ON the electric boost pump brings the fuel pressure back to around 3 to 4 psi. Everything is normal for a minute or two and the same thing happens again with the boost pump again bringing the fuel pressure back down. This cycle of events is repeated about 5 times after which the fuel pressure returns to normal for the remainder of the flight. I have inspected the fuel system, fuel vents, the engine breather and the connections to the fuel pressure transducer and found nothing abnormal. What I can't understand is why turning the boost pump ON would bring the FP back down to normal The LAME (Australian aircraft engineer) I spoke to said the FP can go up if the vents are partially blocked (I can't really understand why??). I rarely fill the tanks to the very top but I did do this before these two flights. Filling the tanks to the top could have got fuel into the vent lines which could have been like a partial blockage and maybe the boost pump eventually sucked the fuel out of the vent line. This is about the only thing I can think of, but I think it is unlikely.
Anyone got any suggestions?

Fin
9A

A restricted engine breather can make the fuel pressure rise.
A defective engine driven fuel pump can make fuel pressure vary up or down.
A defective fuel pressure sender can cause erroneous readings.
I would think the problem is one of the above.
Good Luck,
Mahlon
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Possibly Defective Fuel sender or ground

I would substitute the fuel sender and be sure the sender is properly grounded and try it again.

While adding an audio panel, I had my center panel section which contains a bunch of Van's gauges sitting on my throttle/mixture knobs. With power on, and a knock from my hand, one of the positive terminals from a gauge touched the frame. It immediately knocked out one gauge, but two others including the fuel pressure (or sender) eventually failed.

My fuel pressure gauge would also move up past 10 lbs. It would also vary with throttle, and be in normal range other times. Didn't have a fuel flow gauge at the time. I ended up changing both the gauge and sender, even though I didn't know if one or the other was the problem. All has been fine since. At least the gauge and sender is cheap.

L.Adamson --- RV6A

Fuel pressure senders are also suscceptible to electronic interferences - at least mine is. Check to see whether you are turning anything on or anything is transmitting immediately before your anomalous readings.

erich