Hi All,

Recently (within the last couple of moths) as I climb past 8,500ft, my fuel pressure becomes unstable. It drops and rises, from 13 to 14 PSI down below 10 and then back up again. This, of course, has a noticeable effect on engine power (it drops and then comes back).

By the time I get to 8500ft, I've already done the big pull and am running LOP. If I turn on the electric fuel pump, and re-lean, everything stabilizes.

If I don't use the electric fuel pump and deal with the drop and surges in power up to say 12,500ft, level off and begin to cruz, the fuel pressure stabilizes to around 11 to 12 psi and the drops and surges in power stop.

It's an IO-550N and tach time is north of 250 hours.

Ideas?

Thanks
Kevin