The differential FF gauge is not indicating as it should when leaning in cruise. We are now in the second year of getting it right…after maybe 40 hours total testing! Gauge tested OK, fuel pressures OK. When in cruise and I pull the mixture control back to lean to 10 GPM, with 2300/31 the FF gauche needle goes to its zero stop, hence doesn’t indicate. I have also an second electric FF gauge so no real hassle other then that the diff FF gauge is a PFI on the EL.
My A/P says the following:
Engine – TSIO-360-F (PA28RT-201T)
When carrying out SID97-3 the following readings are obtained.
RPM 700: unmetered 6.0 psi, if we try to enrichen to 6.25 psi, the rpm rise during shutdown is 90 RPM.
RPM 2575: unmetered high @ 55 psi and metered 16 psid. FF 23.8 Gal/Hr. Reducing to 48 psi FF at 21 Gal/Hr when leaned.
Engine is newly overhauled (600hrs). Injection regulator and pump hours are unknown but not overhauled with engine.
Performance good, economy good. EGT and CHT all normal at T/O and cruise.
However, when in cruise @ 31" and 2300 RPM The FF is too low @ ??What would cause this?
Additionally the Piper manual service manual notes unmetered fuel pressure at a leaned to 21 GAL/HR should be 42 psi which contradicts the SID, any comments?
Any comment is appreciated.
