IO-390-D Series Engine Maintenance Manual
© 2020 Avco Corporation. All Rights Reserved
72-20
March 2020
Page 183
IO-390-D Series Engine Maintenance Manual
(2)
Front-mounted propeller governors: Install the gasket and the test plate P/N ST-483, or
equivalent on the governor pad with the air fitting in alignment with the governor oil
passage that goes to the front bearing (forward hole) or left side of the mounting facing
the pad. Refer to Figure 99.
(3)
Rear-mounted propeller governors: Install the left side bottom hole on the test plate P/N
ST-483 on the front bearing and crankshaft transfer tube.
(4)
Connect a calibrated oil pressure gauge (0 to 100 psi) (0 to 689 kPa) to the appropriate
engine oil pressure port on the test plate for your governor location. Install a plug in the
propeller circuit and unused engine oil pressure circuit port.
(5)
Start and warm-up the engine until the oil temperature is within the correct operating
range (Appendix A of the
IO-390-D Series Engine Installation and Operation Manual.)
NOTICE:
The oil pressure must not be more than 5 psi (34 kPa) below the lowest
operating pressure of the operating range when the engine rpm is in the usual
operating range.
(6)
With the engine OFF, remove the plug from the propeller circuit port and install a
compression tester (Chapter 72-30) at the propeller circuit fitting on the test plate.
NOTICE:
Allow 5 minutes after adjusting the first gauge to 40 psi (276 kPa), for air
pressure to stabilize, before reading the pressure on the second gauge.
(7)
Apply shop air to the differential pressure regulator and adjust it to 40 psi (276 kPa) on
the Gauge No. 1 (Figure 100. With the engine at operating temperature, the pressure
reading on the Gauge No. 2 must read 6 to 35 psi (41 to 241 kPa), if the system is
operating correctly.
NO. 1 GAUGE 40 psi (276 kPa)
NO. 2 GAUGE 6 psi to 35 psi (41 to 241 kPa) ACCEPTABLE
Above 35 psi (241 kPa)
Insufficient front main bearing clearance or
a blockage in the propeller governor circuit
Below 6 psi (41 kPa)
Excessive front main bearing clearance
Figure 100
Propeller Governor Circuit Testing
