IO-390-D Series Engine Maintenance Manual
12-30
© 2020 Avco Corporation. All Rights Reserved
Page 92
March 2020
IO-390-D Series Engine Maintenance Manual
Table 1 (Cont.)
Fault Isolation Guide
Problem
Cause
Corrective Action
Ref.
Low oil pressure
(Cont.)
Pressure relief valve is
out of adjustment
Turn the adjusting screw (on the oil
pressure relief valve) to adjust oil
pressure or change the spring as
necessary
72-50
Dirt or metal chips
under the oil pressure
relief valve
1.
Remove, disassemble, and clean
(remove dirt or metal chips) the oil
pressure relief valve.
2.
Complete the “Oil Change
Procedure.”
3.
Complete a cylinder compression
check.
72-50
12-10
72-30
Blockage at inlet side of
oil pump
Remove and clean the oil suction
screen and oil passage on the inlet side
of the oil pump. Refer to the section
"Oil Suction Screen Removal/
Inspection/Cleaning/
Installation.”
12-10
Damaged oil pressure
relief valve seat
Replace the oil pressure relief valve
seat per the latest revision of Service
Instruction No. SI-1172.
Excess internal oil
leakage
Look for:
•
Loose or missing plugs in oil galley
•
Piston cooling nozzles to lock open
during idle rpm
•
Too much bearing clearance
•
Cracks in the oil galley area of the
crankcase
Air leak on suction side
1.
Examine the conditions of these
components:
•
Oil suction screen gasket
12-10
•
Oil sump gasket
72-50
•
Oil pump mating surface to
accessory housing
2.
Replace cracked or damaged parts.
72-25
Relocated oil pressure
take-off
Use only the approved oil pressure
take-off point.
