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Problem
Low oil pressure
(Cont.)
12-30
Page 92
Table 1 (Cont.)
Fault Isolation Guide
Cause
Pressure relief valve is
out of adjustment
Dirt or metal chips
under the oil pressure
relief valve
Blockage at inlet side of
oil pump
Damaged oil pressure
relief valve seat
Excess internal oil
leakage
Air leak on suction side
Relocated oil pressure
take-off
IO-390-D Series Engine Maintenance Manual
IO-390-D Series Engine Maintenance Manual
Corrective Action
Turn the adjusting screw (on the oil
pressure relief valve) to adjust oil
pressure or change the spring as
necessary
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.
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."
Replace the oil pressure relief valve
seat per the latest revision of Service
Instruction No. SI-1172.
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
1. Examine the conditions of these
components:
• Oil suction screen gasket
• Oil sump gasket
• Oil pump mating surface to
accessory housing
2. Replace cracked or damaged parts.
Use only the approved oil pressure
take-off point.
© 2020 Avco Corporation. All Rights Reserved
Ref.
72-50
72-50
12-10
72-30
12-10
12-10
72-50
72-25
March 2020
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