IO-390-D Series Engine Maintenance Manual
© 2020 Avco Corporation. All Rights Reserved
12-30
March 2020
Page 95
IO-390-D Series Engine Maintenance Manual
Table 1 (Cont.)
Fault Isolation Guide
Problem
Cause
Corrective Action
Ref.
High oil
temperature (Cont.)
Oil cooler bypass valve
is not operating
correctly or seating
accurately
Replace the oil cooler bypass valve.
72-50
SI-1316
Leaks in engine
induction system
Identify and correct the cause of all
leaks.
72-80
&
AMM
Oil cooler or oil cooler
lines are fully or
partially blocked
1.
Remove the oil cooler and oil
cooler lines.
2.
Clean and service the oil cooler.
AMM
Too much cylinder
blow-by
Complete a “Cylinder Compression
Check Procedure.”
72-30
Defective oil
temperature gage
1.
Install the master temperature
gage and operate the engine to
compare gages.
2.
Replace the faulty gage if
necessary.
AMM
Higher than normal
cylinder head
temperatures
Incorrect EIS-to-engine
timing
Refer to the “EIS Troubleshooting
Guide” in this chapter.
High manifold
pressure at idle
Air leak in induction
system
Examine the induction system for
leaks. Identify and correct the cause of
all leaks.
NOTICE:
If the induction system
has leaks, the engine will idle rough.
72-80
&
AMM
Incorrect tappets or
hydraulic lifters were
installed
Replace hydraulic lifters with the
correct part number for lifters. Refer
to the latest revision of Service
Instruction Nos. 1529, 1011, and
1514.
NOTICE:
Keep the cylinders and
plungers together as an assembly
when you remove hydraulic lifters
from the engine. If they become
separated, replace with new ones.
Incorrectly assembled body and
plunger assemblies will change the
leak-down rate.
72-20
