Fuel Drain Valve Adapter Assembly Inspection - Lycoming IO-390-D Series Maintenance Manual

B. Intake Pipe Installation
NOTICE: Since there is a corresponding intake pipe for each engine cylinder, make sure the
intake pipe of the correct part number is installed for the respective engine cylinder.
(1) Apply a coating of clean engine oil to a new ring seal.
(2) Install a new ring seal in the groove in the oil sump (Figure 1).
(3) Push the intake pipe into the oil sump until it seats.
(4) Attach the corresponding intake pipe centered on the correct engine cylinder flange with
a new gasket, two bolts, two new lock washers, and two washers. Torque the two bolts to
96 to 108 in.-lb. (11 to 12 Nm).

3. Fuel Drain Valve Adapter Assembly Inspection

The fuel drain valve adapter assembly (Figure 2) is a valve in the induction system that closes
during engine operation and opens when the engine is shut down to allow excess fuel to drain
from the induction system. If the valve is not operating correctly it can either allow outside air
into the induction system during engine operation or fail to drain excess fuel from the induction
system when the engine is shut down.
If your engine has a fuel drain valve adapter assembly installed, examine the assembly as
follows:
A. Remove the fuel drain valve adapter assembly
from the induction system.
B. Examine the fuel drain valve adapter assembly for
damage.
C. Make sure the fuel drain valve adapter assembly is
operating correctly:
(1) The valve is operating correctly if it is open
with no air pressure applied.
(2) The valve is operating correctly if it closes
when 0.75 to 1.0 psi (5.2 to 6.9 kPa) of air
pressure is applied to the outboard side of the
fuel drain valve adapter assembly.
D. If the valve is not operating correctly or if the fuel
drain valve adapter assembly is damaged, replace
the fuel drain valve adapter assembly.
E. Apply a coating of Loctite
equivalent to the threads of a serviceable fuel drain
valve adapter assembly.
F. Install the fuel drain valve adapter assembly in the
oil sump. Torque the assembly to 40 in.-lb. (4.5
Nm).
72-80
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IO-390-D Series Engine Maintenance Manual
IO-390-D Series Engine Maintenance Manual
®
564 thread sealant or
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Figure 2
Fuel Drain Valve Adapter Assembly
March 2020