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IO-390-D Series Engine Maintenance Manual
IO-390-D Series Engine Maintenance Manual
NOTICE: Except as noted, in this chapter the term "magneto" can refer to either the Lycoming
Electronic Ignition System (EIS) or optional, traditional magnetos, depending on the
type of system installed on the engine.
WARNING
FAILURE TO MAINTAIN THE SPARK PLUGS AND IGNITION LEADS
CAN CAUSE ENGINE DAMAGE OR FAILURE.
NOTICE: The ignition leads are an all-weather, shielded wire constructed with over braid.
1. Spark Plugs
Two long reach spark plugs (Figure 1) are installed on each cylinder head (Figure 2) of the
engine for a total of eight spark plugs per engine.
NOTICE: Typically engines with long reach spark plugs are identified by yellow paint on the
cylinder fins between the spark plug hole and the rocker covers where shown in
Figure 1.
Refer to the latest revision of Service Instruction No. SI-1042 to identify the correct spark plug
approved for use in these engines.
2. Spark Plug Removal
A. Make sure that the power is disconnected from the engine.
B. Hold the ferrule and loosen the spark plug nut and disconnect it from the ignition lead.
CAUTION
E. Use the applicable sized socket on top of the spark plug and turn the socket to remove the
spark plug from the engine cylinder head (Figure 2).
© 2020 Avco Corporation. All Rights Reserved
March 2020
74-20 - IGNITION SYSTEM – MAINTENANCE
Long Reach Spark Plug & Location
HOLD FERRULES WHILE LOOSENING THE SPARK PLUG
COUPLING NUT TO PREVENT TWISTING THE CONDUIT OR CABLE.
Figure 1
74-20
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