Lycoming IO-390-D Series Maintenance Manual page 124

Problem
Unable to Unable to verify #1 cylinder @ TDC
time ignition
to engine
(Cont.)
Engine runs Isolate EIS
rough ignition
causing
roughness
12-30
Page 98
EIS Troubleshooting Guide
Problem Isolation
Ignition verified Verify all
as correctly timed spark plugs
to engine #1 are firing
cylinder TDC using CHT
Various
spark plugs
are not
firing
IO-390-D Series Engine Maintenance Manual
Table 2
Probable Cause
#1 cylinder not @ TDC
Verify Ignition harness wires
ignition connected to incorrect
unit is spark plugs
configured
Internal ignition fault
correctly
to engine
base
timing
Ignition Ignition unit not
unit is not configured correctly to
configured engine base timing
correctly
to engine
base
timing
Single Bad spark plug or
spark plug ignition harness
not firing
Pair of Internal ignition fault
spark
plugs not
firing
(1&2,
3&4,
5&6)
IO-390-D Series Engine Maintenance Manual
Corrective Action
Verify location of engine #1 cylinder.
Turn engine to #1 cylinder TDC, reinstall
ignition unit
Check routing of harness wires
Contact Lycoming customer support
Reinstall ignition unit in accordance with
installation instructions
Replace spark plug or ignition harness
Contact Lycoming customer support
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March 2020