Examine Spark Plugs And Ignition Leads - Lycoming YO-233-B2A Maintenance Manual

3. Examine Spark Plugs and Ignition Leads

A. Remove the spark plug connector nuts.
B. Examine spark plug cable leads and ceramics for corrosion and deposits.
C. Examine each ignition lead for chafing, insulation breakdown, frayed wiring, deterioration,
heat damage, wear, and cracking during every 100-hour inspection.
D. Make sure that the lead nuts are attached tightly.
NOTICE: Corrosion and deposits are evidence of leaking spark plugs or incorrect cleaning of
the spark plugs walls or connector ends.
E. Examine each spark plug for chafing, corrosion, wear, and cracking during every 100-hour
inspection. Replace any worn, cracked or corroded spark plug with a new spark plug. Refer
to the guidelines in Table 1 to identify acceptable and unacceptable spark plugs. The
condition of the fine wire ground and center electrodes as shown in figures in Table 1 show
the level of wear indication and condition of the spark plug. Under usual conditions, the
electrode wear is caused by high voltage sparking and corrosive gases formed during
combustion.
Spark Plug Findings
Acceptable Insulator tip gray, tan
Spark Plugs or light brown
No ash deposits
Electrodes intact, not
burnt or eroded
Partially Ash deposits
Worn Spark Electrode burnt
Plugs and/or eroded to less
than half of the
original thickness
More voltage has
been necessary to fire
the spark plugs
Worn Spark Erosion of center and
Plugs ground electrode
Extensive necking of
the fine wire ground
electrode
74-20
Page 164
General Spark Plug Wear/Replacement Guidelines
Condition of Fine
Wire Ground
Electrode on Spark
Plug
YO-233-B2A Engine Maintenance Manual
TEO-540-A1A Engine Maintenance Manual
Table 1
Condition of Center
Electrode on Spark
plug
© 2021 Avco Corporation. All Rights Reserved
What to do
Clean, set the
spark plug gap and
install the spark
plug per applicable
sections in this
chapter and in
Chapter 05-30.
Discard the spark
plug and replace
with a serviceable
spark plug.
Look for excessive
heat sources.
Discard the spark
plug and replace
with a serviceable
spark plug.
February 2021