J.P. Instruments EDM 760 Pilots Guide - Manual (Page 28)

Engine Diagnosis Chart
The following chart will help you diagnose engine problems in your
aircraft. (Views are Percentage views). Notice that there is always one
CHT that is shown hotter than the others.
Display Symptom Probable
Cause
Recommende
d Action
50%
75° to 100° rise
for one cylinder
during flight Spark plug not
firing due to
fouling, faulty
plug, lead or
distributor. Enrich mixture
to return EGT
to normal.
Have plugs
checked.
50%
Increase or
decrease after
ignition system
maintenance Improper timing:
high EGT
→
retarded ignition;
low EGT
→
advanced
ignition.
Check EGT for
each mag to
determine any
uneven timing.
50%
Loss of EGT for
one cylinder.
Engine rough Stuck valve.
Other cylinders
are okay. Have valve
train checked.
50%
Loss of EGT for
one cylinder; no
digital EGT Failed probe or
failed wire
harness. Swap probes to
determine if
probe or wire
harness is bad.
50%
Decrease in
EGT for one
cylinder Intake valve not
opening fully;
faulty valve lifter. Have valve
lifter or rocker
arm checked.
Page 24 Engine Data Management