J.P. Instruments EDM 740 Pilots Guide - Manual (Page 33)

For Your Safe Flight Page 33
Engine Diagnosis Chart
The following chart will help you diagnose engine problems in your
aircraft (unit is in ‘Percentage View’ mode for these pictures).
Display Symptom Probable Cause Recommended
Action
75° to 100° EGT
rise for one
cylinder during
flight Spark plug not firing
due to fouling, faulty
plug, wire or
distributor. Enrich mixture to
return EGT to normal.
Have plugs checked.
EGT Increase or
decrease after
ignition system
maintenance Improper timing: high
EGT
 retarded
ignition; low EGT

advanced ignition.
Check EGT for each
magneto to determine
any uneven timing.
Loss of EGT for
one cylinder.
Engine rough Stuck valve. Other
cylinders are okay. Have valve train
checked.
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.
Decrease in
EGT for one
cylinder Intake valve not
opening fully; faulty
valve lifter. Have valve lifter or
rocker arm checked.
Decrease in
EGT for one
cylinder at low
RPM Low compression. Check compression.