J.P. Instruments EDM-900 User Manual

Page 16 Engine Data Management
Engine Diagnosis Chart
The following chart will help you diagnose engine problems in your
aircraft.
Display
Symptom
Probable
Cause
Recommended
Action
TIT ~100°
higher than
EGTs
This is normal
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
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.
Increase in DIF
at low RPM
Low compression
(blow by) in cylinder
Check
compression.
EGT and CHT
not uniform
Normal for
carbureted engines.
Dirty fuel injectors or
fouled plugs.
Check injectors
and plugs.
Decrease in
EGT for all
cylinders
Decrease in airflow
into the induction
system. Carb or
induction ice.
Check for
change in
manifold
pressure.

J.P. Instruments EDM-900 Specifications

General

Brand	J.P. Instruments
Model	EDM-900
Category	Control Panel
Language	English