J.P. Instruments EDM 700/800/711 Pilots Guide - Manual (Page 28)

Page 24 Engine Data Management
Display Symptom Probable Cause Recommended
Action
(no picture)
Loss of peak
EGT Poor ignition or
vapor in fuel
injection system. Have magneto
tested.
(no picture)
Decrease in
peak or flat
EGT response
to leaning
process Detonation. Usually
the result of 80
Octane fuel in 100
Octane engine. Enrich mixture,
reduce power and
relean mixture.
Repeat to find
power setting
where normal peak
is obtained or run
rich.
CHT
300
400
500
Below 10,000
ft. full throttle
causes EGTs
to rise Weak or defective
mechanical fuel
pump. Apply booster
pump. If EGTs
drop, replace fuel
pump.
CHT
300
400
500
CHT more
than 500°,
EGT normal.
Adjacent EGT
may be low Leaking exhaust
gasket blowing on
CHT probe. Look for white
powder around
cylinder to
determine leak
area.
Large DIF at
low RPM Blow by in cylinder
rings Check compression
Alarms
The EDM has programmable alarms. When a parameter falls outside of
its normal limits, the digital display will flash with the value and
abbreviation of the alarming item. If the condition triggering the alarm
returns to within normal limits, the display will stop flashing the alarm.
If your installation includes a separate panel mounted alarm warning
enunciator light or audible warning, it too will be activated.
There are no alarms for the individual EGTs because the temperature
values can assume different ranges depending on the flight
configuration—run up, climb, cruise. However there is an alarm on the
DIF parameter, the difference between the hottest and coolest EGTs.
DIF—or span—is the important parameter for monitoring the EGTs. See
“Factory Set Default Limits” on page 42 for a list of the alarms and their
factory default settings.