J.P. Instruments EDM 740 Pilots Guide - Manual (Page 35)

For Your Safe Flight Page 35
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 re-
lean mixture. Repeat
to find power setting
where normal peak is
obtained or run rich.
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 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
normal limits, the display flashes its value and acronym. Once the
parameter returns to normal limits, the flashing stops. If you’ve
connected lights to the EDM’s two enunciator outputs, they too will
flash. The ‘Remote FF Alarm’ output (P4-11) activates when the fuel
remaining or endurance falls below your preset limit. The ‘Remote
Alarm’ output (P1-12) activates with all other alarms. Note: Individual
EGTs do not have separate alarms because they can assume different
values depending on the installation and/or flight configuration—run up,
climb, cruise. However, there is an important alarm which occurs when
the difference between hottest and coolest EGT’s exceeds a programmed
limit. This is called the ‘DIF’ alarm. This can quickly warn you when
cylinder combustion becomes abnormal.