J.P. Instruments EDM 930 Primary Pilots Guide User Manual

Page 58

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For Your Safe Flight

Page 53

Troubleshooting the EDM

Common Misapplications

Problem

Situation

Correction

Display freezes or may
be incorrect

A power transient
could cause the
processors to
malfunction

Recycle the power to the
EDM

LeanFind finds a
“peak” too soon

Failure to pre-lean
before performing
LeanFind or stopping
while leaning

Continue to lean without
stopping

Leaning too slowly

Lean more rapidly

Peak not found during
LeanFind

Lean Find not
activated or stopping
while leaning

Lean at the speed of
approximately 10°F per
second

Off-scale EGT
columns, too high or
low

Off-scale EGT column
readings. EDM in the
Normalize view (blue
scales)

The higher sensitivity of
the Normalize view can
quickly go too high or low
off-scale with only small
changes in EGT.

First cylinder to peak
is not the hottest

This is normal. The first to cylinder peak is not
necessarily the hottest

EGTs rise during
single magneto check

This is normal, due to incomplete combustion
persisting longer

EGTs not uniform
during low power
operation

This is normal. Fuel and air distribution is not
optimal at low power settings

Diagnostic Testing on Startup and During Flight

When your EDM is first turned on it tests internal components,
calibration and integrity of the probes. Most alarms are disabled until the
engine has been started.

During flight, probes are constantly checked for inconsistent or
intermittent signals. A faulty channel or probe encountered during start-
up or during flight will be deleted from the sequence, producing a
missing column or blank digital data.

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