Garmin G3X Installation Manual page 357

The following are potential causes for failure of the engine run-up test:
a) Excessive flexing of GSU 25/GSU 73 and/or GMU 22 mechanical mounting with respect to
airframe (see
and instructions).
b) Vibration or motion of GSU 25/GSU 73 and/or GMU 22 caused by neighboring equipment
and/or supports.
c) Mounting of GSU 25/GSU 73 at a location that is subject to severe vibrations (example;
close to an engine mount.)
d) Mounting screws and other hardware for GSU 25/GSU 73 and/or GMU 22 not firmly
attached.
e) Absence of recommended mounting supports.
f) GSU 25/GSU 73 connector not firmly attached to unit.
g) Cabling leading to GSU 25/GSU 73 or GMU 22 not firmly secured to supporting structure.
h) An engine/propeller combination that is significantly out of balance.
NOTE
In some aircraft, attempting the engine run-up test on a day with very strong and/or gusty
winds may cause the test to occasionally fail. However, windy conditions should not be
taken as evidence that the test would pass in calm conditions; an actual pass is required
before the installation can be considered adequate.
190-01115-01 G3X Installation Manual - Post Installation Checkout and Calibration Procedures
Rev. L
Section 10, Section 11, and Section 8 for applicable mounting requirements
Page 19-25